Electric Conversion ?

[dave silva]

> Johnny,
>
> I agree with the first half of your first line, but it ends at the second half of that line because operating temperature window is so small.
>
> People need heat most when OAT gets below 40°F. Heat Pumps that are working from air essentially become useless below about there.
> So, if Teslas has heat pumps for cab heat, they would still need resistance heating.
>
> Even trying to run in the low 40s, residential heat pumps have to be equipped with "flash heaters" that come on and fire a burst of heat to
> defrost the evaporator during low temperature operation.
>
> Matt

That 40 degree figure gets tossed around a lot. My ductless mini-split heat pump makes heat down to 18F (lowest temp since we installed) It makes 3
tons of AC at about 1500 watts

--
Dave & Ellen Silva

1972 Revcon Olds 455, toro drive train. All Stock

 

[hal stclair]

> > Johnny,
> >
> > I agree with the first half of your first line, but it ends at the second half of that line because operating temperature window is so small.
> >
> >
> > People need heat most when OAT gets below 40°F. Heat Pumps that are working from air essentially become useless below about there.
> > So, if Teslas has heat pumps for cab heat, they would still need resistance heating.
> >
> > Even trying to run in the low 40s, residential heat pumps have to be equipped with "flash heaters" that come on and fire a burst of heat to
> > defrost the evaporator during low temperature operation.
> >
> > Matt
>
> That 40 degree figure gets tossed around a lot. My ductless mini-split heat pump makes heat down to 18F (lowest temp since we installed) It
> makes 3 tons of AC at about 1500 watts

Don't know where you get that 1500 watt figure but a 16 seer split Pioneer unit draws 5621 watts heating, 5889 cooling. They also claim 32 f as the
'Minimum Operating Temperature' . I'd sure love to find something near your figure.
Hal
--
1977 Royale 101348,

1977 Royale 101586, Diesel powered,

1975 Eleganza II, 101230,

1974 Eagle Bus 45',w/slideout,

Rio Rancho, NM

 

[adolph santorine]

Hal

Agreed. I’ve never run a heat pump when the outside is less than 40 f

One btu is 0.293 watts according to the engineering formula book I’ve dragged around about forever, but that’s not a measure of the electrical load it presents.

So there’s something I’m not understanding.

We are also bound by 4,000 watt and 6,000 watt generators.

Tomorrow, I’m putting one of these on top of my coach.

https://www.airxcel.com/coleman-mach/products/heat-pumps/mach-10-heat-pump

15,000 btu cooling.

Their spec says 14.2 amps (1,704 watts) to cool and 16 amps heating (1,920 watts) with an asterisk about an optional heating accessory. No where near the .293 x 15,000 from the formula book.

The whole thing sits behind a 20 amp (2,400 watts) circuit breaker.

I looked around at other units, and it seems that 13-15 amps delivers about 15,000 btu of cool.

Dolph Santorine

DE AD0LF

Wheeling, West Virginia

1977 ex-Palm Beach TZE167V100820
Howell EFI/EBL , Reaction Arms, Manny Transmission

>

>>> Johnny,
>>>
>>> I agree with the first half of your first line, but it ends at the second half of that line because operating temperature window is so small.
>>>
>>>
>>> People need heat most when OAT gets below 40°F. Heat Pumps that are working from air essentially become useless below about there.
>>> So, if Teslas has heat pumps for cab heat, they would still need resistance heating.
>>>
>>> Even trying to run in the low 40s, residential heat pumps have to be equipped with "flash heaters" that come on and fire a burst of heat to
>>> defrost the evaporator during low temperature operation.
>>>
>>> Matt
>>
>> That 40 degree figure gets tossed around a lot. My ductless mini-split heat pump makes heat down to 18F (lowest temp since we installed) It
>> makes 3 tons of AC at about 1500 watts
>
> Don't know where you get that 1500 watt figure but a 16 seer split Pioneer unit draws 5621 watts heating, 5889 cooling. They also claim 32 f as the
> 'Minimum Operating Temperature' . I'd sure love to find something near your figure.
> Hal
> --
> 1977 Royale 101348,
>
> 1977 Royale 101586, Diesel powered,
>
> 1975 Eleganza II, 101230,
>
> 1974 Eagle Bus 45',w/slideout,
>
> Rio Rancho, NM
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[billvv]

Dolph,
I might be misunderstanding your comments but I think you are wondering why it makes more energy (in cooling) than it consumes (in electricity).

That's the wonder of the refrigeration cycle. Those 15000 Btus of cooling is heat that is taken from the coach and released to the outside air. The
refrigerant grabs it in the evaporator when it goes from a liquid to a gas then carries it to the condenser which releases it when it goes back to a
liquid.

The energy to compress and push it through the pipes is less than the energy that is carried back and forth.

--
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid
November 2015.

 

[adolph santorine]

Thanks, Bill.

That’s exactly what I didn’t understand.

Dolph Santorine

DE AD0LF

Wheeling, West Virginia

1977 ex-Palm Beach TZE167V100820
Howell EFI/EBL , Reaction Arms, Manny Transmission

>
> Dolph,
> I might be misunderstanding your comments but I think you are wondering why it makes more energy (in cooling) than it consumes (in electricity).
>
> That's the wonder of the refrigeration cycle. Those 15000 Btus of cooling is heat that is taken from the coach and released to the outside air. The
> refrigerant grabs it in the evaporator when it goes from a liquid to a gas then carries it to the condenser which releases it when it goes back to a
> liquid.
>
> The energy to compress and push it through the pipes is less than the energy that is carried back and forth.
>
> --
> Bill Van Vlack
> '76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid
> November 2015.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[johnny]

And that's true heating or cooling - as long as you're above the transfer temperature of the pump. On my 23 foor, iot was 40 degrees, ant which point
the unit simply shut itself off. I woke up in Orlando one December freezing my ass off because it had stopped and it was like 30 outside.
The electric strip heaters work on the figure you gave, less inefficiencies. 1 to .293. An incredibly inefficient way to heat something.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell