New home owner!!! Navien ch-180 won't acknowledge thermostat!!!

Discussion in 'Boiler Forum' started by Jan B, Dec 20, 2017.

  1. Jan B

    Jan B New Member

    Joined:
    Dec 20, 2017
    Location:
    Clifton Park, NY
    My husband and I just bought our new home 3 weeks ago. The house had been vacant for a few months before we occupied it so I am sure the former owners turned down the temps on the system. Initially the system seemed like it was running well. We started getting an error message on it that said there was low pressure on the heating side. We have increased the heating supply water temp to 155 and that seems to have resolved it. Now... the system doesn't seem to be acknowledging our thermostat! I have the house set at 64 and when I came home yesterday afternoon it was 76 in the house. My husband's aide had to put him in shorts it was so warm in the house. I changed out the thermostat to a new one, and it is the basic style Honeywell dial one. No frills or flare. The house stayed that hot until I finally just turned the entire thing off when we went to bed. When I woke up this morning it was 62 in the house and I just talked to my husband and he said it was already to 69!!! Again the thermostat is only set at 64!!! I can't wait to see what this National Grid bill is going to be!!! Anyone have any ideas????? I need help!!!!

    Jan
     
  2. NY_Rob

    NY_Rob In the Trades

    Joined:
    Feb 23, 2016
    Location:
    New York
    Sounds like a shorted t-stat wire, bad relay, bad aquastat, etc.... could be none of those, a combination of them or all three.

    Honestly, without proper diagnostic tools, troubleshooting skills and replacement parts- it's time to call in a professional.
    Not a difficult problem for a pro to solve in a short amount of time.
     
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  4. jac04

    jac04 Member

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    Dec 11, 2013
    Location:
    Connecticut
    Jan- Make sure to tell the service technician about this pressure error as well. Cranking up the supply temp is not really solving whatever problem caused (or is causing) the low water pressure.
     
  5. Dana

    Dana In the trades

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    Jan 14, 2009
    Location:
    01609
    Don't sweat the gas bill. Raising the temperature by fully 10F adds less than 25% to the fuel when the average daily temp is 25F outside, and you're not keeping it at 76F all the time.

    With the Navien set to a fixed output temperature of 155F it's well out of the condensing zone, and delivering ~86-87% efficiency, and it's clearly overheating the house fairly rapidly at that temperature. While you're still debugging things, if you back off to something like 140F fixed temp output on the heating side the room temperature overshoots won't be as severe, and it might even condense a little. If it's still overshooting the desired room temp back off to 130F and you'll definetely be condensing, with better than 90% efficiency.

    While you're at it, measure up all of the baseboard lengths (by zone, if multi-zoned) and report back. The minimum firing rate of the CH-180 is 17,000 BTU/hr-in, and if condensing would be about 16,000 BTU/hr out. With typical baseboard it takes about 75-80' to balance reasonably at condensing water temperatures. If you have 30-40' zones and less than 75' total there is some potential for short cycling if you go too deep into the condensing zone.
     
  6. Jan B

    Jan B New Member

    Joined:
    Dec 20, 2017
    Location:
    Clifton Park, NY
    Well we found out why it was running all the time, there is a toggle switch that was in the "forced air" mode. So now it runs off the thermostat. BUT... it is barely getting above 62 in the house now and it is going at least -15 at night. The "tech" and I use that term very loosely at Navien said that I need to replace my exhaust vent pipe with schedule 80 PVC so I could turn the water temp up to get the house warm. I now know from research that it needs to be CPVC and not what he told me. Attached is a photo of the exhaust pipe that we have. It DOES NOT look like PVC. Any ideas?

    The error message of low pressure keeps occurring which shuts the entire unit off. Not good when you wake up at 130a and your house is 52 degrees.
    The other day I had to reset the unit 7 times!!! Our plumber has a pressure valve that he is going to replace for us and I hope that solves everything.

    Also I think we have about 60' of baseboard in the house and it is all one zone.

    I really hope that we get the kinks figured out. I have a lot of people telling me to get rid of the system. I can't afford to do that though. :(

    pipe.jpg
     
  7. Dana

    Dana In the trades

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    Metal venting is tolerant of higher temperatures than any plastic vent material. If the venting pipe is all metal (hopefully stainless steel, not galvanized) it does not need to be replaced with schedule 80 CPVC. Read the venting section starting on p.37 of the manual very carefully before making any changes.

    At 180F entering water temp 60' of baseboard will deliver about 30,000 BTU/hr. At 155F EWT it'll deliver about 21,000 BTU/hr.
     
  8. Jan B

    Jan B New Member

    Joined:
    Dec 20, 2017
    Location:
    Clifton Park, NY

    I have read that section many times now and I still can't figure out what was installed for my unit. It didn't feel like pvc but didn't look "metal", only if it was painted i guess. The previous owners don't remember who installed the unit either. Is there any way for me to tell?

