Navien Combi Boiler Error E002 - Where to start?

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GoneFishing70

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I have a Navien CH 240 combi boiler set-up that was installed about 10 years ago. On the boiler side it is piped to a coil in my furnace. Recently it started to show code E002 code - low pressure. This occurs on the boiler side and it shuts down the DHW side. I am able to get it to reset by turning off the furnace and boiler for 10 minutes after which I can get the DHW to work again. Runs fine for the day with the heat (30-35psi) and then it kicks out the same error code after several hours. Pressure on the DHW side is 20-25psi.
Any suggestions on where to start with this one? Thanks in advance.
 

Bannerman

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Pressure on the DHW side is 20-25psi.
Pressure seems pretty low as the DHW will usually be the same pressure as your water supply.

If you are relying on an installed pressure gauge, suggest verifying the gauge accuracy by comparing its reading to an additional gauge, perhaps one equipped with a garden hose thread so you can connect it to your laundry faucet or if possible, a boiler drain valve directly at the DHW outlet of the Navien unit.
 

John Gayewski

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I think someone else recently had this same problem on this site. You should be able to search for it. I think it was a sensor. But your pressure does seem low.
 

Fitter30

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Heating side should run 15-30 lbs max that is the relief valve setting. Need some picks on boiler, piping, pumps and expansion tank.
 

GoneFishing70

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Pressure seems pretty low as the DHW will usually be the same pressure as your water supply.

If you are relying on an installed pressure gauge, suggest verifying the gauge accuracy by comparing its reading to an additional gauge, perhaps one equipped with a garden hose thread so you can connect it to your laundry faucet or if possible, a boiler drain valve directly at the DHW outlet of the Navien unit.
Thanks to everyone for your input. I have noticed that after the unit turns off, I get the low pressure (E002 code) or a high pressure (E011 code). After 30 minutes they clear by themselves. I also notice when the unit is running on the heating side, water drips from the back side of the heat exchanger. I am thinking of replacing the water pressure sensor to see if that resolves the issue with the error codes. Then it's off to tackle the heat exchanger.
 

Fitter30

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Thanks to everyone for your input. I have noticed that after the unit turns off, I get the low pressure (E002 code) or a high pressure (E011 code). After 30 minutes they clear by themselves. I also notice when the unit is running on the heating side, water drips from the back side of the heat exchanger. I am thinking of replacing the water pressure sensor to see if that resolves the issue with the error codes. Then it's off to tackle the heat exchanger.
Ever clean the dhw heat exchanger with vinegar and when?
 
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