Cheap Heat electric add-on

[den60]

I'm just curious if anyone has had the Cheap Heat electric heat by Comfort Systems added to their coach? I am thinking about having one added to my coach but would love to get some feed back from people that have actually had one installed. My coach is 40' so I would think that would be a lot of space to heat for one add-on heater but they say it works great on their site. I would like to hear the pros and cons. I think it would be nice to have more options than just using the LP furnace. I love my coach and would rather keep adding the things that I want rather than to trade it for a new all electric rig. I looked at the new all electric rig by Newmar but, I will stick with mine. Thanks to all that reply.

[harold1946]

Pirate wrote:
With cheap heat you still have to listen to the noisy furnace fan, right?

Right, but there is a choise of fan speeds.
I have found that the lower speed allows for not only less noise but better heating. The heating element does not provide the BTU output of a furnace and the lower CFM works great.
I also installed adjustable registers so I could balance the system, using a flow meter, for even heating throughout the coach.

[John___Angela]

Pirate wrote:
With cheap heat you still have to listen to the noisy furnace fan, right?

Kinda. It runs at half speed (if selected). Did a little test the other day and ran one of our furnace motors at 6 volts instead of 12. I was surprised how quiet it was. I know the new dual stage Atwood furnaces also have this option. They kick down to half blower and half burner when within a few degrees of set point. Both our furnaces are hanging in there after 10 years of full time use but when they pack it in I would consider going to the new dual stage for this reason. In my case I used 6 volts to spin the motor just to hear what it would sound like. I wonder if they just drop the voltage or if they use something like a PWM type control. Anybody know?

[pianotuna]

As Lady Fitz might say, please support your statements with research or numbers. Please provide links as well.

jcthorne wrote:
Just an FYI since everyone here sees intent on throwing the numbers around, Attwood propane heaters are actually closer to %60 efficient. Anything over 75% would require a condensing exhaust which is FAR beyond the Attwood's simple design. The RV propane furncaces are very compact and use forced air induction but at the expense of low efficiency. Lots of the BTUS are going right out the exhaust vent.

[pianotuna]

Hi Pirate,

Yes, but mostly it would run the fan at 1/2 speed--that might make it a bit quieter.

[Pirate1]

With cheap heat you still have to listen to the noisy furnace fan, right?

[jcthorne]

Just an FYI since everyone here sees intent on throwing the numbers around, Attwood propane heaters are actually closer to %60 efficient. Anything over 75% would require a condensing exhaust which is FAR beyond the Attwood's simple design. The RV propane furncaces are very compact and use forced air induction but at the expense of low efficiency. Lots of the BTUS are going right out the exhaust vent.

Also, the main reason the propane and electric cannot work together is that the electric or propane systems alone EACH produce sufficient heat to drive discharge air temps to the top of the safe range. The propane beyond the safe range and thus the need to cycle the burner once up to temp in most installations. These units are air flow limited by the duct work and can only distribute about 15,000 BTU/hr. of heated air.

[Lady_Fitzgerald]

pianotuna wrote:
Hi Lady Fitz,

It is my understanding that 50 amp cords for RV's are #6 wire, not #10, so the voltage drop should not be an issue, except at the pedestal.

I do observe significant voltage drop on the 30 amp service on the order of 10% when running 2400 watts (30 foot run to the pedestal with #10 wire). I try to never exceed 2880 watts on a continuous basis.

Yes, 50A cords are 6AWG. I was discussing the highest load scenario on the run from the breaker that feeds the Cheap Heat. That will be 10AWG. However, when calculating voltage drop, one has to factor in all potential resistance, including the power cord running to the RV from the pedestal, and even the wiring feeding the pedestal as well as the total load in the RV and the system feeding the pedestal. Adding insult to injury, loads are highly variable so one has to calculate for worst case scenarios. Even worse, in the case of the pedestal and its feed, you have no control over the variables short of resorting to an autoformer (which will cost you amperage in low voltage events, another ugly variable to deal with) or moving.

