Viessmen 100T boiler wired within a Sunday Plan

Evening all I'm just after some advice on the wiring of the above boiler..

The plumber has wired it as a 4 pipe system.

the system consists of the boiler which is a combination boiler

A cylinder with a 13 amp immersion heater (used as back of up if boiler breaks)

cylinder stat

Room stat

Programmer for heating and hot water

Pump out in the field wiring for instant hot water

Programmer for field pump to programme pump to run at certain times for instant hot water..

I've wired the system as an s plan

So Permanent Live and Neutral to Boiler

Live out from programmer to Common on Room stat

Live out from programmer to Common on Cylinder Stat

Switch live from Room Stat onto the boiler

Switch live from Cylinder Stat to Brown on the motorised valve 

Switch live from the Orange on the valve to a cylinder demand junction box sited inside the boiler..

Heating works fine when the programmer for hot water is off (I. E.no permanent live to Cylinder stat)

When the hot water is set to auto or override the Cylinder stat receives a perman entry live and with cylinder stat set to 60 degrees the switch live from the cylinder stat returns to the coil on the valve (brown) and fires the boiler..

the problem I'm having is the hot watER demand is permanently showing as on at the boiler (small tap symbol)

the water from the tap is red hot so it has Deffo reaches 60 degrees but isn't switching off...)

Is my understanding correct here stat set to 60 water reaches 60 boiler should switch off?? 

I've turned the stat down to 45 and it clicks and voltage goes to 0 volts on the Orange wire  (which I'd expect)

Is my set up and thought process correct here?

Sorry it's long winded but hopefully it's clear 

Title should say s plan not Sunday plan (predictive text  :Salute )

I think a drawing would be clearer as I am not convinced your description is totally correct (probably because mobile phones are a stupid idea for internetting IMO).

You mention S plan but there is only 1 valve?

Do you have a multimeter? Surely the first port of call should be the boiler control panel? Check for the correct voltages there and then if anything is on when it should be off or vice-versa then work out from there.

It's a combination boiler used within a system boiler set up there is only 1 valve and this is purely for hot water..

I've set the cylinder stat to 60 degrees and the boiler is running constantly even though the water temperature is red hot.

I expect the cylinder stat to switch off when the water reaches 60 degrees but it isn't 

When I turn the stat it clicks off at about 45 degrees so I may have answered my own question here but maybe the cylinder stat is faulty...

In the meantime I've turned the hot water programmer off and turned the immersion heater on so they have central heating 

what two port valve has been installed? Sound like cylinder thermostat is working correctly so I bet the valve hasn't been unlatched (some valves do this automatically when energised and some don't) or the micro switch is stuck between grey and orange.

The easiest way to configure a combi to work as a 'system' is to ignore the DHW side of things and use the CH circuit only, use either a 3port, or, preferably, 2x 2ports to direct water to either CH or cylinder. 

I'm with steps on this one, why would you use the hot water side?

Still waiting for a diagram/drawing of some description as something doesn't sound right in the OP.

Is this one valve a three port? 

Sharpend said:

Is this one valve a three port? 

Click to expand...

It's a 2 port valve dedicated to hot water only 

you need a proper plumber that knows what they are doing

steptoe said:

you need a proper plumber that knows what they are doing

Click to expand...

TBF, OP is being as vague AF so if we're condemning the plumber we should condemn the electrician too as I'm still not sure what is going on.

Lurch said:

TBF, OP is being as vague AF so if we're condemning the plumber we should condemn the electrician too as I'm still not sure what is going on.

Click to expand...

maybe they are both well suited to working together,,,,,,,  :C

I am a bit confused here about the lines

Racricket said:

Pump out in the field wiring for instant hot water

Programmer for field pump to programme pump to run at certain times for instant hot water

Click to expand...

can you explain this?

It seems like you are trying to mix stored hot water and instantaneous hot water somehow.

And what is a four pipe system?

Diagram please, and exact boiler model, I can't find viessmann 100T

I took that as being a secondary hot water loop. One would assume that this was off the tank but who knows?

Lurch said:

I took that as being a secondary hot water loop. One would assume that this was off the tank but who knows?

Click to expand...

A hot water loop through the cylinder via a "field" pump which is also pumped via the pump in the combi which is switched on by a flow switch. Might explain why there is constant hot water demand, with the "field" pump off, there could be gravity circulation which will activate the flow switch in the boiler.

Never seen this setup before, usually the DHW side of the combi just serves, for example, a single hot tap and the stored hot water is used elsewhere.

Rob_the_rich said:

A hot water loop through the cylinder via a "field" pump which is also pumped via the pump in the combi which is switched on by a flow switch. Might explain why there is constant hot water demand, with the "field" pump off, there could be gravity circulation which will activate the flow switch in the boiler.

Never seen this setup before, usually the DHW side of the combi just serves, for example, a single hot tap and the stored hot water is used elsewhere.

Click to expand...

Must admit I am not entirely sure what is happening as the OP is light on exact details. It would be fine if the DHW tank primary was fed from the heating circuit but maybe it isn't?

Lurch said:

Must admit I am not entirely sure what is happening as the OP is light on exact details. It would be fine if the DHW tank primary was fed from the heating circuit but maybe it isn't?

Click to expand...

Hi thanks everyone for the input so far.

I don't have a PC and the images I took are too big to download to this topic.

I'm also not on the job at the moment so not sure on water temperature out of the boiler.

The plumber went yesterday to check it out and I haven't heard anything since so maybe it's sorted.

The hot water set up is programmer on therefore cylinder stat on - until water reaches temperature the 2 port valve operates pushing water through to the cylinder until the water temperature reaches the temp on the stat..

The pump is on the pipework and has a switched live from a seperate programmer so no direct to connection to the boiler..the boiler has its own pump in too 

Just an update 

The plumber drafted in his own electrician and after x amount of calls to viesmann it's  finally sorted. 

I'm not sure how I'm waiting for an update if not I'll drive through and look myself but apparently it's do with a link in the thermostat..

I can only presume this would be the cylinder stat..

the cylinder stat is a Gledhill dual aqua stat and the link to the stat and the data sheet is http://www.jouleuk.co.uk/product/dual-cylinder-thermostat/

I connected my permanent live to Common and switch live to terminal 2 

The question I have is why on some stats do the diagrams show another connection on the cylinder stat going from terminal 1 back to the programmer HW off terminal ? 

Ive noticed Y plans show a return cable to the HW off on the programmer and the valve used in a y plan is a 3 port valve which doesn't have the brown cable to energise the motor..

The S plan does have the brown cable to energise the motor but doesn't show a return cable to the HW off terminal in the programmer...

So it seems the plumber has used a 2 port valve on a y plan system hence why I've not wired a 4 core to the cylinder stat 

You cannot use a 2 port valve on a Y plan, because then it isn't a Y plan. It is a physical impossibility.

There are various ways of using the stat, which actually has 2 thermostats in one housing. TBH if you are not really familiar with heating systems in general (which it doesn't sound like you are) then it is probably best to leave these types of things to those in the know.

Without seeing the entire system I couldn't really say what you did wrong exactly, so I will not try and guess how it should have been wired.