Problem with humidifier transformer?

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Old 11-19-06, 03:48 PM
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Problem with humidifier transformer?

This is my first time posting, but I think I have gone as far as I can with researching old threads. This is a great resource for the poor and stubborn, so thank you, thank you.

I just moved into a new house this summer and I have an Aprilaire 440 humidifier with no water flowing. I think I have isolated the problem to the transformer, but want to make sure before I go off spending money.

The feed to the transformer reads 120v when the fan is running, zero voltage when the furnace fan is not running, so I believe the furnace is providing power to the transformer. In both situations, my multimeter shows no voltage on the dc side of the transformer (I did switch my multimeter to read dc).

The next thing I did was to take the transformer to my workbench and hook it up to a 120v source. Still no voltage on the dc contacts. Am I correct to assume the transformer should probably be replaced?

If so, does it matter which brand of transformer I buy as a replacement and where I get it? This one has no brand name, but has the number 1284 on the side. It was physically attached through the knockout hole of a junction box.

I saw that I can purchase an Aprilaire 4010 replacement 24v on the Internet for $18. Would that be a good choice?

Thanks for the help.
 
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Old 11-20-06, 01:08 PM
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That 110Vac transformer is still a 24V ac out. You can try and brush the two 24V wires together fast and see if you get a spark.
Id say get the transformer from them then
 
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Old 12-05-06, 09:54 AM
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Transformer trouble - what am I doing wrong?

OK, I established that the transformer for my Aprilaire 440 was at fault and replaced it. Turned the unit on and everything seemed to be working. Gave myself a big pat on the back and bragged to my wife.

A couple of weeks later I noticed that the house seemed very dry again and my three year old is hacking. I tested the new transformer (an Aprilaire 4010) and it appears not to be functioning.

Before I replace this one, I want to make sure I'm not missing something. I tested the 110 vac feed to the transformer and it seems to work find (reads 110 vac when the fan is on, 0 vac when the fan is off). I removed the transformer and tested it on my workbench. No voltage on the secondary side even when 110 vac is applied to the primary.

Am I missing something, or did I just get a bad transformer?

Thanks for your help.
 
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Old 12-05-06, 11:07 AM
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rneusner: The only thing that comes to mind here, is the transformer to small ???? By that I mean the volt amp of it. A transformer for a furnace should be 40va or better. it will still be 110V in and 24V out
 
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Old 12-05-06, 11:16 AM
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That's a good suggestion. I'd think since it came from Aprilaire that it would be adequate, but I'm going to check anyways. Would it show the rating on the transformer?
 
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Old 12-05-06, 03:51 PM
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You might also check the voltage when the fan comes on. That can go up and down. Also is the solenoid good??
 
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Old 12-05-06, 04:13 PM
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I'm pretty sure that the aprilaire 4010 is a 10 VA... It should say on the transformer.
 
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Old 12-12-06, 12:33 PM
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Angry Very puzzled - does this violate laws of physics?

Hi,

Thanks for all the help so far. Based on discussions so far, I replaced the transformer for my Aprilaire 440 humidifier a second time. It lasted for all of about 2 minutes before it stopped working.

This time I measured the voltage on the primary side of the transformer and it reads 190 vac (checked this several times). I'm thinking this is what is destroying my transformers.

I tested the voltage at the emergency shutoff switch that supplies power to the gas furnace and it reads 120 vac as expected. I've looked around the furnace and can't see any obvious sign of a second hot wire that would be giving me a 240 vac potential (there could be one concealed somewhere, but I don't know why this would be the case).

Other possibly relevant information: 1) the furnace is a 20 year old Rheem gas furnace that seems to be in good working order; 2) the transformer feed line turns on and off when the furnace fan operates as expected; 3) the line used for a transformer feed is also used to power a Honeywell whole house air filter.

Here are my questions:

1) Would 190 vac fry my transformers?
2) What could be going on here to cause this high voltage. I didn't think that was possible with 120 vac feed and a normal furnace?
3) What would be a logical next step?

Thanks for all your help.
 
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Old 12-12-06, 12:49 PM
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Sounds like whoever hooked it up ran it right off the motor leads. There will be induced voltage when done that way. You should get a current sensing relay like the Aprilaire A50 relay. You simply put it around the common wire and run your power through it instead of directly off the motor wires. When the blower comes on the relay senses it and closes sending clean 120v to the transformer.
 
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Old 12-12-06, 01:05 PM
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3) the line used for a transformer feed is also used to power a Honeywell whole house air filter. Can this be feeding some power back on you????? Turn it off and see what you get then to the Hum transformer.
Id also put a new transformer in but dont tie it to the solenoid and see what it does. It could have a short in it.
 
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Old 12-23-06, 04:38 PM
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Smile Postscript

Great suggestion. It turns out that the problem was that the transformer was hooked up directly to the motor leads. Installed the Aprilaire A50 as suggested and now everything works fine. Thanks guys.
 
 

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