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    Please critique this design (64 Posts)

  • indevrede indevrede @ 12:24 AM
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    Please critique this design

    I'm not sure if I've seen this exact design anywhere, but it contains many of the concepts that I learned about on this website and others. The cartoon is below. Here are the system specs:

    * Design day heat load 40k BTU/hr (@ 15F outdoor).
    * Lochinvar Knight WHN-055
    * primary-secondary with closely-spaced tees
    * Turbomax 23 reverse-indirect DHW piped as a series buffer in the boiler (secondary) loop, on the boiler supply
    * Thermostatic mixing valve for DHW (115F setpoint)
    * System (primary) loop has a Grundfos Alpha in delta-P mode, probably running @ 14 gpm when all three TRVs are open
    * Each of the three 50-ft baseboard runs will be "zoned" with TRVs, one on each run
    * A single indoor-reset thermostat will be set a few degrees above target, used as a high-temp cutoff (i.e. ODR will be the main feedback)
    * The boiler pump will be controlled by the boiler (0-10V signal) for constant 35F delta T, probably running between 0.5 and 2.5 gpm
    * The boiler will control its supply temperature with outdoor reset (160F on design day, minimum 145F)
    * The boiler will sense the Turbomax temperature and treat it as a zone, calling when the tank temperature drops below 145F
    * The boiler will disable the system pump whenever the DHW zone calls
    * I didn't draw the air separator and Y-strainer, but they will be included
    * (side note: there will be a drain water heat recovery system)

    I think the advantages of this design are:
    * No short cycling, even with 50ft fin tube zones at 110F
    * Return temperatures will vary between 110F and 126F (design day), so the boiler will condense most of the season and maybe beat 90% efficiency on design day
    * Even heating within a zone: Design day baseboard temperature of 134F has 8F delta T
    * Primary/secondary piping satisfies Lochinvar's recommendation
    * Only 2 pumps needed
    * No expensive controls beyond what's included with the boiler (unless you count the built-in controls on the pumps)

    * (un)availability of small, inexpensive, efficient circulators with 0-10V control?

    So, what do you all think? Glitch, fix, or something else? Please critique. Note that this is for a retrofit, so the baseboard is a design constant (obviously radiant would be preferable).
    This post was edited by an admin on March 18, 2014 9:33 AM.
  • Eastman Eastman @ 1:42 AM
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    boiler pump

    The boiler pump would be configured to always run with the system pump somehow?
  • indevrede indevrede @ 7:41 AM
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    The boiler should operate the system pump whenever there's a space heat call ( and turn off the system pump if there is a dhw call).
  • heatpro02920 heatpro02920 @ 7:11 AM
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    I think I would

    Replace the Lochinvar with a Triangle Tube solo 60
    Replace the T-23 with a smart 40 and no mixer {I don't like putting indirects on a unit this small, but I have done it and it works}
    Install a g-foss alpha on the primary
    Install 3 t-stats and use bumble bees for each 50ft run
    Install a bumble bee on the indirect
    Install a taco zone control for the 3 heating zones and let the tt' control handle ODR, DHW, ect...

    But we all do things differently, your design will work, I don't normally use trv's with baseboard or mixers with indirects, I use trv's for radiant panels and fhw rads, and mixers on DHW with tanklesses and undersized indirects... I am not sure what your DHW needs are but a smart 40 fits most residential properties...

    Looks like a fun project, good luck with it...
    This post was edited by an admin on March 18, 2014 8:28 AM.
  • indevrede indevrede @ 7:51 AM
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    Why not trvs?

    Thanks for the feedback. Just curious, Do trvs and baseboard not go well together? I was going to use the remote style.

    When you install a system as you described, is there no issue with short cycling? My design day heat load is 40k btu/hr ( 35k if I do a good job with air sealing and insulation).
  • heatpro02920 heatpro02920 @ 8:46 AM
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    Nothing wrong with trv's

    I think designated delta t circs would be a better option... I dont see how you will short cycle... say a single zone calls for heat, it turns on its designated circulator, ramps up for a minute, then gets its reading, the circ slows down to match your preset delta say 15-20 degrees, Now the unit will modulate to match the load {the solo 60 goes down to 16K btu's}. With the odr taking care of the water temps, your burner taking care of the fire rate, and you circ taking care of the flow rate, you will get the most out of your run times...

    The only issue I see {which I have installed a smart 50 with a solo 60 and it works} is that the low amount of btu's these small mod cons put out can be an issue if there is a lot of dhw being used...
    The customer I installed the 60-smart 50 setup with, said when it was very cold out and he had house guests, he had to play with his t-stat set back, because they were set to heat the house up in the am when they woke, and that is when everyone was trying to take a shower, so now the house wouldnt heat up until the tank was satisified, this could take a while when you have 2 showers with 5 people trying to showers back to back...

