| Author | Message | ||
| Jim Wilkerson (Wagwar)
Registered Member Username: Wagwar Post Number: 5 Registered: 12-2009 Posted From: 149.173.6.51 Rating: N/A |
Hi, I have reviewed previous threads and archives, but I still have some basic questions regarding A/C. The bus I'm looking at has had the coach A/C removed and has two rooftop units. The inverter and house batteries are not enough to support running either of the rooftop units while running down the road. I know that I could run the gen to run the A/C, but I don't like that idea. What are my other options for A/C while running down the road? Can the engine alt. (24 v) run the A/C if it was fed through the inverter? The inverter is 3000 watt Trace, but probably 12 v not 24 v. How many amps does the alt need to be to support one or two rooftop units? How large an inverter is needed? Are there inverters that accept 12v and/or 24v? How much is this likely to cost? Thanks, Jim | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1811 Registered: 10-2003 Posted From: 71.58.71.157  Rating: N/A |
what kind and model of coach with what engine do you have? | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1758 Registered: 12-2000 Posted From: 76.71.105.107  Rating: N/A |
Way back, I did some math and determined that running two roof airs via the Trace 4024 inverter, driven by the stock 24V MC8 alternator, the electric load on the alternator is close enough to what running the stock AC fans is to be a draw for this busnut. The inverter needs some good ventilation, makes lots of heat. And then I stopped thinking about it. happy coaching! buswarrior | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 158 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
My only A/C is the roof top air. I run my Powertech 10kw going down the road with no problems. It does knock off about 1/2 mpg. Good LUck, TomC | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1036 Registered: 10-2006 Posted From: 69.19.14.22  Rating: N/A |
There are DC 24V air cond , that would work just fine , but then you are stuck with the same sized bill for a HUGE battery charger so you can use them from house current. Big Alternator is on the bus , Good Sine wave inverter is next purchase. With proper wiring you might use 2 smaller inverters than a big buck (but great!) Trace. FF | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 471 Registered: 10-2003 Posted From: 74.244.14.221  Rating: N/A |
I also run my powetech 15 KW going down the road. At 1/2 - 3/4 of a galln an hour I can buy a lot of diesel for the cost of setting up a good inverter/battery/alt combo | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 472 Registered: 10-2003 Posted From: 66.165.176.62 Rating: N/A |
I hsould add if I wanted to get away from running the gen I would probably look to an auxilary engine driven AC compressor and unit like this http://www.welchindustries.com/ | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
Registered Member Username: Pete_rtsdaytona Post Number: 587 Registered: 1-2005 Posted From: 97.104.18.110  Rating: |
If you have the standard Detroit Diesel 50DN gear driven generator common on MOST buses: It is capable of producing approx 4600 watts at idle - (600 rpms) 7000 watts at 1000 rpm and above Inverters have about a 10% lose Rooftop AC units 13kbtu-15kbtu approx 1800 watts (compressor and fan on - run watts) - 24v 3000k inverter will support one AC unit ok 24v 4000K inverter will USUALLY support 2 AC units (if you run very very little other items (like refer) Inverter SURGE amps need to be 1.5 to 2 times the required watts to start the AC units (most good inverters have fairly high SURGE watts) Batteries provide a BUFFER between the inverter and the 50DN generator (Two type 31 12volt truck/bus batteries would likely be minimum - (without the engine running - two type 31 batteries could keep ONE AC running (at full power) for only 15 minutes or TWO ACs running for 7.5 minutes before the batteries went down to thier safe discharge level of half power capacity) The problem using 12v inverters on a 24v system is BATTERY BALANCING (keeping the upper and lower batteries fully and equally charged !~! | ||
| ED Hackenbruch (Shadowman)
Registered Member Username: Shadowman Post Number: 210 Registered: 11-2003 Posted From: 75.211.18.179 Rating: N/A |
We usually just open the windows next to us. Only been a couple of times where it was hot enough to use ac. | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1040 Registered: 10-2006 Posted From: 66.82.9.62 Rating: N/A |
"We usually just open the windows next to us." It took a whole bunch of digging ,about 6 years and some fancy footwork to get the custom rubbers manufactured , BUT we too enjoy the "70 AC" . At 70 mph the 4104 style opening windows in our sportscar scoop &BLAST air into the coach, with an open rear window its pretty cool. Noisey tho , but am moving the rubber gasketing to the frame from the opening glass and the radio antenna from the mirror arm. No noted increase in fuel use , but below 25mph its only so so. FF | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 433 Registered: 2-2001 Posted From: 184.0.0.219 Rating: N/A |
