help with coleman basement units

ruthi · November 27, 2009, 05:24:56 AM

We have 2 coleman basement units that are 2 tons each. Is one unit enough to make it plenty cool? We dont have any road airs. We have done overkill on all the insulations in the bus though. And we only have 3 windows, tinted in the bus. Also, if we installed the 2nd unit, would it need to be vented separately, or can it run through the same duct work at the same time. We are having a hard time getting everything to fit in the basement. We definetly want enough air to stay plenty cool, especially when going down the road. We also want to have as much water and holding capacity as possible. Right now we have allowed for 100 gallons of fresh water, and 100 gallons of gray, black tank. Using it the way we do, with 4 people, we could use more, if possible. But, working and moving a lot, in most cases, we have the opportunity to dump about once a week. We are putting in a washer and dryer,inside the bus, which will be used occasionally. But, to make a long story short, we are running out of compartment room. We have to keep one compartment availiable for tools. We are a little concerned too that if one air unit breaks down, it would be nice to have a back up. Any advice from those that have gone through this?

Len Silva · November 27, 2009, 06:07:24 AM

I would definitely want two. If you find yourselves in Arizona or Florida, one will not get it, no matter how well insulated you are. When I had my 4104, I used two Dometic basement units, both connected to the same distribution system with a two stage thermostat. When one would do the job, that's all that ran, when it needed two, the second would kick in. I also installed a double throw switch in the control circuit so that I could change which unit had priority. I would switch them once a month or so, to keep the wear even on them.

RickB · November 27, 2009, 06:15:28 AM

Ruthi,

I am hoping Nick will confirm my suspicions but I have two colemans that take up almost my entire 2nd bay and I have certainly felt that having both running on high has not been adequate at times. If you are parked in the open with no shade available and it gets above 80-90 degrees I would say you will struggle with both running on high. You are doing one of the best things you can do by insulating your ductwork mine is not insulated and only Nick or someone who has been able to see the results firsthand will be able to verify what kind of help insulating will be, but insulating certainly can't hurt.
So my vote is install and use them both...

As far as your capacities go. There are too many variables for anyone to guess better than you. Do you take "army" showers?
Meaning do you get your hair wet, shut the water off, shampoo, turn the water back on to rinse etc.? or do you just hop in and take a shower? Do you wash alot of dishes or use paper plates? Those kind of questions lead to vastly different consumption levels.

I know it's hard giving up the bay space for the 2 colemans but it is worth it in my opinion. The builder of our conversion decided to cut the bus down the middle lengthwise as far as AC, electrical, etc. which means my colemans are on opposite sides of the bus. If Nick or someone has devised a better plan maybe you can get away with using half of a bay for the colemans. Just a thought. Good luck and I hope this is helpful to you.

Rick

RickB · November 27, 2009, 06:22:17 AM

Ruthi,

We had a washer dryer rig in our last bus and we used it... ONCE!

The darn things only hold about one pair of pants in them and man did ours use water and electric. In hindsight , we would have used that space for something else and found local laundromats. Maybe the design has changed but the whole concept seemed a bit flawed amd limited by the size of the washer and dryer.

They are also difficult to winterize well. We really struggled to get every last drop of water out of ours and we obviously weren't going to use RV antifreeze in our washer. So, it froze with a small amount of water and broke a bunch of stuff internally.

Rick

ruthi · November 27, 2009, 06:22:44 AM

Rick, how big are your units? Ours are 24k btus. I know we dont want to be hot. We had an airconditioning man come out to give us advice. He said the 2 ton units are what they install in some houses, and 1 was more than enough. I knew I had heard of those on the boards that said they had two installed. As far as water capacity, we take one minute showers, use paper plates, and conserve as much as possible. We have a 60 gallon tank right now, and it will usually last around 5 days for 4 of us using it sparingly.

ruthi · November 27, 2009, 06:26:55 AM

Rick, we have a front load washer and dryer to install. We work on the road most of the year, so it will get a lot of use, and it stays running or plugged in year round. I hate having to use the washers at the truck stops, so, when we go there to dump and fill, we can use our own set, then dump and fill again. Every now and then, we are in areas where it is hard to find a flyin J, and we have to stretch the water a little farther. Camp grounds are hard for us to dump, because of the size of bus, and trailer we tow.

ruthi · November 27, 2009, 07:12:42 AM

Len, what size were your units? What size ducting did you use? We are getting so much conflicting advice from so many different professionals, it is getting crazy. Dont want to have to do this twice.

belfert · November 27, 2009, 07:37:25 AM

If you run both units at the same time through the same ductwork you'll need to basically double the size of the ductwork.

If you don't have enough airflow the units can ice up and quit producing any cold air.

Len Silva · November 27, 2009, 07:39:27 AM

Ruthi,

I had two 15k in a 35' bus which was not all that well insulated. They struggled on a hot day, particularly when underway.

