want to add 5th circuit to AC system

R

richard waters

New member
Feb 8, 1999
1,236
0
0
Netters,

Gee seems quiet this morning. I guess everyone
went to Rayne.

Well anyway if there is anyone left aboard here, I
do need some advice.

I just installed a new Sharp microwave/convection oven
that I got from Maytag Sam. It's going to be great, but
it can consume quite a bit more power then the old
microwave it replaced. Therefore, I want to have it
on its own AC circuit. I have the OEM breaker box
and only 1 roof air. Currently there are 4 circuits.
I want to add a 5th. I know GM finished GMCs of
my vintage could have 5 circuits, with the 5th
for the 2nd roof air.

Does anyone know how they did that? Did they take
one of the slots and put a double breaker there instead
of a single? Are the breakers available anywhere?

Or any suggestions on what I can do here?

Thanks,
Richard Waters '76 PB, Troy, MI
 
Richard,
I too am installing the sharp unit also. I am adding an extra 20 amp
circuit just for the unit. I haven't look inside the CB Box yet to get
the model of the circuit breaker used. Until I do that I won't know if
they make a dual breaker to fit that box. Probably won't be until later
in the week before I get to the electrical. I a mounting ours above the
counter and new cook top along with redoing the vent/light assy to fit
in the back. Be aware that the sharp need to be vented in the back to
let the heat out, the vent exits on the top left. That can get quite
hot when using it as an oven. I will let you know if I find out anything.

- --
J.R. Wright
GMC GreatLakers
77 Eleganza II
Michigan

>
> Netters,
>
> Gee seems quiet this morning. I guess everyone
> went to Rayne.
>
> Well anyway if there is anyone left aboard here, I
> do need some advice.
>
> I just installed a new Sharp microwave/convection oven
> that I got from Maytag Sam. It's going to be great, but
> it can consume quite a bit more power then the old
> microwave it replaced. Therefore, I want to have it
> on its own AC circuit. I have the OEM breaker box
> and only 1 roof air. Currently there are 4 circuits.
> I want to add a 5th. I know GM finished GMCs of
> my vintage could have 5 circuits, with the 5th
> for the 2nd roof air.
>
> Does anyone know how they did that? Did they take
> one of the slots and put a double breaker there instead
> of a single? Are the breakers available anywhere?
>
> Or any suggestions on what I can do here?
>
> Thanks,
> Richard Waters '76 PB, Troy, MI

- --
J.R. Wright
GMC GreatLakers
77 Eleganza II
Michigan
 
John,
I guess we're here alone on the net with all the others
apparently gone to Rayne.

The Sharp unit does output a lot of heat. I've been concerned
about the amount of heat. I installed mine under my new
cooktop. To keep allow the excess heat to escape, I ended up
punching 6 3/4" holes in the bottom of the cooktop
that is directly above the exhaust vent of the new oven to let
the heat escape up through the the cooktop. As a test I heated
the oven to 400 degrees and though very warm, nothing got
excessively hot in the area. You can't see the holes unless you
open the cooktop up.

I want that dedicated circuit for the new oven because the
existing oven outlet is connected to all the other coach outlets.
I have an inverter on that circuit and while it would handle the
load from the old microwave, there is no way the inverter
will handle the new oven load. Therefore, I don't want the
inverter connected to the new oven at all. Also, I want to be able
to run my quartz heater and the microwave at the same time.

I would appreciate any information that you learn about the 5th
breaker. This is something I don't have to do for a while.
Richard

> Richard,
> I too am installing the sharp unit also. I am adding an extra 20 amp
> circuit just for the unit. I haven't look inside the CB Box yet to get
> the model of the circuit breaker used. Until I do that I won't know if
> they make a dual breaker to fit that box. Probably won't be until later
> in the week before I get to the electrical. I a mounting ours above the
> counter and new cook top along with redoing the vent/light assy to fit
> in the back. Be aware that the sharp need to be vented in the back to
> let the heat out, the vent exits on the top left. That can get quite
> hot when using it as an oven. I will let you know if I find out anything.
>
> --
> J.R. Wright
> GMC GreatLakers
> 77 Eleganza II
> Michigan
>

