Help/Advice requested, undoing some iffy "modernizations" of a 1920s water radiator system.

TheKaiser

Yeah, those suggestions sound good to me. Regarding the Reverse Return vs. Direct Return, I really only have a rudimentary understanding of the various applications where you'd want to do one or the other. In the 3rd or 4th post down I was talking with Jamie Hall and he seemed to think it was still worth doing Reverse Return and I figured it couldn't really hurt (other than more labor and pipe required) but also don't see much benefit, based on this excerpt I found in a guide on heating design "The designer should attempt to select all terminal units with nearly-equal pressure drops if a reverse-return arrangement is to be used. If the above considerations cannot be met, the primary advantage of a reverse-return piping arrangement will be lost, and the use of a lower-cost direct-return system would be more practical."

"If terminal units have widely varying pressure drops or if throttling-type valves are used to control flow rates, it is generally advisable to use a direct return piping arrangement."

As Jamie pointed out, these radiators themselves will have very little pressure drop, however, on further consideration, I realized that there are 2 radiators that have either exceptionally short or long runs of 1/2" piping going to them, relative to the rest, plus the tenants may be using the radiator valves to tune flow to their liking, so that seems like there may end up being widely varying pressure drops, and hence Direct Return may be all that is needed.

TheKaiser

WHOLE OTHER QUESTION for you guys regarding this same heating system, and I am hoping this is an easy one to diagnose. These boilers are about 15yrs old, and for the first time this year, I noticed water frequently leaking out the pressure release/blowoff valves that comes out the downspout onto the floor. I'd initially thought the valves were crudded up or failing, but on closer inspection it seems that the pressure in the hydronic system is varying wildly as the boiler cycles on and off. Basically, what will happen is when the boiler is in it's off cycle, the pressure drops in the system, to as little as 0-5psi, based on the gauges on the boilers. Then when the boiler cycles on, the pressure increases up to 25-30psi, and this cycle seems to repeat every time the boiler goes on and off. If I have the line feed ball valves open, so the pressure regulator auto-fill can operate, when the pressure drops in the boiler the auto-fill valve will release more water from the city water line, bringing the boiler system up to about 12psi. Then, when the boiler cycles on again, as I am sure you can guess, I get the pressure increase, but now it is starting from 12psi rather than 0-5psi, so the pressure increase exceeds the 30psi mark, and the pressure release starts dumping water onto my floor.

I've only recently discovered the cause of this, and have been keeping the ball valves on the feed lines closed, which keeps things in check, but I am still a little puzzled as to the underlying mechanism. Do you have any idea of what causes this sort of phenomenon? At first I thought it was due to the temperature increase in the boiler, but the weird thing is that one of them (the one that leaks less) and which only has about a 20psi increase is exhibiting a 45 degree swing from 140f in the off cycle to 175f in the on cycle, whereas the one that has a the 30psi increase and leaks more is exhibiting a 10 degree swing from 165f to 175f, so that seems odd that the one with a smaller temp swing is experiencing a greater pressure increase. The other thing that occurred to me is that if there is a lot of air in one of the radiators, maybe when the hot water gets to it there is a greater expansion of it, so in other words, its not so much related to the boiler temps as it is to what temp water happens to be pumped down the line (which will have a delay that offsets it somewhat from the boiler cycle). One of the systems might have more air than the other, leading to the differing temp/psi ratio. Or could this be caused by the expansion tank bladders failing? They are the same age, but simultaneous failures on both systems would be pretty far out.

Anyway, thanks in advance for lobbing any ideas you have my way.

Jamie Hall

Classic water logged expansion tank. Couldn't be more classic! Time for a new tank. Or tanks

Ironman

A homerun system is not as difficult as you’re imagining it to be. The pipes can be grouped and hung together using 3” or 4” PVC sleeves like we did on this job.

You can also remotely mount one or more of the manifolds and use two 1” pipes to feed them.

mattmia2

What is the threader for?

also, what kind of expansion tank is it? could just need to be drained if it is a compression tank or the precharge to be replaced if it is a bladder type tank. might just need maintenance rather than replacement.

Ironman

mattmia2

Dec 29, 2024

What is the threader for?

also, what kind of expansion tank is it? could just need to be drained if it is a compression tank or the precharge to be replaced if it is a bladder type tank. might just need maintenance rather than replacement.

The threader was for gas piping.

I’m not sure what you’re referring to with the expansion tank. Everything was replaced on this job except the standing cast iron radiators.

The original system had no expansion tank: they left an air cushion in the very top portion of the rads. That resulted in almost all of the old black iron piping being plugged with sludge after 80 years. That’s why all the piping was replaced.

mattmia2

Ironman

Dec 29, 2024

https://forum.heatinghelp.com/discussion/comment/1830451#Comment_1830451

The threader was for gas piping.

I’m not sure what you’re referring to with the expansion tank. Everything was replaced on this job except the standing cast iron radiators.

The original system had no expansion tank: they left an air cushion in the very top portion of the rads. That resulted in almost all of the old black iron piping being plugged with sludge after 80 years. That’s why all the piping was replaced.

two different posts. the expansion tank is about the OP's relief valve

TheKaiser

mattmia2

Dec 29, 2024

What is the threader for?

also, what kind of expansion tank is it? could just need to be drained if it is a compression tank or the precharge to be replaced if it is a bladder type tank. might just need maintenance rather than replacement.

The tank is an Amtrol Extrol EX-30. Thanks to all of your input, I did check the pressure and try adding air, but after adding air, and then putting the pressure gauge back on it, I had water leaking out of the Schrader valve, so I'm pretty sure the bladder/diaphragm is ruptured. I recently had a Granite Group location open a few hundred yards down the street from this house, so they hooked me up with a new house brand equivalent expansion tank and Taco Hy-Vent (the old one's rubber seal crumbled in my fingers when I was inspecting it). We're luckily experiencing an unseasonable, but welcome, warm spell in Southern New England, so I have the new setup 3/4 of the way configured, and will be re-pressurizing/bleeding it tomorrow, fingers crossed.

EdTheHeaterMan

 I had water leaking out of the Schrader valve

Time for a new Extrol #30

TheKaiser

Wow Ironman, that is a super tidy home run installation! Thank you for the pics, as that does re-perspective the concept in terms of how neat and compact it can be! Out of curiosity, do you do any sort of labeling of the pipes so you can identify them at midpoints, or is PEX so reliable that it's unnecessary, and you only need to worry about it at junctions? I am already a bit down the road of doing the conversion to a 2-pipe system for this urgent 1st floor setup, but I would still be open to doing a home run, as the 2nd floor has the same fundamental shortcomings. I'm thinking I'll see how this 1st floor setup works, and depending on how well it balances, I'll decide which way to go for the 2nd floor.

TheKaiser

Hi Jamie, thanks for the diagnosis!👍️ That seems to be right on. I tried adding pressure to the tank and then checked the pressure with a gauge, at which point water came dripping out the Schrader valve. Upon unscrewing the tank from the system, I found it was heavy as heck, and clearly full of water, so you were right-on regarding it being waterlogged (which means an irreparably ruptured membrane/diaphragm/bladder based on my understanding).

Ironman

Label as much as you want. We kept each pair zip tied together at various points.

FYI: that’s PAP (pex-Al-pex). It’s more rigid than pex, requires less support, and has far less thermal expansion than pex. It’s similar to soft copper, but slightly less rigid.