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Old 11-25-2010, 12:12 PM   #1
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240V service question


Hi. I'm new here but not new to electrical/electronics (electronics expert, but only marginally experienced electrical DIY). Apologies in advance for the long-winded post.

My heater went unused for the summer and now wont turn on. No Fan either.

A service guy came out and said my controller board was obviously arced/charred and needed to be replaced - $600. And that it wasn't worth doing because of the age of the package unit (over 20 yrs). OK, I get that it's old and probably on it's last legs, but I checked that board before and after he left and there is no arcing or char marks anywhere.

In my troubleshooting experience, things just don't stop working for no reason. Leaving the unit idle for several months and now being unrepairable doesn't square with that it was working perfectly the last time it was used. I'm in So Cal, so the heater never gets used for more than a few months a year.

Now to the strange part: I have 3 wire service to the HVAC unit (BLK-RED-GRN) and voltage, but I can only read 120-0-120 BK-GRN and RED-GRN. I get 0VAC when reading across BLK-RED. The controller board is connected across BLK-RED and there is a small 240V - 24V step down transformer connected to it. Again, I read 120V on each of the primary transformer leads to ground, but 0V across the primary and no 24V on the secondary.

Somehow between now and last time it ran, I've lost a valid 240V service. It doesn't make sense that it is reading like 2 parallel lines off the same main bus half since it obviously requires a full 240 swing. If so, how am I still reading 120-0-120 at the HVAC? Nobody has touched it but me and I haven't made any changes.

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Old 11-25-2010, 12:38 PM   #2
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240V service question


You're sure you have not done any other electrical work namely changed around the breakers in your electrical panel?

If you get 120 volts from red to ground and 120 volts from black to ground and zero volts from red to black then the red and black are not connected to the power source properly. You may have moved a circuit breaker or circuit breaker connection so the red and black are no longer connnected to the opposite legs (bus halves) of the incoming 120/240 volt service.

Or a possibility that there was an electrical problem outside your house this past summer and the power company reconnected things incorrectly with both of your 120/240 volt legs on the same side of the line.

Do you have any other 240 volt equipment including an electric stove and is that working properly?

Note that your red-black-green is considered a 2 wire 240 volt only circuit. No 120 volt lights or other equipment are supposed to be connected to the green other than for grounding of the respective chassis and/or framework.

To be fully code compliant the red and black from that circuit must be on a double wide double breaker where the handles are linked together so that if one trips the other is flipped off.

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Last edited by AllanJ; 11-25-2010 at 12:49 PM.
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Old 11-25-2010, 12:58 PM   #3
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240V service question


Definitely no changes to the breakers/panel.

But that was my question, basically - how I'm getting 120-0-120 at the HVAC without being able to read 240. I am reading BLK/RED referrenced to HVAC chassis ground. If the breakers are not making valid contact to the buss halves, why does 120V appear on both BLK and RED?

Sounds like you are saying that the 120-0-120V reading is a red herring and go check the buss connections anyway. That's the only thing that makes sense to me at the moment. There is one dual-ganged 60A breaker for the HVAC. Makes sense?

Stove is gas, but I didn't think to check the dryer.

Thanks for the tip!
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Old 11-25-2010, 01:10 PM   #4
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240V service question


You're an electronics expert? Then you should see what's going on here.

Take one of your 12.6VAC CT transformers. Power a small lamp with it.

Now unhook one wire. Leave the lamp connected on the other side.

Hook your multimeter probe to the CT and check the voltage at both ends of the lamp. What is it?



Plain and simple, one leg is open, the 120 you're seeing is going through the load (heater).

First guess? Cycle the breaker. A couple times. A lot of times if it's a pushmatic. If it's a GE, push it HARD into the off position then switch it ON very quickly, then cycle it "normally" one more time. I don't know any specific mechanical quirks for other brands.



Even without this specific guess (or if my specific guess is wrong), you know what to check. Electronics is generally more complicated than electrical wiring. The same basic theory still applies.

Do you have proper 120/240 at the breaker? If so, there's something opened in between.
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Old 11-25-2010, 01:33 PM   #5
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240V service question


Alan, the wife is warming up now and the hugs I got belong to you.

It was the breaker. I cycled it on and off several times and checked voltage before calling a serviceman. My next mistake was assuming the service guy checked the breaker first as I had done originally.

This time I pulled the breaker completely and cycled it until I got repeated continuity on both switches consistently.

All good now.

emolator, thanks to you as well - shouldn't you guys be eating turkey somewhere???

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Old 11-25-2010, 03:41 PM   #6
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240V service question


Not trying to slight Alan, but emolatur hit it right on the head. One side of your breaker was not making contact and cycling it closed the open. I would replace that breaker as a precaution.

I just finished my turkey
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Old 11-25-2010, 04:03 PM   #7
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I'm really curious about his brand of breakers, for two reasons:

1- I'm keeping a mostly-mental but somewhat-written collection of notes regarding peculiar misbehaviors of electrical equipment.

2- tripping one side and not the other IS a common misbehavior of the dreaded FPE breakers, and the result is a jammed-up common-trip mechanism that will then never trip again, at all.
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Old 11-25-2010, 05:35 PM   #8
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I tried what Alan suggested, then came back and saw emolaturs post which confirmed my results, so both answers were really helpful.

I couldn't read the brand, but it looks like the attached pic - a metal connecting rod tying the two toggles with an aluminum washer between them. I tried resetting the stupid thing at least a dozen times before pulling it out of the panel and mauling it into submission.

