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Joined on March 25, 2009

Last Post on April 16, 2014

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No time for a drawing, but

@ April 16, 2014 11:18 AM in Modifications to Hydronic System

No more circulators than what you have now.

Boiler loop incorporates the boiler, the boiler circulator, the boiler protection thermostatic bypass, and the supply and return "trunks" as you have them now but with two changes: 1) the trunks are connected at the end, creating a loop, and 2) instead of radiator, underfloor and DHW circuits connecting to the boiler loop the way they do right now (supply to the supply trunk and return to the return trunk) they should be connected to the loop each via a set of closely spaced tees, to achieve hydraulic separation. Each of those circuits then has a circulator to induce flow within the circuit. If you put the higher temp circuits upstream of the lower temp circuits the temperature drop won't matter - in fact, it will be beneficial.

You're not addressing hydraulic separation

@ April 15, 2014 7:55 AM in Modifications to Hydronic System

Circulators will still compete with each other in your proposed scheme. Why not create a boiler loop (with the thermostatic protection bypass) and pipe each of the (radiator, underfloor, DHW) circuits into the boiler loop with closely spaced tees?

Bug trap

@ April 14, 2014 8:38 AM in Bug trap

Finally got around to installing a condensate neutralizer on my TT PS60 and cleaned out the condensate trap. There were quite a few small spiders and the like swimming around in it. Due to the design of the Solo, I very much doubt that they came from the intake side; probably crawled down the vent and got washed down by condensate.

I used clear vinyl tubing to connect the trap to the neutralizer and for the first time (and perhaps the last as things tend to get a bit dirty on that side of things - the trap itself turned reddish) got to enjoy watching a steady trickle of condensate during a DHW call.

The plot thickens

@ April 11, 2014 8:28 AM in home owner

There's no 7/8" copper pipe in common use that I know of, so if you're measuring the outside diameter then we're talking 3/4" ID nominal. The Stratos couldn't pump more than about 9 gpm into 50 feet of 3/4" type M copper pipe, which would be a bit over 5 feet/second, and that doesn't even take into account the head loss of your tubing that's attached to the copper pipe, so it's not likely to be velocity erosion. However, the 16f is an iron pump and you likely have other iron components on a system with a lot of tubing that has no oxygen diffusion barrier; could it be that iron corrosion has created some grit particles that have eroded away the soft copper over time? At the very least your ferrous components should be inspected for corrosion and you should have your water checked.

Heartbleed bug

@ April 10, 2014 7:36 AM in Heartbleed bug

By now, at least some of you have probably heard of the bug in software that enables the secure communications between (some - reportedly about 66%, including this one) web servers and browsers (and a lot of other non-web stuff), called OpenSSL. has more info, but suffice to say that it's a very serious bug that allows bad guys to steal any data from the vulnerable server's memory, such as passwords and even the server's own private key that can be used to decrypt any data sent to, and from, the server in the future, unless the key is changed. If you want to see if any website you frequent is currently vulnerable, you can type the address into the domain name field at and it will generate a nifty report for you. (HeatingHelp is not currently vulnerable, although it might have been in the past and its SSL certificate may need to be reissued - Dan?)

It's probably a very good idea to use this as a reason to change your passwords to any web sites where you have accounts, but especially those tied to your bank and investment accounts, your personal information, etc. And when you change those passwords, be sure to change any "forgotten password recovery" questions and answers, don't use the same (or similar) password for critical and noncritical sites (so that one silly website slipping up in the future doesn't expose all of your accounts to the bad guys) and use a password manager (such as or ) to deal with the multiple passwords in a way that won't hurt your head too much.

Before and after can be tricky in a circle

@ April 8, 2014 10:29 AM in Mixing valve location (before/after pump)

Post drawings of the two options you have in mind. Typically you need two circulators, one for the mixed loop and one for the heat source loop.

Having a hard time understanding this

@ April 7, 2014 3:01 PM in DIY Solar advice

So the "magic" of these collectors is that they cool the glazing by "ingesting" outside air. But where does the heated air go, then? It must displace some other heated air that then gets discharged somewhere, along with any heat it carries...

It's working really well

@ April 7, 2014 9:16 AM in Add-on fans for old convectors

I made baffles from 1/4" plywood to attach to the back of the outlet grill and cut out discharge holes for the fans. The fans are mounted on the back of the baffle. I have four fans on the 60" element and two fans on the 36" element. The fans are 120mm PWM ones, although I'm not using PWM right now; I just have them running open (with the only real control being a snap disc that closes at 90 - I really should have chosen a lower temp) and this has, serendipitously, worked really well, keeping the temperature in this room consistent with the radiant ceilings in my other rooms. I selected the fans for advertised quietness rather than airflow (don't need much of the latter) and I actually have them wired two-by-two in series so that the voltage across each is 6V.

Keep in mind, though, that I triple-stacked the convector elements in the enclosure and piped them in counterflow. I don't imagine that it would work nearly as well with a single-pass element.

