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Old 12-07-2019, 05:53 PM   #1
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1976 25' Tradewind
grover beach , California
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15000 BTU heat pump

I'm going to replace my A/C On Airstream, Alma 1976, 25 foot tradewind. I was looking at heat pumps? I wanted to replace my unit with 15 K, BTU domestic penguin II. However after talking with a local RV repair he said that my RV wiring could not support the 15 k BTU unit and to use 13.5 BTU? I was looking at the specifications and the units look similar. Has anyone put 15 k A/C on older trailer with 30 amp service?
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Old 12-07-2019, 05:59 PM   #2
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I would suggest you ask him to be more specific about which part of the wiring. I replaced a 13,500 with a 15,000 but on a 2007. At the time the AS dealer did state that they needed to do some checking to assure that the wiring between the unit and the thermostat would work....and that the wiring from the panel to the unit was sized correctly.

I did use an AS dealer if that makes any difference in knowing what is behind the walls or to call JC to find out from them. If you had a better idea of what or how much wiring he is referring to a better decision could be reached.
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Old 12-07-2019, 07:16 PM   #3
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2017 30' Classic
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Hi

You may have number 12 wire, or number 14 wire running to the A/C unit. Number 12 is fine for 15,000 BTU. Number 14 gets into the "that depends" region.

Bob
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Old 12-07-2019, 08:02 PM   #4
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Current Limits

A 15,000 BTU unit will draw at most 18Amps when voltage is a bit low at 110V. High Quality surge protectors will shut down below 110V. It will draw about 16 Amps when voltage is higher at 120+. 12AWG, 12 Gauge is rated for 41 amps, 14 is 32, and 16 is 22 so all would be fine. If your unit has 18 gauge wire I would be shocked but if it does then you'll have to replace the wire.

Summary: As long as your wire is 16 or thicker, you are good to go for 30Amp service. Make sure the breaker is 20 Amp and don't run a hair dryer, coffee pot or what not while the water heater (10Amp) and A/C are both on. If you do plan to do that switch the water heater to propane. Also you can get a bit of help from your inverter to handle the extra load so turn it on if you have so short term load.
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Old 12-07-2019, 08:09 PM   #5
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The 120 volt wiring should work just fine, if it will support a 13500 unit. The amp draws are nearly identical.
The 15K needs to have 12v going to it to power the thermostat, as well as have the thermostat wired separately. The 13.5 can use a manual ceiling assembly.
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Old 12-07-2019, 11:52 PM   #6
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Interesting, just curious how the different generations of thermostats are changing the wiring needs. I am not electrical so find it good to learn what to look out for what my mind finds simple connections are not so simple.
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Old 12-08-2019, 06:26 AM   #7
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Thermostat and control wiring

The thermostat and all the controls run off 12VDC at very low current draw (<100 Milli amp total) in RVs and 18-24VAC for nearly all HACV systems no matter where they are used. Internal logic boards, instruments and communication buses run at 1-5VDC so wire size is more a question of durability and ease of installation, really any wire size down to 24 gauge is fine from an electrical standpoint for the controls. In practice, less than 18 gets so small it is harder to make good connections, is easy to damage and corrosion is more of a problem.

For the earlier discussions the wire size applies to the primary feed to the heat pump not any of the control wiring.
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Old 12-08-2019, 07:00 AM   #8
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[QUOTE=BayouBiker;2313993] If your unit has 18 gauge wire I would be shocked

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Old 12-08-2019, 07:30 AM   #9
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Quote:
Originally Posted by BayouBiker View Post
A 15,000 BTU unit will draw at most 18Amps when voltage is a bit low at 110V. High Quality surge protectors will shut down below 110V. It will draw about 16 Amps when voltage is higher at 120+. 12AWG, 12 Gauge is rated for 41 amps, 14 is 32, and 16 is 22 so all would be fine. If your unit has 18 gauge wire I would be shocked but if it does then you'll have to replace the wire.

