Pyro Meter Tails!

[Piratepete]

:willy_nilly: Domestic client called me to quote for some sockets and a CU change. Stunned to see the meter connected to the existing fuse box by 2 core pyro using the bare sheath as the earth conductor. Was this common practice in the 70s and did it comply back then or even now?

The supply is 60 Amp, the Fusebox is some 4 metres from the meter. The termination of the cable is enclosed at the fusebox end but not in the cutout/meter box where the two single insulated tails connect directly into the meter. The cable diameter (bare) is 13.39 mm. Can't seem to find this in my tables to check the rating.

Is there anyway I can reuse the pyro, as replacing it will be a nightmare! Because of the distance, I'm thinking of installing a 60A switch fuse in the meter box and try to get the cut-out upgraded to 80 Amps (minor point of compliance).

Cheers
Pete

 

[davesparks]

In some parts of London it was once a requirement to use pyro for the tails, can't remember which boroughs but I might be able to find out. I think Chelsea may be one of them.

If it tests out ok then of course you can reuse the pyro, it's a damn sight better cable than any plastic insulated carp. You might wish to apply some heatshrink to the tails as they connect in to the meter though, but if you are fitting a sw fuse then just gland it in to that as normal.

 

[trev]

:willy_nilly: Domestic client called me to quote for some sockets and a CU change. Stunned to see the meter connected to the existing fuse box by 2 core pyro using the bare sheath as the earth conductor. Was this common practice in the 70s and did it comply back then or even now?

The supply is 60 Amp, the Fusebox is some 4 metres from the meter. The termination of the cable is enclosed at the fusebox end but not in the cutout/meter box where the two single insulated tails connect directly into the meter. The cable diameter (bare) is 13.39 mm. Can't seem to find this in my tables to check the rating.

Is there anyway I can reuse the pyro, as replacing it will be a nightmare! Because of the distance, I'm thinking of installing a 60A switch fuse in the meter box and try to get the cut-out upgraded to 80 Amps (minor point of compliance).

Cheers
Pete

The pyro will outlive you, me and my grandson mate and he's only 3. New gland on the switch fuse and you're good to go.
You're ok with glanding pyro aren't you?

 

[Piratepete]

The pyro will outlive you, me and my grandson mate and he's only 3. New gland on the switch fuse and you're good to go.
You're ok with glanding pyro aren't you?

Thanks. Your reply not unexpected. No, never done anything with Pyro!

 

[trev]

I love the stuff mate, it can be a bit unforgiving though so if you have any doubts about how to handle it you might want to ask one of your pals who has used it before.
If it goes wrong it can be a ballache.

 

[shanky887614]

I love the stuff mate, it can be a bit unforgiving though so if you have any doubts about how to handle it you might want to ask one of your pals who has used it before.
If it goes wrong it can be a ballache.

trev is right, make sure to at least have a potting tool, stripper is optional but the crimper is very highly recommended.

why not try on some off cuts before taking on this job, no point making yourself look a fool in front of client

 

[trev]

It's an expensive learning curve though Shanky unless he can pick up some scrap ends from somewhere. It'll be even more expensive if he gets it wrong though
You're right though, potting tool is a 100% must have.

 

[trev]

If you google MICC termination video you'll get some idea of what's involved mate.

 

[shanky887614]

look on ebay there are some deals to be had

people sell it for £3+ m

but then there are people like this that are selling 130 for £30

remember there are multiple different sized potting tools f = 16mm
20mm,25 and i think 30 but im not sure about any others

 

[jaypp]

trev is right, make sure to at least have a potting tool, stripper is optional but the crimper is very highly recommended.

why not try on some off cuts before taking on this job, no point making yourself look a fool in front of client

Haven't you got any left you can offer him?

 

[davesparks]

The OP has said the cable is 2 core overall diameter is 13.39mm, that suggests that it is an imperial cable as it is an exact match for 2 core 0.0145".
To confirm this the markings on the pot and gland will be either 527 or 594.
The nearest match metric equivalent parts are:
Gland - RGM 3H10 25
Pot - RPS 3H10 25 (requires soldering onto cable sheath)
Seal - RPS 2H10 25

Current rating for bare (14th edition regs) 70Amps, volt drop 4.5 mV/A/m

This is taken from the pyrotenax imperial to metric conversion chart for MICC

If it is the imperial cable then it will need more experience than a couple of practice ends before tackling the job. It'll more than likely need a bit of annealing and lots of fettling to work it without it snapping/cracking.

The nearest metric 2 core MI to that diameter is:
2H6 - 12.6mm
2H10 - 14.4mm

 

[davesparks]

remember there are multiple different sized potting tools f = 16mm
20mm,25 and i think 30 but im not sure about any others

Pots are referenced to the size of the thread on the gland, so follow the same standard sizes of everything
Ie 20mm, 25mm, 32mm and 40mm.

