Skip to main content ↑ ↓
Topic: ROOF AC QUESTION (Read 940 times) previous topic - next topic

ROOF AC QUESTION

When I am going down the highway can my roof ac units work off the house batteries or do i need the generator to be running.
Rick & MJ Berry
1998 U320 40'
Ohio

Re: ROOF AC QUESTION

Reply #1 –
You need the generator to be running. Unless you have a large inverter and big lithium battery bank. I can run min for 5 hours off the battery but won't do it unless I have to.
'99 U320 40 WTFE
Build #5462,
1500 Watts Solar 600 amp Victron lithium
2012 Jeep Grand Cherokee Overland Hemi
Instagram bobfnbw
Retired

Re: ROOF AC QUESTION

Reply #2 –
So did you say earlier that one of the units works through the inverter and i suppose the other does not?
Rick & MJ Berry
1998 U320 40'
Ohio

Re: ROOF AC QUESTION

Reply #3 –
Rick,

Most coaches come from the factory with the A/C units wired through the main breaker panel.  This means they either require shore power or the generator running to operate.  Some forum members have modified their electrical system to allow the inverter to power one or both A/C units.  As Bob mentioned, to run a air conditioner off inverter requires a sizable house battery bank, a large capacity inverter, a big alternator, and (usually) a "soft start" module installed on the A/C unit.

Except for the newer "all electric" coaches, running A/C off inverter is not very practical.  Best to use the generator going down the road.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: ROOF AC QUESTION

Reply #4 –
As a FYI, the IH45 has the second AC unit from the front on one of the Inverters from the factory. 

It is one quick way to run the batteries down when not connected to shore power and engine or generator is not running.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: ROOF AC QUESTION

Reply #5 –
100% of the coaches of your vintage will only run the roof A/C off the generator FROM THE FACTORY.

Have a few upgraded their electrical system SUBSTANTIALLY. Enough to run one A/C-- yes.  But this is the very rare exception.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: ROOF AC QUESTION

Reply #6 –
Thanks for the info.
Little by little.
Rick & MJ Berry
1998 U320 40'
Ohio

Re: ROOF AC QUESTION

Reply #7 –
Good info. So any good reason to NOT run the generator while traveling down the road?
1996 U295-36, Cummins 300hp, 8.3. Build number 4864. Vin number 1F97D536XTNO54271. Purchased October 31, 2019.

Re: ROOF AC QUESTION

Reply #8 –
Quote from: dans96u295ft –
Good info. So any good reason to NOT run the generator while traveling down the road?


The only downside I have found is the extra fuel you use. :D  :D  :D

We run ours in summer or any other time we need AC.
1998 U320 40'
2005 GMC Yukon
MC# 17609

Re: ROOF AC QUESTION

Reply #9 –
Using generator to run AC is a good reason for exercising it.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: ROOF AC QUESTION

Reply #10 –
Quote from: 18360 –
So did you say earlier that one of the units works through the inverter and i suppose the other does not?

Correct. Mine is wired to run the front AC unit via the inverter panel only. The other is thru the main circuit breaker panel.
Haven't tried running it off battery power alone since I switched to the Attwood AC and soft start. Going down the road we run the genny. If I ever changed out the alternator to a high capacity one, I could run it via that I suppose with the solar. But at this time my alternator doesn't charge my house batteries. Future project.
'99 U320 40 WTFE
Build #5462,
1500 Watts Solar 600 amp Victron lithium
2012 Jeep Grand Cherokee Overland Hemi
Instagram bobfnbw
Retired

Re: ROOF AC QUESTION

Reply #11 –
Quote from: Bob and Julie –
Correct. Mine is wired to run the front AC unit.  If I ever changed out the alternator to a high capacity one, I could run it via that I suppose with the solar. But at this time my alternator doesn't charge my house batteries. Future project.

I would ask AM Solar what is the best way to connect your current engine alternator to charge your lithiums, since they are the ones that did your lithium  batteries for the previous owner, they will have detailed info on that install.  They probably are the ones that wired the front a/c to run off the inverter.

97 U295 40, Build #5040, 6C8.3 325 HP
Oregon Continuous Traveler
Samsung Residential #RF20HFENBSR,
Xantrex SW2012, (3)AGM8D Hse, (2)AGM Grp24 Eng, Victron BMV-712, 1800w Solar 4 LG & 2 Sunpower
Extreme Full Body Pt w/hdlmps, new furn/floor, 4 down Lexus 2004 GX470 AWD curb weight 4,740 lbs
Prev: 1990 Barth, 10L 300 2 yrs; 91&92 Monaco Signature, 10 yrs, 10L C 300 &  6C8.3 300; 1997 ForeT 6C8.3 325 since May 2017.  Employed by Guaranty RV 14+ yrs.  Former VW New Car Dlr/Service Dlr, Sales Mgr, Rv Sales, and Service Adviser from 1968-2017
"Don't criticize what you can't understand" Bob Dylan

Re: ROOF AC QUESTION

Reply #12 –
My thoughts exactly Jack.
Thinking about putting a very large 300 plus amp alternator in at some point. Setting like an electrodyne or ecotech alternator going through a DC to DC charger.
'99 U320 40 WTFE
Build #5462,
1500 Watts Solar 600 amp Victron lithium
2012 Jeep Grand Cherokee Overland Hemi
Instagram bobfnbw
Retired