Navien NCB-240 Combi Boiler - DHW is fine, NO HEAT

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Handstied

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Partner replaced a 1969 American standard gas boiler and dying water heater with a Navien NCB 240 Combi Boiler. Heat was fine from Feb thru April. Off for last 5 months, DHW works very well at all times.
Cold snap and expected heat to come back on without issue. Heard it "click on" when I lifted the lever on the thermostat.
Yes, you read that correctly, lifted the lever. Boyfriend is the homeowner and decided he did not want the new thermostat and remote for the Navien combi Boiler. In fact he didn't even ask the installers to leave the Navien thermostat/remote her paid for.
So the thermostat that was connected to the American Standard boiler was wired for the Navien. I quietly pitched a fit because it made the most sense to install the new thermostat, but hey it's not my house. I just live here.
So 2nd night of no heat and a record low temp. BF wants to go tinker around with things and even though he's an engineer I'm not wild about thought of him messing with anything gas related. He' has a paid maintenance contract but will take 2-3 weeks for them to service it he says.
Terry Love forum literally saved our lives about 8 years ago when we had dancing disco lights and a weird power surge. BF shrugged it off, but from the assistance of TL members I alerted the Power company and it would have had dire consequences without that phone call.
So here I am again with a less pressing but annoying matter.
What's the most probable issue? Valve not opening / switching to heater from DHW correctly?
Thanks
 

Fitter30

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Installers should of left a owners manual tell how to access the boiler read outs. Shows if it's calling for heat and temps.
 

Breplum

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The first simple check is to confirm the thermostat is calling for heat with an ohmmeter or jump terminals on the board.
You can find NSS local and trained repair contractors on Navien's website, but Navien tech desk doesn't like talking homeowners w/o full technical background.
The install manual shows how to pull up basic data on the display and there is a troubleshooting icon on the display, but that only goes so far w/o the repair handbook. Frankly, Naviens are like all condensing products so complicated that we rely on the tech desk constantly.
They should have a one year factory warranty that any includes labor, just find someone in your area who is NSS. To be NSS, they are contractually required to return your phone call within something like an hour and required to make service calls at Navien-paid rates IF under the one year mark.
After that, it is parts coverage only.
 

Handstied

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Update. Tech came out after I posted this.
The first simple check is to confirm the thermostat is calling for heat with an ohmmeter or jump terminals on the board.
You can find NSS local and trained repair contractors on Navien's website, but Navien tech desk doesn't like talking homeowners w/o full technical background.
The install manual shows how to pull up basic data on the display and there is a troubleshooting icon on the display, but that only goes so far w/o the repair handbook. Frankly, Naviens are like all condensing products so complicated that we rely on the tech desk constantly.
They should have a one year factory warranty that any includes labor, just find someone in your area who is NSS. To be NSS, they are contractually required to return your phone call within something like an hour and required to make service calls at Navien-paid rates IF under the one year mark.
After that, it is parts coverage only.
A tech from the company that installed it came out after I posted this. The heat turned on while he was here. Since it suddenly worked, he just gave the system a quick lookover and told homeowner to schedule his annual clean up before February '23. Been running it at night for 9 of last 12-13 days. Tonight the heater's not working properly. Heard it turn on when I raise the thermostat and can see PSI rising (from 13.2 to 21.7) DHW fine as usual. I will pass on the info about NSS. Thank you for that information!
 

Handstied

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Take a few pics of the boiler and surrounding piping and pumps


Not working again.
Tech came out, took cover off, said he need advice from Navien. He sat in his truck for 3 hours than told us that Navien never returned his call. He added he didn't really know much about Naviens. He said he would ask someone else to come out who understood them. He said he had no idea what was wrong.
Fast forward and when the HVAC company was contacteds they said no one was scheduled to come out because the tech told them he got error code for sensor and that a sensor would need to be ordered. They said they would need Navien to sign off on it.
Explained that tech never mentioned an error code.
They said they will get a sensor and fix it tomorrow.
Does any of that make any sense?
 

Fitter30

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The old mercury thermostat when u look at the bulb and turn it down u can see the contacts. If the boiler fails to heat when turn down the thermostat the contacts will spark when the mercury breaks the connection. They you know the stat was calling for heat.
 

Handstied

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No issue with a sensor after all.
Luckily a seasoned tech supervisor showed up at the behest of the HVAC dept manager.
It WAS the awful and terrible 3 way valve that was causing the issue.
Finally cozy and looking forward to a warm Xmas. God bless all of you out there traveling anywhere in the US this weekend!
 
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