BDR91 not activating unless boiler demand greater than 50%
Posted: Thu May 14, 2020 11:33 am
I've been having an issue with the heating in one room with a single radiator and HR92 radiator valve for some time and finally decided to spend some time trying to resolve the problem.
The symptoms for the room were that it would often heat up first thing in the morning, but then not get warm later in the day.
On doing some analysis I found that for that particular room, irrespective of the difference between the set point and actual temperature, the boiler relay would not turn on. The room only heated up when other devices (other rooms or the hot water) demanded heat, the other devices do trigger the boiler relay.
Looking at the 'System Summary' screen I can see that the maximum demand from this room never got more than 15%, even with a 20 degree difference between the set point and measured temperature. Other rooms show between 5 and 100% depending on the temperature difference.
Using one of the other rooms as a control, it would appear that the boiler relay will only turn on if the Boiler Control demand is about 50% or more (26% does not turn it on, 56% does).
I've tried a complete factory reset, including unbinding all devices and doing a reset of all the bound devices. I've tried swapping the HR92's between rooms, both while bound and clearing/re-binding them, and the result is the same. This particular room will not demand more than 15% and thus will never trigger the boiler relay.
I came to the conclusion that the only possible cause of the issue is related to the actual valve on the radiator and it's travel. So, I have set option 6 on the HR92 for this room to 1 from 0, the heat demand will now go to 100% so the room does heat up, however as the boiler will not fire until 50% demand, the radiator does not come on until the differential is more than 1 degree or so.
So, my question is, is it normal behaviour for the boiler to require 50% demand or more before the wireless relay is triggered?
The symptoms for the room were that it would often heat up first thing in the morning, but then not get warm later in the day.
On doing some analysis I found that for that particular room, irrespective of the difference between the set point and actual temperature, the boiler relay would not turn on. The room only heated up when other devices (other rooms or the hot water) demanded heat, the other devices do trigger the boiler relay.
Looking at the 'System Summary' screen I can see that the maximum demand from this room never got more than 15%, even with a 20 degree difference between the set point and measured temperature. Other rooms show between 5 and 100% depending on the temperature difference.
Using one of the other rooms as a control, it would appear that the boiler relay will only turn on if the Boiler Control demand is about 50% or more (26% does not turn it on, 56% does).
I've tried a complete factory reset, including unbinding all devices and doing a reset of all the bound devices. I've tried swapping the HR92's between rooms, both while bound and clearing/re-binding them, and the result is the same. This particular room will not demand more than 15% and thus will never trigger the boiler relay.
I came to the conclusion that the only possible cause of the issue is related to the actual valve on the radiator and it's travel. So, I have set option 6 on the HR92 for this room to 1 from 0, the heat demand will now go to 100% so the room does heat up, however as the boiler will not fire until 50% demand, the radiator does not come on until the differential is more than 1 degree or so.
So, my question is, is it normal behaviour for the boiler to require 50% demand or more before the wireless relay is triggered?