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Old 10-16-2015, 12:05 PM   #1
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NTI-150 boiler won't shut off blower motor


The gas-powered boiler in our house works well except that after it finishes a heating call, the fan won't shut off. This is annoying because the next time the boiler comes on it will trigger an ASC (Air Switch Closed) error because well.... the fan is still on sending air through the air switch... makes sense.

It just runs forever on some low setting.... So I can unplug the blower and this will open the air switch, and the boiler will then run fine when I plug back in the blower motor....

Research on the internet suggests I need to "unstick" my fan relay, however there isn't any that I can see on this furnace.

Where is the "fan relay" equivalent on this furnace? I have already replaced the entire sentry 2100 controller. I was pretty sure that would do it, but it hasn't. Do I need to replace the blower and motor assembly?

Any hints or suggestions on where to go from here is appreciated. I don't want to pass the winter standing around downstairs unplugging and plugging back in my blower fan!

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Old 10-16-2015, 05:45 PM   #2
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Check for 24 volts across terminals B and D. May have a loose 24 volt connection. Or the transformer may have now completely failed.

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Old 10-16-2015, 06:22 PM   #3
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I quickly looked up the manual. This is a modulating boiler right? The blower is a vfd. You should find 40vdc on pin 1(red) and 0vdc on pin4(blk). This is on the 5 pin connector. There should also be a 120v (blk) connected. When the boiler is running, pin 4 will be somewhere between 0 -35vdc. If it's anything above 1vdc when it's supposed to be off, the control is bad. I suspect the vfd circuit inside the blower is defective.

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Old 10-17-2015, 03:11 PM   #4
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Okay! Definitely voltage going through the red wire there. I think the take home message for me here is the relay is buried in the blower assembly.... so I'll order that part and hope there's enough new parts in that bundle of joy to solve it. Thanks for the guidance!
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Old 10-17-2015, 07:35 PM   #5
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Just remember that it's not the traditional off and on that you might be used to. There might not even be a relay at all.

Cheers!
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Old 10-28-2016, 04:15 AM   #6
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Re: NTI-150 boiler won't shut off blower motor


Sorry to bring up an old thread but I am having the same problem. Did you ever resolve the issue? As soon as I power up the boiler the fan comes on and stays on. If it gets a call it displays the ASC error and cycles between a high and low fan setting. Technician replaced the sentry 2100 control unit and put in upgraded air pressure switch and then gave up. If I leave the power on the blower but disconnect the low voltage wires coming from the sentry 2100 unit the blower ramps up to top speed.
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Old 10-28-2016, 08:20 AM   #7
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Re: NTI-150 boiler won't shut off blower motor


Quote:
Originally Posted by havi View Post
.. If I leave the power on the blower but disconnect the low voltage wires coming from the sentry 2100 unit the blower ramps up to top speed.
That means the blower motor is good.

Edit:
ASC means that the blower motor is being detected as on when it should be off. Either through the communication pins or the pressure switch. Double check the pressure switch wiring.

Cheers!

Last edited by supers05; 10-28-2016 at 08:26 AM.
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Old 11-14-2016, 11:54 PM   #8
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Re: NTI-150 boiler won't shut off blower motor


Just wanted to post a follow up in case anyone comes across this thread with the same issue. I ended up ordering a new blower/motor unit and it has fixed my issue. The old fan would ramp up and stay on for a few seconds before dropping to a lower setting and would throw the ASC code due to this. Even when I bypassed the pressure switch the fan would not fluctuate and the boiler would heat up to 200 and then trip out. If a call ended often the fan would stay on at the lower setting. The odd time it would shut down completely a few minutes after the call ended.

Now when i turn the boiler on, the new blower starts for a half second and turns completely off until a call is received. When a call is received it fires up in a matter of seconds and constantly adjusts the fan speed accordingly with the gas input valve to maintain 190 degrees. When the call ends it turns the fan off within a second or two.


Below is the part number for the blower/motor unit:

Trinity 82053-1 EBM Blower & Motor For T150-200
RG148/1200 - 3612 (55667.21120)
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Old 11-15-2016, 07:37 AM   #9
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Re: NTI-150 boiler won't shut off blower motor


So the control board on the motor assembly wasn't communicating the speed right. The motor is probably OK. Unfortunately it's not easily separatable, as a spare part.

I'm glad that you got it working. Thanks for the update.

Cheers!

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