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need to downgrade breaker (from 40amp to 15amp) for new hvac?

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need to downgrade breaker (from 40amp to 15amp) for new hvac? walknonsunshn 06-24-2007
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Posted by on June 24, 2007, 8:03 am
Hello,
I recently had a home inspection in preparation for selling my house.
The inspector informed the buyer that I need to downgrade the circuit
breaker (from 40amp to 15amp) for new hvac? He said he sees this
problem a lot. My father, who does a lot of DIY including some
electrical, says that if we change to 15amp when the hvac switches to
aux. heat it will blow the breaker?

I need to find out if this really needs to be changed, the inspector
warned the hvac unit could be damaged if this isn't changed. But I
don't want to have the change done if it will cause problems when the
unit goes to aux heat.

I'd call the hvac installer, but, clearly, they didn't think it was
necessary to change the breaker & I'd really like an independent
opinion on this.

ALSO, is changing a breaker best left to an electrician or might this
be something we could do ourselves?

Thanks in advance for any input.
WJ


Posted by RBM on June 24, 2007, 8:36 am
If the unit has an electric heating element in it that requires a 40 amp
feeder, you don't want to change it. It may be possible that two feeds are
required, one for the blower and a separate one for the heater and your
father installed an improper jumper to feed both. I would call a local
electrician to give a look




> Hello,
> I recently had a home inspection in preparation for selling my house.
> The inspector informed the buyer that I need to downgrade the circuit
> breaker (from 40amp to 15amp) for new hvac? He said he sees this
> problem a lot. My father, who does a lot of DIY including some
> electrical, says that if we change to 15amp when the hvac switches to
> aux. heat it will blow the breaker?
>
> I need to find out if this really needs to be changed, the inspector
> warned the hvac unit could be damaged if this isn't changed. But I
> don't want to have the change done if it will cause problems when the
> unit goes to aux heat.
>
> I'd call the hvac installer, but, clearly, they didn't think it was
> necessary to change the breaker & I'd really like an independent
> opinion on this.
>
> ALSO, is changing a breaker best left to an electrician or might this
> be something we could do ourselves?
>
> Thanks in advance for any input.
> WJ
>



Posted by on June 24, 2007, 11:14 am
Thank you for your responses.

We didn't do any of the wiring ourselves, the breaker is the same from
the prior HVAC unit (ca. 1987), I'm fairly certain the contractor who
installed the hvac a few months ago didn't make any change to the
breaker(s). He seemed quite competent and earnest, so I'm a little
reluctant to accept the inspector's word as gospel. Either way, I'm
concerned about a liability situation down the road, so I'm trying to
research this prior to having someone in to make a change.

The inspector stood in front of the breaker box pointing to the 40amp
breaker when he made the statement, so I'm pretty certain he's
referring to the breaker. The buyer read aloud a liability disclaimer
based upon the inspector's report.

I read all of the literature that came with the unit - an electric
heat pump/air conditioning unit w/air handler.

I did find this within the paperwork for the new unit (not sure if
this is relative):
<i>
This unit is designed for single-phase electrical supply. DO NOT
OPERATE ON A THREE-PHASE POWER SUPPLY. Measure the power supply to
the unit. The supply voltage must be in agreement with the unit
nameplate power requirements and within the range shown in:
Nominal Input 208/240
Minimum Voltage 187
Maximum Voltage 253
</i>
I don't mind saying this is pretty much greek to me, but does this
mean if I check the plate on the unit I'll be able to tell what kind
of breaker is best (based upon the range info above)?

I plan on having someone come in to make the change, if it's
necessary, but I'd like to have an idea of whether it needs to be done
before 'going there.'

Again, thank you so much for any input.

WJ



Posted by RBM on June 24, 2007, 11:36 am
Yes, but what Bill Allerman posted is important as well. The feeder cable
must be sized for a 40 amp breaker, which would be at least #8. Look on the
unit's name plate for an amperage rating or even a recommended circuit
breaker size. The full load amperage will determine the size wire and
breaker required







> Thank you for your responses.
>
> We didn't do any of the wiring ourselves, the breaker is the same from
> the prior HVAC unit (ca. 1987), I'm fairly certain the contractor who
> installed the hvac a few months ago didn't make any change to the
> breaker(s). He seemed quite competent and earnest, so I'm a little
> reluctant to accept the inspector's word as gospel. Either way, I'm
> concerned about a liability situation down the road, so I'm trying to
> research this prior to having someone in to make a change.
>
> The inspector stood in front of the breaker box pointing to the 40amp
> breaker when he made the statement, so I'm pretty certain he's
> referring to the breaker. The buyer read aloud a liability disclaimer
> based upon the inspector's report.
>
> I read all of the literature that came with the unit - an electric
> heat pump/air conditioning unit w/air handler.
>
> I did find this within the paperwork for the new unit (not sure if
> this is relative):
> <i>
> This unit is designed for single-phase electrical supply. DO NOT
> OPERATE ON A THREE-PHASE POWER SUPPLY. Measure the power supply to
> the unit. The supply voltage must be in agreement with the unit
> nameplate power requirements and within the range shown in:
> Nominal Input 208/240
> Minimum Voltage 187
> Maximum Voltage 253
> </i>
> I don't mind saying this is pretty much greek to me, but does this
> mean if I check the plate on the unit I'll be able to tell what kind
> of breaker is best (based upon the range info above)?
>
> I plan on having someone come in to make the change, if it's
> necessary, but I'd like to have an idea of whether it needs to be done
> before 'going there.'
>
> Again, thank you so much for any input.
>
> WJ
>
>



Posted by on June 24, 2007, 1:37 pm
On Sun, 24 Jun 2007 11:36:02 -0400, "RBM" <rbm2(remove
this)@optonline.net> wrote:

>Yes, but what Bill Allerman posted is important as well. The feeder cable
>must be sized for a 40 amp breaker, which would be at least #8. Look on the
>unit's name plate for an amperage rating or even a recommended circuit
>breaker size. The full load amperage will determine the size wire and
>breaker required
>
Nope, not on an HVAC condenser. Read the label on the condenser and
size the breaker/wire accordingly
You should see miminum circuit ampacity, that is the wire size based
on 301.16 (not 240.4(D) so 12ga is good for 25a, 14ga 20a.
Then look at maximum branch circuit over protection size and that is
the breaker you can use.
It will NOT be what you would think. This is for short circuit
protection, not overload protection, that is internal in the
compressor as a general rule.
You can very well see a 40a breaker on 14 ga wire.

All that said you still have to wire and protect the heater strips in
the air handler like a regular circuit, using the 310.16 rating on the
wire. Again that will be in the installation instructions as to what
wire and breaker combo you need for each heater option size.



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