    He called me about the issue and I told him not to use a setback while he had house guests, OR to set the setback to catch up before they tried to shower... He let me know that that remedied the issue perfectly, and he never noticed an issue again...
    I always warn my customers, when using setbacks and priority HW, the unit can not do 2 things at once....

    I am not super familiar with the knight boilers, but I prefer the TT units over them, although the important part is to get a contractor that knows what he is installing... So I would take a knight installed by a knight tech over a tt installed by a knight tech {although anyone familiar with mod cons will get it done, future service is a concern}....

    The trvs will work and they are nice, but I like designated circs rather than a single circ doing all the flow management...

    This is really just my preference, I like to use as few mechanical valves as possible, if I can get around external valves I will... I dont like mixers on DHW {unless it is code and needed}, I dont like mixers on radiant {I would rather use a separate plate exchanger and aquastat}, I just prefer to go with out them...

    Do the math on materials, Im not sure if you are doing the install yourself or have a contractor, but Ill bet the bumble bees vs trv setup and single circ is not a big price difference....

    I hnoestly would look into a rinnai tankless too, if you can fit it, the cost wont be considerably more than the indirect and you will not have any DHW issues... Sounds like a medium/small home so a tankless may be a good idea... I have done a bunch of mod cons and installed tanklesses rite next to them..
    This post was edited by an admin on March 18, 2014 8:51 AM.
  • indevrede indevrede @ 9:22 AM
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    Re: short cycling: I just considered the smallest zone output (50 ft * 160 BTU/ft/hr = 8k BTU/hr) and the boiler minimum output (11k BTU/hr) and the mass of the water in the loop. Without a buffer, the mass is about 4 gal, so with a boiler setpoint differential of 10F,  10F * 4 gal * 8.3 lb/gal / 3k BTU/hr = 7 minutes. Not horrible, but not great. The reverse indirect buffer adds over 200 lbs of mass, so short cycling goes away.

    Re: night setback, understood. I wasn't planning to use it, thanks for the confirmation.

    Re: running out of hot water, I'll be using a drain water heat recovery unit, so my 55k boiler will be effectively about a 90k boiler, enough for endless hot water for a 2 gpm shower.

    Again, thanks for the advice & insight.
  • Zman Zman @ 8:58 AM
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    I am not sure how you will get the boiler to condense.
    With 145 degree setpoint and minimum boiler flow rates I don't think you will get the low return temps.
    I am not a fan of reverse indirect and low temp heat.
    The lochinvar is a good choice for mixing although you have to add a mixing module.
    Never use a smart tank for reverse indirect. They are steel on the outside.
  • Paul48 Paul48 @ 9:32 AM
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    What happens when the DHW is at 140*, and there is a call for heat?
  • indevrede indevrede @ 10:08 AM
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    Good question

    Depending on set differential and target 145F DHW tank temperature, the boiler may get a call for DHW (as a zone) when the tank is at 140F. In that case, the boiler will turn on the boiler circulator and supply whatever temperature is set by ODR (between 160F and 145F) until the DHW is satisfied (modulating according to PID, of course). While the boiler is satisfying The DHW zone, the system circulator will shut off (this is key, and I'm really thankful that Lochinvar allows this configuration).

    After the DHW is satisfied, the system pump will turn on in order to satisfy the space heating call (if there is one). If no space heating call, then the system pump won't turn on, and the boiler pump (and blower) will turn off.

    I really appreciate these questions, thanks. And, anyone with experience with Lochinvar SMART control configuration please chime in to make suggestions or corrections to my plan.
  • Paul48 Paul48 @ 10:19 AM
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    Once the DHW is satisfied, it will then switch to heat if there is a call. But according to your drawing, it will continue sending hot water through the indirect.
  • indevrede indevrede @ 10:27 AM
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    Always through the indirect

    The Turbomax 23 is a reverse indirect, so it's acting like a 26 gallon series buffer in the boiler loop. Every time the boiler fires, hot water gets pushed through the tank. If no one's using DHW, then the output of the buffer = input temperature. Even if the bottom of the tank is "cold", i.e. 35F below the top, it will only take a few minutes to heat the entire tank to the same input temperature (160F to 145F depending on ODR) . Once the bottom of the tank = the top, then you're looking at a conventional primary/secondary setup.
  • Paul48 Paul48 @ 10:32 AM
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    Mixing Valve

    The setting for the mixing valve for domestic is different at different temps. How do you ensure no one gets scalded?
  • indevrede indevrede @ 10:34 AM
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    Thermostatic mixing valve

    Thermostatic mixing valve
  • indevrede indevrede @ 9:55 AM
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    Setpoint = boiler supply

    Reply to Zman's post titled "Condensing?"

