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Old 08-11-2020, 08:43 PM   #1
Mini-Skoolie
 
Join Date: Jun 2020
Location: Ohio
Posts: 26
Year: 2003
Coachwork: Bluebird
Chassis: All American
Engine: Cummins 8.3
Alternator charged battery bank for dash heat/ac

I've spent a bit of time digging through old posts and a lot of situations come close to mine but none quite what I've got going on. I've got a 40' pusher with two under seat heaters and the in dash heater/defrost, no ac.

During my conversion i plan on building a physical wall behind the driver and passenger jump seat with sliding doors to isolate the area. The cockpit will be the focus of HVAC while driving and treated as an un-heated/cooled "mudroom" for shoes and coats when parked.

I'm looking at an 8'x8'x8' cube that i want to heat and cool using the existing vents in the dash with an electric ran unit. My current thought is to have a voltage regulator coming off my alternator into a dedicated battery bank then an inverter to run a residential style ac until with a heating coil. I'm considering a separate unit just for defrost.

Has anyone done anything similar? Does anyone have suggestions as to what to do differently?
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Old 08-11-2020, 09:28 PM   #2
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 13,619
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
I use engine driven A/C for driving.. the only reason to use an electric unit while driving is if you want it to also function while parked.. ie a camper A/C over the driver area run by an inverter and alternator .. which in turn can be used for A/C when you are parked on generator or shore power..



12 / 24 volt DC moile A/C is low BTU and wont begin to cool you on the road.. even in a rear engine bus.. you can reliably get 40-50k BTU out of a single compressorrun by the engine.. a sanden enhanced SD7 will give you upwards of 60-70k..


in my DEV bus I gutted the driver heater box and installed a heat / cool evaporator unit.. its about 20,000 BTU A/C and I think 25,000 BTU heat.. that runs my driver heat and A/C.. i left my original right-side defrost / door heater in.. although I completed rebuilt it.. this gives me extra heat for cold winter into the right side of the glass and the cold stepwell..



I ducted out dashboard vents and floor vents that i can open and close as desired for the heat / cool (left) side.. a separate heater unit was installed to operate the left side defrost.. I split the air intake of the defrost unit from outside air and off the evaporator of the heat / cool.. so in effect if I turn on the compressor in the driver unit i have dehumdified defrost like your normal automobile has.. an 8x8x8 area you may want a slightly larger heat / cool unit.. I have a 40-50k as my midship heat / cool cabinet unit.. ive got the lines and such running to it to get as much as i can out of it.. which it does real well.. my bus is all stock no tint / factory walls, seats, factory everything so it requires lots of A/C..



there is an in-dash evaporator thats made for Thomas HDX's


this one is a somewhat shallow depth heat/cool ducted where you can set for heat or defrost with a dial.. and has 30k BTU of A/C..


https://proairllc.com/960-electric-a...ool-dash-unit/


something like this could likely be mounted in dash next to or inplace of ther step well system..


https://proairllc.com/wm2030-medium-...-construction/


theres all kinds of stuff.. I used an oopen-frame device with flex ducts coming off it and moubted it inside the old original heater cabinet which I had gutted out since it was broken and the coil was leaky..


with my dash air, the midship and now i inmstalled a rear system.. im able to keep the whole bus in the hot 102 degree dallas heat in the mid 70s inside on the road..
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Old 08-12-2020, 03:03 AM   #3
Bus Crazy
 
Join Date: Nov 2016
Posts: 1,766
You need no battery bank for anything powered by an alternator while driving.

The engine Starter batt is enough of a buffer, keep that in parallel.
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Old 08-12-2020, 03:48 AM   #4
Bus Geek
 
Join Date: Sep 2015
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Year: 2002
Coachwork: Thomas Built Bus
Chassis: Freightliner FS65
Engine: Caterpillar 3126E Diesel
Rated Cap: 71 Passenger- 30,000 lbs.
I just saw Chris' DEV bus here in Texas. It was in the 90's when he started it up. After a minute, the air intake thermometers were in the 80's. After 5 minutes, all were reading in the 70's. This was with the passenger door open.


