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Discuss Boiler control circuitry in the Central Heating Systems area at ElectriciansForums.net

spud1

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Arms
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We are currently doing a site of 15No. new build houses. The 15No. plots are the last of 40No. approx on the site (We have taken over from another electrical contractor who has been thrown off site).

The previous electrical contractor has wired the supply for the S Plan boiler control circuitry in the previous 25 plots in an odd way. Whereas I would normally have a switched fused spur in the airing cupboard adjacent to the wiring centre for isolation of all control circuitry and a 3 pole isolator at the boiler position for isolation of the boiler (P Live, switch live and neutral) only, they seem to have wired the supply to the wiring centre through two switched fused spurs (in series) the first at the boiler location and the second adjacent to the wiring centre.
I see how this serves the purpose of isolation of all control circuitry (including the boiler itself) from both locations but its seems to me rather odd practice to have 2No. switched fused spurs in series like this. I think it increases the likelihood of confusion during future fault finding (e.g. one fuse blows, engineer attends to correct and finds the other fuse intact and rightly assumes this is the only fuse protecting the boiler circuitry). I also think it increases the potential of accidental energizing of the control circuitry and wiring centre while being worked on in the future (e.g. Heating engineer swaps a faulty cylinder stat in the airing cupboard in 5 years time, isolates from switched fused spur adjacent to boiler downstairs only, customer comes home and inadvertently turns the spur back on not knowing it is being worked on).

Would appreciate your opinion on this one?
 

snowhead

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Mentor
(e.g. Heating engineer swaps a faulty cylinder stat in the airing cupboard in 5 years time, isolates from switched fused spur adjacent to boiler downstairs only, customer comes home and inadvertently turns the spur back on not knowing it is being worked on).

Would appreciate your opinion on this one?
It doesn't seem the most logical way, but most boiler set ups I've seen only have 1 fused spur to isolate the whole circuit, and that could be sited anywhere.

In a house it's unlikely someone would not know of the presence of a tradesman.
The person working on the equipment should have it suitably isolated, locked off where possible and a warning notice displayed.
 

spud1

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Arms
  • Thread Starter Thread Starter
  • #3
Very true, safe isolation and locking off at the consumer unit would be the proper action during any maintenance, my example is assuming the engineer who is carrying out the work is'nt necessarily a competent electrician but maybe a heating engineer/plumber who would be less likely to be aware of safe isolation procedures. My example regarding the homeowner inadvertantly energising the control circuitry again is an assumption of perhaps another family member coming home not knowing someone is working on the boiler control. We have always installed 1No. switched fused spur to isolate and protect all control circuitry but always site 3pole isolation next to the boiler too for local service isolation of that boiler.
 
S

Spark1979

All the time I've done heating systems I've never fitted two fused spur, I've always put the spur in a logical place, combis next to the boiler, y and s plans either next to the boiler or wiring centre depends which type of boiler it is and how it wired. Surely one of the spurs should just be a double pole switch then only one fuse can blow
 
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