    I'll have the boiler control the boiler supply (hot water coming out of the boiler), not the system supply. Because of the higher flow rate in the primary loop, the system supply will be 134F on design day, but the boiler supply will be 160F. Return temp will be 126F. With ODR, the boiler supply will vary down from 160F to 145F minimum.

    Again, the system supply is not controlled directly, but instead will be a function of
    * the boiler supply temperature (controlled directly by the boiler)
    * the boiler loop flow rate (controlled directly by the boiler for 35F delta T)
    * the system loop flow rate (controlled by the delta P pump)

    Example 1: in the shoulder season ODR calls for 145F boiler supply. If 3 zones are calling, that's 150 ft* 160 BTU/ft/hr = 24k BTU/hr. The flow in the boiler loop is 24k / 500 / 35 = 1.4 gpm. The system loop is at 14 gpm (max for alpha in delta P mode), so its delta T is 3.5F. So, the system supply is 113.5F and the return to the boiler is 110F.

    Example 2: again, shoulder season and 145F boiler supply, but this time only one zone --> 8k BTU/hr. Boiler loop is 0.45 gpm. The delta P pump would probably be 7 gpm (50 feet of 3/4 copper has 6 ft head loss at 7 gpm). So the delta T in the system loop would be 35*0.45/7 = 2.3F, and so the system supply would be 112.3F.
    This post was edited by an admin on March 18, 2014 10:10 AM.
  • Paul48 Paul48 @ 10:26 AM
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    Please explain

    "Design day heat load 40k BTU/hr"
    You say you have 24k btus of emitters?
  • indevrede indevrede @ 10:29 AM
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    Three 50ft zones of fin tube

    Three 50 ft zones of fin tube. At 110F, they each put out 8k BTU/hr. At 130F they each put out 13.3k BTU/hr.
  • Paul48 Paul48 @ 10:36 AM
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    Got mixed up with your shoulder season example. It's an age thing, I guess.
  • indevrede indevrede @ 11:58 AM
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    Almost like a reverse indirect hydraulic separator

    I've convinced myself that the design in the first post is exactly the same as a reverse indirect (like an Ergomax) piped as a hydraulic separator / low loss header / buffer that connects the boiler loop to the system loop.

    So, nothing really new or unique here, and it should work fine. Now I just have to figure how to add 0-10V speed control to a Grundfos Alpha...
  • Gordan Gordan @ 1:41 PM
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    How is the DHW zone heat call generated?

    If aquastat, you're going to have a conflict between ODR and the aquastat. Either way, there's a conflict between the fixed temp operation of DHW and ODR operation of the heating system.
    There's a major difference between a dual-tapping buffer tank and what you're considering here; namely, the return water from the system will mix with and dilute the hot water at the top of the buffer tank if you pipe it in the usual supply-at-top fashion. You will be continuously tempering the buffer tank.
  • indevrede indevrede @ 2:46 PM
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    With a lochinvar temp sensor

    In the DHW thermowell.

    Re: continuous tempering, the DHW tank setpoint (aquastat) and the DHW boiler supply setpoint will both be 145F, which is the lower limit of ODR. I think that should work perfectly, see this section of the installation manual: (I'll be configuring the DHW as a zone with system pump "forced off")
  • Gordan Gordan @ 4:23 PM
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    So let me see...

    During the shoulder season you potentially have both DHW hysteresis and ODR hysteresis to worry about. If (DHW setpoint - DHW differential) < (ODR setpoint - ODR differential) this would result in a DHW call during a space heat call, which would force the space heating cycle to be interrupted so the priority DHW call can be satisfied. This could work out pretty well, but you have to sweat the details. If, at some future point, you wanted to bump up the DHW setpoint in order to get more first draw capacity, this would have a bearing on all of your parameters.
  • Gordan Gordan @ 4:27 PM
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    Actually, upon further reflection...

    At times, during low heat demand periods, your boiler's burner will cycle off while the call for heat is still on. This would mean that the return water that would be tempering the tank would be (considerably) cooler than the 145 F setpoint, potentially causing the DHW call to be initiated even though there's no DHW demand. So here's a circumstance where space heating, absent DHW demand, generates a DHW call and interrupts space heating.
  • indevrede indevrede @ 4:37 PM
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    Both excellent points

    Gordan, thanks for posting. You're identifying issues that I hadn't fully thought through.

    Following this train of thought (self-interrupted space heat), is this a bad thing? The boiler's not short-cycling, and cold water isn't being pumped through the space heating zones, so what's the problem? The boiler is filling the buffer with heat, then sending some of that heat to the space heating zones, then pausing to fill the buffer with more heat, and so on.