20mm and 25mm crimpers are available as the hand operated type whilst the 32mm and 40mm are only available as the 3 bolt & plates type.

 

[davesparks]

Ye gawds I'm a sad barsteward!

 

[trev]

Ye gawds I'm a knowledgeable barsteward!

Fixed that for you Dave.

 

[shanky887614]

Pots are referenced to the size of the thread on the gland, so follow the same standardization sizes of everything
Ie 20mm, 25mm, 32mm and 40mm.

20mm and 25mm crimpers are available as the hand operated type whilst the 32mm and 40mm are only available as the 3 bolt & plates type.

actually dave ive got a smaller than 20mm crimpers on my desk


f type is 16mm.

a lot of motors we get have 16,20,25mm threads etc so all standard size but everyone starts at 20mm for some reason

 

[shanky887614]

and we are all sad barstewards chatting on here when we should all be sleeping, im up in 6 hours hopefully i dont wake up at 2am again like yesterday

 

[davesparks]

actually dave ive got a smaller than 20mm crimpers on my desk

I never said you didn't did I? I've got a set of 16mm crimpers lurking somewhere along with some 5/8" and 3/4"

What I listed is only those that are currently in production and relevant to the topic.

16mm is still listed as a standard size of conduit, but good luck getting hold of it! It's a relic from the days of imperial stuff, 5/8,3/4,1,1 1/2, 2 became 16,20,25,32,40(38),50(52)

I've got 16mm conduit taps and dies, taps were used for fitting 16mm stuffing glands into some scaff tube, the dies are unused.

 

[shanky887614]

i thought they still made 16mm pots, guess not then

 

[davesparks]

i thought they still made 16mm pots, guess not then

Expanded on that post a bit now

 

[appspark]

If you google MICC termination video you'll get some idea of what's involved mate.

In college we got shown a video called, wait for it, "The Terminator" straight from the 1970's prysmian factory.
We still use pyro on alot of our jobs for fire alarms, nothing quite like ordering 500 glands to cheer you up.

 

[trev]

Most fire alarm work up here is done with that crap FP stuff now. Bloody awful stuff.

 

[shanky887614]

Most fire alarm work up here is done with that crap FP stuff now. Bloody awful stuff.

same here.

the designers are idiots though, they speced a 70mm tp swa for our bms panel

it only has a 40amp main isolator and swa needs to go in the side then bend up into isolaror say 10" off bottom of panel

 

[Piratepete]

Thanks Dave Sparks for your detailed information. Your statement above is the one that bothers me most. The pot currently sits just below the meter with the leads directly connected. It will take a full right angle bend to get it into such a position that it can connect into a switchfuse. I have the added complications of getting the cutout upgraded and the meter connected into the switchfuse at the same time. Then there's the CU end to deal with where the Pyro is far too long to fit into the top of the main switch. I suppose I could mount the new CU lower on the wall and extend all the other cables (only 4 circuits).
I'm tending to think that this is a job to pass on to a pyro man. As I don't work full time anymore, I now have the luxury of being able to decline the jobs that look like being an absolute Pain in the Arse ! This looks like one.
Cheers
Pete

 

[davesparks]

Why does the cutout need upgrading?
I can't say without seeing the job, and I might need a tin hat after saying this around here but I might consider using a bit of discretion and keeping the pyro as the tails without a switchfuse.

Whereabouts in the country are you? There will no doubt be a member nearby who can assist with the pyro.

 

[CockneyReject]

same here.

the designers are idiots though, they speced a 70mm tp swa for our bms panel

it only has a 40amp main isolator and swa needs to go in the side then bend up into isolaror say 10" off bottom of panel

You can say that again mate

last commercial new build I was on they spec'd 100a supplies for the lift, bms, alarm and fire alarm panels

35mm 4c SWA for the lift and bms, bms panel was mounted right next to the mains and and had a 40a isolator and the lift was spec'd for a 32a commando plug with its 100a supply and 35mm SWA

the two alarm panels were spec'd for 16mm SWA's, I was in the office when our engineer rang the consultants and tore them a new one over it lad on the phone didn't know what to say

oh and they passed on using pyro for the fire alarm as they weren't sure if it would last the 30 year life the building had been given, it really does make you wonder where they find these clowns

 

[Piratepete]

Why does the cutout need upgrading?
I can't say without seeing the job, and I might need a tin hat after saying this around here but I might consider using a bit of discretion and keeping the pyro as the tails without a switchfuse.

Whereabouts in the country are you? There will no doubt be a member nearby who can assist with the pyro.