Some years ago, Consumer Reports had a section where you could calculate the size of a room air conditioner. When I did the calculations for a bus, (all four sides of the "room" exposed, no attic, window area etc) the numbers were high (don't remember exactly). Throw in a steady 70 mph wind and they go up to very high.

I can cool my 1500 square foot house in Florida with three tons, but it would be marginal for a 320 square foot bus.

Len

Len Silva · November 27, 2009, 07:40:51 AM

Quote from: belfert on November 27, 2009, 07:37:25 AM
If you run both units at the same time through the same ductwork you'll need to basically double the size of the ductwork.

If you don't have enough airflow the units can ice up and quit producing any cold air.

Yes, absolutely, you have to size the ducts for both units. I should have thought to mention that.

ruthi · November 27, 2009, 07:49:55 AM

Hmmmm, well, right now, we have 52 inch total for the duct which is 10 inches more than needed, so we would have to increase it to 32 more inches to have them flow together? Or, make a separate ductwork for the 2nd unit. Does increasing the amount of vents, and, or having more vents as well as larger vents cut down on the amount needed?

TomC · November 27, 2009, 09:08:26 AM

I have three 13,500btu Coleman roof airs. I also have 2.25" of sprayed insulation, single pane lightly gray tinted windows. Driving in 108 degree weather (the hottest I've been in), two of the roof airs will do the job. I have tried all three running, then my wife has to put on a sweater. I don't believe you'd need two of the 2 ton units-over kill. I would install one and give it a season of work. If you feel you need more, Duotherm makes the truckers A/C's which is a self contained unit that can be either mounted in the bay or inside at the base of a cabinet. They make them in 7, 11 & 14,000 btu/hr. Personally, I'm using two of the 15,000btu Penquins that are made for ducting with remote thermostats, mounting them in the basement of my truck. If they don't cool enough, I will also add the trucker A/C to supplement them. I'm using Penquins basement mounted since they cost half of what a basement unit does, just duct the in and out air, and the condenser hot air can be ducted also since the Penquin uses a squirrel cage blower that can easily be ducted. Then if repair is needed, anyone knows how to work on roof top units, or they can easily be replaced, as compared to a basement unit. As of the first of the year (when I'll be buying my Penquins) the freon is being changed from R22 to more environmentally friendly R404A (I believe). Good Luck,TomC

Nick Badame Refrig/ACC · November 27, 2009, 10:15:05 AM

Quote from: ruthi on November 27, 2009, 05:24:56 AM
We have 2 coleman basement units that are 2 tons each. Is one unit enough to make it plenty cool? We dont have any road airs. We have done overkill on all the insulations in the bus though. And we only have 3 windows, tinted in the bus. Also, if we installed the 2nd unit, would it need to be vented separately, or can it run through the same duct work at the same time. We are having a hard time getting everything to fit in the basement.

Hi Ruthi,

First, you say you have the 2 ton coleman basement units. If so, they are 26, 000 btu's each and each have 2 compressors in them that

require [2] 120v power legs/curcuits each to operate. My first question is, do you have enough power to operate both basement units together

off your generator while rolling down the road?

In my coach, I have two 15,000 btu single HP units [stacked] which add up to 2 1/2 tons [30,000btus] of air. Not 26,000 btu's like a duel coleman.

Even my house A/C units are not enough A/C for over the road use.. Thats why some of us choose to leave our 11 ton bus OTR air system operational.

Now, if you have enough power to run 2 duel coleman units for road use, your next issue is duct design and proper insulation to have a system

that will proform where you need it. Obviously, while traveling down the road, your biggest heat load/loss is the front windshield and the air leaks

around your entrance door, windows, and the front dash area which none are insulated or very little... So, you will have to incorperate a way to direct

most of your CFM's to the front somehow and be able to redirect it back to the rest of your coach when you are parked.

Not trying to hamper your plans at all. I'm just trying to give you the the proper ways to accomplish what you need for cooling underway..

Good Luck
Nick-

ruthi · November 27, 2009, 11:16:50 AM

So, right now we have a powertech 12 kw gen. And you said you have 30000 btu. Are you able to keep yours cool with just that running? If it is necesserry to have them both we will, just didnt know if it would be needed. Obviously, ours would be a little less with only one 2 ton. If you get a chance, can you please call and talk to hubby? I think you have the number from other post. Thanks for your time.

robertglines1 · November 27, 2009, 11:42:25 AM

Nick is the professional....For what its worth we have 2 14700 in the basement ,one ducted to the drivers area,one ducted to the kitchen area;also one 10000 in the bed room area...We are total electric with a 7.5 kohler gen set... all run OK and other appliances also.on a 100 degree day they will hold 72 degrees on the road..we also have a very small ceiling fan mounted above the driver to pull the heat off the ceiling(helps a bunch)good luck!