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Connecting Evohome to Worcester RI for modulation

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diselsamm

Good afternoon
I am expecting delivery of the Evohome ATP926G3001 package this week.
Is it possible and how exactly can I connect the the Evohome system to a Worcester Ri boiler to convert it to modulization? Is Greenstar Ri Open therm compatible?

My understanding is I need to connect a Worcester Bosch EasyControl Adapter or similar bridge to the EMS on the boiler and to the BDR91T. Is that possible? I am also not 100% sure I can use a Worcester Bosch EasyControl Adapter for a Bosch RI boiler, what else could I use?
Thank you
 
diselsamm said:
Hi, I am not sure I understand this. The Ri has an EMS plug and is able to modulate.
Click to expand...

But not usable for control / not sense compatible

As you have a cylinder that needs to be kept at 65c

So if you wc / opentherm it regulates the flow temp this is no good for the cylinder
 
My understanding is that most systems with a hot water cylinder already have it configured as a separate heating zone controlled by a motorized valve (e.g., a 2-port or 3-port valve). The boiler provides full power for the hot water cylinder when it's called for, bypassing modulation.

  • With OpenTherm:
    • OpenTherm primarily affects space heating and modulates the boiler’s output to match the heat demand.
    • When the cylinder demands heat, the boiler typically switches to full output (non-modulated mode) to heat the cylinder efficiently.
Evohome also has dedicated hot water kit (e.g., ATF500DHW), (I do not have this kit and currently have a wired HW wired thermostat), which includes a wireless cylinder thermostat and relay for the hot water zone.
  • Evohome ensures the boiler is fired at the correct time to heat the cylinder.
  • The Evohome Controller communicates with the OpenTherm Bridge to signal a higher output for hot water demands while continuing to modulate space heating when the cylinder is satisfied.
Is this not correct?
 
diselsamm said:
This Dutch product should work (Nefit OpenTherm EMS converter | Plugwise - https://www.plugwise.com/product/nefit-opentherm-ems-converter/?lang=en) with the Ri as long as the Ri using EMS version 1. Do you happen to know what EMS version is used in the Ri? However I have not thought about the effect of modulation on the HW cylinder side.
Click to expand...

I don’t believe the ems port is usable it’s there but not fully built in

Also how does it know when the hot water is being heated it doesn’t, it’s a dumb (in wiring sense) all it’s looking for is 240v on the heat terminal

Also that bridge is for the Worcester compacts eg system boilers or combis

You will require a new boiler if you want to go opentherm eg Viessmann’s 4 pipe system or ideal vouge 2 switch live terminals
 

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