Central heating wiring

[yellowvanman]

I've got to wire up a central heating system:

Boiler has integral pump.

3 circuits:

Heating with own valve and pump

Towel rails with own valve and pump

Hot water with own valve.

Because the heating and towel rail have their own pump I have to somehow switch them on individually without turning the other pump on. I've done this before using contactors but is there something more elegant that can be used? As it stands I would need 2 contactors to 'seperate' the Towel rail and heating pump from each other.

 

[somersetsparks]

Could you not just connect them into the brown of each valve? so they come on as the valve opens?

EDIT- you would at least have to check whether your stats would take the load!

 

[electric will]

Why not use a s type wire the live output from programmer/stat into the valve and pump, so when it puts power in to move the valve it'll start the pump, then boiler when valve full open

 

[electric will]

Why do you need the other pumps isnt the one in the boiler big enough. Or why not just fit a bigger pump after the boiler but before the valves?

 

[yellowvanman]

CH heating is a long route and I'm only wiring up what the plumber has installed.

The wiring as I see it is not as easy as some of you have described or so I think.

The usual case of CH/TR and HW is that when the valve opens it closes the relay contacts (orange & grey) in the valve which is then used to call the boiler. But if I did that each time a call was made to the boiler all the pumps would start and in some cases the valve may not be open.

Eg. If CH was called want the CH valve to open, when it opens turn on the CH pump and start the boiler. So in effect the CH pump and Boiler would be connected together. If CH is now turned off and the Towel Rails were called, TR valve needs to open and then turn on the TR pump and start the boiler, so now the TR pump and boiler needs to be connected together but disconnected from the CH pump now.

Bit difficult to describe here but hopefully the example should explain my problem.

 

[electric will]

Connect the boiler the normall way with orange and greys in the valve switching it but the extra pumps wire these so when the valve gets power from stat/prog the pump also gets powered up.
Only small prob the pump will start a few secs before the valve fully opens but can't see it being a problem

 

[somersetsparks]

^^^ thats what I was trying to explain!^^^

 

[electric will]

^^^ thats what I was trying to explain!^^^

Its not the easiest thing to explain I can see the circuit in my mind but to put it into words is another matter. Stats should handle the extra load of another pump, the whole system should be on a 3 amp fuse anyway.

 

[yellowvanman]

^^^ thats what I was trying to explain!^^^

See that now!

I would have liked to have avoided starting the pump before the valve is fully open, not sure what 'damage' it could cause! Also what if the valve is stuck shut the pump won't like it! One of the pumps used supposably costs big money because its got some 'intelligence', needed for the very large CH loop.

 

[somersetsparks]

Probably go with the contactors then mate, better safe then sorry!

 

[electric will]

Plumber could fit a small bypass loop to each one? That smart pump may have a over run feature which would cause problems. Need to find out more about that

 

[electric will]

It wouldn't hurt the pump running for a few secs while the valve is opening, these pumps are only circulating pumps with a impeller. Not a positive placement pump