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NTI boiler sending heat to furnace when not needed

Rickards421Rickards421 Member Posts: 10
edited February 3 in THE MAIN WALL
Hi all, new here, thanks in advance for any help you can provide!

New ish to me townhouse, 8 months or so, first winter (GTA, Canada).

NTI boiler (Tft85) - heating domestic hot water (with tank) and furnace (Airmax Maxair 50ep2)

Thermostat kept at 20c during day, 15c at night. Fan always on in winter. Humidifier installed a couple months ago.

Few days ago came home to 24.5c. Assumed it was from the sun (huge south facing windows warm up my main floor on sunny days). Thought nothing of it.

Last couple of nights I've woken up sweating to 23c+. Yesterday I swapped thermostats (there are two, one in main level that we use, and one downstairs that I keep off. I'm told they can be used in tandem but we don't.). Assumed this would expose a bad thermostat, but no dice.

Last night I turned off the furnace and air handler and now am finally getting around to dealing with this problem.

It seems that the boiler (or valves, not entirely sure how this system regulates) are sending hot water to the furnace when it's not needed. (Because the fan is running and the house is well above the called for temp) The supply water pipes to the furnace are hot as they get when heating, but the stat shouldn't be calling for heat. In the diagnostics on the boiler it shows a demand for domestic hot water, but there is not hot water being used in the house.

Where do I start chasing this? I think by swapping the stats I should have eliminated that as a problem, but should I be starting with a new stat? Should I be calling NTI?

Thanks in advance!


  • SuperTechSuperTech Member Posts: 1,383
    Do you have a zone valve stuck open? That piping looks awfully small. What size PEX is that?
  • kcoppkcopp Member Posts: 3,523
    Piping does look small...also looks like some Non- Oxygen barrier tubing. Piping looks incorrect too.

  • HVACNUTHVACNUT Member Posts: 3,465
    Try swapping the zone valve heads. Does the other zone work as intended?
  • Rickards421Rickards421 Member Posts: 10
    edited February 3
    The white is 1/2", the red is 3/4".

    Are the zone valve heads the orange things? Can the be swapped without plumbing?

    What is oxygen barrier tubing and how would I tell? - edit, googled this. Looks like the red is o2 barrier, but the rest def isn't.

  • DZoroDZoro Member Posts: 1,035
    Any reason for the constant on fan?
    You maybe getting some ghost flow of hot water to the air handler. If that is so, with a constant on fan you would be getting unwanted heat into the ductwork.
  • STEVEusaPASTEVEusaPA Member Posts: 4,305
    Anyone else have luck hanging circs off of pex...looks like future trouble.
    Maybe gunk from non O2 barrier has created build up on the components, affecting their operation.
  • SuperTechSuperTech Member Posts: 1,383
    I've had problems with the three way valve in those boilers. Perhaps that is why you are getting unwanted heat in the hydro air unit. You really got to go through the low voltage wiring and see what is going on and see if the zone valves and three way valve are being energized or not.
  • Rickards421Rickards421 Member Posts: 10
    Constant on fan to keep humidifier running through the night to keep humidity up.

    Would "ghost flow" raise temp several degrees?

    Also I kept fan on all the time a while before this issue started happening.

    Supertech, what would I be looking for? Is there a schematic anywhere I could start with?
  • SuperTechSuperTech Member Posts: 1,383
    The humidifier should be able to bring the fan on when it needs to, you shouldn't have to leave it on all the time.
    I would try to turn the heat on and off by the thermostats and see if your zone valves (the orange Belimo valves) open and close when they should. You should be able to notice a change with the lever on the valves. Same thing with the three way valve inside the boiler. If you have a voltmeter you can check for 24 volts AC at the valves when the heat is calling.
  • Rickards421Rickards421 Member Posts: 10
    Ok I will give that a shot when I get home this afternoon. Thanks!
  • Rickards421Rickards421 Member Posts: 10
    edited February 3
    Alright, small update.

    I plugged the stat back in, cranked it to 28c and watched what happened in the utility room. I've got the fan on auto as recommended.

    (Closer picture attached) the bottom right is a normally closed valve, that runs in to furnace. It smoothly and quietly opened after the boiler fired up, as displayed by the lever on the side.

    The top left valve is a normally opened valve. It does not have a lever (edit1- there is a spot for a lever... But no lever), and I have no idea what it is doing as it is so quiet. (QUESTION- under what conditions would this valve close? Also how might I tell when it's moving without the lever? Super tech is this what you meant by checking w voltmeter, actually at the valve? Can I take the cover off these?) Edit1- I pulled the actuator off the valve, it seems to be held at approx 25% closed. Def not all the way open.

    Then I turned off the heat at the stat.

    The bottom valve running to the furnace then closed back up as far as it could go, according to the lever.

    I've left everything back on run, at normal heat, with fan on auto, to watch what happens. I don't know exactly what position it started in and I wonder if it was not closing up (I thought the lever was to take it off, yeah...)

    Will update on Tuesday.
  • Rickards421Rickards421 Member Posts: 10
    Morning all,

    Everything worked perfect last night. Temp dropped, furnace didn't run at all at night, as per thermostat temp set at 15c for nighttime. Kicked in this morning as it was supposed to.

    Re-humidifier, it won't run unless the fan is running, it can't call for the fan to run. Is there any reason not to have fan running all the time? As a relevant side note and reasoning, my place is a 4 story town, and the 1st floor is much cooler than the top. Keeping the fan running keeps the air at a much more even temp. So it would be nice to keep it going all the time, with added benefit of humidifier.

    Thanks again for everyone's help.
  • HVACNUTHVACNUT Member Posts: 3,465
    Constant fan is fine. I run mine for a steam humidifier and ionization generator. And I have hot water baseboard heat.
    I do have the option of leaving the thermostat on auto and then energize the fan motor for 50% nominal on a humidity demand.
    But the ionization generator is working 24/7 and it needs airflow.
  • Rickards421Rickards421 Member Posts: 10
    edited February 4
    How would one set up the humidifier to demand? Mine only turns on when the pressure valve says to.
  • duffy_4duffy_4 Member Posts: 69
    I think your condensate drain line should be looped in a circle before it goes to the drain. Doesn’t look safe way it is
  • DZoroDZoro Member Posts: 1,035
    May have to do a upgrade to either your humidifier control system or thermostat.
    Still wondering on a constant fan on situation, is the zone valve opening up? Or are you getting ghost flow?
  • SuperTechSuperTech Member Posts: 1,383
    It sounds like you ww> @Rickards421 said:
    > How would one set up the humidifier to demand? Mine only turns on when the pressure valve says to.

    Typically a humidistat will take care of everything from reading what the indoor relative humidity is, it will switch on the humidifier and the fan motor. Most Aprilaire humidistats can easily be switched from bringing on the fan motor anytime the humidistat is calling or only allowing the humidifier to come on during a call for heating. These humidistats also can be setup with an outdoor air sensor. The sensor allows the target relative humidity setpoint to vary depending on how cold it is outdoors.
  • Rickards421Rickards421 Member Posts: 10
    Ah, mine is not quite that fancy.
  • Rickards421Rickards421 Member Posts: 10
    Hi all,

    Wanted to drop in and say thank you to everyone for their help. It seems that one of the valves was stuck, and everything is working ok now. I learned a lot about this system this go around.

    All the best
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