Navien CH210 ASME LP sometimes ignores thermostat's call for heat

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MikeG88

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Just over a month ago I had a new Navien CH210 ASME LP unit installed (it actually replaced a non-asme unit that was having issues with the infamous mis-firing- error 12). This new unit seems to fire up fine, but a few times now it has ignored my Honeywell heat only thermostat's call for heat. I heard the t-stat 'click" and my single Taco circulator start. Usually the unit would fire up in a matter of seconds, but it didn't, after a few minutes I tried lowering t-stat and raising but that didn't work. No error code on Unit or remote controller, no reaction from unit at all. You might suspect the Taco One Zone Switching Relay is bad, but the problem is obviously very intermittant. Best solution to get it going seems to have been when I unplugged unit and circulator/Relay- waited a few minutes, plug unit in and wait for it to go through the initialization and settle/quiet down, then plug circulator in.

I called factory but they didn't want to help me directly and said I should have plumber check it out, the plumber who installed both units is not Navien certified, and previously has said I should have Navien tech do any "internal" testing/work (he's a fine master plumber- just admits he is not familiar with the brand's specifics). Unit is under warranty as re-install, unit and labor, was on my home-builder's dime. I called a few techs from the Navien list (a couple I had used with old unit), many are far away or don't want to tough a unit they didn't install, or in the case of one I had good luck with before- wont work on them anymore.

Any ideas on the problem and/or finding someone who can work on it, is this something a non-Navien plumber can do if willing to delve into? This isn't the time of year to hesitate and risk it not restarting.
 

Dana

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Properly installing boilers and heating systems is more than a plumbing exercise- it requires an understanding of how hydronic systems work, and it requires doing the math. Simply spelling "Heating and Plumbing" correctly and having plumbing license isn't sufficient qualification. Some master plumbers have learned quite a bit about hydronic heating in the field, but there are often big gaps.

When it comes to de-bugging the internals of a modulating condensing boiler, you're way beyond plumber territory. When de-bugging the hydronic design the plumber may or may not know enough to deal with mod-cons, even if they have a good success record with non-modulating cast iron boilers. Has this guy been certified by ANY mod-con boiler manufacturer?

Do you know if it's plumbed primary/secondary (and if so, how that was implemented), and whether the flow rate(s) are correct?

A picture of the near-boiler plumbing, and a description &/or schematic of the system radiation, pumps & valves would be useful.
 

Jac04

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When my CH-180 ASME was first installed, I had the same issue. I found that it is very easy for the wire connections inside the unit to be made improperly. The plumbers stripped the t-stat wires, shoved them in, and tightened the tiny screws. They never checked the connections and some were loose (the wire was not positioned correctly in the screw connector). Same goes for the connections at the zone valves.

So, I would check those connections first. You will need to remove the front cover to check the internal connections. Remember to isolate the equipment from power before touching anything.

I have found that Navien basically wants nothing to do with directly helping a homeowner, no matter how knowledgeable you are. Where are you in CT? Maybe we can start a user's support group! Hehehe.
 

MikeG88

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Hi Dana and Jac04,

I found a local plumber that was Navien certified and was able to come out. At first it seemed that the short T-Stat wire from the single zone relay was damaged or at least not making good contact. Factory tech support had him short out the two contacts and it worked every time while he was here. (I will admit those tiny screw did feel spongy and the stripped wire ends were a bit chewed- so an intermittent, maybe even thermally exacerbated, connection was feasible). Shortly after he left problem came back. Seemed that whenever it happened was after a DHW cycle. I tried restarting everything a few times and noticed once the T-Stat icon on the remote was even gone? I let it sit for a few hours and it eventually came back, but when I took a shower again the next morning it didn't come back (at least before the plumber arrived). He spoke with tech support- they were leaning toward the 3-way valve hanging up after DHW cycle, but he was leaning toward the PC board. The let him swap out the PC board and it seems to be working at this point, he said if problem comes back- then would swap 3 way valve. He even called me the next morning to verify it was currently working.

The 3 way valve on my prior Navien would hang up and make an unique noise as it tried to switch (it eventually died and was swapped out) - I haven't heard that noise come from this unit. That unit was removed because the error code 12 problem could not be resolved.

Will post update after giving a chance to see how it goes over a few more days time. Just glad this unit is under warranty.
 

Jac04

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That unit was removed because the error code 12 problem could not be resolved.
Interesting, my original CH-180 ASME unit was replaced due to error 12 & error 3 issues. They tried replacing most of the 'guts' of my original unit including the PC board with no effect. After some investigation, I found that the LP piping system was inadequate, but the installer wouldn't admit it was undersized. So, as soon as they scheduled unit replacement, I got a competent LP company out to put in a properly sized piping system. Once the new unit went in there were no error 12 or 3 problems. That was a little over a year ago.

Back to your current issue: One other thing - After you shut off the DHW, while the t-stat is calling for heat, the unit is supposed to shut down for a very short period (like 5 seconds) before re-firing. It is part of the firing logic, but I have not checked the schematics to see what sensor(s) provide info to the computer board to tell it what is going on. If your problem persists, then the sensors may be something to look at.

What company did you get to service your Navien? I need to find a NSS in my area 'just in case'.
 

MikeG88

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As far as LP supply, everybody that has inspected and measured said it is well with recommended specs- both static and the drop as it pulls. I never did have an error 3. Just error 12, and my first major snow storm with it I had an error 10 due to snow up to the vent, so I know to watch out for that.

I had noticed that the burner shuts down going from DHW to space heat (assuming there is a call) and restarts (sometimes I think it runs a longer purge cycle first- maybe dependent on how hot the unit was running to make DHW). The problem happened after a DHW cycle- but I dont think it was always happening when there was a concurrent call for space heat. I had tried lowering and raising the t-stat thinking along those lines, and also restarting unit- by unplugging and/or the button on the remote controller. Sometimes it was successful but usually not. Sometime leaving it unplugged for a while would work. Also I did notice the T-stat icon on the remote missing at least once- which would make me think the computer wast recognizing a T-stat was hooked up or the method of control. Unit seems to be working fine now -but I am not calling for DHW any more than needed until this really cold period passes (really don't need to totally lose heat right now). I will keep sensors in mind though if problem starts up again.
 
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