> >
> > Netters,
> >
> > Gee seems quiet this morning. I guess everyone
> > went to Rayne.
> >
> > Well anyway if there is anyone left aboard here, I
> > do need some advice.
> >
> > I just installed a new Sharp microwave/convection oven
> > that I got from Maytag Sam. It's going to be great, but
> > it can consume quite a bit more power then the old
> > microwave it replaced. Therefore, I want to have it
> > on its own AC circuit. I have the OEM breaker box
> > and only 1 roof air. Currently there are 4 circuits.
> > I want to add a 5th. I know GM finished GMCs of
> > my vintage could have 5 circuits, with the 5th
> > for the 2nd roof air.
> >
> > Does anyone know how they did that? Did they take
> > one of the slots and put a double breaker there instead
> > of a single? Are the breakers available anywhere?
> >
> > Or any suggestions on what I can do here?
> >
> > Thanks,
> > Richard Waters '76 PB, Troy, MI
>
> --
> J.R. Wright
> GMC GreatLakers
> 77 Eleganza II
> Michigan
 
Hi guys - I'm still here...

I would love to see some pic's of the installation. My original oven is in
pretty sad shape. The convection/microwave might just be killing two birds
with one stone.

Patrick

> -----Original Message-----
> From: Richard Waters [mailto:digitek]
> Sent: Friday, March 17, 2000 10:24 AM
> To: gmcmotorhome
> Subject: Re: GMC: want to add 5th circuit to AC system
>
>
> John,
> I guess we're here alone on the net with all the others
> apparently gone to Rayne.
>
> The Sharp unit does output a lot of heat. I've been concerned
> about the amount of heat. I installed mine under my new
> cooktop. To keep allow the excess heat to escape, I ended up
> punching 6 3/4" holes in the bottom of the cooktop
> that is directly above the exhaust vent of the new oven to let
> the heat escape up through the the cooktop. As a test I heated
> the oven to 400 degrees and though very warm, nothing got
> excessively hot in the area. You can't see the holes unless you
> open the cooktop up.
>
> I want that dedicated circuit for the new oven because the
> existing oven outlet is connected to all the other coach outlets.
> I have an inverter on that circuit and while it would handle the
> load from the old microwave, there is no way the inverter
> will handle the new oven load. Therefore, I don't want the
> inverter connected to the new oven at all. Also, I want to be able
> to run my quartz heater and the microwave at the same time.
>
> I would appreciate any information that you learn about the 5th
> breaker. This is something I don't have to do for a while.
> Richard
>

>
> > Richard,
> > I too am installing the sharp unit also. I am adding an
> extra 20 amp
> > circuit just for the unit. I haven't look inside the CB
> Box yet to get
> > the model of the circuit breaker used. Until I do that I
> won't know if
> > they make a dual breaker to fit that box. Probably won't
> be until later
> > in the week before I get to the electrical. I a mounting
> ours above the
> > counter and new cook top along with redoing the vent/light
> assy to fit
> > in the back. Be aware that the sharp need to be vented in
> the back to
> > let the heat out, the vent exits on the top left. That can
> get quite
> > hot when using it as an oven. I will let you know if I
> find out anything.
> >
> > --
> > J.R. Wright
> > GMC GreatLakers
> > 77 Eleganza II
> > Michigan
> >

> > >
> > > Netters,
> > >
> > > Gee seems quiet this morning. I guess everyone
> > > went to Rayne.
> > >
> > > Well anyway if there is anyone left aboard here, I
> > > do need some advice.
> > >
> > > I just installed a new Sharp microwave/convection oven
> > > that I got from Maytag Sam. It's going to be great, but
> > > it can consume quite a bit more power then the old
> > > microwave it replaced. Therefore, I want to have it
> > > on its own AC circuit. I have the OEM breaker box
> > > and only 1 roof air. Currently there are 4 circuits.
> > > I want to add a 5th. I know GM finished GMCs of
> > > my vintage could have 5 circuits, with the 5th
> > > for the 2nd roof air.
> > >
> > > Does anyone know how they did that? Did they take
> > > one of the slots and put a double breaker there instead
> > > of a single? Are the breakers available anywhere?
> > >
> > > Or any suggestions on what I can do here?
> > >
> > > Thanks,
> > > Richard Waters '76 PB, Troy, MI
> >
> > --
> > J.R. Wright
> > GMC GreatLakers
> > 77 Eleganza II
> > Michigan
>
 
> Hi guys - I'm still here...
>
> I would love to see some pic's of the installation. My original oven is in
> pretty sad shape. The convection/microwave might just be killing two birds
> with one stone.
>
> Patrick

Patrick, that's what I figured. I thought I would kill 2 birds with one stone
too.
This oven seems to do it all. Besides nuking food, it will bake, grill, roast
and
cook by convection.

