Oil Boiler cable size

[buzz30]

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

 

[telectrix]

sent you a pm. i'd get it checked. sounds like a bodge to me.

 

[Spoon]

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?

 

[buzz30]

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.

 

[Wilko]

Hi Buzz - can I ask what has concerned you about the work done? Maybe some pics will help .

 

[buzz30]

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.

 

[Wilko]

This is where pics can help folks to comment. Having said that, if it was able to be done in one run of cable there's less to go wrong over time.

 

[Spoon]

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.

 

[buzz30]

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.

 

[telectrix]

that's where i've been going wrong. not been boiling the flowers.

 

[Wilko]

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.

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.

 

[telectrix]

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.

too much information before beer o'clock. .

 

[Silly Sausage]

sent you a pm. i'd get it checked. sounds like a bodge to me.

Sounds like they've used three lengths of left over cable to me

 

[davesparks]

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.

1.5 is bigger than required, but it's the smallest size armoured cable is commonly made in.

 

[davesparks]

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.
.

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.

 

[Spoon]

1.5 is bigger than required, but it's the smallest size armoured cable is commonly made in.

and also the smallest cable you can use for 'power circuit'. (Table 52.3) (excluding flex)

 

[davesparks]

and also the smallest cable you can use for 'power circuit'. (Table 52.3) (excluding flex)

This isn't a power circuit, it is part of the heating controls so is a control circuit.

 

[Spoon]

This isn't a power circuit, it is part of the heating controls so is a control circuit.

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..

 

[buzzlightyear]

Their is only one buzz ,the other is a imposter.

 

[davesparks]

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..

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