    Or am I missing something? (I'm also wondering if this is why typically people put buffers on the return, not the supply)
  • indevrede indevrede @ 4:51 PM
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    Maybe it *will* short cycle?

    Still trying to think this through. Maybe the boiler will short-cycle because I've effectively cut out the buffer from the control loop.

    Just a guess, but could moving the control sensor from immediately upstream of the tank to immediately downstream help? One problem I see is that there would be a long lag in the response so I'd guess the boiler would fire at 100% a lot of the time, possibly every time...
  • Eastman Eastman @ 1:46 AM
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    delta control apparently only goes to 25

    A forum member named smihaila asked Lochinvar detailed questions about some of the more advanced pump control features on the boiler you are considering.

    From a post titled: Some answers from my Canadian Lochinvar rep

    Q3: What fine-tune parameters are available in the "Smart Control" logic
    for the customization of the "Const Delta-T" operation which seems to
    be supported via "0-10V BLR PMP OUT"?

    A3: The Knight Smart System controller will always try to maintain a 20F Delta T (Default) but has a range from 15 – 25 using the PC Software.
    This post was edited by an admin on March 19, 2014 1:48 AM.
  • indevrede indevrede @ 8:14 AM
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    Thank you, this detail is really important.
  • SWEI SWEI @ 11:33 AM
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    Lochinvar boiler pump control

    I'd double-check that one if I were you.  I'm pretty sure someone at Lochinvar gave me different info about a year ago, but I don't have notes on the conversation.
  • Zman Zman @ 1:59 PM
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    I am following your logic.
    I have real concerns about the low flows you are running through the boiler.
    For one, the heat exchanger could be damaged. This is why they recommend primary secondary.
    Secondly, If the flow goes too low,the flow will become laminar rather than turbulent.This will trash efficiency.
    I would run this one by Lochinvar.
    I guess a worse case scenario would mean you have to raise the temps and lose some efficiency. (actually the worst case would be a damaged boiler that is not warrantied)
  • indevrede indevrede @ 3:46 PM
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    Here's the relevant page from the installation manual. Nothing about laminar flow there, and it appears to show flow all the way down to 0 gpm even for the largest WH boilers. But I think you're right, I should confirm with Lochinvar.
  • remodel remodel @ 4:36 PM
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    boiler flow

    If you get a response from loch let us know, I doubt they will commit to saying the boiler can go below a certain flow rate even though there has to be a bottom end. I know p. 36 shows the fixed speed pumps at full fire.  It is relevant that the majority of the time you are at low fire and the pumps are oversized.  I have looked throughout the wall and didn't find much on low flow through boiler just tons of discussions on oversized boiler pumps.    
  • heatpro02920 heatpro02920 @ 8:23 PM
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    I am curious

    What benefits you are getting over something more conventional, don't get me wrong, I love discussing different alternatives to the "norm" but to compare it to the system I laid out in my earlier post, what benefits are you trying to exploit?

    By all means I like seeing guys trying something more than the normal blah blah blah heating system, but I like to see something get more simple vs adding complexion...

    Just curious as to where you are going?
  • indevrede indevrede @ 8:43 PM
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    I should have been more clear

    I'm pretty much stuck with the Knight boiler and Turbomax 23 reverse indirect and 150 ft of baseboard. I have 2 pumps (alphas) and I'd rather not buy more or buy other zone/mixing controls unless absolutely necessary. I want a system that lets the boiler turn down and condense as much as possible, but also not short cycle in the shoulder seasons with 50 foot baseboard zones. In my original post I proposed an arrangement that I thought satisfied all my requirements. After reading the responses in this thread I now believe the design is flawed, but I still hold out hope that if I just pipe it properly I can reasonably achieve my goals.

    The fallback plan is to let go of sub-zoning (ditch the TRVs) and to keep the baseboard as one big zone. Then the risk of short-cycling goes away so I can discard the buffering idea and use the reverse indirect like a regular indirect.

    Again, I'm still hoping that there's a simple solution. Maybe use the reverse indirect like a true hydraulic separator? (with tees on the inlet and outlet) In that case I'm not sure what the flows would look like, or how ODR would work, or where I would put the sensors, or if I would get much condensing or turndown, or if delta P or delta T control would be beneficial, etc. Maybe someone else has an idea?
  • Paul48 Paul48 @ 10:47 PM
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    well do the emitters match the heat loss, room by room?
  • indevrede indevrede @ 8:22 AM
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    Not sure...

    I'm not really sure. It's the typical installation where baseboard is usually along almost the entire length of every exterior wall.

