Converting Evohome Y plan system to OpenTherm with Intergas

[bilbomacuser]

I'm planning to replace our old Baxi Solo 2 50PF boiler (evohome with Y plan, vented hot water cylinder, BDR91's for heat and hot water, wireless cylinder thermostat, pump in airing cupboard, HR92's on radiators) with an Intergas Eco RF and replacing the cylinder with a vented fast recovery cylinder of similar size to the old one:

https://theintergasshop.co.uk/high-gain ... x-450.html

I'm hoping to use an installer that is Intergas approved installer, and buys stock from the Intergas Shop. However, they're not familiar with evohome, so I just want to check that I understand what's required:

BDR91s no longer needed
Pump no longer needed, built into the Eco RF
Hot water ports not used on boiler as 'heat only' function (so the eco RF can function as an open vented heat only boiler - benefit over the HRE OV being the longer warranty and built in pump)
Evohome wireless cylinder thermostat transferred to new cylinder, paired with evohome for stored hot water
OpenTherm Bridge required to connect to Intergas eco RF (I have read that the built in eco RF receiver cannot be used with evohome) - connects to terminals 11 and 12 of the X4 terminals on boiler
Honeywell Three port valve V4073A reversed 180 degrees - so when powered off diverts only to heating, when powered on by white wire diverts to hot water only;
White wire of V4073 connects to connector 5 of the X2 terminals on the boiler (to call for hot water - gives priority hot water). Orange and grey wires isolated (not needed).

Could anyone confirm that the above deductions are correct, and is there anything else I should be aware of?


Addendum:

Thinking about it - to replicate the functionality of the X plan wiring diagram, presumably it needs a BDR91 connected to terminals 9 and 10 of the X4 terminals for the evohome to signal demand for hot water (assuming that this isn't done via OpenTherm) - with separate mains voltage L and N to power the BD91.

[Richard]

Just to follow this post up (sorry for delay).

If you are doing PDHW with an Intergas boiler and you have an evohome system on a Y Plan, you would need the following items.

evohome (evotouch Controller)
BDR91 and CS92A
R8810A OpenTherm Bridge
Intergas Boiler (I prefer Intergas Xclusive as it has a better modulation ratio)
Intergas Cylinder NTC Sensor (you need the ELV high limit stat if you use a Joule Unvented High Gain Cylinder too)
X Plan Upgrade with NO and NC zone valves (we don't recommend rotating a Y Plan valve or using a 3 port diverter anymore, as they have a tendency to slam shut when the boiler goes for DHW demand)

But as you said, pump is in boiler and cold and hot pipes are not used (just left open ended).

There are a load of parameter changes to do to optimise the boiler too, but if your installer buys all the equipment from The INTERGAS Shop, they can provide diagrams and can give paid support if needed.

[bilbomacuser]

Thanks for the reply - unfortunately I didn’t see it before we went ahead with the installation.

What we have is the Xclusive 24, mcdonald vented ultra recovery cylinder, hot water kit with the sensor in the pocket and the bdr91 controlling a diverter valve (goes to heating when powered off and hot water only when powered on) and the boiler controlled by the Opentherm bridge.

The boiler etc were supplied by the Intergas shop, and the installer was recommended by the heating hub.

Everything seems to be working well - the only issue I had was the bdr91 not consistently turning on (I tried everything I could think of for troubleshooting including swapping out the bdr91 for a spare) but in the end it was resolved when I called Resideo and they pushed the 19.33 firmware (I think had been on 17.00).

I have no idea how the boiler was set up other than it sets the boiler to 75 degrees when heating the cylinder, and the heating temperature varies between 30 degrees and 75 degrees depending on the requirements. It says on the warranty info that the boiler was limited to 11 kW (based on the calculated maximum requirement of the house), and when I queried it was told this only applied to heating not hot water.

One question I have is - does this configuration allow evohome to tell the boiler via opentherm whether it’s heating the cylinder or the radiators (and therefore be set to a higher output when heating the cylinder) or can it only vary the output temperature as a proportion of the maximum? Is this the most efficient setup?

Thanks.

PS. Just re-read your message about not recommending the 3 port diverter. Presumably they achieve the same function (if working correctly)? What should I look out for as a symptom of the divertor valve slamming shut? If this happened, presumably the divertor valve could be replaced with the x plan valves - or is the wiring set up to tell the boiler to go into hot water mode too? - ie does this answer my question above, that opentherm does not tell the boiler whether it’s heating the cylinder or the radiators?)

[Richard]

Thanks for the reply - unfortunately I didn’t see it before we went ahead with the installation.

What we have is the Xclusive 24, mcdonald vented ultra recovery cylinder, hot water kit with the sensor in the pocket and the bdr91 controlling a diverter valve (goes to heating when powered off and hot water only when powered on) and the boiler controlled by the Opentherm bridge.

The boiler etc were supplied by the Intergas shop, and the installer was recommended by the heating hub.

Everything seems to be working well - the only issue I had was the bdr91 not consistently turning on (I tried everything I could think of for troubleshooting including swapping out the bdr91 for a spare) but in the end it was resolved when I called Resideo and they pushed the 19.33 firmware (I think had been on 17.00).

I have no idea how the boiler was set up other than it sets the boiler to 75 degrees when heating the cylinder, and the heating temperature varies between 30 degrees and 75 degrees depending on the requirements. It says on the warranty info that the boiler was limited to 11 kW (based on the calculated maximum requirement of the house), and when I queried it was told this only applied to heating not hot water.

One question I have is - does this configuration allow evohome to tell the boiler via opentherm whether it’s heating the cylinder or the radiators (and therefore be set to a higher output when heating the cylinder) or can it only vary the output temperature as a proportion of the maximum? Is this the most efficient setup?

Thanks.

PS. Just re-read your message about not recommending the 3 port diverter. Presumably they achieve the same function (if working correctly)? What should I look out for as a symptom of the divertor valve slamming shut? If this happened, presumably the divertor valve could be replaced with the x plan valves - or is the wiring set up to tell the boiler to go into hot water mode too? - ie does this answer my question above, that opentherm does not tell the boiler whether it’s heating the cylinder or the radiators?)

Did you get this resolved John? I know Pete Toth has been aiding you with your installation.