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Old 03-20-2022, 10:31 PM   #1
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A/C units

Howdy! I have turned on the forward A/C unit on our Allegro Bus and the outside temp was around 85° with bright sunshine and the unit seems to have a hard time keeping the front of the bus cool. Would it have made a difference in the front if all three units were on or do we have a problem? Also, I’ve read some info about these units that said when they get low on refrigerant there’s no way to add any to them. Basically they’re disposable when the refrigerant is low. Can anybody tell me if this bad info or am I looking at replacing an A/C unit?
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Old 03-20-2022, 10:55 PM   #2
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Quote:
Originally Posted by Empty nest View Post
Howdy! I have turned on the forward A/C unit on our Allegro Bus and the outside temp was around 85° with bright sunshine and the unit seems to have a hard time keeping the front of the bus cool. Would it have made a difference in the front if all three units were on or do we have a problem? Also, I’ve read some info about these units that said when they get low on refrigerant there’s no way to add any to them. Basically they’re disposable when the refrigerant is low. Can anybody tell me if this bad info or am I looking at replacing an A/C unit?
If you have a bus with 3 units, one is going to have a hard time cooling. Even though it is localized, you said front unit, heat travels towards cold.

As for the disposable part. In theory, yes, they are a closed system and do not come with charge/fill test ports like a home AC does. I winter in Mexico however, and our local RV guy regularly takes units out, has the local AC shop weld ports in, draw them down and recharge. In the US, the EPA might get on you as to cut the lines and install ports, you let whatever is left in the system into the atmosphere.

Also, the availability of getting RV AC units has been tough. And I've seen some local HVAC guys doing repairs on older throwaway units. I have a Basement AC in my Winnebago, and that is pretty much the repair process. Take the unit out, take to an HVAC guy and they can pretty much rebuild anything that needs to be.
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Old 03-20-2022, 10:58 PM   #3
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Hi Empty Nest; Not an expert here, but considering the amount of area in the front of your coach and what the inside temp. was when you turned on the A/C, you might be expecting the front unit to do more than it is capable of handling. From what I have read here in this forum you can only expect about a 20 degree drop in temp from what the outside air temp is currently at. Turning on at least one of the other units, to me, would have helped cooling the coach. How are your filters behind the grill inside the coach. Have they been cleaned recently? Have you done an yearly maintenance on the A/C units by removing the covers on top of the coach and made Sure the coils are not plugged with debris? Some of these items can reduce the efficiency of the A/C unit. If it is that warm outside it does not take long to get the coach good and warm on the inside and that means that the A/C units will take longer to get things cool. Even in my 34' Windsor I will get both A/C units working together and when the inside temp comes down I will switch one off. Lets see what some others here have to say. You have a large space to cool down inside. Just my opinion here!
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Old 03-20-2022, 11:17 PM   #4
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To determine if an air conditioner unit is cooling properly. Use a temperature sensing gun - compare supply and return vents nearest a unit. Should be about a twenty degree difference.

All air conditioning units are on common supply and return ducts running the length of the coach. So additional units push air throughout the coach - cooling the area closest most effectively of course.

Many have blocked some rearward supply vents partially and/or completely to force for air forward. Our bedroom can be an ice box from the rear unit, so I have vents there blocked.
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Old 03-21-2022, 04:20 AM   #5
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The front AC alone will not keep the rig cool. That is why there are 2 units that run in the main area. You need to run both units. Ours will cool our unit with both running. If you know a good AC guy he can install a schrader valve in the low side of the AC unit and charge it for you.
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Old 03-21-2022, 01:31 PM   #6
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I doubt that you have a problem. We have a 45OPP Bus with three AC units. On days with temps in the upper 70s to low 80s or higher and sunlight coming through the windshield our front AC will not keep up with the heat gain.

Remember that windshield is a huge heat sink. The supply and return duct work is continuous front to back so all three AC units dump into the same supply duct and return using the same return duct.

In order to keep my rig comfortable, I will occasionally use my two windshield fans to circulate air. I usually set my middle AC unit at the lowest temp with the front unit a degree or two higher and my rear unit a degree or two higher than the front unit.
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Old 03-21-2022, 01:45 PM   #7
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The key to keeping the bus cool is manage the zones. I block the bedroom duct so it's totally separate from the living area. With the two front A/Cs, I turn both on and put them on continuous fan so that the air flow basically separates the front from the middle. On mild days they are both on low and on warmer days they both go on high speed. As noted, the front unit alone can not keep the whole coach cool. If you use just the center unit, when that area cools down the front part of the coach will stay too warm. Running them both on continuous fan evens things out.
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Old 03-21-2022, 01:48 PM   #8
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“has the local AC shop weld ports in, draw them down and recharge. In the US, the EPA might get on you as to cut the lines and install ports, you let whatever is left in the system into the atmosphere.”

