I've got the boiler relay bound, with a 19% demand from a HR92 the boiler relay is showing 100% demand, along with the Stored Hot water showing a 100% demand (Due to the 2 port valve set up in the settings).
I've got the boiler relay bound, with a 19% demand from a HR92 the boiler relay is showing 100% demand, along with the Stored Hot water showing a 100% demand (Due to the 2 port valve set up in the settings).
Isn't it a case where the radiator is hot but Evohome has shut the HR92 down?Quote:
Originally Posted by IM35461
The heating only comes on at 21:30 and both rooms were cold.Quote:
Originally Posted by mtmcgavock
20mins later, it now reads 100% for both bedrooms and the list does auto update but not sure how often.
EDIT: One bedroom has now gone down to 60% without having to touch the unit screen
Attachment 1157
Hmm... the demand values seem to be a little... vague.
Attachment 1158Attachment 1159Attachment 1160Attachment 1161
The first image is the actual current demand (broken down by individual radiator in multi-radiator zones). The other three are the demands reported in Evohome.
Something's amiss...
EDIT: I have no idea why these images are upside down, sorry!
If your stored hot water is in a reheat cycle (which I assume it must be if it is showing a 100% demand for the hot water relay) then you will indeed see 100% demand on the boiler relay as well. That's normal. In these conditions only the heating zone valve relay will TPI modulate until the stored hot water demand has been satisfied. Then the boiler relay demand should track the heating zone valve demand and TPI modulate together in time with each other.Quote:
Originally Posted by mtmcgavock
Easy way to tell how frequently the heat demand screen updates when left alone - make a major change to the set point of a zone by turning the dial on an HR92 from well below to well above the current temperature. This will send an updated heat demand a couple of seconds after the motor in the HR92 has finished turning.Quote:
Originally Posted by IM35461
I wasn’t really stating that anything was wrong with them figures.... but you’ve brought up a question. Surely the boiler relay will only ever show a 100% demand or 0% as the output is only a on or off. It can’t modulate in between. I haven’t used any external monitoring before so I’m unsure how this is shown in any other reporting.
From my observations I think the values update as soon as new data is received from an HR92 or other device. It isn’t on a timed update schedule.
If the display matches the radio data, it will show all interim values. The total load (say, 40%) is sent to the relay and it is responsible for turning itself on and off on a 40% duty cycle. The controller doesn't tell the relay to turn on and off each cycle.Quote:
Originally Posted by mtmcgavock
I'm assuming your first picture (very hard to read) is a report from Domoticz with an HGI80 or equivalent ?Quote:
Originally Posted by dty
If so your screenshots would tend to confirm the suspicion I posted about earlier - the percentage display on the controller is probably not the "raw" heat demand figure sent from the HR92, which as discussed earlier is simply the valve pin position travel in 0-100%. (a 0-200 integer in the protocol)
You'll notice that all of the zones which say 0% on the controller but above 0% on your Domoticz (?) dump are well below 30% as a raw figure. This means that although the valve pin on these is not fully pressed down, I'll almost guarantee none of those radiators are flowing any water, as most valves won't start flowing until an indicated 30-40% pin travel on the HR92.
So lets say an HR92 has its pin 25% up, at this point there is still no water flowing through the radiator, but it sends this raw 25% value to the controller. The controller is smart enough to know that 25% won't be enough for water to flow so this 25% does not contribute to actual heat demand sent to the boiler so is truncated to 0%.
So the percentage value shown in the controller for each zone is not the raw pin position sent by the HR92's, but rather the contribution from that zone towards sending an actual heat demand to the boiler, which won't happen until some threshold value from the HR92 is reached, probably around 40%. Make sense ?
If this is how it's working (and I'll know soon enough when I get home and start testing mine) then it's working as intended, and is giving an accurate depiction of how much each zone is contributing towards firing the boiler, which is what we want to know.
What remains to be seen is whether the same threshold is always used for all zones or whether it adapts the threshold to the characteristics of each radiator valve individually, and what the mapping between raw values and zone heat demand contribution to the boiler is. But that's fairly easy to work out with a bit of testing and logging.