It was a pretty simple installation. It fits almost exactly the opening that
the OEM
oven was installed in. All I had to do was take about 1/8" off the side of the

original opening to get it in.

I installed a new gas cooktop over the oven and the two units look just like
they
are a single unit. I'll take some fuzzy pictures with my camcorder and post
them
to my PhotoPoint site so you can see what it looks like.

Maybe John Wright can do the same. His installation is different. He
apparently
installed his overhead. That would make for a very nice installation. I'd
like to
see that too.
Richard
 
If your microwave is not that big, less than 1000 watts, you can
probably run it off another circuit, except the one that is on the Air
conditioner, and the one conncted to the water heater element. These
take up quite a bit of the load. If you really want a separate circuit,
you can get a double circuit breaker (one that takes up the same amount
of space ad a single but has two circuit breakers in the same space)...
that way you would have it on it's own circuit breaker. The issue is
one of total amperage. If you have a 30 amp cord and electrical, then
30 times 120 or 3600 watts is all you should run at one time. If you
have a 50 amp system, then 50 times 120 or 6000 watts is all you can
run. Running the microwave along with one air conditioner and the hot
water element consumes close to 3000 watts ( ie a/c around 15 amps or
1800 watts, and the 1000 to 15000 watt element on the hot water system
would get to the 3000+ watts). However becasue these are not full loads
all of the time, you can easily run a microwave within these parameters.

Hope I did not get you too confused. Please let me know if I can add or
aid you in any way.
al

> Netters,
>
> Gee seems quiet this morning. I guess everyone
> went to Rayne.
>
> Well anyway if there is anyone left aboard here, I
> do need some advice.
>
> I just installed a new Sharp microwave/convection oven
> that I got from Maytag Sam. It's going to be great, but
> it can consume quite a bit more power then the old
> microwave it replaced. Therefore, I want to have it
> on its own AC circuit. I have the OEM breaker box
> and only 1 roof air. Currently there are 4 circuits.
> I want to add a 5th. I know GM finished GMCs of
> my vintage could have 5 circuits, with the 5th
> for the 2nd roof air.
>
> Does anyone know how they did that? Did they take
> one of the slots and put a double breaker there instead
> of a single? Are the breakers available anywhere?
>
> Or any suggestions on what I can do here?
>
> Thanks,
> Richard Waters '76 PB, Troy, MI
 
> If your microwave is not that big, less than 1000 watts, you can
> probably run it off another circuit, except the one that is on the Air
> conditioner, and the one conncted to the water heater element. These
> take up quite a bit of the load. If you really want a separate circuit,
> you can get a double circuit breaker (one that takes up the same amount
> of space ad a single but has two circuit breakers in the same space)...
> that way you would have it on it's own circuit breaker. The issue is
> one of total amperage. If you have a 30 amp cord and electrical, then
> 30 times 120 or 3600 watts is all you should run at one time. If you
> have a 50 amp system, then 50 times 120 or 6000 watts is all you can
> run. Running the microwave along with one air conditioner and the hot
> water element consumes close to 3000 watts ( ie a/c around 15 amps or
> 1800 watts, and the 1000 to 15000 watt element on the hot water system
> would get to the 3000+ watts). However becasue these are not full loads
> all of the time, you can easily run a microwave within these parameters.
>
> Hope I did not get you too confused. Please let me know if I can add or
> aid you in any way.

Al!
Thanks for responding to my question.

The microwave that I have is also a convection oven. The power
requirement rating for it is 1.55 KW (13.0 amps) according to
the stuff I got with it.

I don't have any available circuits to handle that load with the
other things running. Fortunately, I have 50 amp service in
the coach. If I run the 6000 watt generator I'm all set or if
I'm connected to 50 amp shore power. On the other hand
if I'm connected to only a 30 amp shore power outlet then
I know that I get to exercise my "power management" skills.