Any HVAC technician who is EPA certified to handle refrigerants should know how to properly access a refrigerant system for subsequent installation of ports.

But even more - for any “sealed system”, once the system has been properly evacuated, and/or any leak has been repaired or component replaced - that system should be appropriately serviced (evacuated and charged with the precise refrigerant charge as indicated in the unit) thru the process tube, typically mounted on the compressor.
Then, the process tube is pinched off and soldered. No ports should remain as they represent a leak potential.

The LAST thing you want anyone to do, is to break into the refrigerant side of a factory sealed system! There will almost always be visible indications of a leak (oil wet looking copper/aluminum tubing), or an easily detected compressor or (for heat pumps) reversing valve failures.
If none of those indicators exist, the chances are very high that there is nothing wrong with the refrigerant charge, and therefore no reason to access the system.
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Old 05-01-2022, 09:09 PM   #9
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Similar problem

I have 2 rooftop Coleman ACs, The front has a 15 deg drop from inside temp. Rear is only about 10 to 12 deg delta. They are R22 units built in late 90s installed in a 2000 model fleetwood discovery. I know R22 is hard to find and expensive. I may have a couple of lbs of R22 still left.So would it be best to replace with a new AC unit with R134A instead of trying to add R22 freon to my rear AC? In Orlando in March I couldn't find anybody willing to add Freon to a sealed RV. Basically said if anybody adds it then it will leak out. But, it seems somebody capable should be able to do it if they have the R22 freon. The OP having a 2005 I assume has 134A instead of R22. A place in Orman said they could add a Schrader valve but they were not an AC shop and could not add freon.
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Old 05-02-2022, 04:52 AM   #10
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I have 2 rooftop Coleman ACs, The front has a 15 deg drop from inside temp. Rear is only about 10 to 12 deg delta. They are R22 units built in late 90s installed in a 2000 model fleetwood discovery. I know R22 is hard to find and expensive. I may have a couple of lbs of R22 still left.So would it be best to replace with a new AC unit with R134A instead of trying to add R22 freon to my rear AC? In Orlando in March I couldn't find anybody willing to add Freon to a sealed RV. Basically said if anybody adds it then it will leak out. But, it seems somebody capable should be able to do it if they have the R22 freon. The OP having a 2005 I assume has 134A instead of R22. A place in Orman said they could add a Schrader valve but they were not an AC shop and could not add freon.
You might want to look at the price of R134 - was at Harbor Freight yesterday and noticed it was $20 for 12oz can. Probably not as much as R22, but not as cheap as it used to be.

Hard to say if the lower temperature drop is due to low charge or weak compressor on that one unit.

How clean are your condensers? Have they ever been plugged dirty (which raises head pressure and both mechanically and electrically stresses compressors)?

Installation of a clamp on type of pressure tap is a guaranteed leak. Accessing the system using the process tube is the only true way to add refrigerant, and when accessed in that way - the charge should be weighed in after any leaks are located and repaired.

Leaks can often be found by observing oil on the refrigerant lines.

Your refrigerant charge doesn’t “get used up” or go bad. The only reason you would need to add more refrigerant is because you have a leak.
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Old 05-02-2022, 07:42 AM   #11
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I realize my commentary has nothing to do with the AC unit performance, but having a Magneshade might help a lot. I say "might" because we recently purchased ours and I've installed the magnets, but I haven't used them yet. Last summer in the Hill County in Texas was brutal. Couldn't get the coach below 84 in during the middle of the day. Hoping this summer will be a little better with the shades.
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Old 05-02-2022, 09:08 AM   #12
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To determine if an air conditioner unit is cooling properly. Use a temperature sensing gun - compare supply and return vents nearest a unit. Should be about a twenty degree difference.

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You cannot use a "temperature sensing gun" or infrared sensor to read air temperature. These temperature sensing devices read the heat radiated from a solid surface, such as the metal/plastic grill. You must use a thermometer for the air to blow over.

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Old 05-17-2022, 08:28 PM   #13
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We found a magneshade outside and reflectix inside helps reduce the front windshield heat gain by about 15 degrees when it's over 90 outside
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Old 05-21-2022, 08:39 AM   #14
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I have started to insulate the MH using Reflectix from Lowes. It works great on the outside walls inside the cabinets.

Is there any problem with putting it over the windows on the inside of the MH? I was concerned that with reflecting light and heat that it might crack the windows.

Your comments are appreciated!
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