3 phase Sub-board, supply conductor protection

[KAYAK]

Hi folks,

I'm project managing a 30kW PV installation on a social club and could use a bit of advice -

Main board is an old Ottermill F frame (the board has no plates; I had to track down an ex Ottermill employee who ID'd it from photo's).

We'll be installing a new TP&N 3 phase sub-board exclusively for the PV, in the same plant room and within 3 metres of the main board - I'm getting conflicting advice re the connection of the new sub-board to the existing DB1.

• One contractor is advising that it can be connected directly to the main incommer in DB1 because the sub-board is within 3m of it.
• Another contractor is saying the cable must be protected by an MCCB in DB1.

The issue is that the MCCB for this old board (Westinghouse Series C FDB3060L) is a legacy item and eye-wateringly expensive as a new piece. I can buy a used one off e-bay for reasonable money but I'm reluctant to fit 2nd hand gear.

If the conductor can be fitted direct to DB1 without the 60A MCCB it would solve problems - my question: would this be compliant?

Many thanks

 

[shanky887614]

Hi folks,

I'm project managing a 30kW PV installation on a social club and could use a bit of advice -

Main board is an old Ottermill F frame (the board has no plates; I had to track down an ex Ottermill employee who ID'd it from photo's).

We'll be installing a new TP&N 3 phase sub-board exclusively for the PV, in the same plant room and within 3 metres of the main board - I'm getting conflicting advice re the connection of the new sub-board to the existing DB1.

• One contractor is advising that it can be connected directly to the main incommer in DB1 because the sub-board is within 3m of it.
• Another contractor is saying the cable must be protected by an MCCB in DB1.

The issue is that the MCCB for this old board (Westinghouse Series C FDB3060L) is a legacy item and eye-wateringly expensive as a new piece. I can buy a used one off e-bay for reasonable money but I'm reluctant to fit 2nd hand gear.

If the conductor can be fitted direct to DB1 without the 60A MCCB it would solve problems - my question: would this be compliant?

Many thanks

If the swa is big enough to be covered by incomer fuse then no problem with either option

 

[KAYAK]

Thanks Shanky,

There's a 50A 3 pole MCB in the new sub and 3 x 20A 500V fuses in the Otermill DB1 - do you mean the swa between the 2 boards?

 

[netblindpaul]

Why is the cost of the circuit protection an issue at install?
This should have been considered at the assessment stage if the design was being undertaken by a competent person, so fit the correct kit, and do the job right, if the job has not been surveyed and designed correctly then sort out the surveyor and designer so they are looking for new jobs, because they are obviously incompetent.

 

[KAYAK]

#4 -Thanks for the input NetBlindPaul - the surveyors assessment at pricing stage was that the sub-board circuit would be connected directly, without an MCCB being required, so it wasn't costed for.

Now, months down the track, I'm politically locked into a contractor (connected with the facility) who says the opposite.

From a technical point of view, what's your opinion on the 2 solutions - are they both valid or is one or both not compliant?

 

[wozz]

My first concern would be in method 1 of how it would be connect and would it exceed terminal capacity?

 

[netblindpaul]

#4 -Thanks for the input NetBlindPaul - the surveyors assessment at pricing stage was that the sub-board circuit would be connected directly, without an MCCB being required, so it wasn't costed for.

Now, months down the track, I'm politically locked into a contractor (connected with the facility) who says the opposite.

From a technical point of view, what's your opinion on the 2 solutions - are they both valid or is one or both not compliant?

I can't say from where I am, I have not got enough information on the detail of the install apart from one piece, the surveyor/designer is incompetent.
So get them to sign for the design, job done.

 

[Knobhead]

Time to dig deep or go 2[SUP]nd[/SUP] user. There is a company that specialises in Ottermill gear in Totnes I think. It’s run by ex Ottermill staff so they should know what they’re on with.
A few years back they supplied me with fixed isolation contacts for an ACB, I didn’t think they were too bad on price.
I’ve never dealt with any of Ottermill’s small stuff though.

I certainly wouldn’t connect in to the incoming.

 

[KAYAK]

#8 - Cheers Tony, thanks for the feedback - I'll look the Totnes crew up

 

[WaterSparky]

May be wrong, but i think they have moved to Exeter.

Ottermill Switchgear Service - Refurbish - Retrofit

 

[Knobhead]

Nice one!

As I say it’s a long time since I had anything to do with Ottermill.

We had the isolating contacts overheating on the transformer incomer. No idea where to get spares so it was a case of plunder another board to get us up and running.
One thing I do remember, they were absolute pigs to get to. Set off attacking from the front, gave up there and set to digging my way in from the back.
Change three contacts? It must have taken me five hours!

Ottermill ACB’s were good, the fuse switches absolute crap.

 

[londonlec]

I wouldn't loop it off the main DB1 terminals. The conductors wouldn't sit right in the terminals (unless its a bolted connection)

 

[KAYAK]

#10 - thanks WaterSparkey - that looks spot on, cheers