Welcome to Plbg.com
Thank you to all the plumbing professionals who offer their advice and expertise

Over 600,000 posts related to plumbing

Welcome to Plbg.com (aka: PlumbingForum.com) we are the most popular plumbing information sharing, advice, DIY and educational forum on the Web. Ask any toilet, sink, faucet, pump, water quality, and plumbing related questions. Please refrain from asking where to purchase a product, business, pricing, or legal questions, for contractor referrals, or any questions not related to plumbing. Keep all posts positive and no advertising. This site is free and made possible by:  

Post New
Search
Log In
How to Show Images
Newest Subjects
 Radiant heat/pressure issue
Author: Joey c (NY)

Special thanks to Paul CT as well as Packy!!
My latest debacle as follows :
Plumber came by last night and "straightened" out the radiant he was unable to complete Christmas Eve. Now first issue was last night after making a few minor piping changes and what seemed like forever bleeding there was an issue with pressure on the boiler, exceeding 45lbs, safety valve did it's job at 35 so needless to say water water everywhere not a drop to drink!
So plumber decides to regulate pressure on the return side by shutting the return off! So fast forward to 5am and a balmy 60 degree wake up! !!, thank goodness for goose down comforters! !, go to boiler see that return is off, turn return on, upstairs take a quick shower, back to the boiler and looks like time for a bath, apparently the gate valve for the return that I had tured on was the only method of pressure reduction at 12am last nite (OK this morning but you know what I mean) OK now I turn off the radiant get the plumber on the horn he tells me to check the quick fill pressure regulator must be bad, I take that apart turned back the adjustment to factory settings (15lbs.) Blew off additional pressure via return hose bib dropped to workable pressure at around 20psi. OK I get home no call back from my plumber (shouldn't have paid him last night) and see pressure is fine at about 15psi on the boiler gauge. So is my inlet water pressure (water feeder/quick fill) the only thing that can increase or decrease boiler pressure? Turn the radiant back on pressure goes past 40psi, and instant hot tub for 1 again. Now for the radiant side could the introduction of an additional pump run my pressure up like this? I have a 3 spd. TACO pump on the convector/baseboard heating side and a grundfos pump for the radiant what gives here man??
Ps, plumber still hasn't called me back.

Post Reply

 Re: Radiant heat/pressure issue
Author: packy (MA)

"So plumber decides to regulate pressure on the return side by shutting the return off"
what does that have to do with anything???
joey, what you are describing sounds like an expansion problem but you say no pressure increase with the radiant return closed and the rest of the system heating normally ???
"after making a few minor piping changes".. what changes??
can you post a picture of the radiant manifolds and the circulator.
lastly, it shouldn't take 'forever' to get the air out of a couple of 1/2 inch circuits.
anyway, get the pictures posted and i'll put on my sherlock holmes hat and figure this out..

Post Reply

 Re: Radiant heat/pressure issue
Author: Joey c (NY)

I'm on it pack! Thx

Post Reply

 Re: Radiant heat/pressure issue
Author: Joey c (NY)

Pack,
I'm having trouble with photo bucket right now, I will post tmrw early am, I need to edit the pictures to explain which pipes come from and go to. I'm going to attempt while on my commute.
Sorry I didn't get back to you sooner, trying to get the kids, (and myself) to bed
Talk to you in am.
But to answer your question yes the pressure doesn't increase while radiant manifold is turned off, once I turn it on, I have about 30-40sec before the (safety pressure) valve starts to open up starts at a trickle but turns into a stream rather quickly.
I did purchase a new pressure quick fill but as you know I already had installed the new one just over a month ago per your advice. I also have 2 expansion tanks
Have a good night my friend,

Joey

Post Reply

 Re: Radiant heat/pressure issue
Author: Paul48 (CT)

Shut the boiler off. Shut the auto-fill regulator off. Attempt to bleed the pressure on the boiler. If you can't, the knuckle-head has tied your radiant loop into your domestic water.

Post Reply

 Re: Radiant heat/pressure issue
Author: Joey c (NY)

[i1383.photobucket.com]

Post Reply

 Re: Radiant heat/pressure issue
Author: Paul48 (CT)

Hopefully your radiant isn't piped like that coming out of the mixing valve. Why don't you show your radiant return going to the boiler? If it's piped like that, then that's your problem. When your radiant reaches set point of the mixing valve, you're pumping your boiler backwards. Creating a negative pressure at your auto-fill valve.[www.taco-hvac.com] When using a thermostatic mixing valve for radiant heat or domestic hot water re-circ, when the spool is not calling for hot water, the circ is just circulating the water in the loop until it cools. Look at the diagram.



Edited 1 times.

Post Reply

 Re: Radiant heat/pressure issue
Author: packy (MA)

Joey, I'm gonna be blunt.. YOU PAID THIS GUY??

FIRST OFF... he did in fact tie the house cold water into the radiant heat. what a schmuck..
the return from the radiant is supposed to have a tee in it splitting the return water between the boiler return and the cold inlet on the mixing valve. the mixer then open and closes as necessary blending some return water in with the hot from the boiler.
the mixer will open or close the hot port to allow the proper temperature to the feed manifold. in other words there may be times when only a trickle of hot is being pumped thru the floor piping. the return water is being recirculated thru and thru until it cools and then some hot is allowed in to get it back to whatever the mixer is set at. this goes on constantly.
he also took the hot feed for the radiant from before the air eliminating device.
you have my e-mail so just get back to me and we can try to figure out your next step..

