Crabtree f-60 tp&n circuit breaker bs# and short circuit capacity

[Empire]

Morning All,

Having spent many years gleaning information from you all as a non member I've finally needed to join because, try as I might, I just can't find the answer to this puzzle, so here goes.

I've just installed, replaced really, a TP sub board that's being fed from a Crabtree 60A STD O/L (whatever that means) type F-60 TP&N circuit breaker and I have had limited success finding the BS number and short circuit capacity. It's clearly very old, does anyone have any ideas/experience please?

Without being able to confirm, I've decided for the moment that it's a BS3871 with SCC of 3KA. Am I wildly wrong here?

TIA if any can help.
E

 

[westward10]

If this is what I think it is it predates BS3871 and has no type characteristics as such. Does it have small screws which fix it to the front panel of the dist board? Finding any info on these even from Crabtree will be a fruitless task, they have no technical specifications for them. Bottom line you should not really have utilised it for circuit protection.

 

[Empire]

Thanks for the reply.

There were no screws in place on any of the isolators in the panel but there are captive nuts fitted which could indicate they may be used for such.

I didn't consider I couldn't use it especially as exiting cable is swa of sufficient size and surface mounted. This panel is a tomb for whole families of mice and I frankly had no interest in touching it other than testing so what solution would you recommend?

 

[westward10]

The problem is you cannot prove fault protection is maintained. Can you post a pic of it.

 

[Empire]

Oh, yes I see.

This is not working out well.

Sure pic coming.

 

[westward10]

Thanks for the pic, very unusual to see one of those still in service however, you have severe issues here. STD stands for Short Time Delay and this function allows for a fault current upstream to persist for several cycles for the purpose of discrimination, in other words it kind of waits for another device to trip before it takes action. The problem with this is that circuit components and conductors where additional reinforcing measures have not been put in place are subject to undue mechanical and thermal stress. I am not sure how this can be relied upon to provide suitable circuit protection given its age, 50+ years and it's inherent mode of operation.

 

[Toneyz]

I take it that your installation works starts at the newly replaced distribution board. I presume your professional judgement is that under fault conditions the protective device cannot be relied upon to protect the existing SWA sub-distribution circuit then you will need to discuss this with the client to replace.

 

[Empire]

Thank you westward10 for the information, this is much worse than I expected. Oh well, it looks very much like I'll be retiring this old boy and installing something newer.

Yes, anthonybragg, my installation started and finished at the sub board. With this unexpectedly bad information, you are quite correct, the circuit breaker installed cannot be used so out with old.

 

[westward10]

Could be worse it could be a LTD device, Long Time Delay

 

[Toneyz]

Is this in an enclosure on its own from a bus bar chamber I am guessing that a switch-fuse would be installed in its place?

 

[westward10]

Pretty sure that is a dist board. Those five brass inserts on the breaker are what I was alluding to in #2, you fit the cover and then fit tiny screws into them. I have only come across them a couple of times and strangely enough they have one at the museum in Northampton well they did a few years ago, probably where it belongs. We took the cover screws out and then you have to remove all those tiny screws to get the cover off.

 

[Toneyz]

Pretty sure that is a dist board. Those five brass inserts on the breaker are what I was alluding to in #2, you fit the cover and then fit tiny screws into them. I have only come across them a couple of times and strangely enough they have one at the museum in Northampton well they did a few years ago, probably where it belongs. We took the cover screws out and then you have to remove all those tiny screws to get the cover off.

Well, don't expect it to be upgraded anytime soon as the council has no money.

 

[Toneyz]

Anyway back on topic, I think the OP would need to advise the client to upgrade to an MCCB board assuming from Westward's post it is some sort of board that feeds other supplies (sub-mains to other boards) and they could be just as unreliable.

 

[Empire]

Thank you westward10, you are quite correct it is a dist board. A very large one, about 6' wide and almost as high and I'm just waiting to hear how much an mccb replacement unit is going to be, thank you anthonybragg. Most of the circuit breakers here have been removed from service, and from memory only 2 are still used, I guess it's about to become mccb replacements.