The CU is well over 4 metres away from the meter which would normally require a switchfuse, especially as PIR route is up through the cavity wall, then across in the ground floor ceiling void, and down into a cupboard. Is not 3 metres the accepted maximum direct length? The switchfuse would have to be installed in the meter cupboard. Is this still a no no for some dnos?

The job's in Southam, Warks. I've already called one well respected electrician - I quote his reply - hate the stuff, Avoid at all costs!!!

 

[shanky887614]

You can say that again mate

last commercial new build I was on they spec'd 100a supplies for the lift, bms, alarm and fire alarm panels

35mm 4c SWA for the lift and bms, bms panel was mounted right next to the mains and and had a 40a isolator and the lift was spec'd for a 32a commando plug with its 100a supply and 35mm SWA

the two alarm panels were spec'd for 16mm SWA's, I was in the office when our engineer rang the consultants and tore them a new one over it lad on the phone didn't know what to say

oh and they passed on using pyro for the fire alarm as they weren't sure if it would last the 30 year life the building had been given, it really does make you wonder where they find these clowns

the amusing thing is our panel is going to eventually run.

two normal ahu's frost,heating,cooling,filter etc

as well as 8 supply/extract fans

plus other stuff

i think the bigger extract fans are 2.6kw lol. the supply for the ahu's wont be very big

 

[shanky887614]

The CU is well over 4 metres away from the meter which would normally require a switchfuse, especially as PIR route is up through the cavity wall, then across in the ground floor ceiling void, and down into a cupboard. Is not 3 metres the accepted maximum direct length? The switchfuse would have to be installed in the meter cupboard. Is this still a no no for some dnos?

The job's in Southam, Warks. I've already called one well respected electrician - I quote his reply - hate the stuff, Avoid at all costs!!!

pyro is lovely stuff to work with, only rough old codgers or cack handed fools hate it

 

[davesparks]

The CU is well over 4 metres away from the meter which would normally require a switchfuse, especially as PIR route is up through the cavity wall, then across in the ground floor ceiling void, and down into a cupboard. Is not 3 metres the accepted maximum direct length? The switchfuse would have to be installed in the meter cupboard. Is this still a no no for some dnos?

The job's in Southam, Warks. I've already called one well respected electrician - I quote his reply - hate the stuff, Avoid at all costs!!!

If it's well over 4 metres then yes you'll need a sw fuse to make it in to a submain. I thought from your OP it was just 4 metres in which case I'd maybe bend the rules a bit, but yes 3 metres is the normal maximum length.

Experience suggests that people who hate the stuff generally either don't know what they are doing, or like my mentor just hate the endless school fire alarm jobs they used to do every summer.

 

[shanky887614]

why not install a kmf fuse in there that should do it

 

[davesparks]

There's already a perfectly good bit of MICC there, why would he want to install inferior cable to replace it??

 

[shanky887614]

There's already a perfectly good bit of MICC there, why would he want to install inferior cable to replace it??

i only read latest couple and confused myself so edited it when i realised my mistake.

the only reason i was going to mention swa was because of the rcd requirement for new installs less than 50mm in the wall and not mechanically protected etc.

micc doesnt need to be because the outer shieth is the earth

 

[davesparks]

So how would you propose to fit a 1" pyro gland onto a KMF switchfuse?
All of the ones I've seen have been plastic jobbies with nowhere to fit a gland.

 

[shanky887614]

So how would you propose to fit a 1" pyro gland onto a KMF switchfuse?
All of the ones I've seen have been plastic jobbies with nowhere to fit a gland.

bs88 switched isolator

 

[davesparks]

You just open yourself up for it don't you!

Switchfuse or switch fuse disconnector would be a bit closer to the mark.

Which is different to a fused switch or fused switch disconnector.

 

[shanky887614]

You just open yourself up for it don't you!

Switchfuse or switch fuse disconnector would be a bit closer to the mark.

Which is different to a fused switch or fused switch disconnector.

personally id just use a 100amp main switch or whatever like everone else does on new builds

 

[davesparks]

Oh dear, a 100Amp main switch is just that, a switch, it does not include any form of OCPD.

An OCPD is required to make this cable in to a submain due to the distance, ideally an HRC fuse rather than an mcb to give it some hope of discriminating.

 

[shanky887614]

Oh dear, a 100Amp main switch is just that, a switch, it does not include any form of OCPD.

An OCPD is required to make this cable in to a submain due to the distance, ideally an HRC fuse rather than an mcb to give it some hope of discriminating.

why not use a mainswitch so there is an isolator, ocpd aditional ofcourse as well.

 

[davesparks]

You said you would use a 100amp main switch or whatever, which reads as though you would install a 100Amp main switch only or something else.