Source
r/ecobee•
formless63

Installed "ecobee Smart" 4 days ago, humidifier worked fine then stopped last night. With no call for humidity I see 12.5VAC between ACC+ and C?

Problem

EDIT: Solved as per the purpose of my post. I wanted to know if the 12.5VAC on the line was expected, and the rep ITT explained that it is expected. The ecobee sends out some sort of (sensing?) voltage when no equipment is connected, which I discovered in my testing and caused concern (12.5V constantly going to the relay/solenoid would be an issue) - but once the gear was reconnected as per his advice the voltage dropped to the expected 0.0V. The timing and odd voltage were cause for concern that the ecobee was involved in my humidifier failure, but it appears to all be coincidental and not related to the thermostat based on current information.

-------------------------Original:-------------------------

My humidifier stopped working last night. I bought the newest ecobee from my utility company a week ago and installed it on the 27th. Now, when I meter between the ecobee ACC+ and C, I get 12.5VAC?? Has the contact in the humidifier failed somehow to cause this? This should be 0V when there is no call for humidifier, correct?

After a full system power down and back up I am able to get 25VAC on that pair when there is a call for humidity, but when there is no call it drops to 12.5VAC instead of 0VAC. Any insight into what could be causing this?

Heat/Fan work fine. 28VAC between R and C at the board.

Posted Dec 31, 2019, 7:11 PM UTC · edited

314
gregz72•

What does it show for indoor humidity? There is a percentage of variance that the system will not call for the humidifier if the rh percentage is within the window that is normal. Taking showers, doing laundry, running the dishwasher all can affect indoor humidity levels. Unless your indoor humidity levels are in the low area 24/7 of below 45%, there really is no need to call for humidity.

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formless63OP•

I'm familiar with RH%. My house regularly drops below 20%RH without humidity reinforcement. I'm not asking why isn't it calling for it.

I'm forcing the unit to call for it or not based on the settings. I'm asking why it's giving partial voltage when I tell it not to call for humidifier. This is not expected behavior.

1
gregz72•

Bad transformer for the humidifier possibly.

1
formless63OP•

Meaning the furnace's transformer? Metered that a bit today. 29VAC at the transformer with no load. 28VAC at the transformer with heat running. Same readings between R and C as at the transformer. There is no separate transformer for the humidifier in this system. Humidifier is an Aprilaire 700 - forgot to mention that.

1
gregz72•

You humidifier requires its own 24vac transformer. It it is sharing voltage off of the furnace, that can be part of the problem along with if the old humidistat is still hooked up, if it was placed on the side of the furnace on the supply side duct.

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formless63OP•

This is incorrect. Per the manufacturer installation manual, utilizing the 24VAC control circuit without an additional transformer is just fine and most sources prefer this method versus introducing additional relays and transformers as additional points of failure. https://www.sylvane.com/media/documents/products/installation-guide-aprilaire-700-wh-humidifier.pdf They do mention ensuring you have at least 2.0A available in headroom on the circuit, but the relay for the fan plus the solenoid valve combined draw less than 0.35A

This is also the recommended single wire accessory install from ecobee. That is not the question here. While I did consider that there may have been an issue with the furnace's 40A transformer, I have ruled that out as a potential cause based on all other equipment still utilizing it as well as ohming it out, and using an ammeter to confirm the draw is as expected per my furnace manual both with and without load. Additionally, it has worked great on the accessory port of a Nest thermostat for the last four years. It worked fine with the ecobee for about 3 days, and will continue to work if I direct wire it to the fan circuit and bypass the ecobee.

I upgraded to this thermostat for the dev API to link with hass.io - but I need to figure out why it is not controlling the humidifier as expected.

There is not not now, nor has there ever been, a dedicated humidistat installed with the unit. The 700 is mounted directly to the plenum above the furnace as per all manufacturers guidelines. Prior to the ecobee, a Nest controlled the unit utilizing the same configuration.

1
formless63OP•

As additional info - the point of me posting here was really to determine this very odd 12VAC I was seeing on the connection. Ecobee rep explained why I was seeing it and it now makes sense. Sounds like the timing of the ecobee install was just coincidental with a different issue. Current overall thought is intermittent issue with the fan control relay. I had already replaced the solenoid valve with a spare I had before going down the diagnostic rabbit hole.

1
drytoastbongos•

How do you know the humidifier isn't working? Is the fan not coming on, or is the water solenoid not opening, or both?

As far as I recall from my install, the humidifier is wired to C and to the ACC+ from the ecobee. Which suggests the ACC+ floats, and then pulls to ground when humidifier is called for? Have you compared either side to references like ground or the voltage at the furnace transformer?

I think a poor connection at a wire nut could cause this, especially if you see a partial voltage drop. But this is all from memory, so definitely reference the install manual and wiring diagram for your furnace.

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formless63OP•

Both - I monitor the fan electrical draw through a smart meter as well as a flow meter on the wasted water that runs through the panel. Both went idle and stayed there for 4 hours during a call for humidity which triggered one of my hassio alerts to investigate. I can also meter to see that I'm not getting voltage at the humidifier when there is a call for it.

An ecobee rep ITT suggested that the odd voltage with no equipment connected might be normal (some sort of detection methodology the stat uses?) but I haven't had time to reinstall the humidifier assembly and test new readings with it back in place.

Based on a fairly full testing of the furnace control board and the furnace's transformer, that all seems fine. And jumping the humidifier directly to the board rather than through the stat works just fine. Really not sure yet what's causing the stat to not trigger it after a few days of working as expected.

1
ecobeeMattecobee•

Hi there! When measuring voltage, was the ACC+ wire connected to the humidifier or not? In a no-load condition (if the ACC+ wire is not connected to anything but the multimeter), the ecobee can still send voltage to its terminals even if it's not calling for anything. Therefore, it's important that you have the ACC+ wire connected to the control board/solenoid valve while measuring the voltage.

If you wish me to double-check things for you, please DM me your serial number to start with (you'll find it under Main Menu > About). You can also post a picture of the wiring behind your ecobee in the thread.

1
formless63OP•

I measured with the unit disconnected as I was trying to narrow down what the issue might be. Sounds like 12-ish volts is potentially normal to read with no device connected? If so my root issue might not be ecobee related and instead be on the humidifier side, but the 12V was unexpected and I did not find any reference material on this.

I have Rc/G/W/C/Acc+ populated on the ecobee. R/G/W/C on the furnace board. 2 wires from the humidifier, one goes to C on the furnace board, the other is Acc+

I'll message over with the serial, but I currently do not have the humidifier in place as I removed it to bench test. I can get this put back together to interface with as needed, though. As a side note, all resistances and amp draws match up fine with spec for the fan motor, relay and solenoid valve.

1
ecobeeMattecobee•

Based on your description, your wiring seems to be fine. I recommend rewiring the humidifier to the ecobee and then measuring the voltages again (one multimeter lead to the C of furnace board and the other to the ACC+/solenoid wire connection).

​

Let me know the results!

1
formless63OP•

Yes- this worked. I put my meter on those two connections, then connected an extra solenoid valve I have and it immediately dropped to 0.0V - is this some sort of sensing voltage? In any event, that solves my question for this thread and likely rules out the thermostat as the root cause of my failure. The timing was suspect and the odd voltage on that line initially added additional concern for me.

I will reassemble the humidifier tomorrow and attempt to see if it runs again. At this point it seems like the relay may be intermittently failing. I will also get you the serial number in the event the unit is logging whatever might be happening to the point you can see any specifics to provide insight.

Thanks!

1
gregz72•

http://docs.electronicaircleaners.com/aprilaire_humidifier_service_manual.pdf

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