Home » Public Forums » GMCnet » Roof AC Operating Conditions
| Roof AC Operating Conditions [message #180447] |
Wed, 15 August 2012 22:33  |
Pryzl1
Messages: 100
Registered: November 2011
Location: Toledo, OH
Karma: 0
|
Senior Member |
|
|
Went camping last weekend and plugged into 30 amp shore power at the camp site. Started both Duo Therm roof AC units and they ran well for a couple of hours. Front AC unit then then continued to run but did not cool air -- ambient temp at best from the discharge into the coach. Shut unit off and managed to get through the balance of the weekend with only the rear AC unit operating.
I believe both AC units are 13,500 BTU units-older models. Looking for confirmation that I can only run a single AC unit when using 30 A shore power. If that is the case, why were both units able to run for a significant period of time and then one unit fail to produce cold air? The AC unit that "failed" last weekend today runs well and produces cold air. Is it true that the only way I can run both AC units simultaneously is when my 6000W Onan generator is operating or if I'm plugged into 50 A shore power?
This may be a no brainer question for experienced GMC owners but this is the first summer I have used "The Never Ending Story" since I bought it last fall.
John
1976 GMC Eleganza II - "The Never Ending Story"
Partial Restoration - a work in progress
455cc
NW Ohio
Member of the GMCMI, GMC Great Lakers Motorhome Club, GMCES and Dixielanders
|
|
|
|
|
|
| Re: Roof AC Operating Conditions [message #180477 is a reply to message #180447] |
Thu, 16 August 2012 08:36  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
|
Senior Member |
|
|
not sure why the front would just quit and start again. I can't help you with that one.
as far as the 30/50 amp. Here is my opinion:
you should be able to run both the A/C's off the 30 amp if conditions are right.
1. cord length is kept to a minimum.
2. cord ends are in good shape.
3. circuit supplying the 30 amps has good voltage.
4. do not run anything else in coach.
I would not run both A/C units at the same time, plugged into any length of 30 amp extension cord. I would keep the 50 amp cord/plug. just to a 30 amp adapter(of good quality), and then into the 30 amp outlet.
Really keep an eye on how hot the cords/and especially the adapters/cord ends!
I also just replaced the 50 amp cord end on my GMC, and found that even though it looked very clean, and in good shape on the outside. Once I took it open, there was a ton of corrosion on the wires/connections.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
|
|
|
|
|
|
|
|
| Re: Roof AC Operating Conditions [message #180486 is a reply to message #180483] |
Thu, 16 August 2012 09:55 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
|
Senior Member |
|
|
What I am trying to say:
wire length is a combination of all systems. how far is the outlet that you are plugging into from the panel. how long is the extension cord you are using.
I burnt off an end of a 25 foot 12-2 extension cord just running one roof A/C. looking back, I had it plugged into a outlet that was the furthest outlet from my main panel.
so even though in my mind i had it just on a shorter 25 foot extension cable, in reality, I had it plugged into 88 feet of 14-2 building wire. 25 foot of 12-2. and finally getting to my 15 feet of 6-3 hooked to the coach. that is over 113 feet of wire.
what I was told is that length of wire of lesser gauge(more resistance) causes voltage drop. causing the A/C to actually pull more amps to make up for the less voltage.
as a test I hooked a 25 foot extension cord into the outlet right at at my panel getting rid of the 88 feet run of wire to the other side of my garage. (had to move the gmc). and the cord end did get warm. but not burnt up hot like it had with the 88 feet hooked up.
I have since ran 6-3 wire to the other side of the garage where i park and added a full 50 amp RV outlet, and replaced/cleaned all connections.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
|
|
|
|
| Re: [GMCnet] Roof AC Operating Conditions [message #180498 is a reply to message #180484] |
Thu, 16 August 2012 10:43 |
|
|
Matt,
I responded to John offlist.
You're right on with the response. Of course, what we didn't know (and I
wrote this in my response) was what demand he ran into with regard to 110v
service. For instance, we can run to ACs at 30-amp if we demand nothing else
of the service and if the two units happen to ask service of the compressors
at separate times. What we don't know is if this was the case until they
both hit the compressors or if he also ran a microwave, hair drier or water
heater that is gas/110. As you know, the engine assist water heaters will
stay hot for quite a while before needing gas/110 to heat the water.
