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2008 Fleetwood: 500 btu coleman roof mount..rv..functioning properly…

Same 2008 Fleetwood has 2...
Same 2008 Fleetwood has 2 13,500 btu Coleman roof mount ducted ac's. In the heat of the day it can get into the mid 90's inside the coach. I took the coach to an RV service center, Coleman claims the ac's are functioning properly. We are not able to use the MH in the spring and summer because of this problem. Will swithing to 15,000 btu units solve my problem, or is there something else going on?
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Answered in 18 minutes by:
5/10/2011
RV Mechanic: Randall, RVIA Certification replied 11 years ago
Randall
Randall, RVIA Certification
Category: RV
Satisfied Customers: 28,726
Experience: RVDA/RVIA Master Certified Technician with many years experience.
Verified
Hi: Thank you for coming to Just Answer with your question. My name is XXXXX XXXXX perhaps I can assist you with this issue.

Are these ducted units or direct discharge? What was the delta temp when they tested them or did they? This is the difference in the return air temp and the discharge air temp.

Do you have any idea what the voltage is at the site where you are plugged in or do you move around? Low voltage is going to affect the performance of these units. Please get back to me with this so I can more fully assess what the actual situation is. R.J.
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Customer reply replied 11 years ago

The units are ducted. I was told when they were tested they were within 20% of the outside temperature at the ac unit itself, but the coach does not get cool. The first time we noticed the problem we were plugged into a 50 amp service in an RV park. Right now I am plugged into a 40 amp service at my home, but only have one unit running. When I took it into the RV service center they were of the opinion I had a problem with the ac units, Coleman says no, they are under warranty. The RV service center has suggested I upgrade to 15,000 btu units. I will do this if that is what it takes to beable to utilize the coach, but you would think Fleetwood would put the correct size when manufactured. One other thing unit for the rear of the coach in in the main cabin, not the rear bedroom. It has been suggested this could be the problem, but I don't know how that could be fixed.

RV Mechanic: Randall, RVIA Certification replied 11 years ago
You are not going to get as good performance on 40 amp service...........which is a strange amount. Most are 30 or 50. You really need a dedicated 50 amp service with good voltage to operate two A/C units. If the voltage is low..........say under 115 VAC to start with and it will drop when the A/C come on.......then the performance is going to suffer. If you have anything else on in the coach like the water heater on AC mode or the fridge on AC mode then it will be worse yet. Any of these A/C units are rated at 95 degrees ambient temperature. On a hot day it can easily reach 140 degrees or more on the roof in direct sun...........in Texas I am sure that can happen. For each 5 degrees the temp goes up the A/C pulls another amp or 120 watts power. So at 140 degrees the amperage draw goes up another 1080 watts. You only have a maximum of 6000 available at 50 amps. If an A/C is drawing about 20 amps it uses 2400 watts and can go higher at maximum temps. When the voltage is low, the amperage goes up and you actually have less power available. I know this may be some "rocket science" here but it usually helps for people to understand there are limits on what you can run in an RV due to the reduced power available. If you reduce that down you lose available watts. The water heater on AC mode uses about 1400 watts. The fridge depending on the model can be 300 to 500 watts. Add the tv and battery charging and other uses........like the microwave...........you can be "overdrawn" in the power dept pretty quickly. We see dozens of questions like this every week.

So to the solution...........first you need the maximum voltage and amperage you can get to the coach. I like the Voltage Minder by Electra Check as you can plug it into a spare plug and monitor the voltage. It also gives you cycles and shows any ground faults or reverse polarity problems. About $75 at most stores. It gives off an audible alarm when the voltage drops too low for safe operation. Or you can use a multimeter. Ideally, you want to see over 120 VAC to begin with. The higher it is the better perform ace you will see on the A/C units. Next, be sure the filters are kept as clean as possible. Dirty filters make the AC work harder to circulate the air and use more amperage as a result.

These can be tested with a thermometer. The delta temperature which is the difference between the discharge air and the return air should be at least 18 degrees different and up to about 22 degrees. Lower can indicate a problem or just too much heat on the roof and the ducts are warm and losing some efficiency.

Things you can do to make the system work better are: shade the A/C units so they are not in the direct sun. A number of ways to do this. Some parks may not allow this. Another thing on ducted units that can help is to get some sheets of foil backed home insulation that is the styrofoam type and put them on the roof over the ducted areas. They can be weighted with some bricks or tiles. Something to keep them from blowing off. Most of the time this won't even be visible as it will be in the center of the roof area.
This keeps the heat from transferring to the ducts and losing cooling efficiency.

And you can get more cooling with 15K units.............IF you have adequate power to operate them. They will pull more amperage. If you are already "short" then this won't do any good.

Hope that helps.............if you need more or don't fully understand some of what I shared then please get back t me. Follow up questions are included in our fee. R.J.
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Customer reply replied 11 years ago
Don't mean to seem dimwitted, but are you telling me, if I switch the Water Heater to gas, sheild the area of the roof where the air ducts are located with a reflective insulation and have 50 amp service the coach should stay cool? If I purchase Voltage Minder and I have a minimum of 120 VAC I should have enough amps to allow the AC to cool the unit? At what point below 120 do I loose efficiency and can not cool the coach.
RV Mechanic: Randall, RVIA Certification replied 11 years ago
Yes............that is true. Think of electricity like water. If you want more out of the hose you have to turn up the pressure at the faucet. Voltage is pressure. And if you want more to the A/C units you have to cut back somewhere else or increase the supply and pressure.

The reflective insulation will keep the coach and ducts cooler so the A/C don't have to work as hard. The Voltage Minder gives you a digital readout all the time so you always can glance at it to see how the voltage is doing. Any reduction in voltage begins to affect the performance. If you put in a dedicated 50 amp plug to your coach be sure they use large enough wire so as not to cut down the voltage. Again..........that is like water pressure. If you want more out of the hose you have to use a larger diameter hose or crank up the pressure. You can't make any difference to your home so you have to make good use of what is available. When the A/Cs are running the voltage will drop............that is natural. So long as it stays above about 110 VAC you should be fine.
They say you can go down to 95 but you can damage the A/C units if you go too low. More amperage use gives you more heat and that can burn up motors and compressors.

If you do the air temp test you can find out how effectively the A/Cs are performing. You want at least 18 degrees difference. Hold it in the air stream for about 5 minutes or until it stabilizes.

Get back to me if you need more help with this. R.J.
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Customer reply replied 11 years ago
2 quick questions - the temperture guage is specific to ac units or any refrigerant type guage with a probe will work? What is your opinion of a Voltage Booser? The RV parts store sells these for 50 amp units. They are expensive so I don't want to invest if they are not effective.
RV Mechanic: Randall, RVIA Certification replied 11 years ago
You can use a regular thermometer as you hold it in the air stream and don't actually insert it anyplace. A digital should give you an immediate reading. I would not try any "Voltage Booster"...........I think that may do more hard than good. Measure what you have and let me know and that will tell us quite a bit. At the source is the best so we know what you have to work with. If you are running a new service line then keep it as short as possible from the drop off the power line. The longer it is the more voltage you lose from "friction" in the wiring...........just like a water hose..........the longer it is the less pressure you see coming out. R.J.
Randall
Randall, RVIA Certification
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Satisfied Customers: 28,726
Experience: RVDA/RVIA Master Certified Technician with many years experience.
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RV Mechanic: Randall, RVIA Certification replied 11 years ago
Thanks for that very generous bonus............much appreciated! Please tell your friends about our service here at Just Answer. If you need more on this just come back to this post. Bookmark it and you can go right to it. Be safe...........R.J.
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