The Efficient Home Forum

Hi, is it possible to adjust the thermostat setting on individual HR92 TRVs? Some of our TRVs are located behind curtains so it would be good to adjust this setting within the TRV rather than set it to look for, say, 29 degrees when we really want 21 degrees. I know it's just a number but it would be good if we have this adjustment capability. Thanks.

Ha, I've just found the HR92 manual that gives me all the advanced settings so I'll try doing this through parameter 8. It's also great that we can disable the 'open window' function. Here's hoping!

Adjusting the thermostats offset will have no effect.

If HR92's are behind curtains, you need to have a separate thermostat within the room as they will not operate correctly. Anything that 'hinders' the convection current around the radiator will cause issues with accurate temperature control.

Okay, thanks.

Well, apart from whatever that says above in Russian, the recalibration does in fact help - as could be expected, otherwise why calibrate anything? Calibration adjustment to the maximum allowable 3 degrees brings the heads considerably closer to actual room temperature. Before calibration the heads were reading approx 28 degrees when the room was 21 degrees and this is now approx 24 degree reading for a room temperature of 21 degrees. It's a very useful function and much easier than adding an extra element into the system.

I was told first hand by the guys at Honeywell who invented the HR92's that this is a visual offset. You can show this by adjusting this to different offset settings and then putting them all on the table together. They are just showing the offset temp visually.

More likely the system has settled down (rapid learning phase finished) which means they are now more accurate in their control.

The EVOHOME Shop wrote:I was told first hand by the guys at Honeywell who invented the HR92's that this is a visual offset. You can show this by adjusting this to different offset settings and then putting them all on the table together. They are just showing the offset temp visually.

More likely the system has settled down (rapid learning phase finished) which means they are now more accurate in their control.

It's not just visual, otherwise what would be the point. It applies an offset to the temperature that is measured before it is sent to the controller and before it is used to make adjustments to the radiator valve. It only has an effect if that HR92 is the sensor, otherwise its ignored.

So if you set it to -1 it will think the room is 1 degree colder than previously and therefore will heat the room up 1 degree hotter for the "same" set point than before. I need -1 on most of my rooms and it most definitely does affect the temperature that the room settles at.

I agree completely about the curtains though - it doesn't matter what you set the calibrate to in that situation, you'll never get an accurate reading. A wall thermostat is definitely called for there if you care about the room being an accurate, comfortable temperature.

Hate to disagree but this is not what I was told by the Honeywell team when I was part of the installer trials before evohome was launched. The sensor will read the same information back to the evohome Controller irrespective of the offset on the HR92. It may well have done something when it was a HR90 but in my experience it does nothing except change the display temp. I have never had to adjust it and normally people that do, do so because of HR92 installation or positioning issues.

The EVOHOME Shop wrote:Hate to disagree but this is not what I was told by the Honeywell team when I was part of the installer trials before evohome was launched. The sensor will read the same information back to the evohome Controller irrespective of the offset on the HR92. It may well have done something when it was a HR90 but in my experience it does nothing except change the display temp. I have never had to adjust it and normally people that do, do so because of HR92 installation or positioning issues.

Hi Richard,

I would suggest that Honeywell are "in error" here. It might be their product, but it doesn't mean they never make mistakes. Don't take my word for it - test it for yourself.

Start with calibrate set to 0, set the zone to a temperature a couple of degrees above ambient so some heating is required to reach the target, close the room and let the room stabilise for an hour at the set point. Measure the room temperature with a separate free standing thermometer and take note of it.

Now adjust the calibrate to -3 on the HR92 and wait. After a while (5-30 minutes, whenever it next sends a temperature measurement) the temperature reading on the controller will suddenly drop by 3 degrees and the room will begin heating again. Wait for it to stabilise at the set point again and compare your free standing thermometer - it should now read nearly 3 degrees hotter than before for the same temperature indicated on the Evohome. A negative calibration adjustment most definitely results in a warmer room for the same indicated temperature.

I've tried this test before in multiple zones so I know for sure calibrate works this way on an HR92. (I've never used an HR80 so no idea there) Of course the calibrate setting only has an effect if the HR92 in question is the sensor for the zone, if it isn't, adjusting it does nothing at all, and doesn't even affect the reading displayed on the HR92.

One other thing to watch out for during this test is that adjusting the calibrate setting towards a negative number will sometimes trip the window detection mode! This is because it thinks there was a sudden drop in measured temperature, when really it is just calibrate that has applied a sudden offset to the measurement. Kind of an amusing bug really...

I agree that if the HR92's are poorly situated no amount of calibration will help - but not because calibration doesn't do anything, just because its an impossible to calibrate situation. (Too much localised heating from the radiator) I find I need a calibrate of -1 on even my "best" rooms to match an external thermometer, however in rooms that would seem to require more than -1 it's better to just use a wall thermostat as there is clearly not enough convection past the sensor to give an accurate representation of the room.

If I am wrong I will say I'm wrong, but this is exactly what was stated by Honeywell to me on several occasions. I will give it a go and I cannot rule out that this has been changed in firmware updates. I will ask the question on Monday, as I have a face to face with the Honeywell software team...