air conditioner start up

[DRDEATH]

I am not sure where to put this so someone guide me. I need to know if there is someway or something that can be added to an aircondtioner unit that will help boost it if someone was wanting to switch it over to generator power. I am buying a VA from the UK. I believe it has a 3.5 or 3.7 KW alternator on it. I plan to run it on UMO. I am going to use it for my 220 volt items. I am a little concerned that it might need a little boost to start the AC especially if the dryer might be running. There surly has to be something out there to help the initial start easier. Looking for any advice. I can continue to pay electric company for getting raped in the summer. Mike

[cognos]

Don't know about your dryer, but mine takes 3500 watts on "High". If your dryer is like mine, and you have only 3.5 (or 3.7) KW available for your system, you will likely need another, larger genset to run anything else...

But I may be misunderstanding your question.

[mobile_bob]

UK gear is generally 50 hz and you will be needing 60hz stuff here in the states as well.

not sure how you will get around this, i am not familiar with the unit in question, whether it can
be sped up to produce 60hz and then have the voltage regulated to get the 220-240 you will be needing or not.

that and Cognos' concerns may make this a non starter.

bob g

[DRDEATH]

I am told speading the generator will solve the HZ. Voltage regulator should take care of voltage. I am just concerned about the energy needed to start especially the AC. I will have to ponder this some more.

[vdubnut62]

I have heard of an Easy Start kit for the larger central units, I think it consists of a capacitor bank?
Ron

[Ronmar]

3500W dryer?  If all electric, that is the smallest electric dryer I have ever heard of...  Mine pulls 11KW, most all of this heating element and I think it is pretty typical.  Completely off the plate for my 3KW genset. 

As for A/C startup, you can't get something for nothing.  It takes a certain ammount of energy to start, and that it pretty much that.  You can soften the blow a little, but not any significant ammount IMO, as the energy required still has to come from somewhere...  The soft start kits I have read about also usually incorporate a delay timer, that forces the unit to set for a certain ammount of time after a shutdown to allow as much pressure to bleed off as possible.  The A/C units I work with at remote locations have timers on their power circuit to prevent the units from trying to immediatly restart after a power failure.  If they were allowed to do so, they would usually pop their circuit breakers due to high head pressure on the compressor causing an electrical overload.

I have wondered about this a little, and would be curious what would happen if you installed a bypass valve into the A/C unit, connecting the compressor inlet to the oulet at startup.  this would take a lot of the pumping loads off of the motor/compressor.  Once up to speed, the valve could be closed to apply load to the already running compressor.  Much like an unloader valve on an engine powered compressor.

For the small engine/generator, it may be more practical to build up an A/C unit using automotive components and drive the compressor directly from the engine.  This would leave room for a large surface area condenser, perhaps even underground for some geothermal benefit, on the high pressure line run into the dwelling where the evaporator is located. 

Good luck. 

[DRDEATH]

Ok Ronmar so now you have my intrest dont stop. I have heard of using automotive compressor for homes but I am not sure how big of one you would need. Somehow my idea has to work. I just havent figured out the right combination. Any information you have of using automotive compressor please send to me. Or if have have sites to go to. Now remember it has to be the KISS method or I will be lost. I have often wondered if AC lines could be put underground to help. I mean the outside temperature is > 100* underground could be as cool as 70*. Surley that would have something to do with helping out cooling. For some reason our electric bill jumps about 200 dollars a month for 3 or 4 months. I dont like a hot house. I am going to get some better windows which will help. I cant imagine the VA engine using WMO with a % of df #2 diesel could use that much. Maybe I am wrong. It would not be the first. If nothing else I am not tied to the electric company. That in itself would be worth the 200 dollars. Mike

[Lloyd]

Actually you have a couple of options....Number one being if you have a battery bank and an inverter say a Victron Unit that is designed to for boost start...so that a smaller prime power gen-set can be sized.

or you could go with modular AirC units that run on DC such as I mentioned in this topic...http://www.microcogen.info/index.php?topic=1083.msg12679#msg12679

My guess is most co-gens are better, with a prime bat bank instead of a prime ac gen-set...it's just so much more efficient.