Dear lord, does anyone proofread any more?

@ April 4, 2014 12:09 PM in Stinkbugs

Moreover, how is a person with this low a literacy level allowed to work in journalism?

Here, maybe this helps.

@ April 4, 2014 10:34 AM in Auto fill/back flow preventer. Is it necessary?

If not, I'm out of tricks.

Good luck.

@ April 4, 2014 10:30 AM in Auto fill/back flow preventer. Is it necessary?


Ok, try it

@ April 4, 2014 7:39 AM in Auto fill/back flow preventer. Is it necessary?

What on god's green Earth does an aquastat buried within a tank have to do with the output water temperature from the heat exchanger? That will depend on the flow on either side of the exchanger, the input DHW temperature (which varies), the input boiler temperature (which varies) and the efficiency of the heat exchanger. Think about it some more.

Thermostatic is for safety

@ April 3, 2014 1:04 PM in Auto fill/back flow preventer. Is it necessary?

Arguably you need it on the DHW even more than you need it on the space heating side. On the heating side it's there to protect your emitters from damage due to overtemperature; on the DHW it's there to protect your butt from damage due to overtemperature. An aquastat will interrupt the charging of the DHW tank when the water around it is at the set temperature, but what happens to the water higher in the tank? It may approach the temperature of the boiler water unless you're purposely diminishing the efficiency of the heat exchanger somehow.


@ April 3, 2014 8:26 AM in Auto fill/back flow preventer. Is it necessary?

OWBs typically have some built-in buffering capacity, but a smarter control strategy (than a simple aquastat) could ensure that the DWH is used as a dump zone of first resort. A tempering valve at the DWH outlet would be necessary, but realistically it's necessary in any case.

To the OP, I don't see how the way you have it laid out allows you to bypass the space heating FPHX?

Lock up

@ April 1, 2014 11:15 AM in Boiler Was Plumbed Wrong...

The typical wax capsule thermostatic design one sees would swing to "full cold", which in this case is, of course, not cold. Are there valves that feature internals that would actually shut off flow completely? There might be an issue with longevity if the valve is consistently operating at full tilt to "cold" and the capsule wants to expand more but it has nowhere to go.

Regardless, you're absolutely right that the mixing valve in the proposed setup (whether thermostatic or electric) would not have "full authority" over the supply temperature to that circuit, as it receives mixed "higher temp" and "lower temp" return. This may not be an issue unless we're talking WILDLY divergent supply temperatures, and I don't think we are, in this case.

It'll be fine.

@ April 1, 2014 10:09 AM in Boiler Was Plumbed Wrong...

That will work, but the piping layout as is would not create a good spot for a circulator - it's sandwiched between elbows and it really needs some straight piping, especially on the discharge. While you're cutting in the circulator at that spot you could also correct the too-wide spacing of the tees on the boiler loop. You also do not want to be pumping into the "bull" (middle part) of the tee between the system return and the mixing valve intake.

Not for nothing, but...

@ March 31, 2014 12:21 PM in Modcons in Closets-

It seems that you'd be more likely to use up bedroom air with the closet door open rather than closed.

What happens outside of the heating season?

@ March 31, 2014 10:57 AM in Mod con and plate exchanger

If you need the FPHX to be "warm start" then it seems like you're outta luck when there is no heated return water.

What you're describing is the "cold sandwich" that's endemic to instant-type DHW sources with little to no storage capacity. The way around that is a buffer. I think that the important thing to realize is that DHW production and space heating are sufficiently dissimilar in the nature of their cycles, that the only way to synchronize them and reap significant benefit is to have a LOT of buffer capacity, have the boiler maintain the buffer temperature, and have both space heating and DHW draw from the buffer. Most things in between will not add sufficient benefit to justify the cost and complexity, and some may actually increase the operating expense. A small (or not so small) buffer tank charged by the FPHX that's hydraulically separated from the space heating circuit is the typical alternative to a coil-type indirect.

Why circulate through the fphx with no DHW call?

@ March 27, 2014 8:50 AM in Mod con and plate exchanger

Seems like it complicates things (3-way valve needed) and adds head loss for no benefit. If you have no flow on the DHW side of the FPHX, you're not going to reduce return temperatures.


@ March 26, 2014 10:27 AM in Piping a Wallhung Modcom for concrete radiant.

Yeah, I can see how it could be. I was wondering about that since it looked like it should have cleared anyway. Thanks, Mark!


@ March 25, 2014 7:55 AM in Piping a Wallhung Modcom for concrete radiant.

That dip in the vent where it passes under a beam is problematic. Condensate will pool in it and (partially) block the vent. If the dark (insulated?) pipe going down from the dip is a condensate drain, it needs to be trapped or combustion gases could escape that way. Either way, the manual probably has language in it about exhaust pitch etc. that this would not conform to.

Can you mount the boiler a couple of inches lower, so the exhaust clears the beam without dipping?

Several options

@ March 19, 2014 9:44 AM in Please critique this design

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.)
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