On Sat, 27 Feb 2016 22:02:18 +0000, Bob Minchin wrote:
David wrote:
On Sat, 27 Feb 2016 08:38:15 -0800, harry wrote:
On Saturday, 27 February 2016 12:27:16 UTC, David wrote:
On Fri, 26 Feb 2016 23:46:27 -0800, harry wrote:
On Friday, 26 February 2016 18:16:39 UTC, David wrote:
On Fri, 26 Feb 2016 17:03:13 +0000, Fredxxx wrote:
On 26/02/2016 10:59, 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.
As soon as we know the spec, it might be possible to assist.
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.
For a narrow boat I installed a 3kW inverter (with surge
capability),
150A alternator and 4 100Ah batteries. It can be done though
challenging. I doubt you'll have the space to fit a second
alternator.
(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.
Again without knowing the rating of the air con, and the size of
your portable gen, we're in the dark.
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.
You cannot "blend" 2 AC voltages.
Can nobody see my post of 12:29 today?
This contains the details, but I keep getting "as soon as we know
the specs" responses much later in the day.
With regards to blending two AC voltages, how does solar from the
roof blend into the UK grid, then? Thought it was pushed out of an
inverter and synced with mains - depending on how much you are
drawing at the time you should get all inverter (plus some pushed
back up the wires) or part mains and part solar. Or all mains if it
is night time!
Or am I missing something about how solar power is delivered from
the rooftop?
Solar power is DC.
It is linked to the mains by means of a grid tie inverter. The mains
AC is used to "create" synchronised AC from the DC.
https://en.wikipedia.org/wiki/Grid-tie_inverter
Synchronisng two separate AC supplies is quite another (more
difficult)
matter.
However, in the scenario I am exploring I was looking at blending a
source of 240V AC with the output of an inverter driven by 12V
batteries.
So in this case a "grid tie inverter" might do the trick. That is,
blending the output from an inverter and the output from 240V mains.
However I think that this is likely to be far too expensive (from
memory of solar installation quotes) for the application I was
considering.
I know that the power demand from the A/C is likely to rule it out in
my specific case but I am now exploring general principles. For
instance if you want to run a microwave or hair dryer which is just
over the power output of your genny.
It does raise the possibility of a very limited solar system (couple
of panels on the roof of a motor home) being able to boost the output
of some of the more flaky (especially continental) on site power
supplies on sunny days.
Cheers
Dave R
--
Windows 8.1 on PCSpecialist box
It's just not technically feasible.
The grid tie inverter runs at 400 odd volts You need to have
conventional AC fitted to the engine of your vehicle.
The only practical solution.
As already stated I have conventional A/C fitted to the engine of my
vehicle.
Additionally, the exhaust pipe exits into the awning area, so running
the engine when the van is set up with the awning is not a good plan.
This is looking at ways to use the habitation A/C which is already
fitted.
However the information that it requires a 400 volt grid tie inverter
for a solar system does rule it out for a motor home.
Cheers
Dave R
Add to that, even if you provided the Grid Tie inverter with enough
battery volts, you will possibly be disappointed that it will not give
any output when the grid is not present.
I was assuming "grid tie" was code for latching onto a 240V AC supply from
an external source.
Ummm...yes, the implication is that you would need an external AC source
to persuade the inverter to run (otherwise the safety lock to prevent
killing people repairing the grid would cut in).
Which brings me to wonder if a solar array can keep the home going if the
grid is down.
This would require a reliable cut out!
Cheers
Dave R
--
Windows 8.1 on PCSpecialist box