What you are asking can be done. I have a roof-top A/C unit (13.5K BTU) that runs off our inverter (110 V AC) while driving. We also installed a second 350A alternator to supply the load. While driving with the A/C on high, it draws just under 120A (DC at the inverter). So you may have to either install a second alternator or a beefier alternator otherwise the air conditioning will suck your batteries dry. Note: We also installed a HOUSE battery bank to keep from drawing down the chassis batteries.


Edit: You will want to locate your inverter as close to the alternator as possible to minimize line drop in the DC supply cables. This also reduces the minimum size of the cables.
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Old 08-12-2020, 08:23 AM   #5
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 13,619
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
+1 on the shortest 12 volt cables you can have... when I installed my 2nd battery bank in the back of that DEV bus.. I had to run 4/0 welding cable from the front to the back to not have significant voltage drop between my alternator and my second battery bank. .. if I do something liek that again ill mount my inverter and 12 volt batteries close to the charging source (alrternator)
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Old 08-13-2020, 06:17 AM   #6
Mini-Skoolie
 
Join Date: Jun 2020
Location: Ohio
Posts: 26
Year: 2003
Coachwork: Bluebird
Chassis: All American
Engine: Cummins 8.3
Quote:
Originally Posted by cadillackid View Post
in my DEV bus I gutted the driver heater box and installed a heat / cool evaporator unit.. its about 20,000 BTU A/C and I think 25,000 BTU heat.. that runs my driver heat and A/C.. i left my original right-side defrost / door heater in.. although I completed rebuilt it.. this gives me extra heat for cold winter into the right side of the glass and the cold stepwell..



I ducted out dashboard vents and floor vents that i can open and close as desired for the heat / cool (left) side.. a separate heater unit was installed to operate the left side defrost.. I split the air intake of the defrost unit from outside air and off the evaporator of the heat / cool.. so in effect if I turn on the compressor in the driver unit i have dehumdified defrost like your normal automobile has.. an 8x8x8 area you may want a slightly larger heat / cool unit.. I have a 40-50k as my midship heat / cool cabinet unit.. ive got the lines and such running to it to get as much as i can out of it.. which it does real well.. my bus is all stock no tint / factory walls, seats, factory everything so it requires lots of A/C..



there is an in-dash evaporator thats made for Thomas HDX's


this one is a somewhat shallow depth heat/cool ducted where you can set for heat or defrost with a dial.. and has 30k BTU of A/C..


https://proairllc.com/960-electric-a...ool-dash-unit/


something like this could likely be mounted in dash next to or inplace of ther step well system..


https://proairllc.com/wm2030-medium-...-construction/
I initially wasn't sure what this was for and was planning on removing it but I've since found out that it's a very nice thing to have... Would this heater be able to run through the two things you provided links for?

Follow up question, would this heater be strong enough to provide defrost while i find other means to cool?

Bonus question, would this heater be able to run a heat exchanger for a radiant floor heating system?20200813_070613.jpg20200813_070607.jpg
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Old 08-13-2020, 07:36 AM   #7
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 13,619
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
that heater can be piped to fan-coils and be used to heat the inside of the bus while the engine is off.. for radiant heat im not sure it wouldnt be too hot.. most of those hasve a preset coolant temperature of 170 degrees before they shut off.. I know mine I cannot change that setpoint.. im not sure if on that one you can or not.. ie to make it lower temp for floor heat..
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Old 08-13-2020, 07:46 AM   #8
Mini-Skoolie
 
Join Date: Jun 2020
Location: Ohio
Posts: 26
Year: 2003
Coachwork: Bluebird
Chassis: All American
Engine: Cummins 8.3
I did some research and found that it was rated at a fuel consumption of .4 gallon of fuel an hour... Not sure how reliable that information is but if that's true then I'd be using 67 gallons across 7 days. That's roughly $200 in diesel a week. If there's not a way to throttle the heater then it's not really an option for stationary heat for me, in any form.
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Old 08-13-2020, 02:04 PM   #9
Bus Crazy
 
Join Date: Nov 2016
Posts: 1,766
pot belly wood stove
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