Any problem in swapping phases 'on the fly'?

[guydewdney]

I have 3.6kW on phase #1 and 4.2kW Solar on phase #3

During a sunny spell, I am making more on solar than hydro, and visa versa at night.

So - I have a dirty great big relay / contactor (1600A rated...) which is both NC and NO (two of each). I cant see why, as its a break before make type, that I cant connect the house to the out of the relay, and have one phase on one line, and the other on the other - the net result being that if solar > hydro, then fire relay, and connect the house to the greater power generator.

Would anything really care in my house if I do this? Obviously there has to be some hysterisys to stop it chattering on changeover. The only thing I can think of is PCs - we have one, and it has a (small) ups.

At the same time, I can connect the hydro to say a water or space heater to use up the excess, as its not being 'used' in the house iyswim.

[rogeriko]

I use these relays to swap whole house systems from one phase to another or from inverter to mains. No problem it changes so fast you cant even tell. Just a normal 32a motor relay is fine, you know those large contactors not the little relays in a plastic case. Here often 1 phase goes down and seeing as most houses have 3 phase supplys its easy to swap the entire single phase house from 1 phase to another.

[guydewdney]

big nuff?

[knighty]

guy, is your house all on the same phase ?

would it not be easier to install a new distribution board and spread your loads over the 3 phases ?

[RobNute]

Hi Guy, I just wrote a load of junk about your wheel being unloaded or loaded suddendly during the change over but then engaged brain before posting ( realised that its all still grid connected and after the gti etc), sounds like something else that you need to figure out a way to automate. Best wishes, Rob.

[Philip R]

Guy,

Make sure that your phase swapping exercise does not cause a change in phase rotation or phasing. I.E RYB becoming RBY (123 becoming 132) or a 240 volt LN connection becoming a 415V LL connection.

The consequences for you ( if close by) could cause an injury and a minimum of an uncontrolled spasm of the bottom sphincter ( Did I spell it right?)
Or serious damage to your invertor(s) equipment.

PhilipR

[guydewdney]

N always remains N - so there sholdnt be an issue with it becoming L1 L2 instead of L1 N.

I dont have any three phase equipment, so no motors will suddlenly spin the other way - if thats what the  123 132 comment refers to?

Knighty - I have several consumer units:-
1) main house, cu next to inverters
2) upstairs (some of it....) CU in master bedroom
3) 'Big Room' CU in big room (converted barn on side of house)
4) garage CU fed from CU in master bedroom down loooong wire. Earthed locally.

We have  discussed putting different CU's on different phases - namely garage re-wired onto one of the solar phases - as the garage only gets used in daytime, when theres light.... upstairs and down on the hydro / big solar depending, etc etc. Is it against regs to have upstairs on one phase and down on another?

As the generation is very 'unbalanced' - ie solar 4kw on a sunny day on phase 2 - but hydro 3.6 on phase 1 on a wet day, I'd like to try to make as much use as possible of the power generated. Its complex - I know....

[BruceB]

Is it against regs to have upstairs on one phase and down on another?

Not against the regs.  What you might end up with is two phases in one light switch enclosure where you switch upstairs landing lights from down stairs.  With appropriate warning notices that is OK.  You want to beware of any particular enclosure having to be isolated at two different consumer units.  You also have the issue of the maximum fault voltage becomes 400V rather than 230V (ie between 2 phases), so arguably a bit more dangerous, but happens every day in industrial/commercial situations.

Regards
Bruce

[knighty]

EDIT: ignore this post, googled and idea won't work :-(

[Iain]

Hi Guy
Does a 3 phase inverter automatically spread the generation equally over 3 phases? or can the outputs be regulated on each phase, ie reduce on the red and increase on the yellow/blue? I don't know enough about 3 phase inverters
Just wondering out loud. If you had a 3 phase inverter and the outputs could be controlled independantly?
The other way is to have a new 3 phase dist board and balance all the property loads and have 3 phase inverters to feed in a balanced input.
Iain

[guydewdney]

im not swapping 5 inverters, three of which are brand new......

[Iain]

Hi Guy
I understand it when you say you won't swap 5 inverters. I was just trying to look at the overall picture. On your other post

Update,

just picked up the post - and the leccy bill is in there:-

20/10/2011 - 13171 reading
20/01/2012 - 15952 reading

2781 units in three months?HuhHuh PLUS what I have generated (ok - the last week has been zero on the hydro) - with 2kw of solar on the phase I am using for the house, plus an average of 2kw constant for the hydro (ie 48kWh per day - ie about 4300kWh)

assuming Im using 90% of the hydro - lets say 3800 units, the solar has made 150 units? (the total for two is about 130 units per month), plus the use of 2781 units on the bill

thats 78 units a day - or basically 3kw 24/7


NOW tell me summit anit wrong.

Big loads:-
2 x washing machines (baby in washable nappies)
2 x 500w heaters on at night, one for baby, one for aupair who cant be educated Wink With thermostats, so not actually on all night
1 x fishtank, 21 degrees C - 2 x 150w heaters
low energy lights everywhere
electric hob (induction) + oven
3 freezers, all full to the brim. 2 uber modern, one old and carp, but has been super insulated ghetto stylee


any ideas

You seem to have a lot of imbalance on your system, on both the generation and usage side. I think that all added together are causing you a lot of problems. I suppose my previous post was in the "ideal world"

The other way is to have a new 3 phase dist board and balance all the property loads and have 3 phase inverters to feed in a balanced input.

Whatever you now are trying to do is to "fudge" the system to get it all in balance (for the majority of the time) and to reduce your load.
I don't know if it would be more cost effective in the long term to try and start to alter to a more balanced system now rather than later and if swapping one of the systems(the one that causes the most imbalance) to a 3 phase inverter and selling the existing one would be more cost effective and you would end up with a more robust system.

The trouble is that you have to keep altering something to overcome a problem but if you can reduce that problem from the start the system will be a lot simpler and might even pay for itself quicker.
Just a ramble and a few thoughts but trying to look at the bigger picture.
Iain