Post Reply

 Re: Radiant heat/pressure issue
Author: Paul48 (CT)

Sorry packy...didn't mean to step on your toes. :)

Post Reply

 Re: Radiant heat/pressure issue
Author: Joey c (NY)

Packy, my question to him the other day was, "doesn't the return water go to the hot water inlet side of the mixing valve? So I guess I was half right. My question now, I'm not 100% on anything but what temperature should be supplying the radiant , I guess I'm saying if I'm not calling for heat and the main circ. (For the zone valves convectors/baseboard) but radiant floor IS calling for heat that I would be "pulling" return water through the circ. for the radiant? My high limit is set for 180 on aquastat, with a 15% differential so around 165 boiler kicks on what temperature should the return be to feed the radiant?

Post Reply

 Re: Radiant heat/pressure issue
Author: Paul48 (CT)

Look at the diagram on the bottom of the page that I linked to. I'll explain if needed. It's difficult to grasp how that mixing valve works, but once you get it, it's one of those "lightbulb" moments.



Edited 1 times.

Post Reply

 Re: Radiant heat/pressure issue
Author: Joey c (NY)

I got him to buy it once I showed him the diagram, I knew something wasn't right taking cold domestic and cooling 180 degree boiler heat, I sure hope this does the trick.
The to you and packy.

Post Reply

 Re: Radiant heat/pressure issue
Author: Paul48 (CT)

Right.....nothing cools it, except the fact that you stop adding hot water.

Post Reply

 Re: Radiant heat/pressure issue
Author: Joey c (NY)

Had the "Aha"moment 20 minutes ago, finally realized that the "street pressure" (cold water domestic) that was going to the mixing valve (for the radiant)was upstream of the pressure regulated boiler feed, basically tee'do into that OK now I realize what I have to do now remove cold water feed entirely from mixing valve, tee the return at the radiant manifold drop 1' down to create "thermal trap" bring that 1' drop back into the "C" side of the mixing valve (how am I doing so far?) Leave the H side of mixing valve connected to boiler. So off to the supply house in the morning for 3/4" pex tee and hopefully that will do it, thanks for the wake-up call, remembering I'm not a plumber is vital to my success! Think about what is wrong not what is right, man that really was one of the best lines and words to live by.
I'll keep u fellas posted (unlike what I did Christmas eve) sorry didn't get back to anyone about that but yes the supply house was open on Christmas eve, and 200 bucks later I had aquastat installed. I can't thank either of you guys enough.
Joey

Post Reply

 Re: Radiant heat/pressure issue
Author: packy (MA)

no drop down 1 inch for a thermal trap..
that is for when the mixer is used for domestic water supply not for heat.
also, if there are any backflow or check valves integral to that mixer, take them out.
last, (well, nothing is ever 'last' with this job, hahaha) you should be able to purge the circuits much better now. put a hose on the drain at the end of the return manifold and shut the blue valve on the other side of the manifold. open the hose valve and the hot water on the supply side will flow into the circuits and come out the hose valve. put the end of the hose in a bucket and watch for air bubbles. when the water runs clear (no bubbles) you are done. open the blue valve first to get any last bubbles out of that end and close the hose valve.

Post Reply

 Re: Radiant heat/pressure issue
Author: Joey c (NY)

At the supply house now, funny you were mentioning check valves! Cause that was how we started to "remedy" the combined pressure, man I tell ya this kid (plumber) is "OK" I mean he's really conscientious and just got really thrown off by the existing (new) 1/2" loops that you previously helped me out with I've been a relentless troubleshooter for many years when I was with the railroad (now I'm still working for the RR but I'm in management. "Stop don't shoot! I did it for the family")
But my heart is still in the field, unfortunately this whole project that I'm working on (the house)
Has somewhat hindered my focus at work but I think after today I might finally be able to put this behind me. OK enough about me! So NO drop, I'm going to email you a picture once I get home prior to cutting the tee into the return and wait for the "Green light "

Post Reply

 Re: Radiant heat/pressure issue
Author: Paul48 (CT)

I keep trying to get you to understand "how" the thermostatic valve is working when piped correctly. That one little piece of information would make everything clearer. You disappear for lengthy stretches, then come back and say you've re-piped the whole house. We try to give you a game-plan...A-B-C.....confirm...proceed. We get the "A" out, and the next thing we hear, you're at the supply house. It's not good.

Post Reply

 Re: Radiant heat/pressure issue
Author: Paul48 (CT)

There is no problem with the auto-fill regulator feeding in where it is. The problem is only because of how the mixing valve is piped. If you look at your picture, where the radiant return manifold not goes to another return manifold. Instead have it go back to where the "C" is on the mixing valve, and tee it there. There's other things that are not "ideal", but they can wait until the weather turns.

Post Reply

 Re: Radiant heat/pressure issue
Author: packy (MA)

it might be easier to understand if the 'C' on the mixer was an 'R'..

Post Reply





Please note:
  • Inappropriate messages or blatant advertising will be deleted. We cannot be held responsible for bad or inadequate advice.
  • Plbg.com has no control over external content that may be linked to from messages posted here. Please follow external links with caution.
  • Plbg.com is strictly for the exchange of plumbing related advice and NOT to ask about pricing/costs, nor where to find a product (try Google), nor how to operate or promote a business, nor for ethics (law) and the like questions.
  • Plbg.com is also not a place to ask radiant heating (try HeatingHelp.com), electrical or even general construction type questions. We are exclusively for plumbing questions.

Search for plumbing parts on our sponsor's site:




Special thanks to our sponsor:
PlumbingSupply.com


Copyright© 2017 Plbg.com. All Rights Reserved.