Afternoon all,As I sit here in the campground, sweating (as it's in the mid 90's), My trailer AC unit doesn't seem to be keeping up with the expected cooling temperature delta.I've been told (or read maybe onhere) that the delta between intake and exhaust should be 40 degrees.I removed the cover for the intake (it's both ceiling vented and has vents that open on the output side, held my thermometer in the air blowing down and it was about 62 degrees. I then put the thermometer down on the counter while I resealed all the cracks and crevasses with aluminum tape - I figure every little bit helps, right? Anyway, the temperature in the trailer is 82 degrees.I checked the air filter - and I cleaned it the last time I was out - and yes, it's still clean. I expected a temp delta of 40 degrees and I'm only seeing 20. Model 8333e856Coleman MachI'm assuming it's a 13,500 btu unit - So - my questions:1. Is a 20 degree delta acceptable or am I expecting too much?2. Am I missing anything?Thanks in advance!Josh

most ac units will only get a 15 degree diff from intake to outake

The Coleman-Mach website says "output temperature range of 16-22 degrees lower than the temperature taken in at the filter."

I always thought 40 degrees is the delta for AC Units...Oh well. It's not keeping up with the heat here. I think it's the ceiling ducts are full of restrictions and the volume of air coming out is relatively low - and yes, I have the manual controls for air flow on the output closed up tight. That fan puts out tons of air, but I think the ducting in the ceiling is too restrictive and it's not allowing a good flow of air. Thanks everybody!Josh

Just a quick footnote.The temp of the air coming out of the ducts is about 50 degrees - which makes sense if there is a lot of back pressure from the fan pushing the air out of the ducts.If the air moves across the coils, slower, it'll cool more than if the air moves faster. I can't believe they designed the evaporator to move the air across it slower though. That makes no sense. of course the follow up question is this:If there is that much resistance in the ceiling vents, should it be that way?Just a thought.again, thanks!josh

coleman Mach - Temperature Differential model 8333e856

jodeb720
Explorer
Aug 14, 2017
After returning and talking to my BIL's (both of them went with me) neither of them had issues cooling their TT's. One had the dump out of the AC unit (but in a 20' trailer) and the other has a 27' with ducted venting.

I'm thinking the Jdubya is correct. If I open the grates on the output of the AC unit - it'll put 90% of the cooling in an area - but not in the bedroom; However, if I think about the size of the ducts - I'm guessing that it's unable to move the air through the AC unit effectively to reduce the air temp.

As to the 40 degree delta, I'm not sure where I got it - but I thought I read it on here.

Ironically, the input temp on the AC unit was about 85 degrees, the output temp in the duct was 55 degrees - but I suspect it's a volume issue - moving enough of the air through the AC unit to remove the heat effectively.

I had the blinds drawn and the vents closed - but didn't have foam in the vents or the shower skylight.

Thanks!

josh
CJW8
Explorer
Aug 14, 2017
There is a guy on here that claims 40 delta T. The only way that is possible is because he is getting recirculation but he doesn't believe it.
j-d
Explorer II
Aug 14, 2017
I quickly read this thread and if a couple items were addressed, I missed them:

1. How OLD is this system and have the COILS, particularly the Evaporator Coil, at the front of the unit, under a sheet metal shroud, been Cleaned?

2. It's ducted, so is the ducting OK? I don't have a ducted, but I understand there can be problems right at the unit where flow is reduced.

3. On the roof, is there baffling (foam blocks) along the vertical edges of the Condenser Coil, so air being exhausted out the sides, isn't being sucked around the corners of the Condenser?

Remember, a 20* "Split" doesn't mean the coach won't get below 80* if it's 100* outside. Once it cools the interior to 95* then split means the cool air can now be 75*. If it cools the interior to 80* then you could (at least theoretically) drive it down into the 60's. But, as mentioned, if the A/C lacks the capacity to bring interior temperature down at all, then this can't happen.

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coleman Mach - Temperature Differential model 8333e856

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