NCB-240 Pressure Issue R.NG?

cj5

Hi All,
Had my heat exchanger replaced due to a leak a couple weeks ago.
I had been checking on it periodically to make sure it was running ok.

Today though I found that the bucket under the heating system pressure relief valve was overflowing. Pressure reading on the unit was 35psi.
Relief valve and expansion tank seem ok.

I believe previously the unit was set to around 12psi but during heating would get into the low 20s.

I checked the R value which sets when the makeup water feed when the pressure gets too low. Supposed to turn on at 4psi less than the set value.
According to the manual the default value is 12psi and can be set as high as 30psi.
Oddly, the R value is set at NG. Does anyone now what that means?

I drained water out of the system to get it back down to around 12psi. It's running around 18psi when he space heating is on. I'm monitoring to make sure it doesn't climb back up and put a bigger bucket under the pressure relief valve.

So if you have any ideas about what could have caused this or what are setting of R.NG means I'd really appreciate the help.

Thanks

cj5

Even after I drained water out of the heating loop it has climbed back up to 30psi.

I had the 3 way valve replaced a little over a year ago. Wondering if it is cracked open a little and the 55psi domestic water is seeping into it. Is that possible?

Or maybe the auto feed is feeding when it shouldn't be because it is set to the NG level instead of 12psi.

Or the heat exchanger is cracked somewhere letting the 55psi domestic water into the heating loop.

Is there a seal somewhere that could be bad that would cause this?

I wouldn't think the pressure sensor is bad since when the mechanical relief valve goes, the pressure reading is close to 30psi.

Big Ed_4

The Tech that did the work ... are ,their eyes on this........

GGross

The only thing I can find for this model that would read NG in the parameters is the fuel type, if you are on natural gas I would imagine you are looking in the wrong part of the control. You need to access the advanced settings per the install manuals instructions and look for the correct parameter, to access the advanced settings you must enter a password

cj5

The service guys are coming tomorrow but I like to understand the device that I rely on to heat my home as much as possible. I did follow the instructions in the install manual. Perhaps it's mislabeled. I didn't attempt to enter the password. Didn't want to inadvertently mess things up. Thanks for the input.