Furnace BTUs 18 vs 30

pianotuna wrote:
Hi DC,

It depends on the RV and where it is. I can keep my RV warm (23 c, or 74 f) at -36 c (-33 f) with 19000 btu's (peak load including, inverter/charger, fridge and water heater of 5400 watts). Most folks would not be in their RV at those temperatures.

I've already explained how a too large furnace may allow pipes to freeze.

My opinion and advice are to go with the smaller furnace, heated basement, tank heaters and pipe heaters.

I have tested down to -36 c. SDparkowneroperator has RV'ed down to -43 F, so perhaps ask him what he recommends.

I hope to never be in those temps, camper or house. I think your stance is reasonable.

I have no real experience camping in sub-freezing temps (though I spent a lot of time in my RV in sub-freezing temps while swapping out the engine!) but...it's fun to speculate anyway.

I get the argument that a larger furnace will get the living area up to the set temp faster and then shut off. But I think the point pianotuna is making is that the storage areas (where tanks and pipes are) will cool faster than the living space. So, a smaller furnace running for a longer period of time will give off more constant radiant heat to those areas. At least that's how I interpreted it. Again, I have no real world experience but my fresh water and plumbing is all in areas that aren't directly heated by the furnaces, but since the ducts run through they warm those spaces. I kind of get the small furnace argument.

Pianotuna... Never mind.

:R

Hi DC,

It depends on the RV and where it is. I can keep my RV warm (23 c, or 74 f) at -36 c (-33 f) with 19000 btu's (peak load including, inverter/charger, fridge and water heater of 5400 watts). Most folks would not be in their RV at those temperatures.

I've already explained how a too large furnace may allow pipes to freeze.

My opinion and advice are to go with the smaller furnace, heated basement, tank heaters and pipe heaters.

I have tested down to -36 c. SDparkowneroperator has RV'ed down to -43 F, so perhaps ask him what he recommends.

Pianotuna, a large furnace will keep a coach whatever temperature you set the thermostat to. A smaller furnace may or may not do so do to the lack of available BTU's. Your pipes and tanks will be no colder, in fact quite the opposite, with the larger furnace. If you want to frame this discussion in terms of -30 to -40 that will apply to very few folks as camping in those conditions seriously borders on the insane. :E

If it is going to be that cold you might just want to stay home snug and warm in the stick and brick and wait for better, safer conditions. BTW: It looks like ole man winter has arrived early here in Tucson.... it got down to 42 last night. We are looking at a high of only 58, dang, I may need to wear long pants out on the golf course this afternoon. :B

As always.... Opinions and YMMV

CPBIGGS wrote:
I don't know Bruce, he said BTU not BTUH.

The "H" (or "h" in the case of cooling) is assumed. Ratings are typically in "BTUs"

nomad297 wrote:

CPBIGGS wrote:
Starcraft left a message. They only offer an 18K BTU, (not BTUH)

:h

If it's not BTUH, then what is it? BTU per minute? Per day? Per week? Is sort of like saying you inflate your tires to 80 PS. Pounds per square...what?

It is BTUH. I know what I'm talking about.

Bruce

I don't know Bruce, he said BTU not BTUH.

Hi DC,

If the furnace doesn't run often enough and you do not have tank heaters the tanks and/or pipes may freeze. I'm talking about temperatures in the -30 to -40 area. The better insulated the RV floor and the larger the furnace, the worse the issue.

If a smaller furnace runs all the time--then the tanks won't freeze, and the air inside the RV will be mixed fairly evenly. This means no cold spots or drafts can be created by poorly heated areas such as the "step" inside a class C. Therefore it is more comfortable.

Does that help with my original statements?

I found out the hard way that my fresh water system, which is inside the heated area of the RV, would freeze up when I was driving--because the living quarters were heated by the engine/dash heat. I tried a 1500 watt heater under the sink and still had freeze ups.

The final solution was a thermostatically controlled dual window fan which I used to replace the cold air return grill for the furnace. The thermostat is mechanical and is near the water pump. This had the happy effect of pressurizing the duct work and solved the freezing problem.

Desert Captain wrote:
"The closer the furnace is to 100% run time the more the comfort."

"With a larger furnace the tank heaters become even more necessary."

Huh? :h

You are going to have to help me out with those two statements. I would have to argue that a larger furnace that has to run significantly less to maintain the same temperature, in addition to being more efficient will generate less noise (a part of overall comfort).

A larger furnace, generating more heat, in no way necessitates a greater need for tank heaters. Most folks just crack the cabinet doors or a drawer or two to facilitate the abundant warm air's circulation. If anything a coach with a larger furnace might be just fine with no tank heaters.

I have tank heat but have yet to run it as the large (35K BTU) furnace keeps our little 24' C so toasty with minimal run time. On a typical night below freezing the furnace only kicks on a few times for 5 minutes with the thermostat set at 65. Less furnace is a problem not a solution.

As always.... Opinions and YMMV.

:C

CPBIGGS wrote:
Starcraft left a message. They only offer an 18K BTU, (not BTUH)

:h

If it's not BTUH, then what is it? BTU per minute? Per day? Per week? Is sort of like saying you inflate your tires to 80 PS. Pounds per square...what?

It is BTUH. I know what I'm talking about.

Bruce

SteveAE wrote:

CPBIGGS wrote:
Starcraft left a message. the floor is insulated at R22 and the roof at R24.

I really like the way that RV manufactures can magically get higher R values per inch than home builders can using the exact same (or often inferior) materials.

Steve

You are making incorrect assumptions of the insulating products that are available today. I spend 50 hours a week purchasing commercial and residential building materials, which includes insulating products. There are a myriad of combinations of different products that can be used to create R24 ratings within a 3" space. The answers I was given to my questions were quite satisfactory both in the products used and the manufacturing process of the walls, floor and roof. I know have no doubt the walls, floor and roof are substantially insulated for an 18K furnace. I am not convinced, at this point, an 18K furnace will be enough to overcome heat loss through the windows and slide.