    The main issue is that the finished basement is cold and the top floor is too warm, which is why I thought zoning would help balance. I guess I could put some effort into "permanent balancing", like adjusting flow rates. Also I plan to increase attic & band joist air sealing, so that should help with evening out temperatures.
  • Gordan Gordan @ 8:47 AM
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    Stuck may be a bit harsh

    These are very fine components and will work marvelously. Considering the low, low price of an electric water heater which could be pressed into service as a buffer, it seems like insisting on using the Turbomax for that purpose creates more issues than it solves. Break out the DHW function from the heating system and you're free to optimize both for their usage patterns.
  • indevrede indevrede @ 8:55 AM
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    OK, I'm listening

    You're right, a 30 gal electric wh is really cheap. Where would I connect it  & what temperature would the boiler control?
  • Gordan Gordan @ 9:44 AM
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    Several options

    1) You could get rid of primary-secondary, pump through the boiler, and pipe the buffer in series with the boiler. Supply might be better than return from the point of view of acting like a capacitor and "evening out" the supply temperatures coming from the boiler, so no expansion/contraction at the emitter. Advantage: simplicity, direct return to the boiler minimizing return temperatures. Disadvantage: you have to worry about boiler flow, but with the decoupling of DHW and space heating you now have the ability to tinker with the ODR curve making sure that those TRVs remain open or mostly open. Another disadvantage: during a DHW call, you can't continue to satisfy the space heating from the buffer. Boiler control strategy is ODR with constant circulation.

    2) You could keep primary-secondary and pipe the buffer downstream of the boiler tees. Alternately, you could use the heating element tappings as a second set of tappings to configure the buffer as a hydronic separator. Advantage: the buffer stays online during a DHW call, and you can decouple system flow from boiler flow. Disadvantage: some return mixing may/will result, you have more components, and control strategy is more complicated (though I think that the Knight's control handles this with a system supply sensor, and the boiler pump can be configured to only come on when the burner is ready to fire.)
  • indevrede indevrede @ 8:45 AM
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    New approach

    OK, forget the reverse-indirect-as-buffer idea.

    The minimum output of the boiler is 10k BTU/hr. I want to avoid short cycling in the shoulder seasons when one 8k BTU/hr zone is calling. The usual strategy is to increase the system mass (maybe with a buffer). But another possibility is to somehow make a single-zone emit a minimum of 10k BTU/hr.

    Is there a cheap & easy way to do this? It would be like temporarily boosting the ODR setpoint when only one zone calls, but returning to the regular ODR setpoint when two or three zones call.

    Another idea is to just manually disable the TRVs in the shoulder seasons and run as one large zone.
  • remodel remodel @ 10:05 AM
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    heat loss room by room

    indevrede...I was in your situation post fact (I am just a homeowner so take it for what its worth) after finding out my boiler was oversized.  Do as Paul48 says and run your heat loss room by room using slant fins program for ipad or their HE2 program (do a google search, I just downloaded it a month or two ago).  Also maybe do some spreadsheet work to determine heat loss per element (flow rate, btu/ft etc to determine your output at your last fin tube) see where that puts you and you might find out you need more element.  Might be able to ad some high output at the end of the loop which might help with delta tee (something I plan to do next season).  Also the loch has some controls to help with short cycling, i.e. ramp delay, large differential offsets maxing out the boiler below 100% of fire.  You can't get away from some short cycling or fussing over condensing all the time, something that took me a little while to realize.       
  • Gordy Gordy @ 6:40 PM
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    Starting at the finish line

    I will reiterate what others have said.

    Do a room by room heat loss.

    Determine existing base board out put at what water temps you wish to use to be condensing.

    It is possible you may have base board enough to lower the supply temps if envelope upgrades have been made to the structure after the original heating design was installed.

    Or you may fall short with what is existing, and have to add more, or sacrifice a higher supply temp if that is not possible.

    Remember also with ODR your not going to need high water temps most of the heating season even if your base board is just enough at design conditions. So at design you might sacrifice efficiency with out condensing, but be condensing at warmer temps.

    But you don't know any of this with out the heat loss, and emitter outputs start with that.

    I would not ditch the TRVs either.
    This post was edited by an admin on March 19, 2014 6:41 PM.
  • indevrede indevrede @ 9:18 AM
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    I thought I did this already

    I did a whole-house heat loss: 40k @ design day (with some envelope improvements). That means a 55k mod-con is sufficient, which is the most important question.

    I did a baseboard analysis: Three 50 ft runs. That means the radiation is oversized (good) and should match the design day load at about 130F avg temp.

