Navien NCB-240 runs water from the relief valve pipe

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Plumber'sSon

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It has been extremely cold for couple last days here in Boston, so I turned my second heating zone on for the first time in the season.
Yesterday morning the temperature shown by the thermostat was 62 although it was set for 65. I went down and saw both zones were working.
This morning I went down to the boiler room and saw a paddle on the floor. The water was coming from the pipe attached to the 30 psi relief valve.
I turned the system on and off several times I saw the pressure on the display rising to 40 psi. Sometimes the valve would open, couple times I opened it to purge the water. Anyway, it starts poring the water again and I had to shut the system.
I called a company which installs the system but nobody replied (it is a Holiday).
So, I am facing a heat less day / night.

The radiator pipes sounded like there was air in the system.

What could be done meanwhile?

Thanks
 

Plumber'sSon

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It has been extremely cold for couple last days here in Boston, so I turned my second heating zone on for the first time in the season.
Yesterday morning the temperature shown by the thermostat was 62 although it was set for 65. I went down and saw both zones were working.
This morning I went down to the boiler room and saw a paddle on the floor. The water was coming from the pipe attached to the 30 psi relief valve.
I turned the system on and off several times I saw the pressure on the display rising to 40 psi. Sometimes the valve would open, couple times I opened it to purge the water. Anyway, it starts poring the water again and I had to shut the system.
I called a company which installs the system but nobody replied (it is a Holiday).
So, I am facing a heat less day / night.

The radiator pipes sounded like there was air in the system.

What could be done meanwhile?

Thanks
It was rather a puddle of water on the floor :)
 

Reach4

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A failed or undersized expansion tank could product that symptom. Therm-X-Trol is a top brand, but there are others.
 

Plumber'sSon

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I saw Errors 351 Abnormal auto feeder valve and most recently 353 Abnormal water pressure sensor.
A maintenance guy showed up and saw the 353 error. He is going to replace the sensor.
The PSI reading by the way is crazy - up to 50
 

Dana

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If the pressure relieve valve is opening up it's not a problem with the sensor- more than 50 psi IS an abnormal pressure!

If the expansion tank is not properly charge, or it has failed or if it is undersized the system pressure can go quite high. Most boilers come fitted with 30psi relief valves, but most can be safely re-fitted with 50 psi valves. But putting in a higher pressure valve isn't the solution. The solution is to set the idling/tepid system pressure to 12-15psi, set the pre-charge on the expansion tank to match. If after bleeding the system pressure down to 15psi, if the expansion tank is has failed and is full of water it'll thud rather than ring when you tap on the air-valve end of it.

If the system has an auto-fill valve that is set too high or leaking water from the potable side to the system side, that too could create abnormally high pressure in the system.
 

hulabaloo

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Hi guys,

Going to try and revive an old thread here...

I'm in the process of converting my 53 year old house from hydronic baseboard heat to radiant floor heat. I've been lurking in these forums for some time and have learned so much. Hoping to learn much more from you all about my particular install, but first I've created a problem for myself that I'm hoping to correct.

I finally bit the bullet and cut out the old radiators, and so first attempted to shut off water to the heating system. I didn't at first notice the nice convenient ball valves hidden behind the expansion tank, so turned off the make up water valve, then started cutting. I incorrectly assumed that the DHW and space heating systems were independent, but the boiler soon threw a code for a make up water valve and stopped making DHW. I soon thereafter discovered the heating shut off valves, closed them then turned back on the make up water valve. It flashed an "air" message for a bit, cycled the pressure relief valve a couple times, then appeared to resume normal operation.

However, whenever someone runs hot water the pressure relief valve will cycle and let out a not insignificant amount of water. I've got a 5 gallon bucket under it and estimate that it catches 4 gallons per day. ( I have a large family, and most of us know how to use the hot water levers). I've manually cycled the pressure relief valve to attempt to clear air, but don't think that's working.

Anyone have any ideas on getting my system working properly again? It will likely be a couple months before I test run the new system, which I'm hoping will allow the water to pass by the expansion tank / air separator again....If that's even the problem.

Thanks in advance
 

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Fitter30

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Boiler is valved off in the second pic. 1 story house 12# is more than enough pumps off. Secondary pump is not in the pics is the flow up theres arrows on the pump casting.
 

hulabaloo

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Sorry for the late reply, I thought I'd get an email when there'd been a response... Not exactly sure what you mean. I valved the boiler off because I've removed all the radiators and drained the lines. My problem now is that every time someone runs hot water from a faucet (because this is a combi-boiler) I get at least a cup's worth of water from the pressure relief valve (on the upper left side of the boiler) I've got that orange bucket catching the water now, but I've been dumping it twice a day. I was thinking of soldering the "out" and "in" 1-1/4" copper pipe together, so that I could re-open the valves and bring the air separator and expansion tank back into the loop, but want to run that plan by sharper minds just in case that isn't advisable.

Eventually I'll finish the radiant floor system, then re-plumb the whole area. I'm just looking for a temp fix to stop the pressure relief problem. I'm also going to try and move this post so that it's not riding on the coat tails of a long dead thread.
 

hulabaloo

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It will come as no surprise to most here, but when I soldered the "out" and "in" legs together it solved my problem. Thanks.
 

Soaring Eagle

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I have a Navien 240E and I changed out the expansion tank a few months ago because the pressure relief valve was constantly letting go! However recently I've been noticing large amounts of water on my basement floor and it comes from the pressure relief valve! What should I check to see why this is happening. I don't have much experience with these Naviens but I do have experience with traditional boilers. This has got to be something simple that I'm overlooking but I don't know where to start with this. I'm definitely going to call in a professional but I need to try to understand why this is happening and where to check. Thanks
 
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