Heating Help

sensors

@ May 22, 2011 11:28 AM in aq251 reset

The boiler return sensor is optional, it's used to protect the boiler from low return temps.
the supply sensor should be measuring the temperature out of the boiler, make sure it's placed upstream of the DHW T so that it can measure supply during DHW production.
This control is designed to work with special communicating thermostats. they do more than just display the outside temperature, they "communicate" with the reset control about the actual room temperature if it's rising or dropping, and how far from target it is, this information is used to determine what the supply temperature should be (Indoor Tweek of the ODR). and to sync the run cycles of the installed stats as best possible.

Sound like you should spend some more time with the supporting literature, getting the sensors in the right places is crucial, but you also need to commission this thing and the default settings may not cut it.

zone sync without boiler control

@ May 17, 2011 1:52 PM in Zone Load Synchronizing - Is it worth it?

Rob,

Can you wire a Tekmar zone manager without a boiler control (420 or whatever)? How does the zone manager get it's power?

While the backside wiring on the newer tn2 house controls and need for an external transformer is a bit less tidy, I appreciate the lower cost of this this line and the two wire thing is huge for retrofit.

upstream

@ May 17, 2011 1:33 PM in glycol feeder and mold

It's before the fill valve, I stated it wrong the first time, thanks for catching that.

I'm really not not sure what the pre charge should be. The one pictured is just at the factory preset of 12 and it works fine. I guess I'm a little nervous that this could be putting to much strain on the rubber by stretching it further than it should, so in the future I'll probably bump up the pre-charge. I'm a little less inclined to mess with a pre-charge since I'v learned that it's pressurized with nitrogen and I don't have a nitrogen tank.

I included a pressure gauge to monitor the glycol charge and a boiler drain for initially purging air from the top of the tank and pipes leading to the fill valve. This system is actually just charged with water, but I like the idea that there is a finite amount of make up water especially on a radiant system with so much pipe and the increased chances of a leek. This actually was put to the test twice when the insulation contractor and then the flooring guys punctured the tubes, it was a mess but considerably less fluid was spilled than would have been if the system was tied to the domestic lines. It's been running for two years now with no noticeable drop in pressure. The configuration of the boiler fill valves makes it possible to boost the charge without introducing air into the system (if it is ever necessary). The main reason I did it this way was because it was new construction and there was no water in the domestic lines, mid winter construction project.

I vote yes

@ May 17, 2011 12:25 PM in Zone Load Synchronizing - Is it worth it?

I think you are overstating the price difference a bit, between conventional stats and zone relay VS. a synchronizing control such as the tekmar TN2. If you want this much zoning your already committing a lot of resources to thermostat wiring, zone valves, isolation, etc. Were not supposed to discuss pricing but i think if you subtract the cost of all the conventional stats and relays this upgrade is less than you state. Considering the significant cost and relitivly long payback periods of a Ground source geo/radient system I think it's silly not to include this.

Alternately I'd consider pairing down the number of zones even consider omitting indoor feedback altogether if the house is tight and doesn't have any crazy glass features this can work fine for a set it and forget it type. Balancing manifolds can help match areas of the house with different loads. Do you really need this much control, slabs are so sluggish anyway , they are not well suited to setback and will disappoint the user who wants to make frequent changes to a thermostat setting.

If you feel you must have so much zoning and don't want to use a synchronizing control consider leaving a perimeter loop of each individual zone"wild". IE don't kill all the loops in a zone when the stat is satisfied. Leaving a perimeter zone wild will help moderate the inertia issues and micro load cycling.

Also I believe that honywell makes a paired down AQ zone control that does synchronization without all the other stuff.

Attribution

@ May 17, 2011 8:58 AM in glycol feeder and mold

Yes Mark you have presented this idea before. I am indebted to the wall for great ideas like this one.

As an early adopter of this technique, perhaps you can shed some light on the etymology of the term "pig".

