Does 15000 btu Dometic AC need to be replaced? Compressor drawing 11.75 amps

[Bhawk]

I have 2 Dometic Brisk II 15000 btu ACs B59516 on my (new to me) travel trailer.  One does not seem to be cooling that well.  On a 95+ degree day the compressor was pulling from 11.75 - 12 amps and the air just seemed slightly cold, however the unit on top did have a small stream of condensation coming out of it.  The other unit at the same time was pulling 13.25 - 13.5 amps and was cooling very well.  The air coming out of it was noticably colder.  The unit pulling 11.75 amps has clean coils and everything else seems to be working on it, just is not cooling well.  If anyone familiar with what these compressors should pull in amps, please reply and let me know what the compressors (blue wire) should be drawing in amps when running on high cool on a hot day.  Also, please advise if I need to replace the one not cooling that well, based on amp draw.  Thanks.

[Ray,IN]

Your units nameplate states startup and running ampere draw when the unit is operating properly. Before spending money check the free fixes first.

Remove the air return panel to view the return air and chilled air duct-work. Many times the installer fails to insure the panel separating them is completely sealed. This allows chilled air to be sucked back into the warm return air flow.

Install new air filters, check the coils on the roof unit, insuring they are clean and fins are not crushed/bent. Fin combs are cheap and make it easy to straighten fins(just buy the right teeth/fin per inch).

Use a small thermometer to measure inside air temperature, now measure chilled air outflow. There should be approx. 20° difference, if so the unit is operating properly.

Dometic Duo-Therm service manual.

Edited July 29, 2021 by Ray,IN

[Bhawk]

2 hours ago, Ray,IN said:

Your units nameplate states startup and running ampere draw when the unit is operating properly. Before spending money check the free fixes first.

Remove the air return panel to view the return air and chilled air duct-work. Many times the installer fails to insure the panel separating them is completely sealed. This allows chilled air to be sucked back into the warm return air flow.

Install new air filters, check the coils on the roof unit, insuring they are clean and fins are not crushed/bent. Fin combs are cheap and make it easy to straighten fins(just buy the right teeth/fin per inch).

Use a small thermometer to measure inside air temperature, now measure chilled air outflow. There should be approx. 20° difference, if so the unit is operating properly.

Dometic Duo-Therm service manual.

Thanks for the suggestions.  The units did get a little hail damage so I have spent a few hours up there with a fin comb.  Best I can tell, everything between supply and return is sealed up and the coils are clean.  I will pick up a couple of thermometers to check the difference in temp.  I did find in the online manual that the compressors are rated at 13.2 amps, so the one not cooling is a bit low.  Thanks again!

[Kirk W]

Most HVAC technicians will tell you that the Delta T for air conditioners should generally fall between 16 and 22 degrees Fahrenheit. It can be too high which will cause a freeze up but that would not appear to be your issue. I also found an operating manual that is specific to the air conditioner that you have which may be of some help. It is possible that your unit has lost refrigerant and RV air conditioners do not have recharge fittings on them. I used to know a tech who would install those fittings and recharge RV a/c units but he has retired and I have not heard of anyone doing that since. An unloaded compressor would draw less current, but I do not know how much less. How old is the a/c that we are working with? 

[Bhawk]

26 minutes ago, Kirk W said:

Most HVAC technicians will tell you that the Delta T for air conditioners should generally fall between 16 and 22 degrees Fahrenheit. It can be too high which will cause a freeze up but that would not appear to be your issue. I also found an operating manual that is specific to the air conditioner that you have which may be of some help. It is possible that your unit has lost refrigerant and RV air conditioners do not have recharge fittings on them. I used to know a tech who would install those fittings and recharge RV a/c units but he has retired and I have not heard of anyone doing that since. An unloaded compressor would draw less current, but I do not know how much less. How old is the a/c that we are working with? 

Thanks for the reply and the manual.  It is different from the one I have.  The unit is on a trailer built in 2017.  

[Kirk W]

It is possible that it has failed, but that would seem unlikely at this point. Most RV a/c units will last at least 10 years even with heavy use and 20 years isn't uncommon.

