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Discussion Starter · #1 ·
Just built a small 325 foot addition and put radiant hot water hear in the floor. Used a 25 gallon hotwater heater and installed two air leaders (one on return and the other on the supply line. Alson installed a pressure/tem gauge. Its a closed system but I cannot keep the pressure up in the system. After it runs a few minutes it drops to zero. Water seems to be flowing in and out of the system; the floor gets warm and there are no leaks. Questin is what does the pressure keep droping? I have a way to increase water/pressure but it drops to zero after a few minuites of the circulator running.
 

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I need a little help understanding your installation.
"Alson installed a pressure/temp gauge". What does that mean?
I understand that it is a closed system but how is the water being supplied?
If it's a closed system, water isn't flowing in and out of the system.
You have a "way to increase water / pressure".
What do you have? Do you have an automatic fill valve?
If you do and you are losing pressure you have a leak or a check valve not working.

And what type of water heater are you using? That is for curiosity, not related to your problem.
 

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Discussion Starter · #3 ·
Installed a 25 Gal gas hot water heater to supply hot water to in floor tubing to heat the room. The system I put together has a cold water feed that I can attach a hose to fill the tank. Once full the heated water travles out of the tank through the system. as the hot water leaves the tank it passes by a gauage that I installed that indicates pressure and water temp flowing through the system; the gauage is followed by a auto releife vault for bleeding the system; after the bleeder, is a gate that is used to stop the water from flowing into the system; pipe continues to a second bleeder before the water returns to the hot water heater. I also installed a gate to drain the system for repairs. All gates are open and water flowes from the tank through the system and back to the tank and the floor is warm. Maybe the pressure gauge is not necessary? No water seems to be leaking just wondering why the pressure gauge drops to zero. The gauge registers 20 PSI before it blows the releife value. So I thought the system should have that 20 PSI of pressure. Am I wrong? do I even need to pay attention to the pressure since the tank is full and the hot water is doing its job?
 

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Boilers have a fill valve. They are also checkvalves that maintain the pressure on your system. Usually 12-15# is adequate. You need some pressure for the circulator pump to work properly. You also need an expansion tank. "In theory" you wouldn't need a gauge.
But a gauge will tell you if everything is working correctly. You have relatively low temperature so your circumstance is different.
Is this a system you designed on your own or have you followed a plan from a hydronic supplier? Radiontec, for example has a lot of online knowledge at your fingertips.
 

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Instead of a text description of your system, it would help us if you could draw a sketch showing all the system components. You haven’t mentioned a pump in your description, but I assume that there is one. If you can’t do a computer generated sketch, something on paper that you’ve then photographed would be adequate.

Photos would also help us to understand the different components of the system.

Is the in-floor tubing in concrete or under some other flooring material?

How do you know that you do not have a leak? Have you run a pressure test? In my system I pressure tested the tubing and manifolds at several times operating pressure for a day. When I was satisfied that there were no leaks I put the system into operation.

If the relief valve on the system is set at 20 psi, then your operating pressure should be significantly below that. Is the pressure gauge upstream or downstream of the pump?

A successful hydronic heating system should have no air in the loop. But, water is highly incompressible, so having a closed loop system filled with water means that there is no room for expansion. Just raising the temperature of the water by turning on the heater would cause the water to expand slightly and with no expansion room in the system the pressure would increase dramatically. That’s the reason for the expansion tank that Missouri Bound mentioned. If you don’t have one that could be the cause of the dramatic pressure swings that you’re seeing.

Pressure and temperature gauges are essential for you to know what’s going on with the system. For example, if you’ve put hardwood over hydronic heat the manufacturer will have specified a maximum subfloor temperature when used with hydronic heat.

Chris
 

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Discussion Starter · #6 ·
I do have an expansion tank and the system is one I put together with information I gathered online. The system is in concrete and I did pressure test the system. One of the designs I found online had a "pressure/temp gauge so I put one on the system before the pump. I keep the water temp between 120-130 degrees. Ill try to get a sketch up and I am very thankful for all the support and advice you gents have provided.
 

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You mentioned you pressure tested the system. Was that just the tubing or the entire system? Your pressure valve could leak, you could have air in the system. Do you have a automatic air vent? They do go bad. And of course what about the gauge? They are susceptible to leaks like any other part. How about a drawing or at least a list of your components and the order in which they are installed?
You may as well go through all of this before you pick up the phone and call a hydronic systems expert.
 
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