As I have mentioned before, my house is on 3 phase power. I have 2 Spinny meters which spin very nicely in a backwards direction when fed with solar power and one electronic meter which registers any current flow as a charge.
The only 3 Phase thing I have is the ducted AC so I am able to run it for free on 2 phases and pay for the 3rd.
Sounds OK but the recent hot weather and the need to have the thing on constantly has meant that one leg of power has been costing upwards of $6 a day just for the AC. May not sound much but we are fast heading to $400 just for the AC this quarter.
I have been trying to appreciate the low cost power I have with teh other 2 phases but having an excess of power on both of them and having to cut down on the AC just because of one phase has got the better of me.
Spoke to my mate in the AC game yesterday and he " approved" my idea for feeding the 3rd phase with solar and said it should not cause any problems with the phase rotation or voltage sensing. I pulled the cover off the thing today and started digging round the boards etc and should be no problem getting to what I want.
The grand plan is to stick another array of about 4KW on the roof with a 2 Kw inverter and feed that to the L1 Phase which is the electronically metered one. I can tap into the compressor Contactor and turn on a relay with that which I can then switch the inverter in and out with. This won't be perfect, will only work during the day which will be better for cooling than heating but anything will be a help. There will also be a delay between the compressor cutting in and the inverter booting up but again, better than nothing and on really hot or cold days the thing will be barely switching out anyway.
I ran the AC today and took some measurements with my clamp meter. 19XX Watt on that phase which is the most loaded one with the compressor running, about 800 with the fan only running on the evaporator which runs all the time on cooling even when the compressor shuts off. The fan of course runs on the L1 phase which is exactly the one I don't want it to run on and can't be changed.
I am OK with having an array strictly for the AC only but I also intend to run a DPDT relay with the inverter output so when the AC is not running, the relay will be feeding power to one of the other phases. This will be a help in winter especially when power generation is short.
The thing I'd like to do to make the most of this is be able to limit the output power for the Evap fan as well. Don't care about " wasted" output, I would like to be able to reduce the power when the fan was running then have another relay bypass what ever limiting device I put in place to give full power when the compressor kicks in. This would have the double advantage of keeping the inverter on song as well which would mean a big power saving in both powering the blower and the inverter being already booted up to supply the main power for the compressor.
Question is, what is the best practical way to limit the current when only the blower is running?
Thoughts run to using a 500W halogen flood light tube ( or 2 as I'm not sure they will pass 500W when used like this?) or maybe a PWM controller which is then bypassed for full power with another relay.
That's probably my preferred option and would allow a lot of fine tuning on the PWM but wondering if the educated people here have a better idea?
It would be nice to be able to limit the solar feed in, I could then direct the unused array to another inverter BUT, solar generation is highly variable and what is producing 1kw in summer sure as heck won't be in winter nor on a cloudy day. Regulating DC is a pain as I have not seen any PWM's capeable of handling the voltage and current anyway.
As such the control of the AC side seems much simpler and easier.
My mate was concerned about Voltage drop on the solar phase until I explained that the mains would be Connected at all times and the feed in would be to supplement that just like it is now on the other phases. I am also hoping that the PWM won't cause any problems as I know it makes some of my inverters hum a bit when on the line but I am more concerned about the board on the AC. Not sure if a cap in circuit would help with that?
Anyway, that's the Bright idea, any Ideas, suggestions or heads up on anything I may have over looked or forgotten?