Lloyd

[Ronmar]

Well from what I have read, a typical automotive A/C is around a ton to a ton and a half of cooling capacity.   That equates to roughly 12K-18K BTU per hour.  That is about the size of a window A/C.  That much cooling takes probably 5 or so HP from the engine to accomplish.  That is the issue with doing it electrically.  Starting a 5HP electric compressor is no easy chore for a small generator.  A car is much smaller than a room in a house, so why so much A/C?  So it dosm't take an hour to cool down the car on a hot day. The car is also poorly insulated. It is far easier to spool up that 5HP worth of compressor directly off the generator, about the same way I power my 6HP worth of belt driven generator.  Of course if I power 5HP worth of A/C, I can't power much else with my 6HP of supply...  As for KISS, well that depends on you.  This would involve stripping the A/C components out of an auto, and connecting it to your engine, and extending the plumbing(rated to 300 PSI) into your home, then evacuating and recharging the system.  Belt driving an auto A/C off of an open wheel slowspeed engine would probably be the easiest part:)

[DRDEATH]

Ronmar I must have been tired when I read your post yesterday. After I read this last post and backed up to the previous post it seemed to make more sense. I can see one problem is that 1 unit would not be large enough. So I guess I would be back to square 1. I think the unit we have is probably a 2 or 3 ton system. We have 1500 sqft home. Are there larger AC systems like maybe in truck systems. Would you still be able to hook this up to the thermostat so the generator would be able to start and stop automaticaly like the SOM is suppose to? What are the systems like that keep trailers refigerated while going down the road? I have noticed there are lots of them around because the EPA has forced truckers to change them. One more question I would still be able to use the parts I already have in the house ( A coil ) I believe is the proper name for it. So I would only be plumbing the outside components right? Thanks for your help. Mike

[mobile_bob]

the 2 cylinder "climate control" units (formerly "york") come in three differing displacements
the largest of which is around 10 cu/in and is used on large trucks with the walk in sleepers.

they are capable of running r12, r134 and r22, and perhaps other freons

the 10 cu/in model running at 4000rpm and pumping r22 will make about 2.5-3 tons iirc or approx 30-36kbtu's.

from memory sanden makes a few larger displacement compressors as well.

then there are also a number of open drive compressors available that can be up to as many tons as one would likely ever need,
that use some of the other freons.

there are also the direct drive refer units like carrier and thermo-king both of which are highly refined and are auto starting, usually two
speed or variable speed which varies the engine speed to match the load and in doing so increase the fuel consumption.
one of those units could turn a well insulated 1500sq/ft home into a nice refrigerator if not a meat locker.

in any case it is doubtful you will save any money driving an AC system with a diesel engine, unless of course your fuel is very low cost or free.

unless of course you are using the waste heat from the engine to drive an absorption chiller/cooler system, which in my opinion is the holy grail of
space cooling using a cogen as it should be used. if you can accomplish an absorption cooling system off the engine waste heat, then you can compete with the utility quite well using pump diesel.

Forum members such as WGB are very knowledgeable when it comes to air conditioning, perhaps he and others can add to the conversation.

bob g

[DRDEATH]

Bob this why I cam over here to this site. I want to use everything from the engine I can. I would use the noise if I could. Give me some more guidence on this heat chiller from my exhaust. Is there simple instructions out there. Also one of the compressors would run from an 8 hp engine correct. Mike BTW have you recieved my check? It should have went out a week ago.

[mobile_bob]

yes i received your check, just need to know how you want to be listed

bob g

[Westcliffe01]

Study on using adsorbtion type coolers on over the road type semi trailers.

www.metrans.org/research/final/00-07_Final.pdf

[mobile_bob]

Westcliffe:

hey thanks for the link, a lot of useful info in that one

if you don't mind, go ahead and post the link down in the "white papers" section also
so that it can be easily accessed later should the need arise.

thanks
bob g