Radiant floor heat overpressure

[Baw335]

So I have a radiant floor heat that was installed when I bought the place. It's heated with a hot water heater and the circulation pump is controlled with a dial thermostat. I don't think the previous owner had any idea what he was doing when he put it together based on other stuff I have found in the house. The issue is, when he temperature gets to the desired setting, the thermostat turns off the circulation pump and the system pressure rises from a normal 20-25 (warm pressure) psi to as high as 60 psi when I shut down the system. If I wouldn't have shut down the system or turned on the circulation pump, It would likely go a lot higher. I turned down the water temperature on the hot water heater and that helped a little. Think I have an issue with my expansion tank?

 

[Bondo]

Think I have an issue with my expansion tank?

Ayuh,.... I agree, the tank is probably fulla water,....

I also question whether ya got a T&P valve, as it should blow off the excess pressure at 30 psi,....

 

[Baw335]

Definitely don't have a release valve, I'm planning to add one when I fix the cobbled together pvc piping and replace the 2x4 that is propping up the taco pump. Pic for enjoyment.

 

[Reflex]

A couple of things to check:

1) If you're using a tank type water heater to supply heat, it likely came with a T & P that seeps at 150 psi and blows at 210 degrees. Installing a 30 psi T & P valve may help from a pressure standpoint, it will allow air in your system and water out of your system.

2) I agree with your assessment on the expansion tank. If it's not waterlogged, it's likely not pressurized properly. I'd suggest installing a pressure reducing valve and a check valve on the cold supply before inlet of the water heater and then setting the expansion tank to match the pressure on the PRV. The expansion tank needs to be on the tank side of the PRV or on the return side of your radiant loop. Remember, the expansion tank must be removed or the the pressure in the system must be atmospheric (0 psi) in order to properly charge the tank. Why? Air can be compressed, water can't.

3) A properly sized and charged expansion tank will help your tank type water heater last significantly longer in any application.

Best of luck,

Reflex