PV confused as to how many ac isolators im fitting

[peterkenney]

hi om new to pv. were just installing a system on a cottage (tt) .im confused as to how many ac isolators im fitting at the moment im thinking two 'one each side of yhe dc generating meter .Anybody help the mcs guy comes next week

 

[Doc Hudson]

Welcome to the forum, I have moved your post to start a new thread as you are asking a new question. It makes it easier for others to follow rather than adding your question onto another unrelated thread that is nearly 12months old. I have also moved it to our Solar PV section.

Doc H.

 

[ProDave]

Normally just a DC and AC isolator next to the inverter. What makes you think you need one between the meter and the CU?

And at the risk of stating the obvious, the meter goes in the AC side. It's NOT a "DC generating meter"

You should have got this finished and signed off by the end of today. 3rd March is the final qualifying date to get the 43p feed in rate. From tomorrow it's down to 21p

(even an install signed off today may later be reduced to 21p if the DECC are allowed to appeal a previous high court ruling to the supreme court and win that appeal)

 

[sparkytim]

One AC Isolator at the INVERTOR as Dave points out, and another at the C Unit to isolate feed INTO Cunit from PV when working IN C Unit.

 

[cm304eex]

Hi

I normally put an AC isolator after the inverter then another between the meter and the CU.

 

[binky]

bit overkill, what's wrong with turning off at CU

 

[cm304eex]

Nothing that's the way my boss likes it doing and who am I to argue with the boss.

 

[NozSpark]

The Co. that I've just done some for have

CU---AC ISOLATOR (adjacent to meter)---GENERATION METER---AC ISOLATOR (adjacent to inverter)---INVERTER---DC ISOLATOR---PV STRING

 

[sparkytim]

bit overkill, what's wrong with turning off at CU

All the installs I have seen have 4mm AC cct to /from Invertor connected into a spare way of the existing CU

They all have an AC isolator fitted to protect anyone working INSIDE the CU due to delay in shut down of Invertor when normal supply is turned off (can be up to 5 secs I believe)

 

[NozSpark]

All the installs I have seen have 4mm AC cct to /from Invertor connected into a spare way of the existing CUThey all have an AC isolator fitted to protect anyone working INSIDE the CU due to delay in shut down of Invertor when normal supply is turned off (can be up to 5 secs I believe)

So therefore wouldn't it be best to use a standalone CU for the PV installation so that you can be absolutley certain of your disconnection times.

 

[sparkytim]

It would seem that would be the better way to do it, but as I have found all that I have seen so far just bang a 16 Amp MCB in a spare way, even came across one who had pinched MY 16 amp MCB fitted preiviously for a radial socket circuit and put my circuit into the 32 Amp MCB next to it serving a Ring!

I think we are going to find a lot of things like that on PIRs from now on.

 

[SteveT]

The Co. that I've just done some for haveCU---AC ISOLATOR (adjacent to meter)---GENERATION METER---AC ISOLATOR (adjacent to inverter)---INVERTER---DC ISOLATOR---PV STRING

as above every time otherwise if you only fit one, if you need yo do work on CU end you could still have live at PV MCB, so you would have to go into loft to isolate (cost of AC isolater = about

 

[binky]

I only normally fit additional AC isolator is CU is quite remote from inverter, such as in attic - saves hassle of getting into attic

 

[peterkenney]

thankyou sorry ive just started doing this bro

 

[peterkenney]

thats the one nozspark the napit guy checked it

 

[thebuckets]

as above every time otherwise if you only fit one, if you need yo do work on CU end you could still have live at PV MCB, so you would have to go into loft to isolate (cost of AC isolater = about �8)

Grid connected inverter must be configured to prevent 'islanding' so if mains fails no PV! If mains returns the inverter can re-start without warning whilst you thought it was all safe!!!

i have one wired like this but meter is an mcb sized one fitted inside the con unit therefor ac could remain live in the con unit  (albeit only at the meter incoming side) unless ac isolator in loft adjacent to inverter was isolated.

In  this case would it not be wiser to have the ac isolator placed before the meter? ie string dc isolator inverter ac isolator ( inloft) ac isolator adjacent to con unit meter mcb

 

[roys]

Thebuckets, bit late in replying to this post are you not, it is 3 1/2 years old!!!!

 

[thebuckets]

yes im aware of that just confirming that ac isolator before a con unit fitted meter is the better option than metering then isolating so leaving a portentially live end in the con unit

 

[Lurch]

How is there a still live circuit in the CU? If you leave the main switch on then the whole CU is live, if you turn off the main switch the PV stops generating. I do not see how there can be a live supply into the CU that would not be live under normal circumstances on a non-PV circuit?

 

[thebuckets]

would the ac feed from the pv not remain live at all? the 4mm comes from the ac isolator in the loft direct to a rail mounted meter in the CU then out to another ac isolator before feeding the mcb in the CU. is there any problem with wiring the ac isolator before the meter?