Question OASIS (AQUAHOT?) When to use Electric Heat vs. Diesel Burner

[docj]

What is Comfort Hot Heater? I can’t find these.

The Comfort Hot was something that was installed by Rixen's in Sandy OR. I've never seen it available for retail sale. Jim Rixen wired it so that it uses the two 20A A/C circuits which, obviously, aren't in use when you need to use heat.

 

[osuallen]

One thing to consider in making this sort of decision is the relative thermal output of the diesel burner and its electric backups. In the case of my Hurricane, the burner is rated at 45,000 BTUs and one should assume that it has a thermal efficiency of ~60-70%. At 60% it is providing ~27,000 BTUs/hr. By comparison, the Comfort Hot heaters which I had installed to provide an electric backup were designed to operate off of a 20A circuit so I'll assume they provide roughly 2000 watts each of heating. Electric resistance heating is usually assumed to be 100% efficient. That means the electric heaters provide just under 14,000 BTUs/hr of heat. So the electric backup is providing ab0ut 50% of the energy of the diesel burner.

The combustion process on a non-condensing boiler is ~80-82% efficient. There are some thermal losses through the boiler shell and circulation piping, however much of that heat loss is to conditioned space. The overall system thermal efficiency is probably more in the ~75% range.

 

[docj]

The overall system thermal efficiency is probably more in the ~75% range.

I'm quite willing a accede to your knowledge of this; the purposed of my post was illustrative not definitive.

 

[CaptainGizmo]

My head hurts.

When it gets cold, I turn the Electric Aqua-hot on.

When it gets really cold, I turn the Diesel Aqua-hot on.

?

@Neal, I can't recall specifically, but I think the OASIS manual does talk about lowest temp thresholds. I just looked up my Aqua-hot and it, indeed, suggests to switch to Diesel for temps below 50º. I find this to be very consistent with other's standard practice.

 

[docj]

When it gets cold, I turn the Electric Aqua-hot on.

When it gets really cold, I turn the Diesel Aqua-hot on.

If you have a heat pump your options are a bit more complicated. Heat pumps are more electrically efficient than the backup heaters on an Aquahot or Oasis. At temperatures temperatures above ~50F the coefficient of performance (COP) of most heat pumps will be ~2.5 which means they use 2.5x less electricity to produce the same amount of heat. Different brands will have different COPs but they're all going to be in the 2.5-3 range.

As the outside temperature falls the COP of a heat pump decreases, but as long as it can produce any heat at all it will still be at least as efficient as the backup heaters. I've now determined that my heat pumps do quite well at temps >45F and are reasonably effective in the 40-45F range (the front HP can't keep up with the thermal load of all the glass in the front of the MH.)

So my "rule of thumb" is to use the HP if the temps are predicted to be ~43F and to switch to the electric backup if the temps are in the 30F-43F range. Below 30F the diesel is the only option.

To those who may think this is too complicated to bother with, I would like to point out that this winter, with the heat pumps, I am saving ~$30/mo in electricity compared to my bills at the same location last winter. For us that represents a roughly 15% decrease in total energy usage.

 

[Kevin D Pem]

Wow guys. you have to many options. When I get cold I get up and put more pellets in the hopper.