    Any room-to-room or zone-to-zone imbalances will be handled in initial and tweaking, as will the ODR curve.
  • indevrede indevrede @ 11:59 AM
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    Please critique this NEW design:

    Set aside DHW for the moment. I've been chewing on this idea:

    Suppose it's 56F outside, so the total home heat load is 10k BTU/hr . Suppose also that the baseboard setpoint is about 110F, so each zone can emit 8k BTU/hr. What if each motorized zone valve opens in sequential order 1-2-3-1-2-3-1-2-3 etc? There would be overlap, so that, 75% of the time only 1 zone is open (8k radiation) and 25% of the time 2 zones are open (emitting 16k). So the average baseboard output is 10k BTU/hr, which matches the total house load, which matches the minimum boiler output. The boiler runs continuously, never shutting off, and no buffer tank required.

    Here are some hard numbers: zone 1 open for 3 minutes, both zone 1 and zone 2 open for 1 minute, zone 2 open for 3 minutes, both zone 2 and 3 open for 1 minute, etc. If desired, you could increase the valve open time up to about 8 minutes per valve, but longer than that the boiler would begin to cycle on and off.

    Now, what happens when the outdoor temperature drops below 56F? Then, the relative time 2 zones are simultaneously open increases. When it's cold enough, 3 zones have to be open at least some of the time to meet the load, and finally all 3 zones will be open all the time to meet a 24k BTU/hr total home heat load.

    To reiterate: from 10k to 24k BTU/hr total home heat load (between 56F and 36.4F outdoor temp) the boiler is never turned off, and the return temperature is exactly the same, about 110F. ODR setpoint is also constant.

    Above 24k BTU/hr heat load all 3 zones are always open, the boiler is always on, and the average baseboard temperature rises from 110F to 130F according to ODR.

    Below 10k BTU/hr heat load (i.e. above 56F outdoor temperature), boiler cycling is unavoidable, but the boiler fire-time would be about 10 minutes at 60F outdoor temp. Not bad!

    Now onto piping: I'm thinking the best way is with primary-secondary. The primary (space heat) loop would have a delta P circ and the secondary (boiler) loop would have a small circ set to constant rate, say 3 gpm, and control the supply temperature of the system loop (not the boiler loop). The delta P circ should automatically switch between 4, 8, and 12 gpm when 1, 2, or 3 zones are calling. The zone delta Ts would range from 4F up to 6.6F on design day.

    If you're still reading and interested, I'd pipe the DHW as priority off the boiler loop with its own small circ.

    So, the total equipment tally is: 3 circs (one of which is delta P), and 3 motorized zone valves. I also need some way to control the zone valves, which probably needs to feedback off outdoor temperature, or possibly boiler output (averaged over hours and possibly excluding DHW calls). I write control software for a living.

    What do you all think? I know I've glossed over zone and room balancing issues, I was just considering the whole-house perspective.
  • Paul48 Paul48 @ 12:07 PM
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    I'm just not sure what type of windows you have to use to allow space travel.
  • remodel remodel @ 12:55 PM
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    55 will work

    55 will work nicely, radiation sounds good and DHW too.  You will get your ODR sussed in, the loch has some cool controls that you will be able to manipulate.  I plotted house load and ODR output v. outdoor temp to really fine tune my ODR but at the end of the day fin tube loves hot travel next.  The posts are good, keep us posted as to how the install and performance goes.     
  • ced48 ced48 @ 10:26 AM
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    I've Found Water Temps

    below 120 degrees in slantfin, just don't seem to heat that well. I have been running nothing lower than 120, or higher than 140, seems to work well for me. I get run times of 1/2 an hour, or so, off maybe 40, 45 minutes. I know this isn't what the guys who want there modcons to always run like, but it works for me.

    I also think if you go with the TT 60, not the Loch 55, yo will have problems with the TT not modulating down enough-
  • indevrede indevrede @ 2:01 PM
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    Maybe this has been done

    This snippet (image below) is from the brochure for the Honeywell AQ2000 series. "Zone synchronization" and "Boiler Short Cycle Protection" sound like what I'm proposing. Does anyone have experience with the AQ252 or similar?
  • indevrede indevrede @ 2:48 PM
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    OK, this is a controls issue now

    More googling. Tekmar TN2 does zone synchronization also. Not sure what their logic is, but I found this picture on their website.

    Anyway, the piping for this scheme will be the standard design that Lochinvar shows in the setup manual (P/S with priority DHW and zone valves). This zone sync stuff I introduced is really just a controls issue, so I'll probably post in the Controls category if I have any other ideas/questions.

    Thanks to all who chimed in. Some of you suggested zone valves and P/S piping, which I initially resisted but have now seen the light.

