Air in Noritz Combi Boiler/Warmboard Radiant Heat

49North

I purchased a spec new construction which has a Noritz Combi Boiler NRCB199DV and a Warmboard radiant heat system. Some water drained from the pressure relief valve since before we moved in in June. However, since turning on the radiant heat system in September, there has been intermittent hard vibrating of the Noritz unit pressure relief valve for many seconds after hot water was turned on anywhere in the house. We finally convinced the installer to come out to check the unit and he determined that pressure was far too high in the hot water line at 40 psi and that there was a lot of air in the lines. He is coming back to bleed the Warmboard lines, a big job he says. He expressed concern about the 40 psi and possible wear and damage to the unit due to the strong vibration of the pressure relief valve and discharge pipe. There is a bit of rust discoloration where the hot water from the pressure relief valve discharges onto the sidewalk and on an adjacent pony wall paint. How much should I be concerned about wear due to the high pressure and vibrations, and rust/corrosion due to air in the lines over a period of about 6 months? The water is fairly hard here with calcium scale. It sounds like bleeding the lines fixes the problem; I am concerned about how this could affect the life of the unit.

Ironman

I assume that you're talking about the hydronic side and not the domestic?

The relief valve on the hydronic side is usually set at 30 psi. The pressure in the system should never exceed 25 psi. If it does, then something's wrong. It could be a bad fill valve, a water-logged expansion tank or one that's under-sized, etc.

The tech needs to find the CAUSE of the high pressure and correct it.

1PI

Hi 49 North.
Perhaps you are asking if the closed loop Warmboard radiant side of the Noritz was exposed to 40 PSI for 6 months instead of 15 PSI ,will this history of high pressure compromise any part of the heating system or the boiler?
Assuming this was your question here is my reply:
If the closed loop space heating side of the Noritz was at 40 PSI the temperature relief should have released.
In my opinion , I have no concern with the 40 PSI exposure.
I do not believe this 40 PSI exposure will compromise the Noritz or any components that are part of the closed loop heating system (except the relief valve).
Best Regards- PI

49North

Thank you for your responses. I talked with the manufacturer and they agreed that the pressure relief valve, which is set at 35 psi for the hydronic part of the system, should have protected the system, and since no high pressure error message appeared, not to worry. They are concerned that the high pressure may be due to, besides air in the Warmboard lines, a faulty air expansion tank on the hydronic line, so said that needs to be tested as the bladder (I think that is the term used) should be set to 12 psi. I am still not sure, if the problem is in the hydronic side of the system, why we keep getting a long groaning noise lasting several seconds when water begins to be used on the domestic side...unless the heat transfers over to the hydronic side. Once the air is out of the hydronic side, we'll see.

Ironman

Air in the lines does not cause excessive pressure unless it's in the heat exchanger and causing it to flash to steam because it's blocking flow.

49North

Bob, That may be possible because we are getting loud groaning noises for several seconds when we turn on hot water on the domestic side...perhaps the unit is also heating the air on the hydronic side in the heat exchanger. Bleeding the air from the heating supply line at the unit has reduced pressure to around 32 psi (creeping up from 27 psi the past few days).

DZoro

You have been only running 6 months with these issues? The install doesn't sound too good. Rust already, hard water you need to have your water tested and conditioned. The boiler wont last long in those conditions. Air bled, combustion analysis performed (results left inside boiler), water conditioned, pressure tank sized and checked, 15psi operation, all to be done ASAP.

49North

DZoro, thank you for your comments. We occupied in late June, and first noticed problems (loud noises) when the we started to use the radiant heat in September. I am not sure why the domestic side of the unit started to make a groaning noise when water was turned on only after we began to use radiant heat, but it did. I have been told that there's nothing to rust in the system...so perhaps the rusty color is brown paint washing off where warm water from the pressure relief valve discharges outside. PSI still at 30 which is high. The company that installed the Nortiz unit promised to come back several days ago to finish bleeding the hydronic line, but has not yet. The water here leaves calcium deposits, but people do not use water softeners in this area that I am aware of....I can look into it.

skippy76

49North, I am having the same issue of loud noise when running domestic hot water.  What was the solution?