Sorry for long delay, busy day. Here are the pics as requested.IMG_2094.jpgIMG_2095.jpg
Evohome cycle rate and other settings
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Originally posted by bruce_miranda View PostSo this means that if you have no Boiler relay or Zone Valves configured in the Evohome, you can't change the relay parameters. Your CH and DHW relays will be using the default TPI parameters that you cannot change. I new one for me.
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OK, but because you are using the micro switches of the CH and DHW valves, you have no parameters available to change that. The only way around that, is to add a 3rd BDR91 configured as a Boiler relay that then controls the boiler. Evohome will then expose the Relay parameters that you can then adjust. You will need to disconnect the micro switches from triggering the boiler.
P.S. I wonder what happens if you simply bind a Boiler relay but don't actually connect it to the boiler. Evohome will make the relay parameters visible which then when set (I think) affect all relays. That might be also worth trying. All you will need is a powered up BDR91.
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Originally posted by Fly100 View PostI have noticed a little short cycling. Approx 8 mins between boiler firings.
Does your "short cycling" match changes in the BDR91 states (i.e. green light on and off)? I suspect not but I am very happy to be put straight.
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Originally posted by bruce_miranda View PostTPI is built into the BDR91, you cannot get around it. The screens just allow you to vary the default TPI parameters.
I suspect that Fly100's configuration has no BDR91 that is set up to receive TPI instructions from his controller and so neither of his BDR91s will be performing TPI.Last edited by Edinburgh2000; 5 February 2021, 11:11 AM.
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The controller doesn't send anything other than Heat Demand to the BDR91. Its the BDR91 that then decides how to work based on that Heat Demand instruction. It either uses its default TPI parameters or the overridden ones.
The BDR91 can bind itself to the controller using several internal modes. Only the DHW mode performs no TPI. All the others perform TPI. The newest BDR91T can also be bound as a Heat Pump control and even that needs to switch of, by default, once per hour.
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