GCH but no room stat

[SparkyTris]

I'm trying to work out the wiring for a gas central heating system in a flat...
there is a Suprima 40 boiler, circulating pump, two zone valves (one for DHW, one for radiators) and a thermostat which is lashed onto the side of the vessel (with a small hole cut into the insulating so the thermostat couples sraight on to the copper)
there is a potterton ep2002 which appears to have been used as a wiring center.

I cannot find a room stat anywhere.

I'm a bit short of time and would really appreciate any help on what might be "going on" here, and any recomendations as to how it could be improved. (putting in a room stat seems like a good idea but where should it go and is there already one wired in)

I was hoping that the wiring arrangement may be "recognized" by one with more experience than I...

 

[SparkyTris]

the image (which is supposed to be a sketch of the wiring center) is tiny here, I don't know why. sorry

 

[doitall]

Can't see the pic it's too small.

A standard S plan wiring in conjunction with the boiler requirements would do the job

 

[SparkyTris]

Apologies for my total and complete incompetence.

I think if you hover over that image you can zoom it to a visible size.

I'm going to replace the programmer & backplate so I've got to work out what's what in the wiring center.

so far I've got:

supply to programmer = 1 x T&E
thermostat on copper cylinder = 1 x T&E
CH zone valve = 2 x T&E
DHW zone valve = 2 x T&E
supply to boiler = 1 x T&E
supply to circulating pump = 1 x T&E

that accounts for the the 8 x T&E I have entering the wiring center.



help greatly appreciated!

I

 

[doitall]

What wiring center it doesn't look like anything conventional.

Download the S plan in the link below, you also need the boiler MI.

http://www.honeywelluk.com/downloads/Systems-Plans/

 

[ChrisR]

That's normal for an EP2002 - the ABCD connections are just "spare" so used for any connections.

3 is HW on, 4 is CH on.

Normal would be to have the wire from 3 go off to the cylinder stat and back to the connection block then to the Brown wire of the relevant 2 port valve.

Yours probably does that.
So it's ditto for the heating, from terminal 4 off to the stat and back to the other 2 port valve.

Put the stat somewhere appropriate for the property and how you use it. Can be the hall or the living room, not by a radiator/window etc, and make sure the rad which affects the stat mostly, doesn't have a thermostatic valve.

A Radio/remote/RF stat might be easiest if the wiring's difficult.
You put a receiver bit near the wires you can get to, and the transmitter bit is battery powered and goes where you wnt. Batteries last for years.
Programmable thermostats are popular these days. Honeywell are nice but there are lots of others.

 

[SparkyTris]

thanks very much for replies so far, vy helpful. Looks like a previous person has used the old electric immersion water heater wiring to connect the cylinder stat in. (I had a look at the HW cyl, there is a pattress box for immersion flex but the flex goes to the lashed-on stat and the immersion element is not connected to anything.) the T&E to the pattress box is 4mm2, matches the thicker wires in my prev. dwg which connect to A and 3.

Do I understand correctly then that the controller switches Live to terminal 3 when it enables the HW system then?

then the cyl stat switches Live to terminal A
then the zone valve ought to be connected to A...?

 

[ChrisR]

I expect it was like this regarding the valves
Their orange wires get connected together and go to the boiler Switched Live.

New room stat would interrupt as shown in red/black.

The boiler SHOULD have a permanent live connection and the Pump SHOULD be connected to the pump output from the boiler, but things often aren't like that.

Your connections to where I've shown "Boiler??" looks wrong - both conductors get together at B and D linked!

All manner of lash up is out there...


Hope this helps
View media item 49640

 

[SparkyTris]

ChrisR thanks vy much for this, just what I was after.
you are dead right, my dwg has at least 1 error. terminal D has only 3 wires connected: the jumper to B and two blacks which are presumably the switched lives from the aux limit switches on the ZV's

where you have drawn boiler, is probably the connection to my PUMP upon which is piggybacked the switched live to the boiler.

 

[SparkyTris]

unfortunately I cannot seem to upload any more diagrams so Ill have to explain this verbally:

I have discovered that my circulating pump is connected direct from the wiring center. ie, it is controlled by the aux switch on either of the 2 zone valves.

there is no room stat in the system. there is a HW stat on the copper.

the programmer controls the CH ZV, and by extension the Aux sw. on the CH ZV.

the programmer controls the HW stat, which in turn controls the HW ZV, which in turn controls the Aux sw. on the HW ZV.

when there is no demand, the zone valves "let go" (and close) and the pump simultaneously powers-down.

I thought that the pump is supposed to over-run for a short period after demand has ceased in order to stop the boiler from boiling...?

inside my Suprima boiler are 3 connections labelled "pump", adjacent to the permanent feed and switched live for controlling the boiler. these are all not connected.
I presume that these cconnections are for doing this pump overrun. could anyone give general advice on this please?
I think I could use the existing wiring to hook up the boiler-controlled pump option.

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[SparkyTris]

On my suprima boiler, there is a temp control knob by which one can roughly adjust the temperature of the water coming out of the exchanger (or so claims the manual).
there is a thermistor and also a limit 'stat ported into the flow pipe coming up from the heat exchanger. this all makes sense. I suppose the thermistor is used in conjunction with the temp ctrl knob to stop the burner. and the limit stat will stop the burner if it All Goes Wrong and superheated water starts coming out of the exchanger.

I cannot get the burner to stop with the knob though. If I turn it back to the click OFF position that stops it but I am running with the temp ctrl knob down at minimum and it is not stopping.

the boiler is in a bedroom cupboard. there is trunking between the boiler and a eaves void. in the eaves void is the circulator, bypass pipe and an expansion leg leading upwards to the F&E tank.

At the boiler, I have noticed that the Flow pipe is hotter than the return pipe.
the pipework is Hepworth grey plastic crap unfortunately and it is trunked in between the boiler and the pump so I cannot confirm properly which pipe is actually output and which is return. I shall dismantle the trunking to confirm this but it appears that the flow & return may be the wrong way round on the boiler, does it not?

At the boiler, there is a feed (expansion?) pipe coming down from the coolant header into what should be the Return of the exchanger. (the one without the sensors on it)

the other pipe (the flow of the exchanger) goes straight out and into the trunking towards the eaves void.