what size generator for a/c

I’ll play along Bruce (just for fun ) at our shop we had a set of HUGE cables, like 000 gauge (about 1/3” of copper wire inside), and they were about 20’ long (so easy to jump any car from anywhere, important in a shop).

That’s the kind of wire/gauge needed to safely transfer large currents over long distance (upwards of 150 amp for 10 seconds).

Today I have some nice 0/1 gauge, 10’ jumper cables, and when being used to start a truly dead car you can feel them get warm in about 5 seconds.

The HiLo lift motor is nothing more than a car starter - so it’s going to draw similar currents (though on the lower end - I’d guess 20A) but for a longer cycle time. From a design perspective, wire heating is absolutely a concern because of the longer cycle time (20 seconds), hence the large cables on the motor.

Anyone want to throw an ammmeter on their motor next time they lift the top?

I blew three, countem, three, 30A fuses on the trailer battery charging line in my Tow Vehicle while trying to raise the top of my trailer after an all-day drive where I also had my trailer refrigerator running on DC. This occurred first in my Nissan Frontier, and second in my Ford F150. I finally learned on this forum that the combination of having a weaker battery from towing all day, having the refrigerator on (which further pulled the trailer battery output down) and then adding the electrical draw of the lift motor to the whole thing was just too much for the 30A fuse in the TV. Interestingly, though, the top ALWAYS went up! But, the next day, the trailer battery was no longer getting a charge from the TV.

Since learning this, I've ALWAYS electrically disconnected the TV from the trailer before raising the top and I've never blown another trailer charging fuse.

Regarding jumper cables, mine are 4 gauge and nothing stops me from disconnecting the truck from the trailer and turning the truck around so that the truck is facing the trailer and its battery is close to the trailer's battery compartment. I suppose if the trailer battery was so flat that I couldn't use the electric jack to get them disconnected, I'd have to use the manual crank on the lift jack, but I'd still be able to do it.

- Jack

Quit honestly, I've rarely had my TV connected nor even hitched to the HiLo when either raising or lowering. I always unhitch and level it before raising it. When the Battery on the '76 was too low to raise it, I always had to place the TV close to the door to run the Jumpers inside to the battery!

I use a cable about as thick as a good jumper cable. Get it at HD from electrical section. There are not pre-made wires, so having store cut it to your length is how it goes. You will need end terminals, also available at HD, or the auto parts store in battery section. *
Home Depot will have all gauges and can cut to length. I started from where the 12+ bolts up to the starter motor, not all the way to the battery. From there I went back to a clean spot under the truck bed, where no oil blows around from the diesel, and put a battery solenoid which is controlled by a switch on dash, then continued to trailer hitch. I used a 2-pole connector plug (ground and 12+). Probably did not need the ground, but did anyway to make it all even and useable if I want to attach power tools or a winch to the plug later. Ideally put a 20, 30 or 50 amp circuit breaker inline somewhere along the wire. The same gauge wire from plug back to trailer battery. Connects directly to battery, not to anything camper based. The longer the run, the heavier gauge wire you need. There are charts on internet, but they never agree with each other about what gauge for what length or run. A childs-finger size gauge wire is sufficient, and you can't really have too big a wire within reason. Measure the copper, not the rubber.

* if you are handy and have scrap handy, use 3/8ths copper pipe or whatever works for your wire. Cut to about 2.5 inch length. Hammer one half flat. Drill hole in flat side. Insert wire in round side and crimp it. Tape it shut. There is a cheap terminal.
You may need to cut or grind the flat side so it has rounded ends to fit your application.
Easier to hammer, drill, then cut, as hard to hold a 3 inch piece of copper in a vice to drill it. Drill while you still have a long piece to hold.

KnottyRig said:

I’ll play along Bruce (just for fun ) at our shop we had a set of HUGE cables, like 000 gauge (about 1/3” of copper wire inside), and they were about 20’ long (so easy to jump any car from anywhere, important in a shop).

That’s the kind of wire/gauge needed to safely transfer large currents over long distance (upwards of 150 amp for 10 seconds).

Today I have some nice 0/1 gauge, 10’ jumper cables, and when being used to start a truly dead car you can feel them get warm in about 5 seconds.

