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Old 06-09-2023, 05:53 PM   #1
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Generator questions

I am building a 50 amp system with 2 roof top 1500 watt ACs with heat pumps from Recpro. I am not running solar and I am not planning on running my AC from the 100 amp/hr battery.
#1 Would you do a 30 amp or a 50 amp generator?
#2 has anyone ran an exhaust pipe up through the roof from an undermounted box?
#3 can you use the remote start feature to use the AC while driving?
#4 should I only enclose the bottom of the mount so it is better ventilated?

Thank you in advance!

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Old 06-09-2023, 07:57 PM   #2
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Quote:
Originally Posted by Runningbearbus View Post
I am building a 50 amp system with 2 roof top 1500 watt ACs with heat pumps from Recpro. I am not running solar and I am not planning on running my AC from the 100 amp/hr battery.
#1 Would you do a 30 amp or a 50 amp generator?
#2 has anyone ran an exhaust pipe up through the roof from an undermounted box?
#3 can you use the remote start feature to use the AC while driving?
#4 should I only enclose the bottom of the mount so it is better ventilated?

Thank you in advance!
1. The Recpro website specifies what type and size of generator is required, and recommends adding a soft start device in some cases. With two units, you should reach out to the vendor to get a specification for the right generator and combination of soft starts.

2. I would never run exhaust no matter how well secured and sealed through the conditioned air space of a bus.

3. My experience is limited to the rental of an RV with an Onan generator. The manufacturer said don't do it but we ran it while on route fifty across the Nevada desert, otherwise we would have died of heat stroke. Making sure the bus is sealed so eddy currents don't draw the exhaust back into the bus would be smart.

4. Adequate ventilation is key to operation and preventing overheating. What does the manufacturer say about enclosing the generator?
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Old 06-09-2023, 11:36 PM   #3
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Powering RecPro Units

Quote:
Originally Posted by Runningbearbus View Post
I am building a 50 amp system with 2 roof top 1500 watt ACs with heat pumps from Recpro. I am not running solar and I am not planning on running my AC from the 100 amp/hr battery.
#1 Would you do a 30 amp or a 50 amp generator?
#2 has anyone ran an exhaust pipe up through the roof from an undermounted box?
#3 can you use the remote start feature to use the AC while driving?
#4 should I only enclose the bottom of the mount so it is better ventilated?

Thank you in advance!
I suggest a 50A Generator, if you'll run both at once, to support the start-up & continuous loads.

Is this the unit you are describing?
Houghton A3800, 15k btu heat, 15k btu ac, dehumidifier


I have one RecPro unit (shown above) already installed on my roof, but I installed circuits for two of thse units. I'll answer a couple of unsolicited questions which may benifit you along the way.

The nameplate rating, on top of the unit, determines both the wire size & breaker size. Also useful to estimate load & consumption.

Our units' nameplate

On the nameplate above, the Minimum Circuit Ampacity is 17.5A, meaning #12 wire or *Larger. The Maximum Overcurrent Protection (MOP) is 25A, aka 25 amp breaker, Max.
Note: Wire size also determines the maximum breaker size, the #12 wire's protection limit is 20A. I chose to increase the size of the wire.



Parrallel to my roof, I ran two dedicated 25A circuits, one to each roof hatch (fore & aft), using #10mc. This size is rated for 30A, based on an ambient temp of 86°. I chose this increase as the unit allows for a 25A breaker AND this also helps the physical limit of the copper. The increased roof temperature decreases the wire's ampacity.


You may find additional insight, into your build, in the threads below.
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Old 06-10-2023, 02:03 AM   #4
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What's the procedure for getting one of these things up on the roof?
I'm thinking of wrapping it in a moving blanket and using a block and tackle. (?)
I have 3 Coleman's now but they're all 16-18 years old
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Old 06-10-2023, 09:36 AM   #5
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What's the procedure for getting one of these things up on the roof?
I'm thinking of wrapping it in a moving blanket and using a block and tackle. (?)
I have 3 Coleman's now but they're all 16-18 years old
---------------------

A block & tackle will work well.
I used a wench, a ramp and a sled.



My Warn wench utilizes a drill motor for power.


I anchored the wench to the opposite wheel.


12ft long DIY ramp is bolted to the bed of the farm truck. The sled is made from a rear seat-back. Two-hole L brackets overhang the sides to combat derailing.


Dura-Blocks, used for mounting conduit atop roofs, make great padded feet for the curved surface


The AC unit is ratchet strapped to the sled.







