The Efficient Home Forum

Hello all,

So I just got the new HCC100 underfloor zone controller, with a Saunier Duval (Glow-Worm for those in the UK) boiler. Since I live in a country where Vaillant can get away with only offering eBus, I had to install the V33 ebus-OpenTherm card into the boiler, so the boiler can speak OT and not just eBus. This of course is not an ideal solution, but the only one I have.

However, I found the following:

If the HCC100 is set as the Appliance Controller, it operates the boiler beautifully, and everything is fine. The boiler fires up, zone valves open, the max. flow temperature is respected, etc.

However, I have radiator valves as well, so I need to use Evohome and R88 as the Appliance Controller, and the HCC100's requests would go through that. T

Unfortunately, the moment I wire the R88 onto my boiler and set it as Appliance Controller, the system is unable to fire the boiler if the heat is requested by the radiator valve zone. It starts the pump, but it never fires the burner. And if the heat is requested by the zones wired to the HCC100, the boiler fires up and there is no maximum temperature, ready to melt my underfloor piping.

My question is: is there any way to use the HCC100 as the Appliance Controller, and therefore the OpenTherm Gateway, so Evohome zones would also request heat through it?For now, I find that when setting up appliance control in Evohome controller, it wants to bind with an OpenTherm Gateway, which the HCC100 is seemingly unable to do.

My sincere thanks if you read and if you have any ideas to share.

A follow up on this, in case it helps someone else in the future:

A controller reset on the boiler helped, it now respects the maximum flow temperature setting set on the boiler (d.71) even with the R88 connected. The flow temperature requested by Evohome is still the maximum temperature supported by the boiler (90 celsius). The boiler is a Saunier Duval Thelia Condens 25 combi (Y plan). There are some identical boilers to this branded Glow-Worm, Awb, and other Vaillant brands.

I also found that the HCC100 cannot be used as an OT gateway, but fortunately it is no longer needed in my case. I am no expert but I think Honeywell could add this feature to the HCC100, so the R88 would not be needed. Their customer support is not aware that this feature is considered for future implementation, which is a pity. It would reduce the complexity of the system somewhat.

AFAIK, the VR33 won't allow max set point to be overridden by the boiler attached to the R8810A. You need an OpenTherm boiler that can set max flow temp to do this (Intergas for instance).

The HCC100 cannot be the master in an evohome system, but if used standalone on an UFH only system, then it can act as the master (but I have not fully explored the functionality of this yet).