What I'm really after here is where can I buy a double circuit
breaker to replace one of the single breakers currently installed
in the breaker box.
Richard
 
I think you can get them at an electrical supply house. Take one of the ones
you have ( a 20 amp) with you and have them get you a double for that circuit
breaker.
al

> > If your microwave is not that big, less than 1000 watts, you can
> > probably run it off another circuit, except the one that is on the Air
> > conditioner, and the one conncted to the water heater element. These
> > take up quite a bit of the load. If you really want a separate circuit,
> > you can get a double circuit breaker (one that takes up the same amount
> > of space ad a single but has two circuit breakers in the same space)...
> > that way you would have it on it's own circuit breaker. The issue is
> > one of total amperage. If you have a 30 amp cord and electrical, then
> > 30 times 120 or 3600 watts is all you should run at one time. If you
> > have a 50 amp system, then 50 times 120 or 6000 watts is all you can
> > run. Running the microwave along with one air conditioner and the hot
> > water element consumes close to 3000 watts ( ie a/c around 15 amps or
> > 1800 watts, and the 1000 to 15000 watt element on the hot water system
> > would get to the 3000+ watts). However becasue these are not full loads
> > all of the time, you can easily run a microwave within these parameters.
> >
> > Hope I did not get you too confused. Please let me know if I can add or
> > aid you in any way.
>
> Al!
> Thanks for responding to my question.
>
> The microwave that I have is also a convection oven. The power
> requirement rating for it is 1.55 KW (13.0 amps) according to
> the stuff I got with it.
>
> I don't have any available circuits to handle that load with the
> other things running. Fortunately, I have 50 amp service in
> the coach. If I run the 6000 watt generator I'm all set or if
> I'm connected to 50 amp shore power. On the other hand
> if I'm connected to only a 30 amp shore power outlet then
> I know that I get to exercise my "power management" skills.
>
> What I'm really after here is where can I buy a double circuit
> breaker to replace one of the single breakers currently installed
> in the breaker box.
> Richard
 
I added some more AC circuits to my coach. Had to add a second service
panel, as the original only had room for 2 breakers. The smallest one Home
Depot had was a 100 amp box with room for 6 breakers---$15. So I mounted it
next to the old one & wired it up. Piece of cake. New 15, 20, or 30 amp
breakers are $4 each. This is the first cheap thing I've done to the GMC.
I will probably remove the old one someday & consolidate everything in the
new box....when too much idle time becomes a problem .

Steve Clevenger
76 Transmode 230
Tulsa, OK.
 
> I think you can get them at an electrical supply house. Take one of the ones
> you have ( a 20 amp) with you and have them get you a double for that circuit
> breaker.
>

Al,
Good idea. I'll give that a try on Monday.
Richard
 
> I added some more AC circuits to my coach. Had to add a second service
> panel, as the original only had room for 2 breakers. The smallest one Home
> Depot had was a 100 amp box with room for 6 breakers---$15. So I mounted it
> next to the old one & wired it up. Piece of cake. New 15, 20, or 30 amp
> breakers are $4 each. This is the first cheap thing I've done to the GMC.
> I will probably remove the old one someday & consolidate everything in the
> new box....when too much idle time becomes a problem .
>

Steve,
Thanks for the reply.

I was just at Home Depot about 20 minutes ago
and couldn't find anything small enough to fit
in the electrical compartment. In there I already
have a TC40, 50 amp automatic generator transfer
switch and automatic inverter transfer switch.
That's all in the same tiny compartment with the
the breaker box and the water heater switch.

I suppose I could redo everything if I could find the time.

What size is the new breaker box you bought?

Richard
 
Totally true, but remember that the GMC Onan is only 50A at 120V, for a total
of 6000 watts. Hence, an expansion such as this will run the A/C on shore
power, but would overload the generator. Perhaps this is where the confusion
comes in, since the GMC has both 50/240V service (shore) and 50A/120V service
(genset) interchangeably feeding a common system.

- - Tim

>
> > If you
> > have a 50 amp system, then 50 times 120 or 6000 watts is all you can
> > run.
>
> Al,
> Actually, a 50 amp service is 50A X 2 hot leads for a total of 50A X 2 X
> 120V = 12,000 watts. (If you plug into 240 volts it's the same thing, as you
> then get 50A X 240V = 12,000 watts, 240V using both breakers on the two hot
> leads). Key point is the nominal 50 amp cord is 4 conductors: 2 hot, 1
> neutral, 1 ground. (The 30 amp cord is only 3 conductors: 1 hot, 1 neutral,
> 1 ground.)
> Further muddying the water, the factory-wired GMCs have 40 amp main
> breakers (2), giving either 40A X 2 X 120V = 9600 watts or 40A X 1 X 240V =
> 9600 watts. As you can see, even this is nearly 3 times as much power as may
> be drawn through a 30 amp 120V 3-prong power cord (30 X 1 X 120 = 3600
> watts), which can't even carry the full output of a 4,000 watt Onan.
> Don't mean to pick nits, but this is one of my pet crusades: If you've
> got a modern 50 amp entrance, stick with it, don't go back into the dark ages
> to a 30 amp. They're not as close as many think.
> My .02. HTH.
>
> Rick Staples
> '75 Eleganza
> Louisville, CO
>

- --
================================================================================
Tim Dawson (tadawson) Owner/Engineer
TPC Services Bellnet: (972)-221-7385
Lewisville, Texas 75067 FAXnet: (972)-221-0393
"The world is complex. Sendmail.cf reflects this...."
 
