Odd control voltage

[coltswin88]

No hostility here, just trying to figure out a problem that has me stumped. I'm actually a pretty laid back guy and I apologize if I came off as rude or aggressive.

[2sac]

I agree, I am new to this and still have a lot to learn. Another tech from a different company had been out there before me and couldn't fix the problem. I just corrected some pretty obvious errors ( r and g wired together, no neutral going from the gas valve to the secondary side of the transformer) As far as the voltage goes, I've gone to a couple bad transformer calls and yes, when they fry they usually fry open on one side or the other. I took the readings from the wires to a the grounded, non-painted internal casing of the furnace. So yes, it might be some problem with the tstat, but it is making connections.

This is not how you take proper voltage readings.

[Joe Harper]

If your 120 supply is good, then take the secondary wires off of the xformer and check the voltage. If you have 24 volts, then you have a short in the low voltage wiring.

[2sac]

No hostility here, just trying to figure out a problem that has me stumped. I'm actually a pretty laid back guy and I apologize if I came off as rude or aggressive.

I think he was referring to me. I come across as a dick sometimes

[Joe Harper]

This is not how you take proper voltage readings.

wow...you guys are harsh..

What 2sac is saying, is that you should be measuring between the hot leg and the neutral, to get the line voltage. If the furnace is not grounded properly, you wont get correct readings. Measuring to ground is more useful on three phase equipment.

[mason]

I think he was referring to me. I come across as a dick sometimes

Sometimes...? : D

What you said though, check control voltage to common and as Harper said on line voltage. Although using the ground can work if present you aren't confirming if neutral is connected all the way to the way to the panel.

Man if this is DIY he's gotten some good tips so far : ).

[Joe Harper]

I think he was referring to me. I come across as a dick sometimes

LOL...

[coltswin88]

The wiring diagram was lost to ages sometime ago. Most of the wiring was right but there were some obvious errors. The incoming power going into the unit was 120 and there was 120 at the transformer, fan relay and the blower itself. I checked the control voltage at the secondary side of the transformer and got 13v(checked to ground) and checked the tstat and still got 13v to the "O" terminal which was not used on the tstat

[mason]

The wiring diagram was lost to ages sometime ago. Most of the wiring was right but there were some obvious errors. The incoming power going into the unit was 120 and there was 120 at the transformer, fan relay and the blower itself. I checked the control voltage at the secondary side of the transformer and got 13v(checked to ground) and checked the tstat and still got 13v to the "O" terminal which was not used on the tstat

What did you get checking both terminals on the secondary side, that's how you want to check it.

[Joe Harper]

Check the xformer by itself, not with any wires on it. This will rule out line voltage and secondary issues. Then you can look into the wiring. What is most likely happening, is that the 24v line, is making contact with the common. This might be a rubbed through spot on a wire, or a relay that is wired wrong.

[IRBH]

[QUOTE]... I took the readings to ground and measured across them. 120 to ground, less than 1 across.[ /QUOTE]


Key sentence here.



Bet if you grnded the blower neutral it would run.

[CleterD]

If your 120 supply is good, then take the secondary wires off of the xformer and check the voltage. If you have 24 volts, then you have a short in the low voltage wiring.

^^^ This is what you should do next. You can just remove one wire but measure between the wires on the transformer, not ground.

[coltswin88]

Thanks! I checked the ground on the power coming in and it looked fine to me which is why I took readings to the inside. The only part still confusing me is that why it would read so low, like I said earlier, I always thought that pretty much either transformers work or they don't. Unless its burned out in a unusual way, I don't see why it's do that. Also THIS IS NOT DIY! I graduated technical school and am epa certified so I'm not just some guy with a cheap meter and general knowledge.

[coltswin88]

Thanks guys! I'm heading back out there in the am so I'll check it out tomorrow ! I have a lot to think about and hopefully I can get it fixed!

[2sac]

Get your post count up to 15 and apply for professional membership. We can give you a lot more help once you're on the "other side". There are educational forums as well

[Joe Harper]

You will get to learn the secret handshake too!

[2sac]

You will get to learn the secret handshake too!

I've been shaking the wrong thing

[coltswin88]

Thank you. I wondered how to become a professional member. I'm really not some guy, I have the student loans and tool bag to back that up haha. Well anyway good night and I'll be on it tomorrow!

[Joe Harper]

I've been shaking the wrong thing

And you wonder why they punch you on the subway....

[Poodle Head Mikey]

Put down your meter and answer my questions.
What is the operating voltage listed on the motor ID tag or plate?
What voltages are listed there on the motor?
What FLA or RLA number is listed there?

PHM
------

It needs 120v to operate. I checked the voltage to the fan relay and the blower itself. Both read 120v but the blower isn't operating at all. So I'm pretty confused between the blower not running and the low control voltage.