3 Phase Distribution Board Dilema

[westward10]

Why the two boards are they metered separately?

 

[davesparks]

Sooo MCCB option, seems like a viable idea but then I'd need to bolt 2 sets of 95mm tails to the switch fuse unless a busbar chamber is used??

No, you'd only need one set of conductors from the switchfuse to the MCCB distribution board, then suitably sized outgoing conductors from each MCCB.

I had to do pretty much the same thing on this job, take an existing 200A feed and split it down to 2x 100A feeds. Previously the fuses in the fuse-switch had been changed to 100A to feed the one outgoing distribution circuit. I needed to add a second distribution circuit so swapped the fuses back to 200A and fitted the MCCB board.
(Yes I fixed the gap in the trunking lid)

The board is an MG25C2 Scheider Merlin Gerin MG25C2 Powerpact 4 - 13 SP Ways, 250A Panelboard - https://electricalwholesalers4u.com/products/scheider-merlin-gerin-mg25c2-powerpact-4-13-sp-ways-250a-panelboard?variant=44704876888310&utm_source=google&utm_medium=organic&utm_campaign=Shopify%20Custom%20GMC%20Feed&utm_content=Scheider%20Merlin%20Gerin%20MG25C2%20Powerpact%204%20-%2013%20SP%20Ways%2C%20250A%20%20Panelboard&gad_source=1&gclid=Cj0KCQiA35urBhDCARIsAOU7QwkSOymDJNpGhIUA29hoH4fm2Mx-5DhK5dkP9ueAsGsdRUrUqr7CY-MaAksFEALw_wcB

 

[davesparks]

I have a roughly 800mm length of 4inch trunking with the Isolator on top, the main dB to the right and a 500mm space between the board and Isolator on top of the trunking for a Ryefield. This seemed like the easiest option and one which I've has experience with! Cost the factor which has lead me here.

The easiest option isn't necessarily the best option and the cheapest option is rarely best.

Fuses vs MCCBs both have their pros and cons.
MCCBs offer convenience of being easily resettable.
With the Ryefield option the whole installation would need to be isolated to replace 1 fuse (removing/reinstating fuses into a live board is hard to justify in a risk assessment without a good reason and expensive arc-flash PPE)

 

[pc1966]

The easiest option isn't necessarily the best option and the cheapest option is rarely best.

Fuses vs MCCBs both have their pros and cons.
MCCBs offer convenience of being easily resettable.

Very true!

With the Ryefield option the whole installation would need to be isolated to replace 1 fuse (removing/reinstating fuses into a live board is hard to justify in a risk assessment without a good reason and expensive arc-flash PPE)

As there is a 200A fused-switch feeding it then easy to do, and if 100A fuses feeding the TPN boards they should be no more likely to be blown than typical house DNO fuses, and will have total selectivity with the 200A ones.

Assuming sensible distribution of loads, overall demand, etc.!

 

[Rockingit]

Wow a few options coming at me here.

Sooo MCCB option, seems like a viable idea but then I'd need to bolt 2 sets of 95mm tails to the switch fuse unless a busbar chamber is used?? In which case we may as well just fit one 95mm tail and use fuses in the chamber?

Please forgive my lack of knowledge on commercial, I'll try to keep up!

Don't forget that 434.2 allows for positioning of the over-current protection to be downstream of the device where downstream protection exists (so your MCCB incomer). As such, you may only need 35mm tails which the vast majority of switchgear would accept being double-lugged (normally one behind and one in front of the bus bolt).

 

[SparkingMad1997]

Why the two boards are they metered?

Whilst maximum demand of the 100 amp main switch is just tetering on exceeding the rated current (and I don't think I can get anything larger than 125A for Proteus) I also need a HVAC board and contactor linked into the fire detection to kill the hvac board in the event of alarm activation.

 

[Flanders]

Eaton MEM EBMSL14102MPMB 14+10way 200amp TPN Split Metered Power and Lighting Board would this board work for you

 

[SparkingMad1997]

There has been some great feedback here guys and all sooooo helpful! All my boss wants to do is quickly me along and cheap cheap cheap! With absolutely no understanding where he's been off the tools for so many years!

So ive taken all of your knowledge and suggestions and think ive decided on an engineering judgment on how I'm going to move forward on this project!
1 - 434.2 is gold here because well... I really don't want to work with cable bigger than I really have to!
2 - MCCB Incomers - Ive never had to consider before and this allows me to comply with the above whilst protecting my DB main switches
3 - I can be cost effective in that two separate MCCB enclosures is apparently cheaper than the Ryefield (which is about a grand according to the boss)
4 - I can be time effective in that making all the links for a Ryefield is time consuming. (im sure you can probably buy somthing prefabricated)
5 - I will use a 100amp MCCB Incomer for the HVAC DB, a 125 Amp for the Main DB

You have all been absolute stars and a great response for my first posting here! Ill have to grab pictures of the final product!
Play safe out there!

 

[ipf]

Photo of existing and sketch plan of required would be useful.
Like to see this busbar chamber.

 

[Rockingit]

There has been some great feedback here guys and all sooooo helpful! All my boss wants to do is quickly me along and cheap cheap cheap! With absolutely no understanding where he's been off the tools for so many years!

So ive taken all of your knowledge and suggestions and think ive decided on an engineering judgment on how I'm going to move forward on this project!
1 - 434.2 is gold here because well... I really don't want to work with cable bigger than I really have to!
2 - MCCB Incomers - Ive never had to consider before and this allows me to comply with the above whilst protecting my DB main switches
3 - I can be cost effective in that two separate MCCB enclosures is apparently cheaper than the Ryefield (which is about a grand according to the boss)
4 - I can be time effective in that making all the links for a Ryefield is time consuming. (im sure you can probably buy somthing prefabricated)
5 - I will use a 100amp MCCB Incomer for the HVAC DB, a 125 Amp for the Main DB

You have all been absolute stars and a great response for my first posting here! Ill have to grab pictures of the final product!
Play safe out there!

One of the things that I have always loved about this forum (above many others) is the breadth of experience and knowledge and the willingness to share that, especially when trying to solve a genuine problem. You’re welcome!!