Clarification of CH wiring (no diagrams!)

[littlespark]

Story is i got called to finish off the heating on a new build as the electrician doing the work was too busy to get back in time.

There were some cables run, and some equipment fitted, and ive done the rest. There is no diagrams.. ive had to google what I can.

Its an S plan system, 2 motorised valves, 2 channel programmer and the tank stat and room stat. The boiler is a Worcester Greenstar 18i System boiler

Permanent supply to boiler, in turn feeding the programmer and both valves.
Switched feeds from the programmer back to the joint box, connected to the tank stat and room stat. These in turn operate the valves, when fully open send another feed to the boiler to tell it to fire up.

Part of the confusion was that the heating engineer had installed a pump on the pipework, where the boiler has an integral pump... so that had to come out.

Everything works as it should up to where the valves tell the boiler to come on. The switch wires from the valves are connected in the boiler to LR with a radiator icon, and LR with a tap icon.
What I think, reading through the 18i installation manual is the 2 valve switch wires are joined together and both connected to LR with radiator... LR with tap has nothing connected to it.

Does that sound familiar to anyone?

(The two LR connections were already connected in the boiler by the previous electrician)

 

[Leesparkykent]

The other pump doesn't have to come out and can be connected to the oranges of the valves. There should be a link between L and LR tap. And connect oranges of the valves to LR radiator.

 

[davesparks]

Use LR heating (radiator symbol) to fire the boiler.
Don't connect anything to LR hot water (tap symbol) this is only used when an integral diverter valve is used and doesn't do anything when this is not fitted.

 

[davesparks]

The other pump doesn't have to come out and can be connected to the oranges of the valves. There should be a link between L and LR tap. And connect oranges of the valves to LR radiator.

No need to link LR tap to anything, it has no function unless an integral diverter valve is fitted.

 

[Leesparkykent]

No need to link LR tap to anything, it has no function unless an integral diverter valve is fitted.

Cool I wasn't 100% sure.. I normally just leave the link in as it's already in place from new.

 

[littlespark]

The other pump doesn't have to come out and can be connected to the oranges of the valves. There should be a link between L and LR tap. And connect oranges of the valves to LR radiator.

But if theres two pumps, coming on at different times (one from the valve, one from the boilers electronics) the water wont flow against a stopped pump? I don't know, but surely it's not needed.

 

[Wilko]

Check the boiler, as it may have external pump connections and that will make sure it runs at the right time.

 

[davesparks]

But if theres two pumps, coming on at different times (one from the valve, one from the boilers electronics) the water wont flow against a stopped pump? I don't know, but surely it's not needed.

You're right ugh the it's not needed, but if it's there then it can be connected to the S/l to the boiler.
The second pump will always run when the valves are open that way, and when the valves are closed then the stopped pump won't make any difference as the water won't be able to flow through the valves anyway. At this point the boiler pump will be pumping through the bypass fitted to the pipework.

 

[davesparks]

Check the boiler, as it may have external pump connections and that will make sure it runs at the right time.

Worcester system boilers don't usually have the pump connections