Problem with New Radiant System
The fella I’m working for is trying to hook up his radiant floor heating system. It consists of a hot water heater, a pump, manifold, and runs of tubing. It’s a closed system and carries tap pressure (40 psi around here). The pump functions perfectly while off-line, but when hooked up to the rest of the system, there’s no circulation. I’m a lowly trim carpenter, not an initiate to these other Mysteries. Can somebody clue me in?
My first guess would be that there is a "dead head" in the system, so the pump is trying to pump into a closed system where the water can't get back to suction. Follow the returns of the piping to see if they are returned to the heater.
Thanks, guys. I passed along all the good advice. He chose to install a pressure tank between the water heaters - necessitating a complete re-do of the copper. Either the tank, the new plumbing, or the repeated bleeding did the trick. Just in time. Headed below zero again tonight.
A couple of simple things to check first: make sure it's not connected backwards and there's no stop valve closed or backwards check valve. Kinda like making sure the cord's plugged in when someone says an appliance doesn't work.
Also consider an air pocket. I had a loop where I had to drop down a coupla inches to scoot through an expansion joint in the slab, and the air pocket there made that loop trickier to fill and resulted in no flow till we diagnosed it.
Edited 1/21/2003 7:04:33 PM ET by Cloud Hidden
There should be some bleeder valves at the high points of installation to allow for the removal of trapped air from the new lines. If not present....the layout elevations may require that they be added.
In my experience 40psi is not a normal radiant heat boiler pressure....12# is common in my locall.
Lastly....the pump is good, maybe the line is kinked? Sure hope it isn't! Hook a garden hose to the boiler drain and see if it will flush back to the loop line drain at the boiler outflow.