My apologies for the missing attribution :)

Glycol Pig

@ May 16, 2011 4:57 PM in glycol feeder and mold

I think the open glycol feeder is a bad idea.

1- glycol will go bad in contact with air

2-glycol can feed bacteria and mold, especially if it's open to the air

How much make up water does a closed loop heating system need?

I favor a very thorough purge and a glycol pig- A dedicated expansion tank (with the bladder pressure jacked up) downstream of the fill valve that is pressurized 25-30 psi with the glycol solution.

SDR-9

@ May 16, 2011 4:39 PM in mixing brands of pipe with manifolds

If the pipe is SDR-9 and so is the manifold you should be fine. Don't use fittings with compression rings or sleeves that were not designed for those fittings. But if it's an SDR-9 fitting and SDR-9 pipe the brands don't have to be the same. (in my opinion)

ground as thermal mass

@ May 16, 2011 4:26 PM in Rigid foam slab insulation

The old Heatway design manual took a similar position on slab insulation. Although the manual was well written and had a lot of good information about radiant heating and control strategies, I wonder if this opinion was researched by the same people who did the rubber compounding for entran-2?

I would imagine it's fairly complicated to model the movement of heat through the ground, lot's of variables. Still I don't think you have to be a math head to understand that an enormous 55 degree heat sink in direct contact with a 72 deg slab is going absorb a significant amount of energy. Yes the earth will warm and a temperature gradient will form under the slab such that the rate of transfer to the earth will gradually decrease and stabilize but they will never reach equilibrium, energy will always be moving into the ground. How much energy is lost to different soil types and what is the point of diminishing return on insulation are interesting questions, I have a memory of an experiment that may have been posted here where temperature probes were placed at varying depths under differing insulation types to try and inform this question.

Also keep in mind that many soils have water moving through them, Imagine how much heat a slab could loose to the earth if (cold) water was moving through the soil directly below. Extruded Polystyrene is our friend, skimping on slab insulation is a false economy.

Viega

@ May 11, 2011 9:26 PM in PEX Installer Preferences

Viega's stainless rings and tools are excellent, and they periodically sell them at a promotional prices.

Occasionally it's difficult to get the tool into a tight space, the expansion system does allow for making connections in confined spots.

As far as temperature is concerned I kind of remember Viega stating a minimum recommended pressing temperature, colder than uponor, but not way below freezing if I remember correctly.

I have some concerns about the plastic uponor fittings becoming brittle over time, especially where they are exposed to high temperatures. I'v seen overheated (but probably not over 180) heat-link manifolds that were totally degraded and I could break apart with my hands.

Viega and vanguard

@ May 11, 2011 8:37 AM in Using Uponor Propex fittings on different pex ?

I would be wary of using an expansion fitting on a non-uponor pipe, but I'm quite comfortable using Viega press fittings on other brands of pex that use compression style fittings.

Viega kind of killed the whole pipe and fitting match argument when they bought Vanguard and said we could use the original press fittings too. What you don't want to do is use a viega press ring on just any type of fitting, the press ring uses a very shallow ridge on the fitting. Viega is now selling their fittings with the ring pre-attached and will phase out the separately sold rings to avoid this.

As far as insurance is concerned, even if you did everything by the book you would probably end up making a choice between filing a claim and loosing your insurance/skyrocketing rates, or just taking responsibility for the problem your self.

cemented in

@ May 3, 2011 3:57 PM in Help!

The fact that those vents were cemented in sounds like trouble, to remove. Could it also be a bad practice by not permitting expansion and contraction.

If you could use indoor air you could halve your vent length. If removing the cemented vents is impossible maybe some kind of controlled outside air supply for the boiler room is an option.

I was curious about the vitdens cpvc venting requirements but couldn't find the specs. As I recall the 100 could do 80ft of 2''. If the restaurant could use a wall vent instantaneous maybe 6 120k boilers could do the trick?

Interesting

@ May 3, 2011 2:14 PM in Help!

