At What Voltage Is A 24v Transformer Considered Too Weak? - HVAC - DIY Chatroom Home Improvement Forum


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Old 12-04-2009, 10:55 PM   #1
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At what voltage is a 24v transformer considered too weak?


I'm working through a furnace issue right now.

My igniter is glowing brightly and it will make the 4 cycles before going into lockout mode.

Upon checking the voltage at the valve, I'm getting 21v instead of 24v. I think that might be keeping the valve from opening. A little bit of research on the internet suggest that 24v-28v is where I should be.

So my question is pretty simple. At what voltage is a 24v transformer considered too weak?

Thanks,
Phil

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Last edited by philp; 12-04-2009 at 11:01 PM.
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Old 12-05-2009, 07:30 AM   #2
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At what voltage is a 24v transformer considered too weak?


Its probably not a problem with the transformer. A stuck gas valve can cause the voltage to drop while the valve is energized.

Your above 20 under load, your generally good.

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Old 12-05-2009, 10:34 AM   #3
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At what voltage is a 24v transformer considered too weak?


Is there a way to manually open and close the valve? Possibly with an allen wrench?

If I can get it moving again, the jam might go away. (At least until I get a chance to replace it.)

Thanks,
Phil
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Old 12-05-2009, 10:36 AM   #4
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At what voltage is a 24v transformer considered too weak?


Nope, check all your wiring for loose connections and harnesses. May be dropping voltage from a loose connection. What brand is it and model #? We may know of ongoing problems with some of them.
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Old 12-05-2009, 11:33 AM   #5
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At what voltage is a 24v transformer considered too weak?


For safety reasons. There is no provision to open the valve manually.
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Old 12-05-2009, 11:47 AM   #6
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At what voltage is a 24v transformer considered too weak?


http://www.diychatroom.com/attachmen...m-img_0667.jpg
Take a good CLOSE look at this beauty.LOL
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Old 12-05-2009, 11:53 AM   #7
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At what voltage is a 24v transformer considered too weak?


LOL... I still see a few of them around.

Yep. Most people that used the manual open, didn't remember to close it. And some paid a high price.
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Old 12-05-2009, 01:21 PM   #8
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At what voltage is a 24v transformer considered too weak?


Now thats SCARY. Fortunately we inherited a few LOGIC skills so we can understand what goes on with machinery. Some people have NONE.
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Old 12-05-2009, 04:32 PM   #9
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At what voltage is a 24v transformer considered too weak?


Quote:
Originally Posted by yuri View Post
Now thats SCARY. Fortunately we inherited a few LOGIC skills so we can understand what goes on with machinery. Some people have NONE.
Some people after they come home from drinking. Didn't care to wait for service. Nor were they willing to wait for the house to warm up and then shut the valve off. Ooops.
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Old 12-05-2009, 05:10 PM   #10
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At what voltage is a 24v transformer considered too weak?


Quote:
Originally Posted by philp View Post
Upon checking the voltage at the valve, I'm getting 21v instead of 24v. I think that might be keeping the valve from opening. A little bit of research on the internet suggest that 24v-28v is where I should be.

So my question is pretty simple. At what voltage is a 24v transformer considered too weak?

Thanks,
Phil
I thought you should get 24.0 vac at the rated VA load with the rated voltage in.
Open circuit voltage might go 10% to 50% higher, because of poor voltage regulation.

What current are you pulling?
A 24v 40 VA 'frmr with 26v open circuit voltage, at 21v, is delivering ~4A.
If Voc = 28v, @ 21v, I = 3A.
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Old 12-05-2009, 05:30 PM   #11
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At what voltage is a 24v transformer considered too weak?


Yoz.

Study how solenoid valves/coils work.
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Old 12-05-2009, 06:04 PM   #12
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At what voltage is a 24v transformer considered too weak?


Quote:
Originally Posted by yuri View Post
http://www.diychatroom.com/attachmen...m-img_0667.jpg
Take a good CLOSE look at this beauty.LOL
Is that a motorize vale. I had one once that need to be oiled. Worked after that.

Real old house. The HO lived in Colorado and rented it out to college kids. He said he would get up at 4 am and feed the coal when it was a coal fired furnace so his mom could get up to a warm house. What a good kid he must have been. Later it was converted to nat. gas.
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Old 12-05-2009, 06:11 PM   #13
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At what voltage is a 24v transformer considered too weak?


It is a solenoid/diaphram valve (non motorized or oiled). Always remember my Grandfather (tough as nails) getting up in the middle of the night at Xmas to throw some logs in the old octupus furnace so we were warm. Great to stand on the cast iron register above it and get roasted.

Last edited by yuri; 12-05-2009 at 06:25 PM.
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Old 12-05-2009, 08:06 PM   #14
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At what voltage is a 24v transformer considered too weak?


We had a coal furnace. Nice heat. But, if you let it go out. Took a long long time to warm the house back up.
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Old 12-05-2009, 08:27 PM   #15
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At what voltage is a 24v transformer considered too weak?


Quote:
Originally Posted by yuri View Post
http://www.diychatroom.com/attachmen...m-img_0667.jpg
Take a good CLOSE look at this beauty.LOL
That one is so old they used it to warm caves inthe Neanderthal era

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