On past projects, I used an extension ladder & manuanlly pushed them up, like this. I'm gettin' too old for that 💩.
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Old 06-10-2023, 04:41 PM   #6
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lol Demac

i appreciate the last photo, as thats kinda the way i'd do it.

last time i swapped an ac, 2 guys on a ladder, first guy has the ac supported on his head and climbs the ladder, guy #2 right behind balancing the ac on #1's head. climb the ladder together, nice and slow.

back to the op. even though its more expensive, i'd go with the 50a gen. swapping power from 30 to 50a is pita. did you wire the 50a? do you have any 240v?

30a only powers one side of a 50a panel. if you have 240v appliances, its anyones best guess if it will work or let the smoke out. adapters are not universal..... stick with 50a and you never have to think about it.
run the exhaust pipe past the skirt of the bus, no need to go up.
i run my gen and power the rooftop ac while driving. no big deal.
enclose your generator as much as you can. they're noisy and any sound proofing you do you will appreciate. im re-doing my gen insulation right now on another thread.

good luck
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Old 06-10-2023, 05:20 PM   #7
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Depending what generator you buy it may come in a sound proofing box. The QD series Onans do. I have a 4000 watt Onan micro lite that is also in a sound proofing box, and has remote start. I have run it many times while driving for a/c. The 4000 watt is rated for only one rooftop plus other small loads. So if you want to run both the larger 50 amp would be the way I would go. I only need to power one rooftop.
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Old 06-10-2023, 07:57 PM   #8
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I have 2, on board, 6oa generators (16kW). They run at 240v, split phase. I have a Westinghouse i4500 that I use through my shore power inlet @ 30a single phase as well as a Powermate 2200, single phase..I haven't bothered making up any jumped connectors so the Westinghouse and Powermate only power A phase (L1). I'm in the building stage so all I need is lights, power tools and coffee and having only half my panel live is not really an issue. The Westinghouse is the ticket right now, it will run everything I need at the moment and it's relatively thrifty on gas. The big diesel generators run at 1.2 g/hr and that adds up. The litte Powermate does lights and the charge controller but also making a cup of coffee turns into an 'event'. It won't start an air compressor reliably and is basically just a backup that I exercise from time to time.

I really like that sled idea. I think I'll steal that to get my panels on the roof. My initial idea was a rope over the top, tied at one end to the panel and a cinder block on the ther side...again wrapped in a couple moving blankets.
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Old 06-11-2023, 03:28 PM   #9
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YIKES on ladders


The pic of the guy pushing the AC unit ahead is definitely over that ladders safe operating capacity. Read the labels on ladders, most have a 200 pound limit. A few have 250 pound limits. Those limits are calculated with the intended angle (think up against a house to get on the house). That low angle reduces the load limit and the weight of man and AC unit almost assuredly exceeds 250 pounds.


The other description of man one on the ladder with the AC perched on his head and man two ALSO on the ladder is certainly unsafe, overloading the ladder, and downright scary. Was there a guy with a beer standing near by telling people "watch this ****" or "quick break out your phone. We might have a youtube video any second"?
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Old 06-12-2023, 10:54 AM   #10
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I forget how I got my ac unit up there. I was young and dumb at the time so I'm sure it was similar to demac's picture with a ladder and brute force.

If I ever need to replace it, I'll likely use a come-along winch and straps from the one of rafters of the shop, back the bus underneath, and then lower it into place.
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Old 06-13-2023, 12:15 PM   #11
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Old School Hazadous Application

I'm liking the ramps more and more
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Old 06-13-2023, 12:43 PM   #12
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lolol in my defense of balancing the unit on my helpers head.

newer ac are a lot lighter than ones from 20 years ago. big, but lighter. removing the old one was shocking how heavy it was in comparison.... its been a few years but i remember like the old one was well over 100lbs, the new was 50ish...
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Old 06-13-2023, 04:34 PM   #13
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I used my Bobcat to put the a/c on the roof.
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Old 06-16-2023, 02:52 PM   #14
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Quote:
Originally Posted by Runningbearbus View Post
I am building a 50 amp system with 2 roof top 1500 watt ACs with heat pumps from Recpro. I am not running solar and I am not planning on running my AC from the 100 amp/hr battery.
#1 Would you do a 30 amp or a 50 amp generator?
#2 has anyone ran an exhaust pipe up through the roof from an undermounted box?
#3 can you use the remote start feature to use the AC while driving?
#4 should I only enclose the bottom of the mount so it is better ventilated?

Thank you in advance!

I have a smaller A/C package so I went with a Cummins Onan 3,600 LP generator. It's mounted between the frame rails and exhaust out the back corner behind bumper. I have remote start/stop inside. Works good with 1 roof air and can connect to a large stand alone bottle for long stays.
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