We run our 6.5KW Onan gasoline RV genset running down the road. It uses about 1/2 gallon per hour (a diesel would use less) and can run everything on board including 2 roof airs, electric fridge, house type electric water heater, coffeepot, microwave TV & lights at the same time. In fact, I have to add a 1000 watt space heater to get the full 6.5KW load. I can't figure why folks buy such large gensets. We've never has any kind of problem running the genset. You know, thousands of RVs, Bloodmobiles, mobile libraries and the Snap On, Mac Tool & other trucks run gensets going down the road with no problem. We do have an exhaust extender that we use to get the outlet above the roof if we're dry camping. | ||
| Larry Nelson (Larryn4106)
Registered Member Username: Larryn4106 Post Number: 45 Registered: 8-2008 Posted From: 173.30.230.77 Rating: N/A |
We run a single roof air off of the inverter which is connected to the chassis batteries. We close off the rear of the coach. Been doing it for 5 years, now. | ||
| Nellie Wilson (Vivianellie)
Registered Member Username: Vivianellie Post Number: 406 Registered: 11-2008 Posted From: 74.4.55.77  Rating: N/A |
Tim - Thanks for that excellent link. Probably most of these guys knew about Welch Industries (?) but I sure didn't... gave me some good(?) ideas. Nellie Wilson | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 1052 Registered: 11-2005 Posted From: 208.54.196.137  Rating: N/A |
There are no problems using the genset running down the road. It probably runs much cooler than when parked anyway. Many bus gensets don't get enough use anyway unless you dry camp in the boonies a lot. The worst thing for gensets is lack of use. | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 475 Registered: 10-2003 Posted From: 74.244.14.221 Rating: N/A |
No problem Nellie. They also do bus maintenance and repair if you are in need in the Atlanta area. Good honest people | ||
| david anderson (Davidanderson)
Registered Member Username: Davidanderson Post Number: 249 Registered: 2-2004 Posted From: 69.153.69.165 Rating: N/A |
It is very convenient to just use the genny down the road. I have 3 rooftops and keep it refer cold when travelling, just my way. When we stop for breaks it still keeps running. That would be difficult with just alternators. I do run my front ac off the inverter if I want to when not too hot outside and can cool the front of the coach with only one unit. I can feel the AC pull the engine rpm down when clicked on at high idle, so there is power taken from the wheels, no free lunch. David | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 1039 Registered: 7-2006 Posted From: 70.212.234.136 Rating: N/A |
David...thanx for that post..would you elaborate a bit on the type and size of your genset? I have yet to try it... a bit concerned about the "float" in the carb...have no specific reason why...just think it might be a problem. Thanx... RCB (Message edited by Chuckllb on December 20, 2009) | ||
| thomas flocks (Taflocks)
Registered Member Username: Taflocks Post Number: 119 Registered: 9-2009 Posted From: 74.76.246.165 Rating: N/A |
i have a honda 6000 watt 50 amp honda propane generator that will only run one roof unit at a time and when at the campark i could also only use one unit before it blew the breaker. with one unit on i noticed my plug at the meter was rather hot, any ideas? | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 246 Registered: 1-2007 Posted From: 208.81.157.234  Rating: N/A |
If the plug and wire are sized correctly for the wattage being drawn, heat normally comes from bad connections. Can be in the plug, the receptacle or the contacts where the two connect. If it worked properly elsewhere then switch to another site. A bad receptacle can overheat and destroy your plug. If the contacts are blue or otherwise discolored they have been too hot. What amperage is your plug, ie 30, 50? What AC units do you have? We run one on a 15 amp plug. Good luck, Don 4107 | ||
| Debbie and Joe Cannarozzi (Joe_camper)
Registered Member Username: Joe_camper Post Number: 195 Registered: 10-2006 Posted From: 98.212.104.155 Rating: N/A |
We utilize both options. We have OTR a/c but in spring and fall, only need the front cruise air off the inverter. We have 1 heart 2500w 24 volt inverter and it does fine. We do need to fire up the gen if any other significant draws are needed with the front a/c on, either that or shut it off for a few while doing other things. In spring and fall the OTR a/c is overkill and just the front a/c does fine and their are also times when it is very hot and the bus is heat soaked and both the front cruiseair and the OTR a/c run togeather. We have used the a/c systems togeather like this many many times. Flexability and redundency. Lets not leave out the Fred option either we have done that too! Many told me a 2500w inverter would not do for 1 a/c. Not so, it just takes power managment when doing it. We have a 50dn alternator and it charges the house going down the road, the inverter is powered by the house batts. | ||
| david anderson (Davidanderson)
Registered Member Username: Davidanderson Post Number: 250 Registered: 2-2004 Posted From: 69.153.48.58 Rating: N/A |
RC, I bought a Wrico 13kw from Dick Wright. It has a kubota engine. I can run everything I want when the genny is on. It's like being hooked to 50 amp. I also use it to run a Lincoln welder sometimes, and I've used it to backfeed to my house in power outages, very handy. David | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 1042 Registered: 7-2006 Posted From: 75.210.128.38 Rating: N/A |
Thanx, David...sounds like a great set-up! RCB |
