Pressure drop in Radiant system

Rob_37

The expansion tank is "now" mounted under the PV150 Air Eliminator. I ran the three thermostatic mixing valves because the rooms all have large swings in desired temperatures and I thought it would be better to do it that way? Wrong? I am not exactly following what was meant by the flow across the take off point. So far the rooms are heating well and the delta T is doing 20 to 25 degrees between supply and return. The main thing was the pressure drop when the boilers shut down. Currently I have no water supply so it is a fill and run job. Eventually there will be water for the fill valve.

Rob_37

Pressure drop in Radiant system

Only second radiant job. Warehouse with approximately 8500 feet of 1/2" tubing in concrete, a Trinity 200 and 150 ganged up. When running the pressure rides around 18 psi. As soon as it shuts down the pressure drops below 5, start it up and the pressure rises again. The pressure guages are on the supply sides of the boilers with the circs pushing in from the return side. Will try to attach a picture. I do have an Amtrol 90 tank on it now!

Thanks,

Rob Blair

hr

Where's the expansion tank?

or where do you have it tied into the system. It should be tied into or at the air purge location.

Why the 3 way thermostatics? I thought those were condensing boilers, and they should be able to run radiant temperatures.

I'm not sure those mix valves will work without flow across the take off points, but I have never piped one exactly like that to know. Where did you get the piping schematic?

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Rob_37

The expansion tank is "now" mounted under the PV150 Air Eliminator. I ran the three thermostatic mixing valves because the rooms all have large swings in desired temperatures and I thought it would be better to do it that way? Wrong? I am not exactly following what was meant by the flow across the take off point. So far the rooms are heating well and the delta T is doing 20 to 25 degrees between supply and return on all zones. The main thing was the pressure drop when the boilers shut down. Currently I have no water supply so it is a fill and run job. Eventually there will be water for the fill valve.

hr

What is the static fill pressure?

the pressure in the system with nothing running?

A circulator moves water through a hydronic system by creating a pressure difference. It lowers the pressure at the intake side and raises it on the discharge. Of course a high head circ will show more of a pressure difference. So depending on where in the system you locate the gauge, it my drop below, or raise above the static pressure.

Install the gauge at the expansion tank connection (the PONPC) and it should stay at or close to static pressure.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"