The HiLo lift motor is nothing more than a car starter - so it’s going to draw similar currents (though on the lower end - I’d guess 20A) but for a longer cycle time. From a design perspective, wire heating is absolutely a concern because of the longer cycle time (20 seconds), hence the large cables on the motor.

Anyone want to throw an ammmeter on their motor next time they lift the top?

Click to expand...

I have put an ampmeter on my 28' hilo and am pulling around 115 amps on the pump motor. This is why if your battery is low when raising the top the fuse in the TV blows. I have blown my TV 30 amp fuse several times and carry a couple of spares. When I pull into a campsite the first thing I do is hookup to shore power and leave the TV ideling to help give the battery a quick recharge while I unhook the RV and level it. I then unhook the elec pigtail and the top then goes up with no problem.

Circuit breakers will trip, then reset when they cool. Same idea as a fuse, but no need to replace.

marininn said:

Circuit breakers will trip, then reset when they cool. Same idea as a fuse, but no need to replace.

Click to expand...

On older HiLos the 30 amp circuit breakers in the pump compartment do not reset after cooling but have a reset button usually on the bottom that you have to press in to reactivate them. These older breakers can be replaced with the newer ones that automatically reset as the older ones go bad.

I was thinking to protect the whole system from trailer plug back. Auto parts store has circuit breakers cheap. I did not realize the pump has one too.
thanks

Just to throw in another data point, the hydraulic pump motor on our 2407T draws 58 amperes while raising (takes 15 seconds) and more than 140 amperes when the seal gaskets meet in the full up position.

George
WB4IPB

Astro those numbers fit the range of typical car starter motors (reduction-gear starters tend to draw a bit less). Above 150 amps would indicate a potential problem. This is why a battery is required to run the lift pumps - until recently an AC/DC converter of that capacity would’ve been prohibitively expensive. (Probably still is today).

You might want to look into a new device on the market called a "soft start". It ramps up the compressor slowly reducing the starting load by around 70%. With a "soft start" installed you can run most RV AC units with a 2000 watt generator.

i got a great deal on a honeywell 2200 inverter generator...i tried to run the a/c on my 86 hilo and it wouldnt...if i turned the a/c to vent..it would run it but if i tried to switch it to medium cool it wouldnt start...i think if i could get it to start it would run...anyone have any info that might help?...thanks in advance

Keystone- I'm assuming thats 2200w peak?

As I understand, the general rule w/even AC is you need a gen that can do 2kw run, not peak.

Your HiLo AC being both old engineering and aged is likely to want all the power it can get to start. A hard start or the soft start kit may help. (I haven't read up on the soft start yet,kinda curious how it compares to the old hard start systems)

yes...mine is 2200 peak and 2k run...i thought about the hard start kits...i'm assuming they are just a big capacitor?

Its been *decades* since I installed a hard start kit. They *used* to be just a piggyback cap. I'm sure there's all sorts of new microprocessor-controlled start systems now.

I could see having a faster cap that a controller would cycle for repeated bursts timed at the peak of AC pulses,to help reduce load on the genny during start, or something similar. So like every 10th or 20th of a second.

Or a controller that would sense current draw and engage the cap as needed during run.Or heck, if it'a just conditioning voltage could help prevent problems.

Due to the age of your A/C the starting capacitor could be dried out and no longer doing its job. I would say replacing it would with latest and greatest in capacitors would be a good place to start. Capacitors are mainly only needed for the compressor to start under load, the rest of the time the motor has much less draw.

i was trying to find the specs on my a/c unit but i dont see any sticker on it...anyone know what the specs are on it?...86 hi-lo 20 ft

Sometime you have to remove the A/C cowling, then remove the electrical cover plate on the A/C itself. The wire diagram and specs are on the inside of this cover plate. Tells you what P/N to use for a hard start and dotted line shows how to wire it in.

i've read on here some guys are running 2 small generators in parallel for double the watts....how is that done?...a cord with 2 male plugs...one on each end and plug the gennies together? ..i bought a honeywell 2200 gennie...it came with a double male plug.....anyone seen this before?

Double male plugs are dead-man makers. You see one of those walk the other way.

Dual-gennies have special adapters to balance the load/throughput. To be honest I've never read up on how they work,but they'd have to use some kind.of isolater to.prevent backfeed between gennies.

Honda seems to have popularized the idea with their small gennies (1k/2k)