HEATING & COOLING
The original plan with the Sprinter was to use the purchased optional Espar diesel heater to heat the van and heat shower water. I bought the Espar and the "auxiliary heat exchanger preparation". That option gave me the Espar piping located under the floor behind the driver's seat. A supply and return pipe for heated water. That proved unusable because pipes had hot water as I expected when Espar was running and engine off as well as unexpected hot water with Espar off and engine running. Did not want hot water inside van in the radiant floor piping during the summer. To use this source I would have to install several valves to eliminate the hot water during the summer. Abandoned that plan. Later Espar failed and cost about $2000 to get it repaired. Conclusion for Transit was to not use an Espar.
The electrical system design includes two inverters. The" house" inverter is a pure sine 1000 watt Magnum MSS1012 that is a combination inverter/charger/transfer switch. It has three functions: Converts house battery 12 volt DC to 120 volt AC, converts 120 volt AC shore power to DC for house battery charging and will transfer 120 volt shore power through the unit to duplex outlets when inverter is off. The second inverter in Sprinter was a 600 watt "vehicle" inverter that provides pure sine 120 volt power from the vehicle 12 volt system. So with the vehicle engine running I have 120 volt AC power available. The inverter could provide power to heat shower water or be used to provide "shore" power for house battery charging.
I then built a shower water heater using a 5 gallon SS beer keg with a kit designed to add a electric heater to a common RV propane heater. Kit designed to allow water heating electrically when plugged into shore power in RV park instead of using propane. Added a coupling to the bottom of the beer keg to install the electric cartridge heating element. Kit came with an adjustable thermostat to control the water temperature. So using the "vehicle" inverter for 120 volt power while I drove gave me 5 gallons of water heated to 90 degrees after 45 minutes of driving. Dropped a tubular 12 volt DC submersible pump down into the beer keg and used a garden hose with on/off garden nozzle. I had a shower enclosure inside the van so could shower anywhere. System worked very well. Not like a shower at home but you are clean when done. The shower water heating method eliminated all the planned shower water piping.
The van heating system also evolved. I first programmed the Sprinter Espar to come on once during the night for one hour. Mercedes limits the run time to one hour. Then in the morning I would run it again. That sort of worked but is noisy and did not provide a constant temperature through the night. Next I experimented with a 12 volt DC heating pad under the sleeping bag. That worked very well and used about the same amount of power that was saved by the refrigerator not running because inside of van was cold. The power usage was about the same and the refrigerator cycled less and I did not wake up due to the Espar running. The only problem was my head was outside the sleeping bag so it was cold. Bought a balaclava to solve that problem.
One other advantage to having the "vehicle" inverter running while driving is the AC/DC refrigerator automatically switches to 120 volt AC power. That allows all the solar panel power produced to be used for house battery charging instead of part to run the refrigerator and part to charge the house battery.
For the Transit there are several improvements. The "vehicle" inverter is increased from a 600 watt inverter to a 1000 watt inverter. There is a selector switch that directs the power either (1) to the charger or (2) the hot water heater or (3) the 750 watt electric baseboard air heater. The larger inverter produces enough power to run the added air heater, use a 625 watt water heater in place of the Sprinter 480 watt to reduce water heating time to 30 minutes from 45 minutes and allows charging the house battery at 50 amps instead of 30 amps. The "vehicle" inverter also has a remote added that allows the inverter to start automatically when the engine runs. In Sprinter I had to restart the inverter after each engine shut down. The Transit gas engine can be idled so I do not have to be driving for the system to function. I also bought the remote start option so I can start the Transit engine while still in bed on cold mornings to heat van.
A van interior air conditioner is not an option due to the high power requirements. Only choice is air circulation. Selected the Maxxair Model 6200K for the roof vent. The Maxxair has a cover design that allows it to be open in the rain and it eliminates the need for a rain sensor that closes the vent automatically. Did not buy the remote because it is very easy to reach the manual vent controls. The fan is very seldom run because there is a 4" x 4" hole in the Transit floor located in front of the left rear wheel and behind the refrigerator. The floor vent has a cord that allows the floor hole to be open or closed. With the floor hole open and the roof vent open there is a natural draft of cool air from under van that goes up past the refrigerator coil and then out the roof opening. It is not necessary to run the roof fan.
I will build a tent inside the van that surrounds the bed platform. Bed platform is 30 1/2" above the van floor across the back of the van. The bottom of the upper side wall cabinets are 32" above the bed platform. The bed platform is 74" long. The bed platform is 54" wide. The tent will be 74"x 54"x 32". A box surrounding the sleeping area. The idea is to capture some of the heat from the person and the DC heating pad inside the tent. The bed platform is also insulated. The tent side toward the van front will have the side wall split for entry. The tent will use a layer of Thinsulate CS150 sandwiched between two layers of cloth for insulation. Tent supports will be 3/4" copper tubing with spring loaded dowels that fit into holes in a board bolted to the van walls. Easy to install and remove. Tent can be used with 27" wide bed for one person or 54" wide bed for two. It might be possible to air condition this small volume with a small air conditioner.