Bradford white dual system hot water radiant heat lines are building pressure
by Carlos Buhler
(Canmore, Alberta, Canada)
Background: We have a pretty standard 8 year old, 47 gallon, dual loop system, natural gas powered hot water tank. Our home is about 2700 square feet located in a cold area of the Canadian Rocky Mountains, Canmore, Alberta.
Our very cold incoming water temp is about +2 or +3 C off the street. Our hot water boiler creates hot potable water through one loop system and heats a second mix of water and glycol running through the sealed, in-floor, 2 zone radiant heat tubing in our ground level floor. One zone thermostat controls the garage in floor heat (an additional 450 sq ft.) and the other zone thermostat regulates our ground floor finished living area of about 1200 sq feet including a semi complete kitchen (we have no 220V stove; just a hotplate, microwave, and toaster oven. We have one 3/4 bath in that area on the ground floor, plus a washer/dryer in the garage for tenants.
A couple lives in this 1200 sq foot area We (a family of 4 w/ two small children) live on the raised level of this 2 level "single family" type home. We have a washer/dryer upstairs also, for us, plus a full kitchen, full bath and a 3/4 bath. The house also has a gas powered, forced air system which circulates warm air mostly through the upstairs area.
Problem: So far, everything is still working. BUT the radiant heat system lines are slowly gaining pressure over a period of several weeks. This is visible on the pressure meter which is normally at 12-15 PSI but climbs now to where it's maxed out at over 35 PSI. I have bled it off twice to bring the pressure back to the correct 12-15 psi but it climbs again.
I am beginning to assume that we have a pin hole leak inside our water heater's radiant heat loop which is allowing household water pressure to seep into the radiant heat line. But could it be something else that is causing this pressure gain, like a pressure relief valve failure between our household pressure and the radiant heat line? There appears to be a separate water line that feeds into our radiant heat loop, presumably to "top off" the radiant heat loop if it somehow lost pressure.
I probably have to replace the whole hot water system if it's a pin hole leak and am preparing myself for the worst. Yet, this means deciding how best to proceed to heat both the radiant, in floor fluid, and our potable water given the advances in the last 8 years.
Questions: What do you think is raising the pressure in our sealed, radiant heat line?
If I need to replace the hot water tank I have now, do you feel confident about these on demand, natural gas tankless systems (like the Rinnai RC 98 HPi interior condensing water heaters together with a three way mixing panel like the HEP Isolation Heat Exchange Panel made by heat link?
There are so many solutions possible out there, and I don't know where to begin!