    As far as the BTU info you gave I hate to sound stupid but can you explain that in layman's terms. It is supposed to be -30 with the wind chill for the next couple of days and I just want to make sure our house and my husband are going to be alright. Since his stroke his circulation isn't what it was and he gets cold easily.
     
  9. Dana

    Dana In the trades

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    Jan 14, 2009
    Location:
    01609
    BTU= British thermal unit, defined as the amount of energy it takes to raise one pound of water one degree F. The rate of heat being delivered by heating systems and sub components uses BTUs per hour.

    The rate that heat is leaving your house is also usually expressed in BTUs per hour, to be able to match the heating equipment's output rate to the maximum needed to keep the house at temperature.

    The heat loss rate from the house goes up roughly linearly with the difference between indoor and outdoor temperatures. For example, if you're keeping it at 70F indoors, when it's 40F outdoors there is a (70F - 40F=) 30F difference, and when it's 10F outdoors (70F -10F =) 60F temperature difference. That 60F difference at +10F outdoors is twice what it is at +40F outdoors, and the rate at which heat is leaving your house is roughly twice as much.

    Wind chill is a meaningless number as far as these estimates are concerned. While heat loss from air leakage goes up somewhat with wind speed, it is nowhere near as rapid as how wind affects the speed at which exposed human skin freezes, which is what wind chill is trying to estimate. The only relevant number is the raw outdoor air temperature, since the house isn't human and doesn't have warm skin to expose. The temperature of the siding and heat loss is really about the same when it's calm as when there is a 25 mph wind.

    A typical brand new fully up to code 1500' house will have heat loss between 18,000-22,000 BTU/hr @ 0F outdoors. A older but tight 2x4 framed 1500' house with clear glass double panes and no foundation insulation can be close to twice that, but with some retrofit air sealing & insulation and window upgrades can usually be brought under 25,000 BTU/hr.

    Without knowing anything about your house other than you recently acquired it doesn't really help figuring out if 60' of baseboard is the appropriate amount of heat emitter, but the higher the boiler temp, the more heat you can get out of what's there.

    Just as with the rate of heat loss from your house goes up with temperature difference, the rate of heat emitted from radiators changes with the difference between the average water temperature and the room temperature. Most specification tables for baseboards & radiators assume it's 65F near the floor, so when the average temperature of the water is 120F, it's a 55F difference, and when the average temperature of the water is 175F it's a 110F difference, emitting twice as much heat. The boiler's output temperature is higher than the average water temperature, since the heat being emitted by the zone lowers the temperature. The last foot of baseboard is typically 10-20F cooler than the first section of baseboard, and emitting less heat. The higher the entering water temperature, the more heat is being emitted, and the bigger the difference between the first and last foot of baseboard on the. The entering water temperature at the baseboard is pretty close to the boiler's output temperature, but for estimation purposes assume the average water temperature is 10F cooler than the boiler when running the boiler at 150F or higher.

    The section of vent pipe in the picture is very clearly metal- tap on it to hear what it sounds like. Or put a magnet on it, see if there is any attraction at all (some stainless alloys would have only a weak interaction with a magnet, but it's usually at least some.) Then go outside and see what it looks like on the exterior.

    [​IMG]

    Nothing about the installation is too confidence inspiring. I appears as if there has been exhaust condensation leaking through the joint onto the top of the boiler ruining the paint, and somebody may have tried to tighten up the seal with a wrap of aluminum foil. Natural gas exhaust is mildly acidic, and will always eat through aluminum foil or galvanized steel, but not stainless steel. It's time to have a pro take a look at it. The wadded up pink fiberglass insulation is also the spitting image of "worst practices", and it's not clear whether the vent pipe is even rated for contact with insulation (though it might be.)

    In the mean time, buy yourself a $50 oil-filled electric radiator for auxilliary heat in the room where your husband spends the most time. Cold snaps come and go, but there is no point to suffering.

    [​IMG]

    These are far preferable to those with fans or glowing orange elements, since the surface temps are reasonably well bounded making it harder to burn your house down with it. (Don't drape your soaked winter jacket over it to dry though.) Any of the building materials box stores or even Target/Wal-Mart type outlets will have a few models to choose from. As long as you limit it to 1500 watts most house wiring can handle it without a problem.

    1500 watts in electricity terms translates to about 5000 BTU/hour in space heating capacity terms. That is more than enough supplemental heat to keep any room that is lagging in temperature up to temp while you figure out your boiler & radiation and house insulation/air-tightness issues.

    [​IMG]
     
    Last edited by a moderator: Feb 10, 2021
  10. fitter30

    fitter30 Well-Known Member

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    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    What is the model of the new honeywell thermostat? Switch for air handler is strange if there isn't one or another thermostat.
     
  11. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    You're looking at a 2-years dead thread (revived by runningman). I think the original poster has moved on!
     
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