Compatible with On/Off boiler control?

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Compatible with On/Off boiler control?

Postby MaikelK » Thu Jan 17, 2019 8:51 pm

Hi all,

Tried searching for it but couldnt find it.
Im controlling my boiler with a Evohome V2 with a BDR91 on/off relay.
This because of the floorheating it would be better roc ontrol this with on/off and not modulate the water temperature!

I got a Remeha Calenta Ace 28C and i want to know if it is possible to use the OTGW as read-only unit to monitor the boiler.

If this is possible or anyone knows what needs to be done let me know!
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Re: Compatible with On/Off boiler control?

Postby hvxl » Sun Jan 20, 2019 11:10 am

No. The boiler is either controlled via on/off or Opentherm. If you have reasons to use on/off, you normally can't use Opentherm as well. For one thing, most boilers use the same connector for both types of thermostats. This is also the case with the Remeha Calenta. When the on/off thermostat is "on", it will short the wires, making all other communication impossible.

I don't know why you believe it's better not to use Opentherm for floor heating. I don't think that's true. But if you insist on using on/off control, I think your best bet to get data from the boiler is to use its serial interface.
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Re: Compatible with On/Off boiler control?

Postby MaikelK » Fri Feb 01, 2019 8:36 pm

I’ve been told that on/off control would provide better and more stable heat to the floorheating.

Im using Evohome and the floorheating zone is also control via a on/off relay and that would also be a much better combination then Opentherm and a on/off valve for the floorheating
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Re: Compatible with On/Off boiler control?

Postby hvxl » Sun Feb 03, 2019 10:32 am

Wikipedia tends to flag such statements with citation needed. You are just making unfounded claims. Why would on/off control of the heater be a much better combination with a floor heating valve than Opentherm? The control methods of the two have no relation to each other.

And someone told you that on/off control would provide better and more stable heat to the floor heating. That doesn't mean it's true. People say lots of nonsense. Unless they can explain why it would be better, I am not convinced. The only two possible states of on/off heating can be replicated via Opentherm by setting the appropriate parameters. So I don't see how on/off control would be better, let alone much better.
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Re: Compatible with On/Off boiler control?

Postby MaikelK » Sun Feb 03, 2019 10:54 am

You can look it up on internet with zone control(in this case on/off relay on floorheating) on/off boiler control is better. If the zone reaches temp the valve Will close. It’s possible the heater stays running.

But you can also explain in your Words why om/off isnt better then opemtherm(i mean modulating thermostaat etc) control
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Re: Compatible with On/Off boiler control?

Postby hvxl » Sun Feb 03, 2019 12:56 pm

MaikelK wrote:You can look it up on internet with zone control(in this case on/off relay on floorheating) on/off boiler control is better. If the zone reaches temp the valve Will close. It’s possible the heater stays running.

That'll be the same for an on/off heater, if not coordinated properly. But what you're actually saying is that it may be easier to coordinate this with an on/off boiler. That may be true. But the original claim was that it's better, not that it's simpler.

MaikelK wrote:But you can also explain in your Words why om/off isnt better then opemtherm(i mean modulating thermostaat etc) control

I already did.
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Re: Compatible with On/Off boiler control?

Postby mwtheplumber » Wed Feb 13, 2019 8:14 am

How many zones of UFH do you have? If a single zone, use the Honeywell HM80 , if multiple zones use HCC80. The Evohome works perfectly well with these and the Opentherm gateway.
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