Old Dorman smith breakers

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Adam_151

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Only had a quick peek at the board today (as we were identifying the relevant circuits), but job I'm on at the moment (various minor works) has a oldish dorman smith board, the breakers look similar to the crabtree C50 range (black with amp rating on the toggle).

Question to anyone who has come across these before, will the type and breaking capacity be printed on them somewhere (as with modern breakers), or will it be a right faff around and be some daft thing like the colour of the writing on the toggle

Will they be to BS3817? or do they predate this (I remember someone on this forum talking about breakers with no magnetic component)
 
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Those look like the ones Eric (although I've only seen them from the front - board cover on)

Thermal only you say? So which british standard would those be to, and how would I go about finding out what the max permitted Zs is?
 
I have had this problem in the past especially with moulded breakers which when supplied have a nice little chart in the box but this is often binned and finding out the parameters of 20 year old stuff is not easy.

Step one ask for the last PIR should be entered on that. Yes I know unlikely but always worth a try I always include note that information taken from last PIR that way if wrong and someone queries it you can say where you got info.

You could ring the firm that are selling them there is a link by clicking on picture.

Or you can assume it will be similar curve to that shown in regs book without the cut off where the magnet bit cuts in.

Looking at those it is unlikely that it will react in anything less than 10 seconds and unless used with a RCD it is unlikely to comply with current regulations.

I would be inclined to give it a code 2 and a note saying this type of MCB is too slow to comply with current regulations and advise the changing of this board is included in the next major refurbishment.

Unless some one else on here has any better ideas.

This has come up before see //www.diynot.com/forums/viewtopic.php?t=144897 but that did not get many people giving useful information either.
 
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I've come accross them before, during an inspection but i wrote a daming report about the board they where installed in and that there capabilities under fault conditions where unknown.
 
In 1989 I returned to UK to work on the building of Sizewell Power station and at that time they were quite common but we were finding problems in getting replacements. At this point the 16th Edition was still quite new and we also had a mixture of type 1,2,3 and 4 plus new B,C and D. And the whole idea of DIN rail mount was still new.
By the time I was working on Connah's Quay power station in 1997 we were disposing of any WMDU's (Weather Proof main distribution units) which still used these and moulded breakers and miniature circuit breakers were replacing them.
The Loadmaster Dorman Smith MCB was to industry like the Wylex fuse board was to the domestic market. But until the 16th Edition came out in 1991 no was was really interested in earth loop impedance or prospective short circuit current and the new innovation was the voltage operated earth leakage trip. We also still used oil switches and welding transformers were still oil cooled as well. And a PCB was a printer circuit board and we had no idea of the dangers in sticking ones hand and arms into the oil to repair things.
We were aware of asbestosis but most people thought the authorities were going OTT and still used fuse boards with big lumps as well as the pads under the fuses.
It has been a time of change the last 20 years but some places are still catching up.
 
I would have thought the install stuff in a power plant would be mainly BS88 fuses and ACBs?
 
[/quote]In 1989 I returned to UK to work on the building of Sizewell Power station and at that time they were quite common but we were finding problems in getting replacements. At this point the 16th Edition was still quite new and we also had a mixture of type 1,2,3 and 4 plus new B,C and D. And the whole idea of DIN rail mount was still new.
By the time I was working on Connah's Quay power station in 1997 we were disposing of any WMDU's (Weather Proof main distribution units) which still used these and moulded breakers and miniature circuit breakers were replacing them.
The Loadmaster Dorman Smith MCB was to industry like the Wylex fuse board was to the domestic market. But until the 16th Edition came out in 1991 no was was really interested in earth loop impedance or prospective short circuit current and the new innovation was the voltage operated earth leakage trip. We also still used oil switches and welding transformers were still oil cooled as well. And a PCB was a printer circuit board and we had no idea of the dangers in sticking ones hand and arms into the oil to repair things.

its typical of british nationalish industry! light years behind and it takes 10 years to get the people and methods used upto date
PCB's in insulating oil was well know about from the mid 80's
I still come across engineers from that world wanting silly bespoke DB's and to wire buildings in MI just makes things so expensive![/quote]
 
What is wrong with using MI?
A majority of our installations (industrial) are done in SWA, conduit/trunking and MI.
 
nothing wrong with MI for the connect environment but compaired with SWA for a industrial building its sooooo expensive to install.

I did a job in a forestry commission vehicle work shop

The DB's where real odd ball things build to the engineers spec, but u couldn't get to the neutral and earth rails once the MCB's where fitted :confused:

he wanted it wired in trunking and MI a real weird design and then he wanted the trunking lids sealed to improve the IP rating??? it should have been wired completely in SWA!

i use some european types of cable (NY etc) its ideal, it can be installed to a high IP rating and its quick to install to.
 
Don't get me going about people who still think it the done thing to get manufacturers in to design custom panels. Why I said, I can put together a nice triple-act of merlins to do the job admirably. Its a long story after that...
 
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