Running portable air conditioners off portable generators

[naskies (Dave)]

Hi all,

After using - and being very impressed by - a fellow IISer's Honda EU20i generator, I'm thinking of getting one for myself to complement my 100 Ah battery when at remote dark sites.

Now that power will be abundant and temperatures are getting hotter, I've also been very tempted by the idea of a portable air conditioner I was thinking that with a small amount of insulation (thick doonah and tarp on top), a small three-person tent would be manageable for a small unit to cool.

A quick Google search shows lots of ~30 kg units of around 3-4.5 kW cooling capacity, and input power requirements below the EU20i's 1.6 kW rating, for around $500 - $800 such as this:

http://assets.glendimplex.com.au/ass...BrochureLR.pdf

Has anyone tried this? I'd be very open to hearing thoughts, suggestions, or whether it'd be a futile effort / waste of money.

Thanks!

[Barrykgerdes]

While anything is possible. Cooling a tent with a portable AC is rather impractical. An AC of that size will need at least a 2KVA generator. I suppose you have a trailer to carry all the gear in?

Barry

[whzzz28 (Nathan)]

Be careful of the inrush current on some of these air cons.
It's the same sort of deal as to why you do not put a laser printer on a UPS.
General load, it should be fine, but inrush current is huge - it will trip the UPS.

I suspect when the compressor turns on there would be a rather large inrush current and your generator may die.

We had a 2KVA petrol generator a while ago. We used it during blackouts.
We were lucky to get maybe 1.5KVA out of it before it became unstable (not to mention hot).

Personally - i wouldn't run an air con on a small generator. If you have a 5KVA or so, then go for it.

[naskies (Dave)]

Thanks for the feedback, gents. I have permanent Fujitsu units installed at home - which I'm very impressed with - but it sounds like portable ACs running off a generator would be inefficient at best.

[gregbradley]

I have direct experience with this. My dark sky observatory has a weekender I built. It has no power so I use generators. My first generator was the Honda EU20i. Very nice little unit, not a lot of trouble with it although it began to blow smoke badly after a few years. I may have been a bit slow to change oil a few times and some heavy wind and dust perhaps. Also a Honda mechanic told me they were prone to cylinder scoring if they idled too long. Well they usually idle unless under a brief load as lights etc are handled easily by idle power.

It would power the house, the observatory. That was my computers, mount, cameras, lights, TV, DVD player and fridge. That was all good. When the fridge compressor kicks in you would hear the generator rev up for the duration of the compressor.

I installed a 1000watt air conditioner. Basically it could only just cope with it. Start up is touchy as some AC engines have ramp up engines and others do a heavy draw at startup. Basically when running I could have TV and DVD player on. But the generator was working hard. Often electric motors will draw up to 3X normal load at startup.

I later got a Yamaha 2.8 KVA generator and it is much more powerful. Even so I have another portable AC which looks just like the linked ones.
It runs fine off the Yamaha but the generator works a little harder than idle. It would use more petrol but would cope. I would change the oil often and keep it in the shade and give it a rest every few hours.

The EU20i though is a bit small for that use. You get to tell which items chew up power. AC drains a LOT. So do hot water kettles, microwaves, anything that heats.

EU30i would most likely handle it easily. But its a fair bit heavier and more expensive. You can get cheap 5kva petrol generators even Hondas but they are not the nice clean inverter power ones like 20i. But perhaps an AC unit does not need super clean power like your laptop would.

Honda EU20i would handle a couple of electric fans very easily though.

Greg.

[naskies (Dave)]

Thanks Greg, your post was very helpful. I found this generator sizing chart page on Yamaha's website as I was checking out the EF2800i's specs:

http://www.yamaha-motor.com/outdoor/...or/sizing.aspx

According to this chart, a typical 10,000 BTU (= 3 kW) air conditioner needs 2.2 kW of power to start... which is beyond the Honda EU20i's 2 kW max supply. Probably explains the touchy starts.

Ideally, I'd like to be able to run appliances like an AC / heater / toaster / fridge / main laptop (in addition to astro needs) so that I can spend more time out at dark sites.

It sounds like EF2800i would be the right starting point for me. It's in a similar price range, size, and weight as the EU20i too. Do you find it much noisier than the Honda EU20i (60 vs 54 dB)? Do you get anywhere near the 17 hr rated running time on a full tank with low loads?

[TrevorW]

If the tent is just for sleeping in try a big fan instead or even a mist water cooler

[gregbradley]

I'd have to double check what Yamaha generator I have - I am pretty sure its a 2.8KVA ( I think they are pretty conservative with the kva rating).

It is much larger and heavier and cost more than the EU20i which is really quite compact. EU20i will run electric blankets no problem as they don't draw much but electrical heaters do (often 2400 watts). A little gas heater is more efficient than electrical but can be a little fumy. I use a little one under my table in my remote observatory and it is great.

Noise is unobtrusive and it is slightly noisier than the 20i but not much. Both have a cheerful sounding engine and I don't find either impinging.

I get about 20-22+ hours on a full tank. I change the oil regularly like after every 4 days of use.

The Yamaha I have is electric start with pull start as a backup.

Its a good piece of gear and I highly recommend it.

Greg.

Originally Posted by naskies

Thanks Greg, your post was very helpful. I found this generator sizing chart page on Yamaha's website as I was checking out the EF2800i's specs:

http://www.yamaha-motor.com/outdoor/...or/sizing.aspx

According to this chart, a typical 10,000 BTU (= 3 kW) air conditioner needs 2.2 kW of power to start... which is beyond the Honda EU20i's 2 kW max supply. Probably explains the touchy starts.

Ideally, I'd like to be able to run appliances like an AC / heater / toaster / fridge / main laptop (in addition to astro needs) so that I can spend more time out at dark sites.

It sounds like EF2800i would be the right starting point for me. It's in a similar price range, size, and weight as the EU20i too. Do you find it much noisier than the Honda EU20i (60 vs 54 dB)? Do you get anywhere near the 17 hr rated running time on a full tank with low loads?

[naskies (Dave)]

I ended up buying a Honda EU20i, partially because it's the largest size that I can easily carry over substantial distances - and the optional for adding a companion unit for 3200W/4000W down the track if needed.

After doing lots of reading online, watching YouTube clips, and talking to people, I learned that the starting currents of the cheap portable air cons can be as much as 600% of the rated operating current!

Inverter air cons apparently have much gentler starting requirements because they can vary the motor speed. Portable inverter air cons are somewhat rare due to their cost, but the DeLonghi PACWE18INV is one such unit. It also uses water evaporating over the condenser to boost the cooling capacity - supposedly has a cooling capacity of 5 kW with a maximum power consumption of only 2000 W. Downside is the price: between $1250 and $1500.

Something for me to think about in the lead up to next summer, perhaps...