Summary: As long as your wire is 16 or thicker, you are good to go for 30Amp service. Make sure the breaker is 20 Amp and don't run a hair dryer, coffee pot or what not while the water heater (10Amp) and A/C are both on. If you do plan to do that switch the water heater to propane. Also you can get a bit of help from your inverter to handle the extra load so turn it on if you have so short term load.
Hi

..... errrr .... not so much ....

https://www.se.com/ww/resources/site...NEC%202011.pdf

You likely want the numbers in the 60C column. 15A is it for number 14

Bob
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Old 12-08-2019, 07:53 AM   #10
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Temperature limits explained

I don't mean to be pedantic but the 60C column refers to the heat limit of TW and UF wires with fairly thin PVC insulation which has a lower temperature tolerance and thus lower current limit before temperature build up becomes a problem for the insulation. TW and UF are not generally used in automotive / RV applications for current load carrying wires. They are used for low current control wiring. THW is more common and has a 75C limit but more typically 90C insulation is nearly always used for load carrying applications.
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Old 12-08-2019, 11:33 AM   #11
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You can buy a wire gauge tool at HD, Lowe’s, Amazon, etc. for cheap. Wiring requirements tables are a Google away. Shouldn’t be hard to figure it all out.
Heat pump back up “heat” mode is electric which draws AMPS.
Heat pump normal heat mode is only good in moderately cold temps. Low 40s and 30 degree temps will be electric heat for sure.
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Old 12-08-2019, 03:24 PM   #12
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I would be “shocked” if the power feed was not #12, (20A). the thermostat wiring might need to be relocated but it’s small and could be easily hidden, if you couldn’t fish it in.
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Old 12-09-2019, 07:31 AM   #13
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Originally Posted by BayouBiker View Post
I don't mean to be pedantic but the 60C column refers to the heat limit of TW and UF wires with fairly thin PVC insulation which has a lower temperature tolerance and thus lower current limit before temperature build up becomes a problem for the insulation. TW and UF are not generally used in automotive / RV applications for current load carrying wires. They are used for low current control wiring. THW is more common and has a 75C limit but more typically 90C insulation is nearly always used for load carrying applications.
Hi

We're talking about the wire that *already* is in the walls of the trailer. There is no choice about which wire to use in this case. The temperature rating applies both to the wire insulation *and* what's around it. Since it's behind a riveted in place wall, there is no way to know if *both* the wire and the other stuff are good to a higher temperature.

Bob
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Old 12-09-2019, 08:20 AM   #14
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That's a fair comment. If one is unsure about the wire, assume it is the one with lowest ampacity is the safe and sensible way to go.

For those who want to know what they are dealing with, generally one has access to part of the wire and the gauge and insulation type is printed/stamped on the wires each few inches.

Thanks for the correction, Bob
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Old 12-09-2019, 08:54 AM   #15
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I have a Dometic heat pump that I am about to put on my '76 and it has a FLA (Full Load Amps) of 13.2 in both heat and cool, with the 20amp line that I have on the AC now it will be fine.


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Old 12-15-2019, 11:20 AM   #16
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Just a thought, especially if something is near the limits of wire capacity, it is worth upgrading. (even to replacing the wire run itself with a dedicated line) For safety of course, but also for efficiency / proper running as with a fridge saying don't use extension cords.. a heavier wire will carry the required amps to have things running properly. Aside, but the same winch on my quad is rated at 2500 lbs with xx wire, but 3000 lbs with xxx gauge...
There have been times when various companies have cheaped out on wire to save weight or the cost of copper.. False economy as I see it.

Cheers,
Rick
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Old 12-15-2019, 07:03 PM   #17
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15000 BTU Heat Pump

Quote:
Originally Posted by larry smith View Post
I'm going to replace my A/C On Airstream, Alma 1976, 25 foot tradewind. I was looking at heat pumps? I wanted to replace my unit with 15 K, BTU domestic penguin II. However after talking with a local RV repair he said that my RV wiring could not support the 15 k BTU unit and to use 13.5 BTU? I was looking at the specifications and the units look similar. Has anyone put 15 k A/C on older trailer with 30 amp service?
I have a 1998--31ft Classic that had 13500 H.P. when it died in 2016 I upgraded to a 15000 and have had no problems. Incidentally I had the Microair Easy Start installed 2 years ago and it has enhanced the performance of unit. Good luck.
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