Central Heating and Hot Water Control problem

[WHPES]

I have the following scenario -

The customer has a newish oil boiler. Instead of s-plan or y-plan, the DHW and the CH are on independent circuits, each with its own pump. The only means of control currently is a timeclock. The boiler kicks in should either the DHW timeclock or CH timeclock ask for heat.

I want to improve the controls. Before anyone says "convert it to an S plan with a single pump", this would mean extensive modification to the room which the customer doesn't want.

Is there a suitable means to include a zone valve in each circuit to prevent water flowing past the pump when not wanted, plus a thermostat to control the boiler & pump for each circuit? My electrician says the only way is to convert to an S plan with single pump but I have seen other similar systems in the past to what I am referring to above, all of which work fine.

 

[Paul Barker]

Yes it is very simple Buy a single socket patress box a connecting strip 4 way and a zone valve for each circuit. Mount it beside the pump. Take three core out of pump place them in connectors 1 live 2 neutral 3 earth

Into 1 put the grey from the zone valve and also the brown from the zone valve. In two put the blue from the zone valve and take out the neutral for the pump from here. Take the earth from 3 to the zone valve and aslo to the pump. In four you place the orange from the zone valve and from here send the live to the pump.

So what happens is the clock calls for heat sends live down the original pumpo feed this energises the syncron motor which opens the valve on opening it throws a switch puting orange leed in touch with grey leed which is fed from the same original pump live so now the pump is energised.

Intercede between clock and zone valve with a stat for best practice.

Nothing else has changed you now have the same as before but zone valve which shut off leaching.

What you cannot do is feed the boiler from the zone valve in this configuration.

If you want to do that then this is how you do it.

Connect pump live to 1 aswell and connect boiler to orange. What happens now is the pump starts as the zone valve beginns to open but the boiler fires when it is fully open, and the zones operate the boiler independently.

 

[migoplumber]

or install a larger bore non return valve on top of the pump. ie if pipework is 22 fit a 28mm nrv with reducers, and so on.
i imagine you allready have a bypass on the header circuit if there is no call for heat on either zone, if not you will need to install one as the NRV's will stop auto convection as well, tripping the high heat stat.