heating question

[vinny electric]

is it ok to wire a heating system with .75 flex as it is protected by a three amp fuse all answers welcome

 

[telectrix]

i would use 1.5mm, not just for the current capacity, but for the mechanical strength of the cable and getting good terminations in the FCU. even with 1.5mm flex, you have to double it over or ferrule it.

 

[Dunc]

I usually use 0.75 flex for all loops from the main wiring centre to the cylinder stat, pump and boiler. All interlinking cables between the wiring centre - FCU, room stat - wiring centre and wiring centre - boiler isolator are done in 1mm T+E or 3 core.

 

[steve.b]

I always use 7 core 0.75 from programmer to cylinder cupboard and use double back box with strip-connectors and blank plate,wiring centres are problematic, use a wireless stat (saves on decor damage & time) then 3 core/4core 0.75 flex to the rest of controls.
Don't forget 3pole isolator at the boiler (fan switch is OK), if your programmer is at the side of the boiler, 4core from
programmer ( 7core,core1 live,core2 neutral,core6 in connector switch wire) to isolator/to boiler, then make a brew.
PS.7core=core3 hot water, core4 heating,core5 hot water off,core7 ??????? scratches head?? EUREKA!! IT'S GREEN & YELLOW (must be earth!!!!) Hope this help you all.

 

[malcolmsanford]

Steve not having done a CH system for a few years is the 3 pole isolator a manufacterers requirement??

 

[nickblake]

i always have my wiring center next to the boiler then you can use a feeed to a fused spur this will then isolate the whole installation so that the boiler can be worked of safely ,even if the MV tank stat is in the airing cupboard easy toconnect up then with the use of an adaptable box etc

 

[steve.b]

It's the REG'S Malcolm. (safe isolation & switching)

 

[malcolmsanford]

i always have my wiring center next to the boiler then you can use a feeed to a fused spur this will then isolate the whole installation so that the boiler can be worked of safely ,even if the MV tank stat is in the airing cupboard easy toconnect up then with the use of an adaptable box etc

All the boilers i have ever done have mostly been on a FCU which are mainly just single pole switches or the old time fav of plug top. But never have had to fit a 3 pole isolator, which is why I asked if it's now a manufacterers requirement.

 

[malcolmsanford]

It's the REG'S Malcolm. (safe isolation & switching)

3 pole which reg is that steve??

 

[steve.b]

Hi Nick! Don't you think it looks a tad un-sightly (you will still need 7core to cill cupboard)
OUT OF SIGHT OUT OF MIND!!!!

 

[steve.b]

Switched fused spurs are double pole (three pole for Y Plan system/LIVE-SWITCH WIRE-NEUTRAL)

 

[malcolmsanford]

Well I would say that most are double pole but you can get single pole.

The supply into a boiler is just L N and E isn't it?, isn't the S/L an internal part of the wiring loom, as I said I've not done a domestic heating system for years.

So if you were taking a dedicated supply from the CU to a boiler FCU you need a LINE S/LINE NEUTRAL and CPC

 

[steve.b]

S/L is looped in the boiler for a combi / loop removed for system boiler(insert sw-wire in S/L)

 

[malcolmsanford]

So the actual feed into the boiler from the double pole FCU on the wall, that connects the boiler to fixed installation is just L N +E earth. So that is not where you would have your 3 pole isolation is it?

So where is the 3 pole isolator, is it an internal component?

 

[telectrix]

It's the REG'S Malcolm. (safe isolation & switching)

please state what reg. that is. i can't find it.

 

[telectrix]

i can see the need for a 2 pole FCU on the boiler as the damn rubbishy things are always failing ( the boilers and ancillary bits that is ) and taking out RCDs.

 

[Dunc]

Steve not having done a CH system for a few years is the 3 pole isolator a manufacterers requirement??

Only if the FCU supplying the central heating system is located away from the boiler. If the FCU is beside the boiler then no additional isolators are required.

 

[telectrix]

steve. this switched L you are talking about. it will be isolated when the L&N to the boiler are isolated anyway, so what's the point?

 

[malcolmsanford]

Only if the FCU supplying the central heating system is located away from the boiler. If the FCU is beside the boiler then no additional isolators are required.

I was not woried about the isolation part dunc, just why the 3 pole part?

 

[telectrix]

perhaps it's because these modern boilers are so big and heavy, it takes 3 immigrant poles to carry in and mount it. then , as they are on less than minimum wage, he wants to isolate all 3 of them before lunch break.