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Oil Boiler cable size

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buzz30

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hi all, just after a bit of advice have had a oil boiler fitted in a outhouse the company also wired it up. They took a 3amp fused spur off the the immersion spur ran 1.5mm 4 core 14 meters to outside junction box 3 meters of armored cable to another junction box then 5 meters in the out house to the boiler. Does this seem ok or do I need to get a electrician in. Thanks
 
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Did you get any paper work from the company what showed they have tested the circuit, like a Minor Electrical Installation Works Certificate?
Have you paid up fully for the boiler?
Did they say why 4 core?
 
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Waiting on the paperwork, the 4 core was because it needed a permanent live for a frost stat I think he mentioned it when quoting.
The other 2 companies that quoted advised the same junction box armored cable junction box but different cable sizes because the gap between the house and outhouse is about 3 meters had to go under the path.
 
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My only concern is cable size and route, we had next door done 2 years ago which has identical boiler position but they run the cable in one complete length with no junction boxes armored cable I’m now wondering if that one is wrong and the new one is ok.
 
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I'm not sure why 4 core though.
It looks like the boiler needed a 3A supply which they took from the 3A spur. A 'permanent live for a frost stat' could be taken from the 3A spur that they have wired from, only needing 3 core.
If anyone is familiar with these boilers then maybe someone could correct me.

OP:
Are you using the switched fuse spur to switch on the boiler?
As above, a single cable would be better, but from what you describe, using junction boxes is not against regs... As long as it's been done correctly.
 
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that's where i've been going wrong. not been boiling the flowers.

[ElectriciansForums.net] Oil Boiler cable size
 
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buzz30 said:
Would 1.5mm have been correct size?
I think the armored is because it runs under the flower boiler where the other house is all concrete.
Click to expand...
Hi - let's say the load was 3A then voltage drop is
0.029 x 3 = 0.087V per metre (figures from Table 4D4A) . If I understand correctly you've about 20m run, so less than 2V drop in that length or less than 1% which is Ok.
 
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Wilko said:
Hi - let's say the load was 3A then voltage drop is
0.029 x 3 = 0.087V per metre (figures from Table 4D4A) . If I understand correctly you've about 20m run, so less than 2V drop in that length or less than 1% which is Ok.
Click to expand...
too much information before beer o'clock. :D:D:D.
 
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Spoon said:
I'm not sure why 4 core though.
It looks like the boiler needed a 3A supply which they took from the 3A spur. A 'permanent live for a frost stat' could be taken from the 3A spur that they have wired from, only needing 3 core.
If anyone is familiar with these boilers then maybe someone could correct me.
.
Click to expand...

A basic oil boiler normally requires a switched live, neutral and earth, the frost stat requires a permanent live. Therefore four conductors are normally required to a boiler in an outbuilding.
From the OP's description the fused spur is located in the house rather than the outbuilding so it's not possible to connect the frost stat directly to it.
 
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davesparks said:
1.5 is bigger than required, but it's the smallest size armoured cable is commonly made in.
Click to expand...

and also the smallest cable you can use for 'power circuit'. (Table 52.3) (excluding flex)
 
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davesparks said:
This isn't a power circuit, it is part of the heating controls so is a control circuit.
Click to expand...

Oh, ok. Must be the way the OP has described it in his post...
So where is the boiler getting it's power from... All confusing..
 
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Spoon said:
Oh, ok. Must be the way the OP has described it in his post...
So where is the boiler getting it's power from... All confusing..
Click to expand...

I may have misunderstood the OP but I think the SFCU is in the airing cupboard with the rest of the boiler controls and wiring Centre and the cable in question is just the cable going to the boiler in the outbuilding
 
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davesparks said:
I may have misunderstood the OP but I think the SFCU is in the airing cupboard with the rest of the boiler controls and wiring Centre and the cable in question is just the cable going to the boiler in the outbuilding
Click to expand...

You could be right mate.

OP: Any change of clarification on this set-up please.
 
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They’ve fitted a new 3amp spur next to the immersion fused spur in the airing cupboard that’s where the programmer pump etc are then run the boiler cable under the floors down the wall in the pantry to outside junction box armored cable to another junction box then the cable runs in trunking in the outhouse to the boiler. Think his thought was the armored cable is going under a flower bed was better protection than a cable in a duct
 
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