[TXiceman]

It seems that Dometic ran through a bad batch of units  4 years ago and there were a bunch of failures.  It is not  unheard of for a 4 year old unit to fail.

Units from a few years back would last 10 plus years up to 20 years.  Now you are doing good to 7 to 10 years out of a unit.

Check the temperature between the inlet and the outlet at the unit with it operating on high fan.  The outlet should be 20 degF lower than the inlet.  Check the temperature of the air with an analog thermometer,  DO NOT use an infrared temp gun as it will not measure air temperature.  It measures the heat radiated from a solid surface.

Ken

[D&J]

The amp draw is directly related to how hard the unit is working, the higher the head presure the higher the amp draw. From what you are describing you have a air leak between the outlet and return. You have to remove the inside cover to inspect the ductwork to make sure you aren't mixing air at the unit. 

Denny

[Bhawk]

On 7/29/2021 at 8:59 AM, TXiceman said:

It seems that Dometic ran through a bad batch of units  4 years ago and there were a bunch of failures.  It is not  unheard of for a 4 year old unit to fail.

Units from a few years back would last 10 plus years up to 20 years.  Now you are doing good to 7 to 10 years out of a unit.

Check the temperature between the inlet and the outlet at the unit with it operating on high fan.  The outlet should be 20 degF lower than the inlet.  Check the temperature of the air with an analog thermometer,  DO NOT use an infrared temp gun as it will not measure air temperature.  It measures the heat radiated from a solid surface.

Ken

Thanks for your reply.  4 years is the age of this unit.  The temp difference was about 8 degrees.  I cleaned the coils and taped up the divider between return and supply.  I did notice that where the freon line comes in through the foam housing there was daylight and the supply coil was a little dirty.  I plugged the hole and cleaned off the dirt.  I tried again and the temp difference was about 12 degrees.  I pulled the hood off the unit that was cooling well and compared the line running to the inside coil and there was significant difference...it was cold and covered with condensation.  The unit not cooling was dry and only slightly cool.  I decided to go ahead and replace the unit and the new unit cools much better, however, the original unit that is cooling works better than the new one...the air coming out of it is around 50 degrees and the new one is about 55 degrees.  Thanks again!

[Bhawk]

On 7/29/2021 at 9:03 AM, D&J said:

The amp draw is directly related to how hard the unit is working, the higher the head presure the higher the amp draw. From what you are describing you have a air leak between the outlet and return. You have to remove the inside cover to inspect the ductwork to make sure you aren't mixing air at the unit. 

Denny

Thanks for your reply.  The divider between the two was not air tight, so I taped it up.  I did notice that where the freon line comes in through the foam housing there was daylight and the supply coil was a little dirty.  I plugged the hole and cleaned off the dirt.  After this and a few other things I decided to go ahead and replace the unit and the new unit cools much better, however, the original unit that is cooling works better than the new one...the air coming out of it is around 50 degrees and the new one is about 55 degrees.  Thanks again!

[TXiceman]

The suction line from the evaporator to the compressor should be cool and sweating.  If it is frosting or icing, the unit is not running like it should.  It could be low on refrigerant or low air flow due to restrictions or bypassing air.  

Ken

[Kirk W]

6 hours ago, Bhawk said:

 The temp difference was about 8 degrees.  I cleaned the coils and taped up the divider between return and supply.  I did notice that where the freon line comes in through the foam housing there was daylight and the supply coil was a little dirty.  I plugged the hole and cleaned off the dirt.  I tried again and the temp difference was about 12 degrees.

Since the minimum differential temperature is 16°, it would seem that your unit did most likely loose refrigerant. While 4 years is a pretty short lifespan, I think that I would have done the same as you.

6 hours ago, Bhawk said:

the new unit cools much better, however, the original unit that is cooling works better than the new one...the air coming out of it is around 50 degrees and the new one is about 55 degrees.

The temperature of the air leaving the a/c doesn't really tell you anything as the exit temperature is a factor of the air entry temperature as well as the amount of cooling. The only accurate way to compare is to measure both the entry and exit temperatures and then compare the differential temperatures. The best tool for doing that is one of the dial thermometers, such as this one or a digital one like the second picture.