Indoor unit

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MAC702 said:
You REALLY need to slow down and be very accurate with your questions. You had the model number all this time?

I'll bet there are no fans (plural) in the ducts, neither.

I install a dozen Goodman furnaces every month, and there is nothing special about that one.
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In addition to this MAC, If I were you, I'd take just a minute to chuckle to myself.

You were spot on from the beginning.

There's still something to be said about those who aren't engineers but sometimes have to lean on their years of experience to get er done. :)

JAP>
 
codequestion said:
I have 16 of these furnance its large public storage each on individual circuit with fans inside connected to ducts.

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If you have a dedicate branch circuit to each blower unit then you should be fine.

What's the question?

What to use as the disconnect?

As stated in the specs the recommended MOCP is 15 amps so the breaker size is already given.

As far as a disconnecting means,

Some use a cord, plug and receptacle for the disconnection means at the unit.
Others use a motor rated 1p snap switch.
Others may use an AC pullout.

Most use what they like the most.

JAP>
 
codequestion said:
Yea it does then the engineer who provided 25A in drawing for each circuit for the furnance is in question. It will not protect it.

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You are not trying to limit the current draw on the unit.
You are trying to protect the branch circuit wiring to the unit.

JAP>
 
codequestion said:
Yea it does then the engineer who provided 25A in drawing for each circuit for the furnance is in question. It will not protect it.

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I bet they just sized it per 3/4 hp @ 120 volt motor application, and worst case starting current scenario. As I mentioned earlier these air handlers typically are PSC or ECM motors and don't have a high starting current like a capacitor start motor might.
 
I would give the engineer a call and discuss it.

If that was not an option, and I had the job, I'd size my wire for voltage drop if the runs were very long, and still size the MOCP device at what's indicated on the unit.


JAP>
 
jap said:
...Others use a motor rated 1p snap switch...
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Right or wrong, I've never seen these installed on a motor-rated switch, unless the common 15A light switch is motor-rated. The only failures I see are from backstab connections.

Is it supposed to be motor-rated if it is only serving as a disconnect, and not as a switch for loaded motor?

The ones that I install from scratch, I prefer a cord-and-plug.
 
codequestion said:
Yea it does then the engineer who provided 25A in drawing for each circuit for the furnance is in question. It will not protect it.

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That jump from a 15 or 20 amp circuit to a 25 amp circuit does make a lot of difference in this scenario.

One that would warrant a phone call to get everyone on the same page now that the recommended MOCP is known.

JAP>
 
MAC702 said:
Right or wrong, I've never seen these installed on a motor-rated switch, unless the common 15A light switch is motor-rated. The only failures I see are from backstab connections.

Is it supposed to be motor-rated if it is only serving as a disconnect, and not as a switch for loaded motor?

The ones that I install from scratch, I prefer a cord-and-plug.
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And most common 15a light switches as your calling them are motor rated.

JAP>
 
MAC702 said:
Right or wrong, I've never seen these installed on a motor-rated switch, unless the common 15A light switch is motor-rated. The only failures I see are from backstab connections.

Is it supposed to be motor-rated if it is only serving as a disconnect, and not as a switch for loaded motor?

The ones that I install from scratch, I prefer a cord-and-plug.
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Some like cord and plug since its cheap, but, can you use your every day cord whip on a 25 amp rated outlet like the OP is up against?
I think not.

In his case, with the label stating MOCP 15 amps, would he not have to use a 30 amp rated disconnect at the unit and fuse it down to 15 amps if he ran a 25 amp branch circuit to the unit like the engineer is callin for ?

I think he would.

To my knowledge there may be overload protection for the motor in the blower unit, but, there is not a fuse block in the blower unit itself, and , using a 15 amp rated cord whip on a 25 amp rated circuit to me is a no-no .

JAP>
 
jap said:
Some like cord and plug since its cheap, but, can you use your every day cord whip on a 25 amp rated outlet like the OP is up against?
I think not.

In his case, with the label stating MOCP 15 amps, would he not have to use a 30 amp rated disconnect at the unit and fuse it down to 15 amps if he ran a 25 amp branch circuit to the unit like the engineer is callin for ?

I think he would.

To my knowledge there may be overload protection for the motor in the blower unit, but, there is not a fuse block in the blower unit itself, and , using a 15 amp rated cord whip on a 25 amp rated circuit to me is a no-no .

JAP>
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Then engineer is calling for 25 amp circuit breaker to non fused 20 amps disconnect switch which connects the fan.

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codequestion said:
The engineer is calling for 25 amp circuit breaker to 20 amps motor rated switch which connects the fan.



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Is overkill but not a violation. If this were a 3/4 hp capacitor start motor on a general motor circuit - that may be necessary to allow the motor to start, could still be 14 AWG conductor on a 25 amp breaker though.
 
kwired said:
Is overkill but not a violation. If this were a 3/4 hp capacitor start motor on a general motor circuit - that may be necessary to allow the motor to start, could still be 14 AWG conductor on a 25 amp breaker though.
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But manufacuter calls for mocp 15 amps. Engineer is runing #10 awg from 25 amp circuit breaker to 20 amps motor control switch. The switch load side is connect to fans.

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jap said:
Some like cord and plug since its cheap, but, can you use your every day cord whip on a 25 amp rated outlet like the OP is up against?
I think not.

In his case, with the label stating MOCP 15 amps, would he not have to use a 30 amp rated disconnect at the unit and fuse it down to 15 amps if he ran a 25 amp branch circuit to the unit like the engineer is callin for ?

I think he would.

To my knowledge there may be overload protection for the motor in the blower unit, but, there is not a fuse block in the blower unit itself, and , using a 15 amp rated cord whip on a 25 amp rated circuit to me is a no-no .

JAP>
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I'd say not many such furnace units are identified to be connected with flexible cord, nor do they meet any other conditions that allow use of flexible cord, unless they are also listed as a portable unit.
 
kwired said:
Is overkill but not a violation. If this were a 3/4 hp capacitor start motor on a general motor circuit - that may be necessary to allow the motor to start, could still be 14 AWG conductor on a 25 amp breaker though.
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And ignore the MOCP of 15 amps indicated in the spec's?

For some reason I feel the information on the unit requires different installation practices than a feed to a strictly motor load only.

JAP>
 
kwired said:
I'd say not many such furnace units are identified to be connected with flexible cord, nor do they meet any other conditions that allow use of flexible cord, unless they are also listed as a portable unit.
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I agree.

I don't hook up blower units with the cord and plug scenario, although I see them every day installed like that.

JAP>
 
jap said:
And ignore the MOCP of 15 amps indicated in the spec's?

For some reason I feel the information on the unit requires different installation practices than a feed to a strictly motor load only.

JAP>
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I meant was overkill for engineer to specify 25 amp circuit, but also think they just saw 3/4 HP and never gave it much more thought and sized it as if it were a motor load only. I have mentioned several times now - the PSC or ECM motors on these units don't have a high starting current like a capacitor start motor would have and will start on a 15 amp breaker.
 
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