Hope your able to influence this one in a positive direction.

flow direction

@ April 28, 2011 5:25 PM in heat transfer between storage tanks

The tank mixing pump, is sucking from the hot outlet of the boiler powered indirect, pushing to a mid-level tapping on the solar tank, and returning to the boiler indirect via the top of the solar tank to the "cold" inlet on the boiler indirect. Not a lot of hours clocked on this pump yet but I have seen the 80 gal boiler tank 15 degrees above it's set-point in march, so I'm glad it's part of the setup.

Home owner called yesterday, the controller was flashing a red alarm, it was an error related to the flow sensor, by the time I got there it had reset and everything was running fine. I did get a bit of air out of the bleeder, I like that the control has these alarm features just hope I don't get more nuisance warnings.

roughen the thread

@ April 27, 2011 7:03 PM in loctite sealing thread

learned something from the video, they want you to roughen the thread, I'v seen euro radiator valve nipples that had little cuts in the thread like this and wondered what it was about, anybody ever do this to male threads?

I do like the ability to reposition the joint by 45deg. without starting over.

loctite 55

@ April 27, 2011 6:53 PM in loctite sealing thread

I'v had no leaks using this stuff, it's now supplied with Viessmann indirects, they used to provide hemp. I found the hemp really hard to wind onto the threads, but this loctite thread has a bit of tack to it. Sometimes it feels like it's bunching up and I'll start over, it's clean to work with. There does seem to be a bit of technique to applying it I think I'll watch the video!

indoor outdoor

@ April 26, 2011 12:21 PM in oversizing mod/cons YES!!!!

Yes, the tn4 and tn2 stuff is uses communicating thermostats and combines indoor and outdoor feedback to determine supply temperature.
It also attempts to sync. the zones and helps with the micro zoning problem you mentioned.

One of the best part is that the stats have authority over the reset curve, so when the user turns down the stats they are in effect making a parallel shift of the curve. Same thing if they want to crank the heat. I think the new and less expensive two wire tn2 house controls work even better than the older tn4 stuff. It's really a great product. I'v never done a honywell aq2000 but it's very similar.

heat transfer between storage tanks

@ April 26, 2011 10:47 AM in heat transfer between storage tanks

I have a two tank system and have some concerns about heat bleeding back from the boiler heated indirect to the solar tank.

The arrangement incorporates a stainless circ to mix the two tanks (differential controlled) this pump line runs from the hot outlet of the boiler tank to a mid- level taping on the solar tank, it has a check valve.

The Hot outlet of the solar tank feeds the cold inlet (perforated dip tube) on the 80 gallon
smart indirect heated by the boiler, this line has no check valve.

I was by the other day after it had been cloudy for a while and the top of the solar tank was around 90 degrees, which seemed surprisingly hot, is it possible that heat is being bled through the single pipe connecting the tanks? should I have a check valve here as well?

This got me thinking that should the check valve stick open it could seriously impact the amount of solar energy collected, it's not easy to detect this sort of thing, and I can imagine a situation like this could go unnoticed for years. Guess thats another reason why energy metering is a good idea, it provides some baselines that would identify a problem like this.

steamback

@ April 26, 2011 10:28 AM in Pipe insulation for steamback systems

I'm a bit skeptical of all this steamback talk.

The only collector that I'm aware of that seems specifically designed to assist this effect is made by Shuco.

These residential flat plates have no internal header, just a single small diameter serpentine pipe, that gets connected in series to the other collectors (max of three I believe)

Seems to me that the combination of a very low volume of glycol in the collector and no larger diameter header is why these collectors are capable of self evacuating so well in stagnation conditions. I would be wary of assuming that just putting a large expansion tank on any collector will effectively protect the glycol from damage. Even where the collector hydraulics optimize this effect I don't think we want to be to casual about stagnation. My take is that steamback is a last resort failure mode.

