Valliant Combi as S plan?

[andycollenette]

I need to wire a Valliant combi as S plan so that the combi can work with a solar system. Currently terminals 3 and 4 on the boiler just go to the clock and room stat. In the new arrangement I want the boiler to turn on if either the HW or CH calls for heat. All the components I am using are Honeywell. Please keep it simple since this is my second wiring job having completed Part P.

From what I have read on other posts it is as simple as taking orange from both zone valves back to the boiler terminal 4. Will this work or is there something else I need to do over and above the normal Honeywell S Plan wiring diagram?

 

[Guest123]

Hi.

As it's a combi, the HW is on demand i.e as soon as soon as you open a HW tap the boiler will fire. The only external controls are for the CH and you can use whatever you want to fire the boiler i.e roomstat, timeclock, valve etc.

 

[gaffer]

What do you mean by two zone valves,because as Lenny says the HW is supplied on demand.Maybe you could give us a bit more info on what youve got.Solar systems are notoriosly difficult to integrate with existing combi boilers as some manufacturers dont allow for this add on.

 

[andycollenette]

I have taken the combi HW side to a single tap to keep the boiler warranty. I am using the heating side as a system boiler - one valve for heating and the other for HW to a cylinder. On the boiler I have 5 terminals E, N, L, 3,4,5. I need to know where to connect these on the standard Honeywell S plan so that the boiler fires when there is a call for heat of HW (or both).

This is what I am planning to do but want to check with someone who is more experienced:

Boiler Honeywell wiring centre
E > Terminal 3
N > Terminal 2
L > Terminal 1 (perm live)
3 > Terminal 1 (perm live)
4 > Terminal 10 (switched live connected to both of the 2 port valve orange wires)
5 > No connection

Remove link in the boiler between terminal 3 and 4.

Does this make sense or will I fry something?

 

[Tester Steve]

Take a look at Lennys post here.

Steve.

 

[andycollenette]

Thanks for the reference.

I wired it up today as per my previous post together with the standard Honeywell S plan wiring diagram and it worked first time.

It was really easy to put a combi boiler with solar panels - there appears to be a common misconception that solar systems don't work with combi boilers, but its not difficult at all and works just like any other system boiler.

 

[gaffer]

Well done mate ,when I first posted didnt realise you were splitting the heat output into two zones thats why I said its hard to add solar.I assume you were using a secondary coil in a cylinder for your solar input.Sometimes its hard to explain to customers with an existing combi that they cant just buy a solar panel and expect it to work. Anyway pull up those green socks and save the planet!

 

[andycollenette]

You are spot on - using a twin coil unvented cylinder - one for solar and the other for the HW.

There is another way to install solar with a combi and that is to use a valve that sends the HW direct to the taps if it is above 42 degrees. if it is less than 42 it mixes it down to 24 degrees so that it can be fed into the combi boiler. Better feeding the boiler 24 degrees rather than 6 degrees (in winter) water. Needs no wiring so is much easier, but less efficient.