Pickup Camper Air Conditioner

Pickup Camper Air Conditioner

Pickup Camper Air Conditioner

I’m building up an AC unit to fit into the cabinetry of my Four Wheel Camper. Space is very limited, and it will be a challenge to make it all fit. The system will resemble a mini-split unit for a house, with the condenser located outside and the evaporator inside with the two connected by tubing. In this case, the compressor will be located inside near the evaporator. I’ll use R410A.

I have two 5000 btu/hr LG window units from which I’m going to scavenge the condensers and the evaporators, and a 10,000 btu/hr 110vac compressor from an EdgeStar portable AC. I’ll stack the condensers and evaporators to give me approx. 10,000 btu/hr AC capacity. I was going to use the evaporator and condenser coils from the 10,000 BTU EdgeStar, but they won’t fit.

The two evaporators will be plumbed in in parallel and will each will have a TXV and a distributor. I can’t find commercial distributors that small, so they’ll be fabricated from the LG capillary tubes. Each evaporator has two circuits, so the distributors will each have two tubes. The two condenser coils will be plumbed in series, since I don’t know how to build a flow divider for parallel operation. A sketch is attached that shows the schematic.

A centrifugal blower will be used for the evaporator and the condenser will use an axial flow fan. The fans in the window ACs and the portable won’t be used. I’ve mocked up the evaporator ductwork with cardboard and masking tape and hooked up the centrifugal blower to characterize the airflow. I get ~290 cfm through it with about 1.3 in. H2O pressure drop. The duct work has a lot of angles and dimension changes that caused most of the pressure drop. I haven’t characterized the flow for the condenser but the axial fan produces 600 cfm with 0 in. H2O and I don’t expect much pressure drop across the condenser since the fan will sit directly in-line with the condenser coils. Both fans have speed control for fine tuning.

To come up with the flow rates that I needed, I checked the flowrates on one of the 5,000 BTU LG window units and on the Edgestar 10,000 BTU unit. The LG 5,000 BTU unit flowed 124 cfm through the evaporator and 217 cfm through the condenser. The 10,000 BTU Edgestar evaporator fan flowed 225 cfm. I didn’t check the Edgestar condenser flow. So I figured the airflows that I have will be ok. I also read that AC people figure roughly for 400 cfm per ton across the evaporator and 800 cfm across the condenser, but I felt that the flow rates that I have are reasonable based on the measured flows through the units that I have.

The ducting for the evaporator will be vacuum-formed ABS plastic. The cold air outlets will be circular vents 3” dia. from a Ford Expedition and will fit into a vacuum-formed ABS manifold located above the front window of the camper (right behind the pickup’s rear window) and below the cab-over bed

I haven’t figured out how all of this is going to be controlled yet. I have the controls from the LG units and from the EdgeStar, so I’ll probably start with one of those.