Info about Coleman Polar Cub 9200btu A/C?

[sdsknifeworks]

Does anyone have any experience with the Coleman Polar Cub A/C? It's about the mallest rooftop a/c unit I can find at 9200btu and for my little minibus I'd prefer to keep ti smaller. Just wondering if anyone knows the startup watts needed for this unit.

I have a '93 Chev minibus and am planning to take it through Oklahoma, Texas, New Mexico and possibly Kansas with several passengers this July and I'm not too eager to do that without some way to cool things down.

I already have a 200 amp alternator installed as well as a 3000 watt inverter. I won't be running the a/c while stationary, just while in transit.

I am WIDE open to suggestions here.

SDS

[roach711]

According to Coleman that unit draws 11.5 full load (start up) amps (1380 watts) and 1010 - 1260 watts running. Your 200A alternator will put out 2400 watts max and the inverter will claim about 10% of that in the conversion from DC to AC so you'll get 2160 watts at max alternator output.

On paper it looks like it will work but maybe someone else will chime in on pitfalls I'm not aware of.

[ol trunt]

I have seen several discussions on the coach forum in which folks have complained that their roof air did not work very effectively when used during driving. The consensus of opinions is that the rush of 60 mph wind through the evaporator did not allow for effective heat (cool) transfer and led to tepid cooling at best. Most shuttle buses have their A/C units either in the rear or on the side out of the gale, probably for this reason.

[nat_ster]

Originally Posted by ol trunt

I have seen several discussions on the coach forum in which folks have complained that their roof air did not work very effectively when used during driving. The consensus of opinions is that the rush of 60 mph wind through the evaporator did not allow for effective heat (cool) transfer and led to tepid cooling at best. Most shuttle buses have their A/C units either in the rear or on the side out of the gale, probably for this reason.

Interesting.

I would have guessed the opposite.

Nat

[Malkieri]

I have wondered about that, it looks to me like the shape would set up a bit of a vacuum like bubble or eddy currents that would not allow air to flow properly through the unit. I wonder if small scoops or angled vanes on the side to direct air through it would improve that.....

[bapos]

This is making my thought of doing a 120v mini split system all the more of a reason to do it? I seriously doubt that most 13k and 15k rv units put out that many btus. If I read correctly there is not organization or standard they have to adhear to (unlike residential units) so I would guess that a 9000btu or a 12000 btu mini split unit will cool a lot better than a rv unit.

I am REALLY wanting to test this theory?

[ol trunt]

Bapos, I PM'D you on this.

[nat_ster]

Some one needs to be the guinea pig with the mini split. If I ever do a AC in my bus, that's what I was going for.

I have a home owner that's looking at one. I may get to install one here before the heat sets in.

Nat

[roach711]

I found two threads on other RV sites where the AC unit was successfully powered from the alternator. One suggestion was to include a couple of house batteries to buffer the system and another was to have fuses and breakers protecting everything. Otherwise, looks like it should work fine.

Found another thread where an RV AC unit wasn't cooling well when driving. Pulling off the cover cured his problem so it does seem that airflow over the body can potentially be a problem. Looks like the majority run theirs on the road with no issues.

[roach711]

Originally Posted by nat_ster

Some one needs to be the guinea pig with the mini split. If I ever do a AC in my bus, that's what I was going for.

I have a home owner that's looking at one. I may get to install one here before the heat sets in.

Nat

Those split systems look to be a natural fit in a bus. Mount the condenser in a vented belly bin or on the rear bumper and hang the evaporator wherever it's convenient. The two I looked at pulled a lot less juice than the same sized RV unit.

[sdsknifeworks]

I hadn't looked at one of those split units but in my short bus I'm pretty limited on where I can place items outside. I have no belly storage for batteries either. I want to check actual alternator output before I buy anything but it's looking like I'll be saving up for this unit.

Thanks for the input guys. I was hesitant to even ask for fear of looking like a big dummy on this stuff.

SDS

[bapos]

I was looking for info on this over the net. Only thing I have really saw was a guy who put a mini in to a casita bumper pull trailer? Seems to work well and he did a very good job mounting it but I don't think it will be used pulling down the road like we do.

I found a mini a while back for 450 dollars on craigslist that I was going to buy to test this but Im not ready for it in my build at the present but there will be one for sure. I might have to get creative with the mounting but was thinking maybe removing a back window and putting in plywood to mount the indoor evap temp to see how it works?

The bad thing is most 120v minis only go to 12k in btus so anything more you have to go to 240v. Which would be cool to run multi evaps off one condenser but Im not upsizing my genny just to accommodate. Not really having any previous bus or rv experience I am not sure how well the acs work in bus and trailers. I know I really like it cold when Satan takes up residency here in Texas during the summer months. I will use my bus as more of a party/tailgate bus so having a few people in there and hot outside temps would like to make sure everyone will be comfortable. I know many people complain that rv units don't pull down super fast and sometimes struggle to keep up in hotter climates. Maybe you guys can confirm or deny this but working in the HVAC biz I know the mini spilt is an ideal thing for our size buses ... big and small.

Im hoping to progress in my build this year so hopefully I can get closer to testing this.

[sdsknifeworks]

I really appreciate all of the input. I was hesitant to ask for fear of sounding like I don't know what I'm talking about........which really, I don't.

So it sounds like the consensus is that, on paper anyway, this SHOULD work. Not ideal for cooling things down while in transit but better than nothing and I'm good with even a decent improvement over the nothing I have now.

