Two port valve wiring

micosoft

Have what I believe is an S Plan Heating System - GFCH.

Had the boiler replaced recently (Pump had failed) and installing a Nest Thermostat and notice that both two port valves (Myson Power Extra) only have two wires attached - live and neutral, but have no Grey or Orange wires. No earth either.

From everything I have read it seems the Grey and Orange or essential to tell the boiler pump when to stop.

Is this acceptable practice? Given every S Plan installation diagram I've seen has five wire connection to the two way valves? Potentially without the "off" instruction is this why the previous pump failed?

Am going to call plumber who replaced boiler but wanted to have some idea. One other item - during the boiler replacement a pump with a temp readout on it in was put beside the water tank.

I'm drawing the diagram but wondering if anyone had thoughts on the above - seems unusual at the least!

John.G

Don't know how the Nest is configured but the normal S system has a permanent live to the grey wire and when the valve opens the end switch connects the grey to the orange to give 230V which either goes independently to the boiler and pump or just to the boiler which then gives a signal as required to the pump (including overrun if installed). Whatever method is used, the pump should run continuously once any zone valve is opened and only stop when all zone vales are closed.

corkgsxr

It seen lots where all the other wires were just cut back.

Id bet ya if you look back the cable yours are too

K.Flyer

micosoft wrote: »

Have what I believe is an S Plan Heating System - GFCH.

Had the boiler replaced recently (Pump had failed) and installing a Nest Thermostat and notice that both two port valves (Myson Power Extra) only have two wires attached - live and neutral, but have no Grey or Orange wires. No earth either.

From everything I have read it seems the Grey and Orange or essential to tell the boiler pump when to stop.

Is this acceptable practice? Given every S Plan installation diagram I've seen has five wire connection to the two way valves? Potentially without the "off" instruction is this why the previous pump failed?

Am going to call plumber who replaced boiler but wanted to have some idea. One other item - during the boiler replacement a pump with a temp readout on it in was put beside the water tank.

I'm drawing the diagram but wondering if anyone had thoughts on the above - seems unusual at the least!

Yes, grey and orange should be utilised to control the boiler subject to the status of the the timer and the thermostat(s).
But.. in a lot of apartments and some house I come across this is quite often overlooked and the valves are solely relied upon to open and close, via the thermostats, when the time clock is activated and that's it.
In some apartments around Dublin 18 they have been installed where there is actually zero connection between the zone valves and the boiler or the time clock!
In your case, do you know if they were previously connected.
Btw, what is the make and model of your gas boiler?

John.G

Don't know if this is helpful or not.

micosoft

Thanks all for replies.

So I have the Nest wired in and it works. The Nest heat connect is wired up correctly and is able to control both heat and hot water. Issues I had were poor connections so after tightening stuff up and replacing a jump lead all is good.

I guess to be specific my concern is those two pumps. K.Flyer is correct - the grey and orange wires have been cut back. They were never connected. It's an apartment and a Celtic Tiger special...

I guess my concern is my understanding is those wires are required to tell the boiler to shut off when the valves close. Especially as one (water tank) is thermostatically controlled. My concern is the boiler will keep pumping against closed two way ports. Every S Plan I've seen has these wires in the schematic.

Boiler is a new Bosch Greenstar.

I'm going to chat with the plumber who replaced the boiler to check in. Perhaps the newer boilers figure out (pressure rise?) and automatically cut out. But I got 12 years out of old boiler and the pump failed in it so hope to get more years on new one...

K.Flyer

The trouble with some apartments, especially if not wired correctly in the first place, is trying to get wiring through voids to get your boiler / timer / stats and zone valves all connected to each other.
You are right to be concerned with the valves closing with the boiler still on. A solution would be to have an automatic bypass valve installed as far from the boiler as possible (hot press?). At least then when both valves close the boiler pump still has a circuit to run on for a while.

micosoft

micosoft wrote: »

Thanks all for replies.

So I have the Nest wired in and it works. The Nest heat connect is wired up correctly and is able to control both heat and hot water. Issues I had were poor connections so after tightening stuff up and replacing a jump lead all is good.

I guess to be specific my concern is those two pumps. K.Flyer is correct - the grey and orange wires have been cut back. They were never connected. It's an apartment and a Celtic Tiger special...

I guess my concern is my understanding is those wires are required to tell the boiler to shut off when the valves close. Especially as one (water tank) is thermostatically controlled. My concern is the boiler will keep pumping against closed two way ports. Every S Plan I've seen has these wires in the schematic.

Boiler is a new Bosch Greenstar.



I'm going to chat with the plumber who replaced the boiler to check in. Perhaps the newer boilers figure out (pressure rise?) and automatically cut out. But I got 12 years out of old boiler and the pump failed in it so hope to get more years on new one...

No.

You need to replace the valves there are get arounds but replacing the valve(heads) is the right answer. As K.flyer mentioned you need a a auto bypass but it should be fitted as a given even if you replace the valves.