Sorry, I must have gotten into the thread late - I thought that the intent was
to add additional circuits above and beyond what was originally installed,
such as electric ovens or (god forbid) a third A/C unit, in which case, the
Onan would become the limitation, not necessarily due to the ability to sustain
more load that stock running, but most likely it would not have enough reserve
capacity to start another A/C, or one of the existing ones if much more load
were added from the original. And yes, I do power both my A/C units from my
Onan quite successfully, but then I still have a gas stove, and don't run the
water heater on generator (typically, here in Texas, I run my generator on-road,
to supplement the dash A/C . . . otherwise we die in 100+ degrees . . . )

- - Tim

>
> > remember that the GMC Onan is only 50A at 120V, for a total
> > of 6000 watts. Hence, an expansion such as this will run the A/C on shore
> > power, but would overload the generator.
>
> Tim,
> Actually, what we're discussing is not an expansion, but rather the way
> the GMC-finished coaches were wired at the factory. Check your maintenance
> manual wiring diagrams. And of course a 6KW Onan will power two roof air
> conditioners with about 10-20 amps left over, depending on the ACs and
> conditions.
> I think the current should be limitted by the circuit breakers, not by the
> shore power cord. ;-)
> My .02.
>
> Rick Staples
> '75 Eleganza
> Louisville, CO
>

- --
================================================================================
Tim Dawson (tadawson) Owner/Engineer
TPC Services Bellnet: (972)-221-7385
Lewisville, Texas 75067 FAXnet: (972)-221-0393
"The world is complex. Sendmail.cf reflects this...."
 
> ones
> you have ( a 20 amp) with you and have them get you a double for that circuit
> breaker.
> al >>
>
> Home Depot has breakers that will fit out GMC boxes. I believe the one I
> purchased was labeled Simens.
> Emery Stora

Emery,
That would be simple. I'll try them this afternoon and let you know.
Richard Waters
 
Emery, Al, Rick, Steve, Patrick, John and
everyone else that responded to my question
of how to add a circuit to my coach.

Adding the 5th circuit turned out to be a non event
sort of like the Y2K. I just went to Home Depot
and got a Square D double 15 amp circuit breaker.
It fits in the same slot as the GMC OEM breakers.
The Seimens breakers looked like they would fit
as well. They had hundreds of them! I also got
a 20 amp double for expansion. I now have a slot
for a 6 the circuit. I don't know what that will be
yet, but I'm thinking.

I installed the breaker and ran a short length of
Romex to a new outlet I installed under the counter
for my new microwave/convection oven. It works
great.
Richard Waters '76 PB, Troy, MI

> > I think you can get them at an electrical supply house. Take one of the ones
> > you have ( a 20 amp) with you and have them get you a double for that circuit
> > breaker.
> >
>
> Al,
> Good idea. I'll give that a try on Monday.
> Richard
 
congrats... now you are an expert at elecctrical modifications.
al

> Emery, Al, Rick, Steve, Patrick, John and
> everyone else that responded to my question
> of how to add a circuit to my coach.
>
> Adding the 5th circuit turned out to be a non event
> sort of like the Y2K. I just went to Home Depot
> and got a Square D double 15 amp circuit breaker.
> It fits in the same slot as the GMC OEM breakers.
> The Seimens breakers looked like they would fit
> as well. They had hundreds of them! I also got
> a 20 amp double for expansion. I now have a slot
> for a 6 the circuit. I don't know what that will be
> yet, but I'm thinking.
>
> I installed the breaker and ran a short length of
> Romex to a new outlet I installed under the counter
> for my new microwave/convection oven. It works
> great.
> Richard Waters '76 PB, Troy, MI
>

>
> > > I think you can get them at an electrical supply house. Take one of the ones
> > > you have ( a 20 amp) with you and have them get you a double for that circuit
> > > breaker.
> > >
> >
> > Al,
> > Good idea. I'll give that a try on Monday.
> > Richard
 
You must log in or register to reply here.
Applied GMC
GMCMI Fall 2026 Rally

Share this page

Share this page
Top Bottom
Back