Dberryco
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Hi folks,
Short story: my new radiant heat installation doesn't work well. I'm having pressure related problems and seem to have no end of air in the system despite it holding pressure with no leaks.
Long story: I have a very simple (at the moment) radiant floor heating system consisting of 10 zones on a 12 zone manifold. I'm using a Grundfos UPS 32-80/2 VersaFlo Cast Iron Circulator Pump 115V, 1/2 HP. I'm filling the system with propylene glycol using a 1/2HP utility pump. It circulates thru a 200K BTU on demand water heater.
The manifold is: http://www.pexuniverse.com/12-branch-stainless-steel-radiant-heat-manifold.
House is small. 700 sqft. basement, 700 sqft. main level, 500 sqft. bedrooms upstairs. Zones are: basement closet, basement bedroom, basement bath, living room, kitchen, pantry, foyer/bath, bedroom upstairs #1, bedroom upstairs #2, bath upstairs.
I'm supplying and returning from the manifold with 3/4" pex. Individual zones are 1/2" pex.
I managed to get it to work for a few days, and for those days, it worked wonderfully. Took about 12 hours to get the cement slab warm, then it was great. Then I noticed my cheap chinese pump was leaking. Hence the nicer Grundfos multi speed model.
Here's what is happening: I turn the system on, and I'm only focusing on the basement 3 zones at the moment. Thermostat turns pump on, fluid flows and I get 1.2 GPM each thru the 3 zones. (Bedroom, closet, bathroom). Each is about 150-200' of 1/2" pex in concrete. Slowly, the flow rate slows to 1GPM, then .8 then .6 and finally flow stops and the water heater shuts off.
I started off with a 1/8HP taco pump and upgraded to the $700 pump thinking that more power was needed. I get the same results using the utility pump and putting fluid into the system. After I shut it off, I have air in the system. I flush the air out, and restart the procedure. It works for a short time, then pressure falls and then it stops flowing.
I've tried narrowing it down to 1 zone. Same result. I've switched to an upstairs zone. Same result. I've concluded I have some sort of vacuum leak or the pump is cavitating, or something mysterious is going on involving differential pressure and hydraulics.
I get the same result when filling the system from a 5 gallon bucket of coolant, or when cycling the system when it's a closed loop.
I have a pressure expansion tank installed. The system holds pressure of 30PSI indefinately, but I have no way of telling if there is a vacuum leak.
Every time I cycle the system, I get air in the lines. They are white pex, so I can see the bubbles move (the coolant is blue).
It's become something of a mystery. It's repeatable, consistent and baffling. There must be something stupid I'm doing or something I've missed. I'm sure someone here has run across this before and maybe has the answer.
My next step failing any better advice, is to replace the manifolds with something I build myself with copper tubing and valves for each zone. I would loose the flow gauges, but I could live with that. I can install automatic valves and individual pumps for each zone if needed, but it seems like an unneeded step if my current manifold works with individual zone thermostats.
Any ideas? Vacuum leak? Too much pump for the job? Cheap Chinese manifold? Forgot to install widget x in location y?
Thanks,
Dan
Short story: my new radiant heat installation doesn't work well. I'm having pressure related problems and seem to have no end of air in the system despite it holding pressure with no leaks.
Long story: I have a very simple (at the moment) radiant floor heating system consisting of 10 zones on a 12 zone manifold. I'm using a Grundfos UPS 32-80/2 VersaFlo Cast Iron Circulator Pump 115V, 1/2 HP. I'm filling the system with propylene glycol using a 1/2HP utility pump. It circulates thru a 200K BTU on demand water heater.
The manifold is: http://www.pexuniverse.com/12-branch-stainless-steel-radiant-heat-manifold.
House is small. 700 sqft. basement, 700 sqft. main level, 500 sqft. bedrooms upstairs. Zones are: basement closet, basement bedroom, basement bath, living room, kitchen, pantry, foyer/bath, bedroom upstairs #1, bedroom upstairs #2, bath upstairs.
I'm supplying and returning from the manifold with 3/4" pex. Individual zones are 1/2" pex.
I managed to get it to work for a few days, and for those days, it worked wonderfully. Took about 12 hours to get the cement slab warm, then it was great. Then I noticed my cheap chinese pump was leaking. Hence the nicer Grundfos multi speed model.
Here's what is happening: I turn the system on, and I'm only focusing on the basement 3 zones at the moment. Thermostat turns pump on, fluid flows and I get 1.2 GPM each thru the 3 zones. (Bedroom, closet, bathroom). Each is about 150-200' of 1/2" pex in concrete. Slowly, the flow rate slows to 1GPM, then .8 then .6 and finally flow stops and the water heater shuts off.
I started off with a 1/8HP taco pump and upgraded to the $700 pump thinking that more power was needed. I get the same results using the utility pump and putting fluid into the system. After I shut it off, I have air in the system. I flush the air out, and restart the procedure. It works for a short time, then pressure falls and then it stops flowing.
I've tried narrowing it down to 1 zone. Same result. I've switched to an upstairs zone. Same result. I've concluded I have some sort of vacuum leak or the pump is cavitating, or something mysterious is going on involving differential pressure and hydraulics.
I get the same result when filling the system from a 5 gallon bucket of coolant, or when cycling the system when it's a closed loop.
I have a pressure expansion tank installed. The system holds pressure of 30PSI indefinately, but I have no way of telling if there is a vacuum leak.
Every time I cycle the system, I get air in the lines. They are white pex, so I can see the bubbles move (the coolant is blue).
It's become something of a mystery. It's repeatable, consistent and baffling. There must be something stupid I'm doing or something I've missed. I'm sure someone here has run across this before and maybe has the answer.
My next step failing any better advice, is to replace the manifolds with something I build myself with copper tubing and valves for each zone. I would loose the flow gauges, but I could live with that. I can install automatic valves and individual pumps for each zone if needed, but it seems like an unneeded step if my current manifold works with individual zone thermostats.
Any ideas? Vacuum leak? Too much pump for the job? Cheap Chinese manifold? Forgot to install widget x in location y?
Thanks,
Dan