New AC, New pump, and MORE FROST!

[O C Diver]

You still have too much flow restriction on the supply side. Here's a simple test. Disconnect the supply duct off the unit and get a short length of flexible duct to run the supply out through the return grate. And run the AC to see if you have enough flow. Ultimately you may need to add another supply duct out the front of the pedestal of your bed.

The amount of condensate sitting in your drip pan bothers me. I shimmed my units so the side away from the drain dosen't have standing water.

Ted

 

[toocoys]

You still have too much flow restriction on the supply side. Here's a simple test. Disconnect the supply duct off the unit and get a short length of flexible duct to run the supply out through the return grate. And run the AC to see if you have enough flow. Ultimately you may need to add another supply duct out the front of the pedestal of your bed.

The amount of condensate sitting in your drip pan bothers me. I shimmed my units so the side away from the drain dosen't have standing water.

Ted

There is no supply duct. It's just an open hole that the fan sucks air into.

My next plan of attack is to enlarge the return area, and shim one side to drain the condensate better.

 

[toocoys]

Although its now cycling on and off normally, and not running non-stop.

 

[O C Diver]

Although its now cycling on and off normally, and not running non-stop.

Does the fan stay on? If not, change the setting as the airflow will quickly defrost the coils between compressor cycles.

Ted

 

[O C Diver]

Does the fan stay on the high setting all the time? If not set it to do so for added air flow.

Ted

 

[LarryM]

That 6" supply hose bothers me. Dometic and others specify a 7" supply duct above 12K. That's with a 550 CFM fan, which is what you have in your system. The air volume across the evaporator coils is definitely determined by the outlet diameter from the fan housing. If you want 18K in the forward cabin, you must have sufficient air distribution capacity. It has to be properly sized end-to-end to work properly.

Flagship states: 4″ discharge grills recommended: 4. This is ~50 sq. in. of supply ducting coming from the fan unit.

A 6" duct has only 28 sq. in. of area, which is way undersized.
A 7" duct has only 38 sq. in. of area, still not sufficient, but might work.
An 8" duct has 50 sq. in. of area which is the area recommended by Flagship for your unit.

I would think a minimum of 7" ducting would be required between the fan unit and the distribution plenum. Especially since the Flagship units only have a fixed-speed fan.

Here are a couple of examples from Cruiseair and Dometic to illustrate this concept:

 

[twistedtree]

There is no supply duct. It's just an open hole that the fan sucks air into.

My next plan of attack is to enlarge the return area, and shim one side to drain the condensate better.

I think you may have your terminology reversed.


The Supply side is air flow from the AC unit to the room. The Return is from the room to the AC unit.

 

[toocoys]

Does the fan stay on the high setting all the time? If not set it to do so for added air flow.

Ted

We have the fan on the "auto" setting.

 

[toocoys]

I think you may have your terminology reversed.


The Supply side is air flow from the AC unit to the room. The Return is from the room to the AC unit.

Probably, I'm not an HVAC technician.

 

[Gmarr]

Toocoys- what does the manufacturers service people say? I think I once referred you to Dometic and the king of service there and all this air supply stuff was what he really helped me on- so maybe there is one with your vendor?

 

[O C Diver]

We have the fan on the "auto" setting.

Switch it to "high all the time". Simply there is only one speed for the compressor, either on or off. It generates the same amount of cold (BTUs) regardless of fan speed. The auto setting has full fan maybe 5 degrees away from the thermostat setting. As you approach the thermostat setting, it reduces fan speed (less air flow over the coil). The concept is more flow or air when you're trying to cool the room down and less flow (noise) when just maintaining room temperature. You system is supply size challenged. You may be close enough that the increased airflow from the high fan setting keeps the coil from frosting.

Ted