Offended

@ April 25, 2011 8:41 PM in Navien Combi Boilers

Sorry if I offended, but i think your still playing games.I don't get your gpm metaphor.
Am I supposed to check your math and prove my hydronic credibility? Chris may have swallowed your bait and lost his cool, but I suspect that's what your fishing for. If your anonymous you never have to say you sorry.

Bold,Capitals, what's the difference?

@ April 25, 2011 7:01 PM in Navien Combi Boilers

Your not guilty of the classic caps lock, but the tricky font size alteration is basically the same.

My issue is this, you are baiting a certain type person with your name, not that you hide your identity, but that your identity is false. Actually I don't even have a problem with that.

What bothers me is the thinly veiled sense of superiority that was revealed in the recent exchange. It's one thing to provoke but condescending provocation is just plain ugly. you should hide your cards better.

If we're going to play the who knows more about combi's game it' your turn to say I was wrong about Viessmann's history importing combies

I think what you would really love is for some proud redneck to embarrass him self by saying something stupid or vaguely racist about what crap they make in korea and how HD is selling out to the Asians etc. Makes good theater but hardly advances the cause of better heating and hot water systems.

viessman Combi

@ April 25, 2011 5:21 PM in Navien Combi Boilers

Hey HDE,

What's with the combative tone, Chris may have been wrong about the Navien but wouldn't it have been nicer to inform us all of this in a more civil manner. If I remember correctly dan has stepped in in the past to say the all Capitals was verboten.

Once you start playing the know it all game you can look kind of silly when your wrong. Since Viessman basically brought the first mod-cons to NA, (real H stamp pressure rated vessels) you might want to review their product history, The 200 series which is currently in it's second generation here in NA was indeed offered with a built in flatplate HX and diverter solenoid making it a true (and probably the first in NA) combi boiler.


Chris may be be acting a bit defensively, but your insinuation that he is too provincial to be familiar with the european comi-boiler nomenclature is insulting. It also gives me a little more insight into your monicker, you revel in inciting those that might be threatened by the big box retailers. It's not that inciting opinion is bad. But I suspect the attitude of superiority you showed with Chris ( ie the you don't know what your talking about because you've never been abroad tone). Is the same preconception you bring to the people you want to incite with your fake name.

I'm not a huge fan of the combi- format except in very space limited applications, problem is that the kind of spaces that don't have room for an indirect are generally too small for an appliance that can make continuous hot water. BTW I the vito combies I have installed are still running quit nicely 2 of them since 2004

Firing rate Vs. Supply target

@ April 25, 2011 1:06 PM in oversizing mod/cons YES!!!!

Cycling is bad, my point (in agreement with JP) is that it's as much a failure of designing intelligent controls than of over sizing boilers. The graphs provided by the O.P show the thermal efficiency advantages of a large HX and low firing rate,while it may be wasteful from a financial standpoint to oversize a condensing boiler, It could (if well managed) actually produce higher efficiencies. I would argue from my observations that even appropriately sized mod-cons using ODR are frequently operating at firing rates that are determined by supply targets and system inertia as opposed to actual BTU loads.

In a perfect system why should the boiler firing rate exceed the actual BTU demands on the structure? How much of each firing cycle (excluding a flame stabilization period) for a typical mod-con is spent at a firing rate that exceeds the actual loads on the system? My guess is quite a lot. I'v noticed that the new Viessman ODR seems a lot smarter (by comparison to the original vito) in regards to boiler cycling, it seems to get into a low modulation rate quickly and permit a fairly wide overshoot and long burn even in low load situations.

I can imagine a multi zone controller that allows the installer to input the actual design loads required by the individual zones (as well as the boiler modulation parameters). The control could look at the various zones calling, their deviations from room target and based on the outside temperature calculate a firing rate as opposed to or in conjunction with supply target. Actually this seems a bit overly complicated, just thought I take a stab at a solution as opposed to just complaining about limitations. I think Chris's solution (Setting a max. modulation on boilers that permit this) is the place to start.