The forth wire on a Ideal Logic 18kw Heat Only System Boiler

[ianmcd]

I beg to differ, but only slightly. The circulating pump is [edit: should be]wired directly from the boiler.
[edit 2: there is confusion in the title; a heat only boiler is not a system boiler, and vice-versa]

you can beg to differ all you want, and I assure you I know the difference between a heat only and a system boiler, OP has a heat only boiler, look at page 37 diagram 2:23 the wiring diagram for Y plan with this boiler, you will clearly see there is NO pump over run and the pump live is a switched live from the mid position valve

https://idealheating.com/uploads/documents/logic-heat-h-installation-and-servicing.pdf

 

[Ray1000]

what is this cable and where does it connect to ?

Sorry for the confusion Ian, I had viewed it on my phone and hadn't seen the red circle ... the grey flat twin is the wire from the original room stat in the hall ... I intended leaving it there in case it ever went back to programmer and room stat.
Ray

 

[ianmcd]

Sorry for the confusion Ian, I had viewed it on my phone and hadn't seen the red circle ... the grey flat twin is the wire from the original room stat in the hall ... I intended leaving it there in case it ever went back to programmer and room stat.
Ray

is the other end of this cable near the heatlink ?

 

[Ray1000]

No Ian it's in the hall but a distance away ... it doesn't pass down the same wall as the Heat Link and the main fused spur is on.

 

[ianmcd]

can you post pics of your loft, showing the boiler and anything electrical near it, same with the wiring centre, that is an unusual place for a fused spur

 

[DP]

I beg to differ, but only slightly. The circulating pump is [edit: should be]wired directly from the boiler.
[edit 2: there is confusion in the title; a heat only boiler is not a system boiler, and vice-versa]

Look at the manual.

 

[DP]

Can someone explain the forth wire shown as being connected to the boiler ... my boiler only seems to have a normal three core cable connected to it as shown on one of my other posts.
Thank you very much
RayView attachment 263203 View attachment 263204

Thorough queries need to be as the boiler may well have two inputs demand wires ie heating and hot water
Look at the manual on page 38. I looked for detail but glancing through the manual may have missed the relevant info. Have seen both 4 and 6 terminals wired for demand.

Reason for this is that hot water heating might need higher temperature and heating not so

 

[Ray1000]

can you post pics of your loft, showing the boiler and anything electrical near it, same with the wiring centre, that is an unusual place for a fused spur

When we moved in 30 years ago it had hot air heating ... with a floor to ceiling boiler and a what seemed like a 24" diameter fan. During the changeover it would have been a convenient place for the fused spur, straight up the wall to the programmer then up into the loft to the Honeywell Board at the side of the hot water cylinder and the pump.

The Ideal Classic gas boiler was a distance away in the garage - It had replaced an Anthracite Boiler which was in a room at the back of the garage ... this was in the good old days when the fuel was supplied free of charge courtesy of British Coal.

There is another fused spur in the vicinity but its for the Emersion Heater.

 

[Ray1000]

[edit 2: there is confusion in the title; a heat only boiler is not a system boiler, and vice-versa]

Sorry for the confusion - I thought ours was a "System Boiler" and I thought the Logic Heat H18 was referred to as an "Heat Only" boiler as opposed to a combination Boiler.

Ray

 

[Ray1000]

For new readers ... Two separate boilers in two separate houses are being discussed, both Ideal Logic, House One - mine has had the live wire to the SL1 IN on the boiler missing for three years, only being highlighted by asking the forum about the other newly installed one in House Two which has the live wire to the SL1 IN quite likely coming from the input side of a fused spur.

If you have a logic heat then the switched live comes from the 3 port valve, this brings the boiler and pump on, the permanent live is there for when the call for heat is satisfied the fan over-run can activate and cool the boiler and store settings, when the fused spur is switched off the permanent live and switched live are both isolated if wired correctly

If a mistake has been made connecting the live to the wrong side of the fused spur I think there was a genuine belief it needed to be "permanently live"

I'm wondering now if the fused spur is all it appears ... why would there be 7 wires in it plus earths?

I had thought the three core cable to the boiler appeared to be coming from fused spur but may be it was coming down behind the plaster from the Honeywell box in the airing cupboard ... I need to do a drawing to explain .....

 

[fixitflav]

If a mistake has been made connecting the live to the wrong side of the fused spur I think there was a genuine belief it needed to be "permanently live"

I hope that's not the case as it's potentially dangerous. If so, you would need to isolate further upstream to remove the live to the boiler. As I said in #5, permanent live doesn't mean that permanent!

 

[Ray1000]

House Two showing position of boiler etc.

Trying to work out what the 7 wires might be in the fused spur, and presumably the 3 core is coming behind the plaster from the Honeywell board

I'll need to get to the bottom of this before a Nest thermostat can be fitted

 

[Ray1000]

I hope that's not the case as it's potentially dangerous. If so, you would need to isolate further upstream to remove the live to the boiler. As I said in #5, permanent live doesn't mean that permanent!

With your help, I fully understand, we are talking about a live that is not switched by any of the controls but would be isolated when main Central Heating fused spur is turned off

 

[Ray1000]

So, if I'm not mistaken ... the Room Stat, Cylinder Stat, Y Plan valve and Pump are only wired to or from the Honeywell Board along with 3 of the 4 wires to or from the boiler.

The forth wire to the boiler comes from the output side of the Central Heating Fused Spur.

The Fused Spur should have 2 wires going in, and 3 wires going out, 5 wires in total excluding earths.

I wonder why there appears to be 7 wires in the fused spur of House Two ?

 

[ianmcd]

The Fused Spur should have 2 wires going in, and 3 wires going out, 5 wires in total excluding earths.

No the usual way is L,N,E in from consumer unit, and then L,N,E out from the fused spur and connected to the wiring centre, everything else is distributed from the wiring centre,switching off the fused spur and removing the fuse should then remove power to any part of the heating system and controls but I understand why yours hasnt been done properly