S Plan

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Hi, can any one help me with the wiring for an S Plan?

I have two pumps, two channel timer, room stat, tank stat, and two motorised valves, all fitted. the stats are currently controling the pumps via the timer. however the boiler (glow worm space saver 60) only has a single mains input for control.

Cheers,

Stu.
 
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I am not a plumber or heating engineer, how many do you think it should have then? surely the boiler heats the water for both and that is why it only has one "input" what you do with the water when it comes out hot is that not why it has 2 pumps? one for heating one for hot water?

Just found this

it only has one "boiler input" is this what you wanted?
 
the property i used to live in had two pumps it was also an s-plan. The property was a bungalow, with the hot water cylinder in the loft. I think the second pump was used to get the hw up to the cylinder.
 
Hi breezer,

thanks for your reply, i have a copy of that plan already. Sadly it shows something called an "auto switch" on the boiler controlling one pump. I don't have an auto switch, and i have two pumps, one for CH and the other for DHW.

I have followed that diagram, but what happens is that when the boiler comes on you need the pump for the calling circuit to come on, and you end up with both pumps on. I think i will have to add a relay, because i cant see another way of isolating the pumps. If you get my drift. The boiler is effectively isolated via the switches in the valves.

Cheers,

Stu.

BTW when i say the boiler has one input, i mean if you supply mains to it, it will come on until you remove the mains (regulated via its own stat). there is only one connection for the mains, and no other way of contolling it. its on or off.
 
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I haven't studied the wiring diagram but one way to go would be to:

use the appropriate thermostat to open the appropriate valve & pump , and connect the two valve auxilliary switches to turn the boiler on. That gives you the isolation you need so one pump doesn't turn the other on.
It means the pump will be working to a closed valve while it opens, which I don't think would be a problem, and also begs the question of a bypass as required by building regs etc. As far as I can see you need two bypasses, one after each pump. ? ?


In fact, the Pump-Plan as sold bu grundfos doesn't have any valves - the pump is turned on by the stat. Must be a relay in that kit somewhere?
 
oilman,

maybe, it does suffer from ketteling.

Chris,

i'll draw it out and double check. The reason i want valves is that, at present (valve in open position, not controlled) the flow via convection is enough to heat up stairs rads and supply DHW (albeit slowly).

Stuart.
 

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