Need help with in-ground heat

[Dcalhoun]

Had a leak in our in-ground heat that was allowing some portions of our concrete to get ice. We found and fixed the leak over the summer but suspected there might have been another smaller leak we could not find. (The leak was detected by forcing air at 100 psi into the system.) I replaced the glycol in the system and also ran some Boiler Solder (following the label instructions) through to deal with the smaller leak. Now that cold weather is here in the Midwest the boiler fired up and the circulating pump kicked on but I have ice forming everywhere that it shouldn't. Ground temperatures in the heated area are not much different than the non heated area. Looks like I am getting hot glycol/water to 2 of the 3 manifolds in the ground but it isn't going any farther. Boiler short cycles but I suspect it is because the mixture s not loosing much temperature since it isn't getting out where it is cold. Any suggestions?

 

[PaulLovesJamie]

I suspect you didnt get the tubes refilled with glycol, there's air in some of the. Second possibility (just a guess), perhaps the boiler solder gummed up your manifolds?
Hopefully somebody who knows what they're talking about will chime in

 

[cantbreak80]

Turn off the gas supply to the boiler or disconnect the neutral wire to the gas valve.
Open the expansion tank/fill port...(assuming closed system without make-up water supply)
Close the supply valves for all the loops.
Turn up the control stat so there’s a “call for heat”…this will turn the pump on.
Open one loop supply valve at a time.
Repeat until each loop is purged of air…adding glycol as needed.

 

[Dcalhoun]

Thanks for the info. I filled the glycol through the expansion tank so wouldn't air have been displaced by the glycol and escape through the open tank? Not knowing how much fluid was remaining in the lines, I put the full prescribed amount of glycol in and then opened the make up valve to fill the system the rest of the way. I did see air bubbles coming up through the sight glass after and periodically opened the expansion tank to let it escape. All the while leaving the make up valve closed except for when I was there to monitor the fluid level. This process went on for several days. I do have a make up supply valve which is normally closed and I opened it up only when the liquid was below the sight glass level to re-pressurize the system to 10 psi. I realize that air could be trapped throughout the system with high and low spots but would it take that long to purge the air?

One other piece of information that might be helpful to someone who knows more than I; when heated liquid is flowing the pressure stays constant at 10 psi, but when it is stopped (when the air temp is high enough) the system loses pressure and falls to zero. As soon as the system heats up again the pressure rises to 10 psi again.

 

[cantbreak80]

Air trapped in a 200’ length of floor heat tubing will prevent liquid flow through that loop. The circulator cannot purge the air because it is likely sized for the flow/head of the entire system.

By running one loop at a time, the circulator only has to overcome the head of a single loop and should easily purge any trapped air.

 

[2Biz]

Do you have 2 service valves with a ball valve in between? If you do, this allows you to use an external pump to purge air from the system. I used a 15 gallon soap mix tank filled half way with glycol and a sump pump from good 'ol Harbor freight when I purged air from my system. One hose goes from the sump pump to one service port. The other service port is the return and goes in the pail submerged in the glycol (so you can see the air bubbles). The ball valve in-between the 2 service ports is shut off to force flow around the complete loop. As CantBreak80 says..Do one zone at a time. It won't work if you try to do them all at one time...Also do you have an air eliminator inline anywhere? Like this?

http://www.pexsupply.com/Spirotherm-VJR100-1-Spirovent-Jr-Air-Eliminator-Threaded-3560000-p

This also helps with any air issues even after the system is up and running. Actually it is needed in a closed loop system to get all trapped oxygen out of the system. Your make up water has oxygen in it and it takes a while to purge.

 

[2Biz]

Like this..... I was actually filtering the glycol in these photos. But I filled the system the same way....Without the filter....

<br>

 

[Dcalhoun]

The problem does seem to be air. One valve we cannot break loose so we couldn't close that loop. After opening up the system we did get a steady but very slow rate of air escaping through the open expansion tank. We ended up removing a supply line at one manifold expecting a free flow of liquid but not a drop came out until we also took off the corresponding return end too. It belched out a bunch of air and then liquid. Flow has been much better and the boiler is not short cycling as it was previously. I still have some cold spots so I will probably have to open the lines at the other manifolds to purge more air. Thanks to you all for responding - I only wish I had two service valves as 2Biz showed in his configuration. There doesn't seem to be an easy way to purge air out of our system.

 

[2Biz]

I only wish I had two service valves as 2Biz showed in his configuration. There doesn't seem to be an easy way to purge air out of our system.

It took me many, many hours of studying floor heating systems to make an attempt at putting one in. Most our systems are/were 30 years old and technology has advanced a little since then! My old system didn't have any service valves in it either...

 

[cantbreak80]

Since you have a pressure reducing valve (water make-up), cap the expansion tank tightly and bump the PRV to 18-20 psi. The increased pressure might squeeze the trapped air enough to allow it to release into the x-tank.

Run the system for a few days with the higher pressure setting.

We can chat about relieving the pressure later.

BTW…what brand boiler system is installed? Got pictures?