    Re: buffer tank, if I added one it would reduce the valve cycling rate, which would certainly extend valve lifetime. Need to weigh that against the cost of buffer tank + installation. Costs add up...
  • Paul48 Paul48 @ 4:11 PM
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    Smart Money

    Would be best spent making sure you could heat the house with 130* water on design day. The output of the baseboards falls off significantly at that temperature. You need to make sure you have enough emitter in each room. I'd use the TRVs in sleeping areas, and let the ODR do it's thing handling the bulk of the home.
  • indevrede indevrede @ 4:27 PM
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    Any suggestions on cleaning baseboard?

    Good point. I'm basing my numbers off of a Slant-Fin chart that you can find on Google, but my baseboard has cheap-looking fin-tube that's old, banged-up, bent, and gunked up with dust and fur and cobwebs. There's no way it's currently going to reach the premium spec for BTU/hr, so I figured I would put in some elbow grease and spend a few days and try to really rehabilitate them. Any tips/tricks? Vacuum, toothbrush and pliers?

    Re: TRVs, all the bedrooms are on a single baseboard loop, so I can't do individual bedroom TRVs without added piping. Plus, I've abandoned the idea of TRVs so I can implement my "zone merry-go-round" control idea (aka space ship). Initially I'll use ODR exclusively, but if there are comfort issues then I'll add some temperature sensors and figure out how to make the zone cycling respond.
  • remodel remodel @ 5:27 PM
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    fin tube

    Heard some talk of fin tube being overrated by 15% .  The one thing I had a problem with was fin tube just does not give off that much heat at those low temps (at least that is what I saw) charts aside, so I would inherently short cycle, hence raising my ODR to some hot water.  Once I did that she would burns a lot longer.  Don't get me wrong on my low end I set her to 115° (with a large diff) water but she's going short cycle anyway (when it is 60° outside) so I get some condensing out of her.  Also study the onboard space ship controls real close (loch 55 smart control) they provide some similar stuff you were mentioning with the honeywell etc..        
  • Derheatmeister Derheatmeister @ 7:34 PM
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    Digital vs. Analog Anti short cycle program..

    I like the Idea of the Reverse Indirect/Buffer combination...This has been done before..I think here in the USA HTP has a product like this..
    I am a big supporter of Buffer Tanks for more that one reason ...Better fuel economy,Keeps the Boiler from short cycling which keep system components from premature failures i.e. gas valves and Blowers...Allows Air and Debris to settle out..
    Separates flow conditions which will not restrict the Boiler flow..If a sacrificial anode is part of that equation this can certainly not hurt...This would be a Analog system..

    If you are worried about Short Cycling with the LOCHINVAR i think that you may be able to overcome this somewhat via the Anti short cycle Program which is adjustable from 0 to 40 minutes ...They also have a Ramp delay which is a 6X6 control (6 Time spans with 6 modulation rates)
    I still think that a Tank is the real thing But if Room and Budget are a concern then the Digital version will also work ..Just not as efficient..... Then again one could argue the Buffer Tanks heat loss which could be 1 deg F/Hr depending on the Insulation/Ambient room temp and other factors..Hope this helps...Richard..
  • Eastman Eastman @ 1:21 AM
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    zone sync

    The Tekmar system syncs the zones at the beginning of the cycle. The thermostats also provide indoor feedback to an ODR module, which adjusts the setpoint to match the loads at the minimum supply temp, and automatically adjusts the differential if required.

    The Honeywell system is probably very similar but I have not read up on it as much.

    As far as I know, there is no zone sync method that uses a hand off strategy, though. That wouldn't make sense if the system is in control of the supply temps and is allowed to adjust them to optimally match the emitters.

    It would be interesting to see someone install an indoor feedback system, they seem pretty rare.
  • indevrede indevrede @ 8:54 AM
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    "Zone handoff" sounds better than "merry-go-round"

    Zone-handoff. Has a nice ring to it.

    Thanks for the info on the Tekmar controls. Their diagram seems to show exactly what you describe and, as you pointed out, it's not quite what I want. (Actually, basically the opposite of what I want. Zone handoff evens out the total load over time, but "zone start-sync" intentionally bunches them together)

    I would add one qualification to your remark that this zone handoff strategy wouldn't make sense "if the system is in control of the supply temps and is allowed to adjust them to optimally match the emitters." ? The other requirement: a lot of mass, so when the individual micro-zones call for heat on a randomized basis they can somewhat average each other out, keeping the boiler from cycling by allowing the modulation rate to remain as low as possible.

    Installation should occur within the next couple of months, so this fall will be when I do the first real tests. I will keep you all posted.
  • Paul48 Paul48 @ 9:58 AM
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    You are not going to get what you want at design day(or lower) temperatures, with the emitters you have.
  • indevrede indevrede @ 10:20 AM
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    I'm not sure what point you're trying to make.

