I have an idea for an issue I have with a y plan.
The new programmer in the ground floor kitchen replaced an old danfoss. There is no wire available back to the 12 way in the cupboard upstairs for hot water off. This obviously causes issues with the 3 port valve.
The gas fitter is unwilling to change to a S-plan and a cable run is problematic.
My idea is to use a small separate contactor where the hot water on live keeps the contactor on, but when hot water is off the live is removed closing the NC contactor to put a separate live on the Grey wire of the 3 port.
Has anyone tried this method before?
Yes that’s correct. So if at the programmer you turn the hot water off, the hot water off terminal goes live and the common at the cylinder stat goes from live to 0volt. This in turn will close my suggested contactor giving a live to the grey wire. So in the end you still switch the hot water off live at the programmer. This should save me having a **** day installing said wire.
The gas lad to me should change it to s plan but that’s not happening.
The theory of what you suggest should work with regards to controlling the heating...
But.. where are you getting the live supply from that will feed through your new contactor switch out onto the Grey 3-port wire?
You said one bit was upstairs and the other downstairs?
I can't see why you would have an additional permanent live from the down stairs programmer up to the heating 12-way wiring centre..? As it only needs "Switched-Lives" such as:-
Heating only ON: (white) via the room thermostat fed from the programmer switched live heating on, plus (grey) via the heating off, either programmer or tank-stat if already hot.
Water only ON: (bypass 3-port) via the tank-stat fed from the programmer switched live water on.
Heating AND Water ON : (white) via the room stat, from the programmer, plus tank-stat on, bypassing the valve direct to orange, boiler fire up!
So normally ALL live feeds into the thermostat(s) & valve(s) will come via one of the programmer channels Water/Heat#1/Heat#2 etc.. And if you disconnect the supply to the programmer, will all of the heating control wiring become dead and safe to work on..? (e.g. for fault finding).
As if you have a different perm live supply through your "Bespoke-contactor-arrangement", that is not fed from the same FCU that is supplying the programmer.. Then that's a bit of a poor design in my book!!
Or does the supply feed into the downstairs programmer actually come from upstairs adjacent to the 12-way control centre?
Personally I don't think I would do it... BUT..
If you can get a common supply for the whole arrangement fed from one point of isolation (FCU),
and it is the only economical solution that the customer will accept..
Then I would make Sketches/circuit drawings/descriptions of the non-standard wiring...
Laminated and fixed adjacent to every key point on the system..!
Plus labels on each box stating... "Non-Standard-Wiring.. See Attached Laminated Diagram"!
So if some poor bod comes along in a few years.. they will stand a bit of a chance of figuring out how its wired!
[ Side Note:- There's a customer by me with a very strange wiring set up.. with a FCU downstairs by the boiler in the garage, and another FCU upstairs by the tank, pump, valves in a sort of airing cupboard..
All off the same CU MCB socket circuit: But you MUST turn BOTH FCU's off so you don't still have some live feeds into the heating control wiring!! ]
I forgot to say..
Welcome back Nicky, to one of our older forum members.. Its been a while since we have seen you..?
But it is great that you re-visited to get an idea of others opinions about if your idea is the best thing since sliced bread,
or just a pile of Cow manure!!!
Hopefully it is all, constructive polite debate, that may also help others who are just "lurkers" resulting from your question..
Which in my opinion is a very interesting real-world problem!!
Heating control wiring is one of those areas that can quickly establish who is a competent electrician or plumber/heating "technician".. as far too many really haven't got a grasp about how it all works!!