Of course, since his coach has been repainted we can also suspect the PO did
something else.
On our Holiday Rambler as well as our current Airstream coach we have to run
the ACs separately when hooked into 30-amp shore power if we also have the
water heater set for 110v or cook with the microwave.
My initial response to John was the response those of us in IT always start
with; "that depends". It's a great way to respond with any reply.
See you at Kentuckiana Kampground.
Byron
Matt Colie wrote:
>
>
> Pryzl1 wrote on Wed, 15 August 2012 23:33
>> Went camping last weekend and plugged into 30 amp shore power at the camp
>> site. Started both Duo Therm roof AC units and they ran well for a couple of
>> hours. Front AC unit then then continued to run but did not cool air --
>> ambient temp at best from the discharge into the coach. Shut unit off and
>> managed to get through the balance of the weekend with only the rear AC unit
>> operating.
>>
>> I believe both AC units are 13,500 BTU units-older models. Looking for
>> confirmation that I can only run a single AC unit when using 30 A shore
>> power. If that is the case, why were both units able to run for a
>> significant period of time and then one unit fail to produce cold air? The
>> AC unit that "failed" last weekend today runs well and produces cold air.
>> Is it true that the only way I can run both AC units simultaneously is when
>> my 6000W Onan generator is operating or if I'm plugged into 50 A shore power?
>>
>> This may be a no brainer question for experienced GMC owners but this is the
>> first summer I have used "The Never Ending Story" since I bought it last
>> fall.
>
> John,
>
> The all the little hermetically sealed units have a thermal overload for the
> compressor. If the supply voltage is low, the compressor will run hotter.
> These things are kind of a course generality. So your rear unit just may be
> more able to tolerate the lower voltage.
>
> If you were running two roof units on a 30amp feed, you probably did have low
> voltage unless that campground was very well wired.
>
> Matt
>
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
--
Byron Songer
Full-timing to enjoy the USA
Former owner but still an admirer
GMC paint schemes at -
http://www.songerconsulting.net
|
|
|
|
| Re: Roof AC Operating Conditions [message #180500 is a reply to message #180484] |
Thu, 16 August 2012 10:59 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
[quote title=Matt Colie wrote on Thu, 16 August 2012 07:47]| Pryzl1 wrote on Wed, 15 August 2012 23:33 |
Went camping last weekend and plugged into 30 amp shore power at the camp site. Started both Duo Therm roof AC units and they ran well for a couple of hours. Front AC unit then then continued to run but did not cool air -- ambient temp at best from the discharge into the coach. Shut unit off and managed to get through the balance of the weekend with only the rear AC unit operating.
I believe both AC units are 13,500 BTU units-older models. Looking for confirmation that I can only run a single AC unit when using 30 A shore power. If that is the case, why were both units able to run for a significant period of time and then one unit fail to produce cold air? The AC unit that "failed" last weekend today runs well and produces cold air. Is it true that the only way I can run both AC units simultaneously is when my 6000W Onan generator is operating or if I'm plugged into 50 A shore power?
This may be a no brainer question for experienced GMC owners but this is the first summer I have used "The Never Ending Story" since I bought it last fall.
|
John,
The all the little hermetically sealed units have a thermal overload for the compressor. If the supply voltage is low, the compressor will run hotter. These things are kind of a course generality. So your rear unit just may be more able to tolerate the lower voltage.
If you were running two roof units on a 30amp feed, you probably did have low voltage unless that campground was very well wired.
Matt
The answer Matt gave you is most likely the reason your front compressor tripped off on its internal overload. When the compressor cooled down enough to restart it couldn't because the voltage was too low on startup so it just tripped the internal over load each time it tried to start. I rewired my 2 air conditioners so I can plug the rear A/C into a seperate 20 or 30 amp campground box when only 30 amp connections are available 2 AC units will not run on 30 amps in hot weather but can function in cool weather. The front unit is a 13.5 but the rear should be an 11,000.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
| Re: Roof AC Operating Conditions [message #180501 is a reply to message #180447] |
Thu, 16 August 2012 11:11 |
zhagrieb
Messages: 676
Registered: August 2009
Location: Portland Oregon
Karma: 0
|
Senior Member |
|
|
John,
You are pushing it asking two units to live happily on a single 30A service. Especially since your units are older and since you don't know what voltage the campground is supplying.