    I'm not trying to be rude (I asked for critiques, after all), but are you implying I won't get as much condensing as I hope? That's true. But that fact doesn't change the piping or control strategy, just the ODR curve and my heating bills.

    No matter what supply temperatures I end up needing, if I implement this zone handoff strategy correctly, I will minimize cycling, maximize efficiency (because I'll be keeping the modulation rate as low as possible for as long as possible) and eliminate short cycling.

    Assuming I was going to get motorized zone valves anyway, the added cost will be almost zero (microcontroller+relays+24V transformer = couch change) plus I get to program and tinker with a control system in my own house. Win-win-win ? (As Michael Scott would say)

    Of course, there's still the possibility that the zone handoff plan has one or more glaring flaws and that I'll have to abandon it. See any?
  • Paul48 Paul48 @ 1:21 PM
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    Pretty Sure

    That strategy falls into the "Six of one...Half-a Dozen of another" category. Based on the definition of a BTU, it should take the same amount of time to heat the water to a certain temperature, whether you are alternating zones, or feeding the home as a whole. I'll stop beating a dead horse about the whole system. I didn't reallize you only wanted to talk about control and stop-gap measures. Best Wishes
  • Eastman Eastman @ 12:40 AM
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    zone hand-off

    Zone hand-off is the opposite of what all these sync systems are trying to accomplish.  The goal is to prevent dispersed calls for heat and always fire into as much of the radiation as possible.

    A hand-off strategy could only make sense if the mod/con was forced to operate at a fixed setpoint.  In this case, even though the burner can modulate, the emitters can not, creating a mismatch between the house's true demand and the systems output.

    In a nutshell, it's better to fire 10k total into all the radiation all the time, as opposed to firing 10k into one zone at a time.  The latter requires higher setpoints, increases temperature swings in the zone, and reduces the connected load to the boiler which increases the cycle frequency.
  • indevrede indevrede @ 7:29 AM
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    I agree 100%. Thanks for explaining it better than I did.

    In my case (three 50ft baseboard zones), I plan to force the mod-con to operate at a fixed setpoint for total heat loads up to 24k BTU/hr (outdoor temps above 36F). Above 24k load, I'll allow the setpoint to rise so that the emitters can match the load.
  • remodel remodel @ 9:31 AM
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    zone hand-off is a cool idea, but you might find that once the hand-off starts the other rooms cool down the hot rooms get hotter.  Even if you adjust setpoints, each area has its own dynamic.  I always thought something like this to would be cool if right at the end of short heat call a zone(s) could open and the boiler could dump some heat (btu/hr), say 5 minutes, then an zone opens etc... 
  • indevrede indevrede @ 10:02 AM
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    You're right, there really should be feedback

    Thinking through this some more, I agree with you that there could be comfort issues if the zone control is unaware of the zone thermostats. I'm still working on the logic, but it would follow something like: "If only zone A is being heated and either the supply temperature is about to reach its upper limit, or zone A's thermostat is about to reach its upper limit, then the zone controller should open the valve for the next coldest zone".

    Clearly the logic needs to be more complex, but you've got the right idea, the zone controller should intelligently wait to turn on and turn off zones according to the zone temperature and the supply temperature, to keep the boiler running as long as possible and as low modulation as possible. In some cases that logic might work out to evenly-spaced 1-2-3-1-2-3-1-2-3 calls (my original proposal), but more likely the timings would be irregular, the order might change, etc.
  • RobG RobG @ 1:49 PM
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    Panel Rads

    It sounds like you plan on staying in the house for some time and money does not grow on trees. As time goes on you would be wise to slowly change out the baseboard with panel rads and TRV's. If you do it one zone at a time, by the time you are done you can crank the temp down and run the boiler at true design temps. Panel rads operate at much lower temps and do not clog up with dust ( they look better and take up less space as well).

  • indevrede indevrede @ 1:54 PM
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    I was thinking that too

    Yeah, we just have pine trees on our property. All they yield is needles and branches on power lines.

    Any thoughts on Biasi Ecostyle radiators? They seem eco-nomical.
  • heatpro02920 heatpro02920 @ 8:23 PM
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    This thread is all over the place

    I love it...

    there are a bunch of companies selling panels in the US, pensotti and biasi are about half the cost of Runtal and buderus per BTU... I havent heard anything bad about any of them...
    although I think they rate them at 180, so really a 24x24 biasi says 4500btus but the panel is only 2700 at 140 degrees... a 24x24 buderus steel panel says 2500btu... Its confusing....

    some of the smaller buserus panels are on sale for around $50 each rite now, not sure how long they will last, I bought a bunch of them as I am sure others did also...
    This post was edited by an admin on March 24, 2014 9:56 PM.
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