In article ,
Chris J Dixon writes:
As part of my central heating refit, I am having a new and
relocated hot water tank with economy 7 and boost immersion
heater elements. I plan to feed these via a Horstmann electronic
timer.

The circuit will have a dedicated 16A MCB (is the voting for RCD
protection or not?)

No RCD protection, but make sure your earth bonding is up to spec.

What are the requirements for further protection? I can't see
the logic in having a separate fused outlet for each element, but
local isolators at the point where the high temperature flexible
terminates seems sensible.

I don't have a clear picture of your intended setup, but
if the max load is 3kW, that sounds fine, except you want the
isolator to also isolate the controller for maintenance purposes.

Should I fit a fused spur unit upstream of the timer instead?

I would expect the instructions would indicate this sort of thing.
If the immersion heater load goes through it, then I see no point.
If it just takes a low current control supply with volts-free
relay contacts, then an FCU with 2A fuse would be a good idea.

--
Andrew Gabriel

As part of my central heating refit, I am having a new and
relocated hot water tank with economy 7 and boost immersion
heater elements. I plan to feed these via a Horstmann electronic
timer.

The circuit will have a dedicated 16A MCB (is the voting for RCD
protection or not?)

What are the requirements for further protection? I can't see
the logic in having a separate fused outlet for each element, but
local isolators at the point where the high temperature flexible
terminates seems sensible. Should I fit a fused spur unit
upstream of the timer instead?

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

Andrew Gabriel wrote:

Chris J Dixon writes:
As part of my central heating refit, I am having a new and
relocated hot water tank with economy 7 and boost immersion
heater elements. I plan to feed these via a Horstmann electronic
timer.

The circuit will have a dedicated 16A MCB (is the voting for RCD
protection or not?)

No RCD protection, but make sure your earth bonding is up to spec.

What are the requirements for further protection? I can't see
the logic in having a separate fused outlet for each element, but
local isolators at the point where the high temperature flexible
terminates seems sensible.

I don't have a clear picture of your intended setup, but
if the max load is 3kW, that sounds fine, except you want the
isolator to also isolate the controller for maintenance purposes.

The tank will be in the integral garage, so for convenience I
want the controller in the pantry, about 3 metres away, as the
cable runs. Max load is indeed 3 kW, as the controller ensures
the two elements cannot be in use simultaneously.

Should I fit a fused spur unit upstream of the timer instead?

I would expect the instructions would indicate this sort of thing.

Pretty lightweight on those aspects. I'm not sure exactly what
the regs require.

If the immersion heater load goes through it, then I see no point.

Yes it does.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

On Fri, 09 Jul 2004 19:59:27 GMT, Chris J Dixon
strung together this:

What are the requirements for further protection? I can't see
the logic in having a separate fused outlet for each element, but
local isolators at the point where the high temperature flexible
terminates seems sensible. Should I fit a fused spur unit
upstream of the timer instead?

IIRC the Horstmann timers have integral fuses so a DP switch feeding
the timer would suffice. The immersion heaters themselves will need a
DP switch each, located near to the tank.
--

SJW
A.C.S. Ltd

In message , Lurch
writes
On Fri, 09 Jul 2004 19:59:27 GMT, Chris J Dixon
strung together this:

What are the requirements for further protection? I can't see
the logic in having a separate fused outlet for each element, but
local isolators at the point where the high temperature flexible
terminates seems sensible. Should I fit a fused spur unit
upstream of the timer instead?

IIRC the Horstmann timers have integral fuses so a DP switch feeding
the timer would suffice.

AKA pcb track

I'm not so sure you're right there

--
geoff

On Wed, 14 Jul 2004 21:44:11 GMT, raden strung
together this:

AKA pcb track

I'm not so sure you're right there

Well, it was a while since I fitted one, I've got six in the garage
but can't be arsed to check at the moment. Might be worth the OP just
confirming the need for a fuse, or not, before installing.
--

SJW
A.C.S. Ltd