Old thermo siphon C plan how was it done?

[ericmark]

New C plan the motorised valve acts as a relay so one can switch the domestic hot water off, and the micro switch in the valve allows the boiler to fire up without the pump running. Even without a motorised valve the N/O contacts on the tank thermostat could be used.

However I know my dad did not have a tank thermostat, and programmer only had 10 options rather than normal 16 he could not have central heating without hot water, but he could have hot water without central heating, he had it set for just 1/2 hour morning and evening as the boiler would cycle on/off all day other wise, in the end I fitted motorised valve then 6 months latter he had whole new system fitted, I remember being a bit peeved after spending so long fitting the valve.

But how was the original system with no motorised valve or tank thermostat wired?

 

[Hot&Cold]

Fig 1

1=hw on
4=ch on

 

[ericmark]

Oh so simple did not think about it, basic idea hot water must be on when central heating running so central heating thermostat only powers the pump. Thanks.

 

[Hot&Cold]

basic idea

Its about as basic as you can get still many in use.