Heat Loss Calculations, Insulation for HVAC?

[buswarrior]

Hello busnuts

In the interest of furthering the busnut science, I conducted some heating experiments at the northern cold weather testing ground with my MC8.

A number of electric, fan forced, 1500 watt heaters, run on the ends of extension cords fed in the driver's toll window, and squeezed shut. Placed on the floor, evenly distributed fore and aft, and aimed fore or aft, as I felt inclined for an attempt at even distribution.

Fahrenheit is used, for the benefit of my southern neighbours.
If you can spell Celsius, you also know how to convert?

An IR temp gun aimed all over to SWAG some temperatures.

Coach is sitting outside and is cold soaked, no lingering heat sources like a warm engine or stuff in the bays.

No breeze to speak of.

Stock roof, stock walls, stock double pane windows. Coach is pretty much open front to back, 2 roof airs on the roof, the whole roof covered in snow, (pretty much the same as my picture over there in the margin) so no clear path for lingering air currents.

Working during the night, so as to get the interference of that pesky sunshine out of the way.

Here's some data:

First attempt:

On one heater (because I plugged the other two into one circuit...) ahem...

in 4 hours, the single had the interior at 12 degrees and the outside steady at 0 degrees.

ok, get it working right and continue...

On 3 heaters, in another 5 hours, inside 41 degrees, outside warmed up to 10 degrees by morning.

Second attempt from stone cold:

With 4 heaters, outside temp steady at 0 degrees:

2 1/2 hours: 43 degrees inside
4 hours: 45 degrees inside
5 hours: 48 degrees inside
6 1/2 hours: 52 degrees inside

and with the novelty worn off, and the electric meter spinning and no government grant to fund this research assignment, I unplugged the lot and went to bed.

Yes, I should have waited for the temp to plateau...

So, someone smarter than me, does the data follow some sort of believable trend?

What else is this good for?

Some vote of confidence in the stock materials?

happy coaching!
buswarrior

[JohnEd]

One 1,500 watt cube will raise the temp inside my S&S 30 footer some 30 degrees.  With 2 heaters I can maintain 74 degrees down to (74 - 60) 14 degrees.  Those 3,000 watts translate to BTU and my propane furnace is rated at 48KBTU.  From 35 degrees it is toasty and the furnace kicks off in less than 10 minutes of run time.  Right back on now, mind you.

You seem to need three times as much heat as I do and you warm way slower with the cubes.  You need to change the watt units to BTU in order to purchase/size a furnace and when you get the number of what is "required" you multiply that by three before you buy.  I would install two and each would be able to carry the entire coach down to 10 degrees.

I guess you are doing as well as can be expected and I would have thought poorer performance.

John

[buswarrior]

JohnEd, I had the good fortune to do my tests down at 0 degrees Fahrenheit, where there is less likely to be influence from lurking unmeasured residual heat in the coach mass.

Without an ambient temperature, heat rise can't be compared directly.

I know enough engineering to be dangerous, not enough to come up with answers!

happy coaching!
buswarrior

[JohnEd]

Without an ambient temperature, heat rise can't be compared directly.Without an ambient temperature, heat rise can't be compared directly.

Not to argue...really.  A btu is a btu and i think it is a unit of energy.  I think it has to do with raising the temp of a liter of water a single degree or somthing like that.  They don't spec the start temp that I have seen.  Adding a btu to 35 degree water should raise the temp one degree and you should get the same result from adding a btu to water that is at 200 degrees using my example.  What am I missing?  Could be all that is in the book, I admit.

Thanks for taking the time...truely,

John

[Lin]

Of course, insulation is the key.  I spoke to someone recently that said his coach was insulated with 9 layers of thermal tile insulation which he claimed was similar to what was used on the Space Shuttle.  He claimed to have very little heat loss and never needed any heat camping in Quartzsite through the winter.  Now, that is nowhere near 0 F, but since it can spend a lot of nights at least down into the 40's, it seemed to be an impressive claim.  For California climate people like myself, basic insulation is fine.  You zero degree folks should bulk up with the best.  Insulated window coverings would also probably be worth the cost.