Hello. My 77 28' is in need of a new A/C unit. The unit we have works but has never been able to keep up with the summer heat in the south. I see a lot of my size RV's have two A/C units and that my be the only way to keep it cool. I am thinking of going with a 15 BTU unit and see if that will keep it cool enough. Any advice on what manufactures are best?
I would like to stay with one if possible because my Gen set will only power one at a time and I would like to keep from adding another 500lb to the roof if I don't have to.

quote:

Originally posted by Neil T.:
Hello. My 77 28' is in need of a new A/C unit. The unit we have works but has never been able to keep up with the summer heat in the south. I see a lot of my size RV's have two A/C units and that my be the only way to keep it cool. I am thinking of going with a 15 BTU unit and see if that will keep it cool enough. Any advice on what manufactures are best?

At 28 ft, you are right on the edge of needing two AC units. But, there are measures you can take. Windows can be insulated with Reflectix bubble foil, particularly the ones the sun hits. Awnings help, too. The windshield and cockpit windows can be blocked with reflectix or their own curtain. We replaced the OEM curtain with one Susan made of insulated drapery material.

You could also isolate the cockpit with another curtain going straight across behind the driver and passenger seats. Since that space is not used, why cool it?

You could also close off the bathroom and just put up with the heat when you use it. This is particularly effective if yours is a rear bath unit.

When we had a shorter SOB with a rear bedroom, we closed it off during the day except for naps.

Is your roof brilliant white? That can make a stunning difference.

As far as brands, I have had several Colemans and Dometics, and prefer the Dometic because of its 3-speed fan motor. Quite often, in high humidity and high heat, an AC will ice up on low fan speed and high is too noisy or drafty. The medium speed is more pleasant, but never iced up for us in irrigated areas of the desert or in AZ during the monsoon season.

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I would like to stay with one if possible because my Gen set will only power one at a time.

There are ways to run two off of one gen or a 30 amp cord.

I did a homebrew that operated one, then the other, then back again, etc. It used a clock motor that turned a cam wheel that operated microswitches which triggered relays. All off the shelf except the cam.

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I would like to keep from adding another 500lb to the roof if I don't have to.

FIVE HUNNERT POUNDS?

Personally we like the Dometic Penguin. We installed one on our 35ft bus 10 years ago (with optional heatstrip) and it worked good (Myrtle Beach SC for example) to cool the front half of the bus. We closed the back bathroom off, so it had to cool about 30 feet. We agree with BillH, it is VERY important to cover the windows. That silver bubblewrap works wonders (big difference in GA hot summers), use your awning and try to park under a tree. We made some thick curtains with extra backing, cardboard works too but not very attractive. And a white roof is excellent.

I have the Dometic Penquin - low profile, and the shroud design helps keep crud out of the coils. Do NOT get the mechanical thermostat shroud, as I went through 3 mechanicals and had to go to the electronic - which is on a different shroud.

Mine is also 28' with one A/C, and I cover the windows and keep the bedroom and bath door closed. It kept me comfortable in 107° in Nebraska.

quote:

Originally posted by Rusty:
I have the Dometic Penquin - low profile...................

Low profile is something to consider for anyone who might go solar in the future. Shading really hurts solar panel output, especially in Winter when the sun is low in the sky. Under 10% of a panel shaded cuts its output by over 50%.

While we are on this thread...

Last year while in DC I decided to turn on my Coleman Mach A/C unit. These are the original, standard profile, 15,000 BTU Air Conditioners for my coach.

Anyway, once I kicked it on I heard what sounded like a heavy load factor. I figured my electrical at the pole was junk, and it really wasn't very hot anyway, so I decided to wait until I had a better power supply to check it.

DC was late in the year and I never did get around to looking at it. Out of sight, out of mind.

So I decided to look at it last week and I turned it on. Same thing... I pulled the interior cover off and grabbed a hold of the squirrel cage and spun it. Nothing dragging, seems very loose and easy to spin.

I turned it back on with the squirrel cage still spinning and it started up. I shut it off and tried to restart it. No dice... If I spun it first it would restart when I turned it back on. Even though it started up, it still sounded like it was laboring during the startup phase.

Researching it on the net it seem that I need a Coleman Hard Start Kit. It appears that a lot of the Coleman units came without this Hard Start kit as it was considered an add on option.

Has anyone installed one of these? Besides greasing it again... does anyone have a recommendation, diagnostic procedures or manual on these units?

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RVP Coleman A/C Hard Start Kit

If the A/C is hard to start-up or is subject to low voltage and spikes then install this kit. Also useful if short cycling is a problem.

Comes with complete instructions

Part #'s
7333-6201 191 61091

Some of your description sounds like it could be just the fan motor. I would narrow it down to either compressor or fan motor first. I have had to replace at least one fan motor when I was a perm in a low voltage park. They seem to go first, for some reason.

I think I would check connections topside and take a clamp amp reading on both fan and compressor. Then possibly replace the OEM caps first. Hard start kits can be hard on compressor motors. The cause should be addressed first.

However, I am not totally down on hard start kits, and may even use one myself to use an AC with our Honda 2000. I may avoid the hard start kit and use the 2500 PSW inverter, and let the Honda run to keep the batteries up whenever the AC is used. This will be easier on both the AC and the Honda, and will avoid running the Kohler Klanker, which is right underneath the bedroom and surely annoys others. If there are quiet hours, the Honda can sit in the back of the toad with a stealth exhaust extension.

I don't like the ad saying the kit is appropriate for short cycling. The cause of the short cycling needs to be addressed first, usually by air flow management. Putting one of those kits on a short cycling AC will shorten the life of the compressor.

Does your AC use a plug or is it hard wired?

quote:

Originally posted by bill h:
Does your AC use a plug or is it hard wired?

Hard Wired In.

Sound like the star cap on the fan motor. Avoid the 'hard start" kit, as they are used to mask other problems

RV units may be different but we just replaced our home central system and all the units we compared have the hard start unit. Here is the description from American Standard:
A hard start kit is basically a start capacitor that has a relay attached to it. Your compressor has 3 windings on it. The start winding, the run winding, and the common winding. What your run capacitor does is create a favorable phase shift of the incomming power across the start winding so it kind of gives you that 3 phase power, but with only 2 hot legs. This allows the compressor motor to start turning. If you have ever seen a motor that has a bad run capacitor, it will just hum until it trips on the internal overloads. What the hard start kit does is kind of the same thing the run capacitor does, but it discharges a quick pulse of power, usually a second or two, and it get's your compressor up to speed much faster than just a run capacitor.

If you have lights dimming when your compressor comes on, by all means add one. I will not install a condensing unit without already including one in my bid. It will increase compressor life and not put a strain on your electrical back to your panel because your not drawing locked rotor amps like you did with out the hard start kit.
Looks like a bad or weak run capacitor may be the culprit.

Long ago i heard that you should start and run your ac at least once a month to keep it in working order.

I have an '88 33' unit -replaced both A/C two years ago with carrier 15k units -- very easy install -- my gen set is the 6500 watt original unit and it powers both units nicely, matter of fact the 30A site power also powers both unit at the same time, start one let it run for a few minutes and then start the other. If I forget and make coffee - then I'm resetting the breaker on the power pole

I got lucky and found a good used Dometic 6003 (low profile) unit with a heat strip on Craigs list for $300. It is 13.5 BTU and works great. I plan on installing both units and converting the RV to 50 amp service. I figure this will save a vacation one day if the A/C unit quits. I will move the center one to the rear and put the new (to me) one in the front. I will post my plans on converting in another post.