Glenn
Glenn Giere, Portland OR, K7GAG
'73 "Moby the Motorhome" 26'
|
|
|
|
|
|
| Re: [GMCnet] Roof AC Operating Conditions [message #180518 is a reply to message #180509] |
Thu, 16 August 2012 12:29 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
This is from the archives for 6/28/11:
Back before 50A service became so common (up until the mid-90's,
really), there were a lot of ideas for running two A/C's with 30A
service:
Some were automatic switches that would allow only one to start at a
time, hoping 30A would serve one while the other was starting.
Sometimes worked, sometimes didn't.
Another automatic device ran one A/C for a while and then the other.
This was most commonly done with a manual switch, as on my '90
Airstream Land Yacht. Obviously these were not a very good option --
worse than having only one A/C really, if one considers the down time
during switching, not to mention the inconvenience.
The option I chose, starting with the Airstream, was to provide a
second, independent, circuit, including CB panel, for the rear A/C. A
10g. cord was adequate for that. Most campgrounds had both 30A and
15A service long before they had 50A service. But for those locations
that did have 50A, I modified a plastic tool box with a 50A pigtail
and both 30A and 15A sockets so I could take advantage of that better
power source. Stick Miller's coach has such an independent circuit.
We (I) haven't yet examined how it's implemented.
If I had a 50A coach, I'd convert it to the 30A+15A arrangement
because I've always found it much easier to manage a 30A and a 15A
cord than a single 50A, even when I had the SOB in which I installed a
very automatic reel.
JMHO,
Ken H.
On Thu, Aug 16, 2012 at 12:41 PM, Larry Davick wrote:
> Somebody here has the rear AC on a separate 110v cord to plug in to shore
> power. It doesn't change the power to the pole but it does increase the
> size of the pipe from the pole to the coach.
>
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
| Re: [GMCnet] Roof AC Operating Conditions [message #180539 is a reply to message #180486] |
Thu, 16 August 2012 16:18 |
|
|
Jon,
As to resistance/voltage drop/amperage drain issue you were told correctly.
Last year I visited with a brother-in-law who let me plug into his 110v/20
amp outlet to run my AC on the coach. This year I did the same thing. The
difference was that I didn't have my short cord with me and he only had a
long cord from the house to my parking spot.
The net was that the fan on the AC would run but when the demand for amps
picked up the compressor wouldn't kick on. The wire on the extension cord
would get quite warm but the circuit breaker didn't trip. I wound up running
the genset for a few hours until it was cool enough to open windows and run
the exhaust fan.
--
Byron Songer
Louisville, KY
http://www.gmceast.com
or check out
http://www.gmcgreatlakers.org
Jon Roche wrote:
>
>
> What I am trying to say:
>
> wire length is a combination of all systems. how far is the outlet that you
> are plugging into from the panel. how long is the extension cord you are
> using.
>
> I burnt off an end of a 25 foot 12-2 extension cord just running one roof A/C.
> looking back, I had it plugged into a outlet that was the furthest outlet from
> my main panel.
>
> so even though in my mind i had it just on a shorter 25 foot extension cable,
> in reality, I had it plugged into 88 feet of 14-2 building wire. 25 foot of
> 12-2. and finally getting to my 15 feet of 6-3 hooked to the coach. that is
> over 113 feet of wire.
>
> what I was told is that length of wire of lesser gauge(more resistance) causes
> voltage drop. causing the A/C to actually pull more amps to make up for the
> less voltage.
>
> as a test I hooked a 25 foot extension cord into the outlet right at at my
> panel getting rid of the 88 feet run of wire to the other side of my garage.
> (had to move the gmc). and the cord end did get warm. but not burnt up hot
> like it had with the 88 feet hooked up.
>
> I have since ran 6-3 wire to the other side of the garage where i park and
> added a full 50 amp RV outlet, and replaced/cleaned all connections.
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
--
Byron Songer
Full-timing to enjoy the USA
Former owner but still an admirer
GMC paint schemes at -
http://www.songerconsulting.net
|
|
|
|
Goto Forum:
Current Time: Tue Oct 08 01:50:45 CDT 2024
Total time taken to generate the page: 0.01281 seconds
|
GMCforum
Search
Help
Register
Login
Home