[2-MTnesters]

Here is a neat video on the Cheap Heat system. Gives info on wire size and touches on installation. Also to answer a wire size question, the 50amp wiring in the Montana (internally and shore cord) is 6AWG. The wiring I have ran to the 50 amp RV hookup I have installed at the house is also 6AWG. Tim

[pianotuna]

Hi Lady Fitz,

It is my understanding that 50 amp cords for RV's are #6 wire, not #10, so the voltage drop should not be an issue, except at the pedestal.

I do observe significant voltage drop on the 30 amp service on the order of 10% when running 2400 watts (30 foot run to the pedestal with #10 wire). I try to never exceed 2880 watts on a continuous basis.

[Lady_Fitzgerald]

pianotuna wrote:
Hi Lady Fitz,

Thanks for the link. I'll read it carefully.

22 amps @ 240 volts--but I believe (or I hope) it is balanced between the 2 120 volt "legs". So wattage is 5280 and btu's are 18016 giving a total daily maximum output with no voltage drop of 432384 btu's.

I see the 50 amp ones are balanced--but the biggest is only 21.6 amps

That means a few less watts and a few less btu's

21.6 @ 120 x 2 = 5184 watts = 17688 x 24 = 424512 btu's per day with zero voltage drop.

I'm not terribly familiar with voltage drop on 50 amp units. Is it an issue from time to time?

As long as the wiring is sized appropriately for the current draw and distance of the run, it won't be an issue. 10AWG usually would be plenty for even the largest unit (that is rated for 30A and only 22A is being drawn). It's not likely an RV will have a run from where the power enters the RV to the Cheap Heat that will be long enough for voltage drop to be an issue. Normally, a 60' run of 10AWG Romex will handle 30A at 240v with only a 2% voltage drop (roughly 5v). I can't see any installation using more than 10-15' from the power source which would keep voltage drop down to 2.4v or less, normally not enough to loose sleep over.

Keep in mind that this is assuming the supply source has been adequately wired. If the wiring to the pedestal is inadequate for the total load being placed on it, for example, then there will be an excessive voltage drop. Calculating voltage drop can be a real headache (and a pain elsewhere) because of all the variables that can be involved.

[pianotuna]

Hi Lady Fitz,

Thanks for the link. I'll read it carefully.

22 amps @ 240 volts--but I believe (or I hope) it is balanced between the 2 120 volt "legs". So wattage is 5280 and btu's are 18016 giving a total daily maximum output with no voltage drop of 432384 btu's.

I see the 50 amp ones are balanced--but the biggest is only 21.6 amps

That means a few less watts and a few less btu's

21.6 @ 120 x 2 = 5184 watts = 17688 x 24 = 424512 btu's per day with zero voltage drop.

I'm not terribly familiar with voltage drop on 50 amp units. Is it an issue from time to time?

[Lady_Fitzgerald]

Ok, I can accept those figures (I never believed the smallest unit would ever be adequate; I just wanted to see if you could actually back it up with something more solid than your opinions); there are a few points, though:

The largest unit draws only 22A (at 240v).

Propane furnaces normally cycle on and off. Cheap Heat can run full time so it usually can put out the same amount of heat as a lager rated gas furnace. Of course, we don't know if that furnace ran full time or not during the night. We also don't know the ambient temperatures.

Aqain, all one would need would be a two stage thermostat (and, if the thermostat leaves the first stage on when it switches to the second stage, a relay) to allow the furnace to switch from electric to propane when and if the temperature drops too low for the Cheap Heat to keep up with.

I stand corrected on the location.

While I'm at it, Trailer Life recently had an article on the Cheap Heat. You all can read it here.

[SWD]

pianotuna wrote:
Hi Lady Fitzgerald.

Please read more carefully. The folks who were visiting were from Tx. The Montana is in KY.

Here are the numbers:

He was running 3000 watts of heaters that's 10236 btu's. He went through 45 pounds of propane, but we don't know the time frame other than it was Thanksgiving. Let's guess it was a week?