Even so, using my multimeter, I found each side took turns working and then not working before I finally got both sides reset.
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Old 11-25-2010, 06:24 PM   #9
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240V service question


Usually red is cosidered hot,
Black is considered neutral,
Green is ground.
Because neutral is normally connectted to ground in main board,
Thats why you are reading 120v
from red to green.
But if your source of supply is normally 120v,
then to get 240v requires connection across two phases.
Your black wire should also read 120v to green.
So the black wire has lost its supply.
Follow it back to the main board and find where.

Quote:
Originally Posted by Illroy View Post
Hi. I'm new here but not new to electrical/electronics (electronics expert, but only marginally experienced electrical DIY). Apologies in advance for the long-winded post.

My heater went unused for the summer and now wont turn on. No Fan either.

A service guy came out and said my controller board was obviously arced/charred and needed to be replaced - $600. And that it wasn't worth doing because of the age of the package unit (over 20 yrs). OK, I get that it's old and probably on it's last legs, but I checked that board before and after he left and there is no arcing or char marks anywhere.

In my troubleshooting experience, things just don't stop working for no reason. Leaving the unit idle for several months and now being unrepairable doesn't square with that it was working perfectly the last time it was used. I'm in So Cal, so the heater never gets used for more than a few months a year.

Now to the strange part: I have 3 wire service to the HVAC unit (BLK-RED-GRN) and voltage, but I can only read 120-0-120 BK-GRN and RED-GRN. I get 0VAC when reading across BLK-RED. The controller board is connected across BLK-RED and there is a small 240V - 24V step down transformer connected to it. Again, I read 120V on each of the primary transformer leads to ground, but 0V across the primary and no 24V on the secondary.

Somehow between now and last time it ran, I've lost a valid 240V service. It doesn't make sense that it is reading like 2 parallel lines off the same main bus half since it obviously requires a full 240 swing. If so, how am I still reading 120-0-120 at the HVAC? Nobody has touched it but me and I haven't made any changes.
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Old 11-25-2010, 06:24 PM   #10
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240V service question


That is a GE THQP two pole breaker. Don't now about years ago but a 60 amp breaker is no longer available in the THQP series. 60 amps is available in a two pole GE THQL series which is two inches wide.
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Old 11-25-2010, 06:25 PM   #11
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240V service question


Don't forget to replace that breaker as soon as possible. If the contacts were having trouble closing, they might not necessarily be making good contact. That could cause the breaker to heat up and eventually melt down or start a fire.
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Old 11-25-2010, 06:25 PM   #12
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240V service question


Quote:
Originally Posted by dmxtothemax View Post
Usually red is cosidered hot,
Black is considered neutral,
Green is ground.
Because neutral is normally connectted to ground in main board,
Thats why you are reading 120v
from red to green.
But if your source of supply is normally 120v,
then to get 240v requires connection across two phases.
Your black wire should also read 120v to green.
So the black wire has lost its supply.
Follow it back to the main board and find where.
Huh???
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Old 11-25-2010, 06:51 PM   #13
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240V service question


Quote:
Originally Posted by McSteve View Post
Don't forget to replace that breaker as soon as possible. If the contacts were having trouble closing, they might not necessarily be making good contact. That could cause the breaker to heat up and eventually melt down or start a fire.
Thanks for the tip! It does get warm, but I chalked that up to the load current. Still, given the problem I had, replacing it is good advice - after turkey and vino, that is...

Thanks to all for your responses!
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Old 11-25-2010, 07:56 PM   #14
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240V service question


The full-width GE breakers are the ones I referred to, I've had a couple fail to close reliably. I am only assuming at this point that the half-width breakers have very similar internal construction. It doesn't seem to be the contacts themselves, but rather the trip mechanism. The handle stays 'on' but barely, and takes very little effort to move to the 'tripped' position - like it is internally tripped but the handle spring doesn't pull it to center. Resetting it (OFF then back ON) mostly repeats the same. My theory is that part of the mechanism gets into a 'tripped' state and doesn't completely reset. Possibly the internal part loses "sync" with the handle - I know they're internally seperate in order to be "trip-free".

Simply resetting it several dozen times seems to have no effect. With all of the ones I've had this happen to, the fix has been to push it HARD to the 'OFF' position, then "slam" it ON (ie, toggle it as quickly as possible), then cycle it once normally. All have since passed my very unprofessional test (plug in a few 500W floodlights and a toaster oven and see if it trips before the wire gets hot) and neither got any hotter in the process than an unaffected breaker. One still feels "weak" in that it is noticeably easier to turn off than the breaker next to it, but I'm sure there's some tolerance/variance in that aspect from one breaker to another anyway. The others work like normal.

Face it, a 60A half-width breaker *IS* going to get warm in use. "too hot to touch" would definitely indicate a problem. Arcing is usually audible if you listen closely enough.



I'm not saying you should or should not replace that breaker, just giving you what I think might be relevant information.
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Old 11-25-2010, 08:58 PM   #15
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240V service question


Quote:
Originally Posted by dmxtothemax View Post
Usually red is cosidered hot,
Black is considered neutral,
Green is ground.
Because neutral is normally connectted to ground in main board,
Thats why you are reading 120v
from red to green.
But if your source of supply is normally 120v,
then to get 240v requires connection across two phases.
Your black wire should also read 120v to green.
So the black wire has lost its supply.
Follow it back to the main board and find where.
Black is never considered a neutral wire.

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