Those split units look promising but without a good option for where to mount it I think I'll go with the roof unit. As soon as I can get the cash set aside I'll be ordering one up and will post up the results.

Thanks again for everyones thoughts on this.

SDS

[nat_ster]

Mount it on the roof. Make so the air passes through it without creating a air bubble around it. As has been said, the mini split only needs a few small lines through the roof, not a big gaping hole like the rooftop units.

IMO anything that is trying to expel heat should be on the roof for maximum air flow. After all heat rises.

This includes the main engine radiator, trans cooler, ect.

Nat

[roach711]

Originally Posted by sdsknifeworks

Thanks for the input guys. I was hesitant to even ask for fear of looking like a big dummy on this stuff.

SDS

The only dumb question is the one you don't ask. I'd guess that all of us here started down the bus conversion trail with a lot of enthusiasm but little actual knowledge. I've picked up volumes of information here that saved me from a host of pitfalls.

Until you raised the question I'd never considered running an AC unit off the alternator. Now i know it can be done so we both learned something.

[bapos]

Agree the only dumb one is the one that isn't asked.

There are a lot of SMART people on here that are willing to help. Granted some things people take with a grain of salt but over all its good info that one can experiment with enough to make a good decision with out shooting in the dark blind.

I enjoy throwing topics out that are not of the norm just cause theres always more than one way to solve a problems.

Its always good to share, or so my mother said.


Bapos

[sdsknifeworks]

Thanks again guys. I do have a question about those mini-split units. On the outdoor unit, would it have to be mounted vertically or could it be laid down flat? If laid down I would think there would need to be a spacer to allow air flow through and around it but only having seen pictures online I was just wondering. If it has to be mounted vertically that would be a pretty big projection off the top of my bus.

SDS

[Redbear]

Originally Posted by bapos

. . . . The bad thing is most 120v minis only go to 12k in btus so anything more you have to go to 240v. Which would be cool to run multi evaps off one condenser but Im not upsizing my genny just to accommodate. . . .

Some gennies can be re-wired for 120/240 volts. For example, the common Onan "Emerald" line of 6 kW RV gennies have two 120-volt windings, which are normally shipped wired in parallel. A couple of minutes with a service manual and hand tools are approved to put them in series, and you have your 120/240 volt genny. Be sure to balance your 120-volt loads on both sides of the neutral, as each hot lead will now only support up to 3 kW of 120-volt loads.

*** Disclaimer: The previous is an approved usage application. What follows is totally unapproved. ***

I don't really want to say this, because I haven't tried it, but it might be possible to get 120/240 volts from a pair of "twinnable" inverter generators. The special parallel pairing boxes for the Hondas are no more than plugging into both units to parallel the outputs for twice the 120-volt current. The inverter circuits must necessarily sense and synchronize the AC waves to be in phase. The reason for the special parallel load boxes is the insulated generator leads. They are configured so if one genny is running, and the other becomes unplugged, you don't have live male prongs waiting to bite somebody.

Anyway, my theory (and it is just that) requires that you have a 240-volt, center tapped auto-transformer, like Outback makes as an accessory for their off-grid inverters. If you connect one inverter genny on either side of the center tap, the inverters SHOULD sync 180° out-of phase for 120/240-volt series operation, in the same manner they sync in phase for parallel operation. But if anyone wants to be the guinea pig with your own generators, I did not tell you I saw it work. And I do not have any inverter gennies to try it myself, but I would if I did.

YMMV. Do not spindle, fold, or mutilate. etc, etc, etc.

[bapos]

sdsknifeworks


To answer your question the condenser has to be mounted vertical. They need very little clearance around them to pull enough air.

I think a multiple evap system like Daikin would be more ideal for our situaltions but as I still wonder if some of the larger stick n staple rvs have two 15k rv units and keep them cool depending on how they are insulated that, but those not being super efficient that if two 12k minis would do a better job?

One point to bring up. You need to make sure your looking at the invertor models. Yes they are more expensive but they require less power to run. So if your shopping for one of these make sure you get a name brand unit. There is a LOT of Chinese made junk. WIll they work... yes but if you cant get parts well they are not worth the money you pay.

My goal is to put one mini in down the road but my bus currently has a rv unit on top of the bus so I will replace it with a 15k unit as the current one is old and not sure how well it works. I would like to start off new and clean. I think the mini will be super easy to put in down the road.

I have read a lot of that rewire to get 240 on those gennys. I have a onan marquis 6500 and I don't think it is able to do that but I would love to put a bigger one in but its hard to justify a 4000 dollar generator in a bus I paid 1300 for but those can be easily moved to new places if I change buses.

[Redbear]

Originally Posted by bapos

. . . . I have read a lot of that rewire to get 240 on those gennys. I have a onan marquis 6500 and I don't think it is able to do that but I would love to put a bigger one in but its hard to justify a 4000 dollar generator in a bus I paid 1300 for but those can be easily moved to new places if I change buses.

I think you are right. I looked up the Marquis, and it is a sweet looking machine. The cabinet looks like the 12kW quiet diesels that we have 3 of on trucks at work. The older Emerald RV line I was referring to definitely can be re-wired for 120/240 per its service and installation manual. But they were old school, and did not have the microprocessor controls that your machine has. I can't find a schematic online, but it seems like the alternator section of your genny probably has a single high-current 120-volt winding.

Almost every page of Marquis 6500 literature repeats the claim that the genny is strong enough to start and run two 120-volt RV air conditioners. A web search did turn up a handful of headers of various forum posts with a few complaints of hard starting, though. I didn't read the links, so I don't know if they were referring to LP or gasoline models.