Propane does 21499 btu's per pound. Lets say his furnace was only 70% efficient? (it is probably 80). 21499 X 0.7 =~ 15000 btu's (rounding down for worst case?)

15000 x 45 = 675000 btu's

675000 / 7 days = 96428 btu's per day from the furnace.

10236 x 24 = 245664 btu's from the two electric heaters

So his heat requirements are 342092 btu's per day.

The smallest cheap heat is 16 amps or about 1920 watts which is 6551 btu, assuming zero voltage drop.

6551 x 24 = 157224

That means the smallest cheap heat is in a deficit position and can't possibly work. But that is no surprize.

The largest cheap heat is 42 amps or about 5040 watts. That works out to 17197 btu's

17197 x 24 = 412728 btu's

This is more than enough and the unit would cycle on and off.

The medium If I remember correctly (they have removed the web page, so I can't go back and check) is 32 amps

32 x 120 = 3840 watts or 13102 btu's (again with zero voltage drop)

13102 x 24 = 314448 btu's. So it might not be enough at night.

Also I maximized the possible output of the cheap heat and minimized the propane furnace. If I redid it with the propane at 80% efficiency and a voltage drop of 10% the medium size probably won't "cut the mustard". Certainly it would be constantly be on during the night, if not 24 hours. Since by design the cheap heat is "either or" the propane furnace would have to carry the entire load at night when the temperatures are the lowest. Too sad, too bad.

If the visit were only 4 days then even the largest 42 amp unit would be being pushed to its limits.

We also don't know if it was 45 lbs of propane--it might be more--or it might be less.

I hope I did not make any errors. This is a "back of an envelope" calculation, so only one step up from a "guess".

I'm sure you have more expertize than I do in this area lady fitz. Please knock the stuffing out of this email so I can learn from you.

Good calculating Pianotuna. thanks for taking the time to do this.

[pianotuna]

Hi Lady Fitzgerald.

Please read more carefully. The folks who were visiting were from Tx. The Montana is in KY.

Here are the numbers:

He was running 3000 watts of heaters that's 10236 btu's. He went through 45 pounds of propane, but we don't know the time frame other than it was Thanksgiving. Let's guess it was a week?

Propane does 21499 btu's per pound. Lets say his furnace was only 70% efficient? (it is probably 80). 21499 X 0.7 =~ 15000 btu's (rounding down for worst case?)

15000 x 45 = 675000 btu's

675000 / 7 days = 96428 btu's per day from the furnace.

10236 x 24 = 245664 btu's from the two electric heaters

So his heat requirements are 342092 btu's per day.

The smallest cheap heat is 16 amps or about 1920 watts which is 6551 btu, assuming zero voltage drop.

6551 x 24 = 157224

That means the smallest cheap heat is in a deficit position and can't possibly work. But that is no surprize.

The largest cheap heat is 42 amps or about 5040 watts. That works out to 17197 btu's

17197 x 24 = 412728 btu's

This is more than enough and the unit would cycle on and off.

The medium If I remember correctly (they have removed the web page, so I can't go back and check) is 32 amps

32 x 120 = 3840 watts or 13102 btu's (again with zero voltage drop)

13102 x 24 = 314448 btu's. So it might not be enough at night.

Also I maximized the possible output of the cheap heat and minimized the propane furnace. If I redid it with the propane at 80% efficiency and a voltage drop of 10% the medium size probably won't "cut the mustard". Certainly it would be constantly be on during the night, if not 24 hours. Since by design the cheap heat is "either or" the propane furnace would have to carry the entire load at night when the temperatures are the lowest. Too sad, too bad.

If the visit were only 4 days then even the largest 42 amp unit would be being pushed to its limits.

We also don't know if it was 45 lbs of propane--it might be more--or it might be less.

I hope I did not make any errors. This is a "back of an envelope" calculation, so only one step up from a "guess".

I'm sure you have more expertize than I do in this area lady fitz. Please knock the stuffing out of this email so I can learn from you.