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I am using the OpenGW with two Remeha Central Heaters in using an open-collector/pressure-vessel setup; which unifies those two Central Heaters as well as a woodburner. A bit of software and OpenGW helps schedule the optimum modulation/balances the two heaters as to keep each or either near the HR optimum; and scales them down when the woodburning stove comes on.

However it would be very nice if there was some way of directly controlling the pump on the Remeha Central Heaters - separate from the burner. Or even just knowing when it is on and off. As that would let us optimise the circulation pumping.

Is there any OpenTherm message for this ? To directly control (just) the pump in the Remeha Central heater; or a trick to fool it ?

And can one somehow reliably infer that it is pumping from some other signal ? E.g. that it is in Central Heating mode combined with something else ?

Suggestions and ideas much appreciated !

Dw.

From what I read is that OpenTherm ID3 has a flag to set pump control. It will depend on your boiler whether that particular flag is supported. How the control then is actually done is another matter, can't find anything on that.

grtz,

marcelr

ID3 won't do you any good. The thermostat reads that from the boiler. So you can't use it to set pump control, only to obtain the boiler's specification of how it should be controlled.

The CH enable bit in ID0 gives you some control over the pump on some boilers, including the Remeha Avanta. When the bit is on, the pump will run. However, when you switch the bit off, the pump doesn't necessarily stop immediately. The boiler may decide to keep it running for while. There is no indication via an opentherm message to determine when the pump is really off.

Ah good. As I was getting nowhere with ID3.

So fair to assume a CH=1 (without any CS; or an CS which is already at CS=10) will switch on the pump of the Remeha; and a CH=0 will switch it off; potentially some time later; as per the boilers preferences ?

Correct ?

Thanks,

Dw

If I remember correctly, the CH command only has effect in combination with the CS command. So yes, set CS=10 and then manipulate the pump with the CH command.

Yes - this works - and for the remea the Heating flag indicates pump running.

Dw