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AC replacement


neilp
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I've just ordered a replacement AC unit for the camper area. The original 7100 btu Coleman still works but struggles a little to keep up in the Texas heat when it's 95F+. Also I want to reduce the weight on the roof as the original unit weighs over 100lbs. I ordered an Advent ACM135 (it is 13500btu which is a bit much perhaps) but it only weighs 68lbs and draws about the same as the Coleman Power Saver units. I think I will install a start cap and maybe a soft start while I have the opportunity as I may want to run on a generator at some point in the future - although I mostly camp in state parks at the moment.

 

I'd like to hear some advice as to how best to remove the old unit from on top of the camper. I'd like to keep it in one piece in the hope of reselling it for a few $$ if possible. I'd also like to minimize the stress on the roof as it's almost 30 years old!

 

TIA

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Each AC unit will be slightly different and it would be best to see if you can find installation instructions on the internet for your specific unit. 

 

If you have some experience with simple electrical connections and using tools it is not a hard job. You remove the interior portion first by removing the cover panel, disconnecting the control wiring, and disconnecting the electric connections inside the electric box. There will be a vent connecting the inside and outside portions of the AC which will have to be disconnected from inside. There will then be 4 or more long hex bolts which have to be undone from within your motorhome. I push the AC unit up from inside the motorhome to detach the seal from the roof membrane; the seal sticks to the roof membrane and it is hard for me to pull up such a heavy unit so I push from inside. 

 

You have to remove the shroud from the unit on the roof before removing. Getting the unit off the roof is a 2 person job as it is heavy and awkward. I've done it alone but would not recommend it. I used 3 ladders and created a more gentle slope which I slid the AC down. It worked but like having a helper instead. You do not want to slide the AC on your roof because the weight could cut a hole through your roof membrane. 

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Times have changed your new one will be a lot more efficient I would not worry about "start caps". They all are designed to fit a 14X14 vent. You'll need a friend because it will not fit through to hole But with at least two people it's not a bad job. The stuff that holds it down is all inside you'll have to remove the plastic stuff and disconnect the wires then kind of pass it to your "friend" on the outside. The gasket will be junk if it isn't with the new AC unit be sure to order one ahead of time. In the gasket kit there is a long piece of gasket and a 14X14 gasket for the hole the long piece fits under the back of the AC unit.

 

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 Mine only had one quick disconnect. Remove cover inside. 4 screw in threads, remove the outside cover and it slides right out of place.. Mine had a tin vent I removed which made it easier to move around. 

 

 If I had to take it off the roof I would definitely get more than one person. Mine is 20 foot and it has a 13500 A/C. It will freeze you out on low.

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Thanks for the replies - I am not too concerned about the electrical side of things, I think that should be easy enough. I am more worried about getting the unit off the top of the camper without damaging the roof - I'd rather not have to stand on too much it as it likely does not have the strength it once did ... I don't have access to a hoist or anything that could help so it's going to be my son and me up ladders!

 

I think a start cap is worth the $30 investment  - I'd rather fit one and not need it than have to install one later with the unit on the roof. It should reduce the initial load considerably as the plan is to use a small inverter generator in the long term. I have the original Kohler now and while it runs it's not economical and it's noisy. I am tempted to add a soft start kit too, but they are a bit pricey for what they are. I can't help thinking that I could make one with a couple of relays and a simple timer circuit - but my electronics classes are a pretty dim memory and I'd hate to screwup my new AC unit! For those not familiar with them a soft start kit delays the fan kicking on for a few seconds after the compressor. This reduces the initial load. 

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I wouldn't go smaller than 2500w (even that size may be too small) on the inverter generator to run a 13500btu AC even with a start capacitor. Research the internet for actual user experiences trying to run an AC that large on the popular 2000w inverter size. You will find anecdotes about people getting their AC to run on the 2000w but most will report it will not work. 

 

I got my 2000w generator to power a 13500btu AC and thought it was going to work. It was unable to start the compressor a second time after the AC had been cycling. I installed start cap and it still was not able to keep the AC cycling. I tried it on a hot day and the generator could not get the compressor started at all. 

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Like your Kohler the old AC is old school. Things have improved a lot! The big plus with a start cap is over coming the compressor head pressure on a restart that is the highest current demand the rest of the stuff blower fan is not so much. The AC start cap is part of the overall design of the AC And being a mobile unit I would think they would take that into consideration. I agree with a 2500 watt generator it is still small enough to be portable once you pass that line they take a big jump in weight and size.

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As mentioned elsewhere, I'm currently using a Champion 2500w inverter generator to run roof A/C and fridge on the road. Seems to be working well, and I really like the light-weight and small footprint on my rear rack. On the flip side, this gen is loud when working near peak load, and the 1.1-gal tank lasts only a couple of hours—need to fill up whenever filling the truck tank. (My roof AC is a 2010 Coleman Mach Low-Profile 9,000 BTU w/EasyStart 364.)

 

 

 

 

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20 hours ago, Ctgriffi said:

As mentioned elsewhere, I'm currently using a Champion 2500w inverter generator to run roof A/C and fridge on the road. Seems to be working well, and I really like the light-weight and small footprint on my rear rack. On the flip side, this gen is loud when working near peak load, and the 1.1-gal tank lasts only a couple of hours—need to fill up whenever filling the truck tank. (My roof AC is a 2010 Coleman Mach Low-Profile 9,000 BTU w/EasyStart 364.)

 

 

 

 

I am surprised the 2500 is working near peak load with 9k and Easy start.  Is your Coleman mach called the Polar Cub? 

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Lot of science involved with generators and start current. Many are capable of generating a good bit more starting watts than running watts. One plus with an AC is it's start cap that helps the generator and the fact the generator is all ready running at 3600 RPM.

 

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