Dirty Coils?

[Heelbilly]

Hey, y'all. Hope everyone is enjoying a nice camping season.

I have a quick question for you more experienced folks. My travel trailer is starting its third summer... I bought it new in 2015. My last trip that needed the AC was last August. Had no problems... Even in the Georgia heat it kept the camper cool and nice. I just got back from my first AC-needed trip of this season. It was only about 83 degrees outside and I was parked in the shade but my AC could only hold the camper at about 78 or 79 degrees. Here are the obligatory details though:

- The compressor did come on... and stayed on... no short cycling.
- I clean my AC filter before every trip... OK...maybe every other trip... but I keep it clean
- The AC was draining properly
- I checked on the inside and made sure return and supply air weren't mixing.
- It is a Domestic DuoTherm 13.5 BTU

The air coming out of the vent was cool, but not as cold as I remember. I didn't have my laser thermometer with me so I can't tell you exactly what the temperature differential was. I would guess it was much warmer than the rule of thumb "20 degree" supply-return difference. Probably closer to 10 degrees, but again, that's a guess...

When I got home today and had my ladder I climbed up on the roof to take a look at the coils to see if they were dirty. There are definitely some bugs and dust, but nothing too impressive...

My question is, does a little bit of dirt make that much of a difference?

I ask because I'm leaving in a few weeks for a two week trip to Key West. I'll want my AC much more then... My trailer is under warranty, so I could take it in, but I hate doing that anyway... Not to mention I'd probably be pushing it in terms of getting my trailer back for my trip. Not sure if it is worth rolling the dice with the dealership...

I'm going to clean the coils tomorrow, but it will be next weekend before I can see if that did the trick since I don't have a 30 amp plugin at my house and my generator is on the fritz.

Anything I'm missing? I figured since an RV AC only holds about a pound of freon, and since the compressor is kicking on and staying on...and cooling somewhat...that a freon leak was improbable?

Any advice? Just trying to decide where to hedge my bet... cleaning the coils myself or going ahead and taking it in to get checked out so I don't jeopardize my big trip.

Thanks, y'all! As always...

[peirek]

TexasChaps wrote:

peirek wrote:

TexasChaps wrote:

peirek wrote:
I have had the thermocouple come loose from the coil and cause a low cooling effect. I can't recall if this allowed the compressor to continue to run however.

You may be able to see the thermocouple from the bottom but on mine I had to correct from the topside. My memory is getting worse, but I believe it just clipped onto the coil.

thermocouple should be in the return air stream not connected to the coil..

Yes that thermocouple controls the room temp i.e. thermostat. The one I am describing determines the coil temp and shuts down the compressor if they get too cold (before freezing occurs). Thinking back, it may have caused the coils to freeze when it was disconnected resulting in reduced cooling.

I would be very surprised to see such a device in an El cheapo RV unit..

Next time I have my outside cover off to clean the coils I will take a picture. I have a Dometic 15.0

[TexasChaps]

beemerphile1 wrote:
For diagnosis, get out your thermometer and measure the in going temperature and the out going temperature. The difference will tell you if it is working correctly.

I think the goal is about 22 degrees difference, someone can chime in with the correct number if I'm wrong.

there isn't really a "correct" number as such, the delta T is a function of ambient temperature and humidity.. but typical numbers would be in the range of 10 to 20 degrees Celsius

[TexasChaps]

peirek wrote:

TexasChaps wrote:

peirek wrote:
I have had the thermocouple come loose from the coil and cause a low cooling effect. I can't recall if this allowed the compressor to continue to run however.

You may be able to see the thermocouple from the bottom but on mine I had to correct from the topside. My memory is getting worse, but I believe it just clipped onto the coil.

thermocouple should be in the return air stream not connected to the coil..

Yes that thermocouple controls the room temp i.e. thermostat. The one I am describing determines the coil temp and shuts down the compressor if they get too cold (before freezing occurs). Thinking back, it may have caused the coils to freeze when it was disconnected resulting in reduced cooling.

I would be very surprised to see such a device in an El cheapo RV unit..

[beemerphile1]

For diagnosis, get out your thermometer and measure the in going temperature and the out going temperature. The difference will tell you if it is working correctly.

I think the goal is about 22 degrees difference, someone can chime in with the correct number if I'm wrong.

[peirek]

TexasChaps wrote:

peirek wrote:
I have had the thermocouple come loose from the coil and cause a low cooling effect. I can't recall if this allowed the compressor to continue to run however.

You may be able to see the thermocouple from the bottom but on mine I had to correct from the topside. My memory is getting worse, but I believe it just clipped onto the coil.

thermocouple should be in the return air stream not connected to the coil..

Yes that thermocouple controls the room temp i.e. thermostat. The one I am describing determines the coil temp and shuts down the compressor if they get too cold (before freezing occurs). Thinking back, it may have caused the coils to freeze when it was disconnected resulting in reduced cooling.

[TexasChaps]

peirek wrote:
I have had the thermocouple come loose from the coil and cause a low cooling effect. I can't recall if this allowed the compressor to continue to run however.

You may be able to see the thermocouple from the bottom but on mine I had to correct from the topside. My memory is getting worse, but I believe it just clipped onto the coil.

thermocouple should be in the return air stream not connected to the coil..

[peirek]

I have had the thermocouple come loose from the coil and cause a low cooling effect. I can't recall if this allowed the compressor to continue to run however.

You may be able to see the thermocouple from the bottom but on mine I had to correct from the topside. My memory is getting worse, but I believe it just clipped onto the coil.

[Heelbilly]

dodge guy wrote:
It`s possible the voltage was low at the campground. If everything else checks out that's what I would go with. try it again with known good 120V.

I didn't think of that! (But sure should have...) The campground was loaded to capacity...

I've got a 10 gauge drop cord and an outlet near where my camper is parked that is on a 20 amp breaker. I may clean the coils, kill all the breakers in the trailer except the AC, and give it a shot!

Beyond dirty coils, mixed return and supply air, and now the solid low voltage theory, I just can't think of anything else that would cause the AC to run properly and just not cool enough on a relatively mild day.

As always, thank y'all!

[dodge_guy]

It`s possible the voltage was low at the campground. If everything else checks out that's what I would go with. try it again with known good 120V.

[Old-Biscuit]

Yes ......due to 'smaller' size of the evap coil and condenser coil being dirty can really affect their cooling abilities.

Condenser coil easiest to clean because it is exposed when you remove roof shroud

Evap coil....after shroud is removed you have to open up sealed compartment to clean evap AND block off opening to inside of rig

[gjcummings]

You can plug in at home. Just run AC by itself. I did it all the time last house we had. We have a Coleman 13.5. Just get an adapter for you 30 amp cord. I carry a 75' extension cord for driveway camping at friends while on the road. Works every time.

[Trackrig]

On ours, and they're all different it seems, sometimes I set it on just circulating air by mistake. And on ours it seems as if I use the "auto" function so that it operates like a thermostat should, it doesn't put out near as cold of air as when I just set it on cold or maximum. I haven't noticed a little bit of dirt on the fins making any difference.

Bill