I want to compare heating systems and I am using the same bus conversion, under the same temps to compare performance. I have chosen three systems to use, we can compare cost of these systems to operate. first the conditions at time of test. We are in Frenchtown Montana and at the time this article is being written it is -5 outside and the humidity is 72% under snowing conditions. The parameters are, 1. each system will be started from cold.
2. each system will be timed on how long it takes to get the bus to 75 degrees from 60 degrees. 3. each system will have the fuel used measured out to determine the amount of fuel used to achieve the desired temp.
We will then convert the fuel used and see what it cost to heat the bus for a typical winter season, here in Montana I tend to use heat from September until late March or April.
We will have the maintenance of each system, fuel used , and annual cost to operate.
let's talk about the hydronic system itself. first we use 6 heat exchangers rated at 8,000 BTU induction 12 vdc
12VDC air handler
Each fan unit has its own thermostat, so each zone is controlled independently.
heat and cool thermostat
The heated water (hydronic heat ) is then circulated thru the heat exchangers by a low amperage water pump
hot water circulation pump
the water then returns to the accumulator tank we used one that is common to a chevy truck with a diesel engine as it has the right rating on the pressure cap of 16 psi
accumulator tank
then its returned to the boiler to be reheated and the process keeps going as long as there is a thermostat calling for heat.the above components are used regardless of which boiler is used out of the three choices.
First system is the Webasto diesel fuel hydronic heating system
WEBASTO DIESEL HEATER
I chose this system for my bus because we are a Webasto dealer I chose it because its a totally rebuildable unit and easy to service. Webasto has more fuel efficient units than this old technology but I am a purest and just love the simplicity of the old school design. Because I wanted three independent heating systems in my build because I want to be able to live off the grid for as long as I want to. With the bus being a diesel engine powered one I don't have to add a fuel source to use it. its rated at 50,000 BTU's and it the Old school system I have used sense the early 80's. its very reliable, maintenance is simple and not needed but once a year.
The test. ok system starting at cold the coolant in the hydronic system is 41 degrees the bus is at 60 degrees inside and we started the diesel burner. the hydronic system will not allow fans to cut on until the coolant reaches at least 100 degrees so the "time" part of this test is going to be how long it takes for the fans to cut on , so the fans cut on at 23 mins into the burn time, I might also add the total coolant capacity of my system is just over 5 gallons not counting the engines coolant which can be diverted in order to heat the engine.
so now we need to get up to temp of 75 degrees. ok now its at 75 it took 49 mins for the Webasto diesel heater to get us to temp. fuel used was just over a quart. Doing the math at the current $4.39 per gallon of diesel $1617.00 per season.
Second heater is a precision temp jr. This is a propane powered hydronic heater
rated at 50,000 BTU's this unit does also have an electric option but we didn't wire this up sense we live off grid and its never going to be a usable option this unit also provides the domestic hot water.
With the system cooled off and the bus back to 60 degrees lets start the Jr. up!
Fans came on at 12 mins into the test and it took 31 mins to get to temp of 75 degrees
we really love this unit as its very efficient and heats up very quickly. Its not the most fuel efficient unit to use but it does get the job done fast and that comes at a price.
cost to own and operate this unit for the season is at current propane prices of $3.49 a gallon
is $1347.00 per season
the last system and the system we use the most is our made in house pellet stove. we us 12VDC to operate fans and the auger system to feed the pellets to the fire box. This stove has an advantage the others don't in that it also radiates heat right from the unit and doesn't depend solely on hydronic heat. With the bus cold again and hydronic water temp back to 45 lets start the stove. The fan on the stove comes on at 100 degrees and has cut on at 6 mins into burn but the hydronic fans have not cut on yet. Hydronic fans came on at 20 mins into burn. this stove will get to the 75 degree temp a lot faster because it has both hydronic heat and radiant heat advantage. the bus is up to temp in 16 mins. and the fans cycled off.
the stove is going to be hard to determine what the fuel is used because the hopper holds 40 pounds of pellets so I know what this stove burns in a season as I have to buy the pellets.
so this stove will burn 2 tons of pellets and this year the pellets cost me $420.00 a ton so its going to use $840.00 it is worth mentioning here that in winters past when the government wasn't causing the inflation with their bad policies it has only cost $410 for the whole season (so how you vote effects us all) so even with the over inflated cost of living these days it cost way less to heat with pellets than with propane or diesel, in fact its way less. 1/2 the price of diesel and almost half the cost of propane. We use the pellet stove most all of the winter but when we travel we use the engines heat to provide the heat in the bus.
So to recap we use four different heat sources. We use the hydronic heat for the clothes dryer, to heat the domestic hot water and to heat the bus. this is a very efficient system to use with multiple back up systems to guarantee we have heat.
Big Dog RV Services built 12VDC pellet stove
with hydronic heat option