On Fri, 26 Feb 2016 10:59:07 +0000, David wrote:

This first post is a place holder in part, so that I don't forget to ask
the question, as I usually do once I get involved in stuff during the
day.

The Motor Home has mains powered habitation air conditioning - that is
an ELectrolux slug on the roof.

So for it to work you need to be on a site with mains electricity.

There is also the issue of the power surge on start-up compared to the
power demand on normal running.

What I would like to be able to do:

(1) Run the A/C whilst driving - that would I assume involve an inverter
which could take power through the 12V electrics buffered by the
habitation batteries (unless the demand needs a direct connection to the
alternator charging circuit instead of via the charge controller which
charges the habitation batteries). This also allows starting the engine,
firing up A/C and then stopping the engine and letting the A/C run on
using the habitation batteries.

(2) Run the A/C when away from mains power - using a small Honda
generator which might be able to meet most of the demand apart from
start-up. I am envisaging perhaps the generator pushing power into the
system whilst the A/C takes power out so that the use of habitation
battery charge is slowed. This probably equates to running a UPS (that
is, power in to UPS for charging, power always out of UPS for running
the device) and using a small generator to keep feeding some power into
the UPS during a power cut. The generator may not fully meet the power
demand but it slows the rate of discharge.

This does seem to demand a lot of inefficiency, though, potentially with
the generator input being converted from 240V to 12V then back again. It
would be nicer if the battery 12V power could be used to boost the 240V
input from the generator so that most of the power comes directly in at
240V.


Bottom line is that one way may require blending two 240V inputs into a
single output, with obvious (I think) requirements to lock the wave
forms of the 240V together.

If I can manage ASCII art:

12V - 240V - Blender - A/C 240V -----------^

I think this is probably not realistic because you would have to prevent
back flow which is why there are so many issues with combining power
inputs connected to the grid. Then again, it is only like combining a
solar panel and mains (but that does allow back flow into the grid).

I need to dig out the handbook for the A/C to check all the power
demands,
but meanwhile does this sound in any way feasible?

I know (2) could be met by just buying a bigger generator, but I bought
the little Honda because I could just shoehorn it into the available
storage and anything bigger is too tall/wide to fit anywhere usable.

The handbook is not entirely clear. *shock*

The unit is an Electrolux Blizzard B1500.

The technical data includes:

Cooling consumption 715 watts
Heating capacity 800 watts.

Looking at the manual it seems that the unit is not designed to be used as
a heat pump when blowing warm air (as you might expect) but has a small
heating element - so from the data it looks to be an 800 watt fan heater
(less a small deduction for the power to turn the fan).

The 715 watts may be the maximum start up for the compressor, or may be
the average after the compressor has started.

Google isn't helping me much so far (apart from several links about the
heater giving of a burning smell then stopping working) but there is one
foreign link which related the "1500" in the brand name to 1.5kW. The fuse
recommended is a 10 amp slow blow, so good for up to about 2.5kW, which
may hint at the expected starting load.

I suppose what I really need is a power meter of some sort to accurately
measure the power draw when it is fired up via the mains.

Can anyone recommend a reasonably priced meter which can do this sort of
thing?

Amazon offers plug in meters from about £7 upwards - to about £55.

In this case I won't be looking for milliwatt accuracy, but who knows what
I might need to check in the future.

Oh, and the generator is rated at 450 watts normal 550 watts maximum at
50Hz. It is badged as a 650W generator as this is the maximum output at
60Hz.

Assuming that the real draw from the A/C is 715W then the generator
couldn't run it stand alone, but could supply a reasonable percentage of
the power.

Cheers


Dave R

--
Windows 8.1 on PCSpecialist box