Is this normal HW behaviour?

[fg61044]

I have just installed an Evohome installation controlling both heating and hot water.

The Evohome controller displays the HW temperature as registered by a thermostat transceiver (CS92) attached to a thermostat insertion sensor.

The sensor is inserted into dry socket in an unvented cylinder.

To test the Hot Water function, I started with a cool cylinder of water 30 Celsius.
The system had been installed 48 hours earlier so everything was at equilibrium temperatures.
The boiler is set to operate at 65 Celsius.
The hot water temperature for this test was set at 50 Celsius.

It took the boiler only 25 minutes to raise the cylinder of water from 30 to 50 Celsius.

My questions is about the temperatures that were displayed on the Evohome controller during this process.
The Evohome controller started out displaying a hot water temperature of 30 Celsius.
This displayed temperature did not update for 8 minutes whereupon it jumped to 36 Celsius.
This displayed temperature did not update for 10 minutes whereupon it jumped to 45 Celsius.
Thereafter the display updated in individual degrees until the temperature of 50 was reached and the boiler duly switched off.

Does anyone know how often the Evohome receives updates from the CS92 (or how often it polls for an update if it acts by polling the CS92)?

Has anyone observed this pattern of infrequent and large temperature jumps when the HW temperature is a long way short of the target temperature followed by frequent but small jumps as the target temperature is approached?

Can anyone explain how the HW temperature display should update?

Thanks
Francis

[Richard]

My CS92A polls every 4 minutes without fail (as recorded by my monitoring software).

Transmission errors can occur where the CS92A is not located in a desirable position or too close to a BDR91 so it then can take longer (reinstall the equipment if this is the case).

[fg61044]

Thank you. I suspect that there is merit in resiting my BDR91.
As explained in another thread, there is limited scope for resiting the CS92.

One thing I would observe is that if the polling of the CS92 is "only" every 4 minutes then there is some considerable scope for the HW to overshoot its target temperature.
Also in the last 5 degrees of temperature rise/7 to 10 minutes, I was receiving temperature changes every 1 or 2 minutes.

Anyway, I will resite the BDR91s and monitor the heating of another cylinder full of hot water.

[Richard]

From monitoring my temperatures over a 2 year period the control is near perfect. You must also accommodate for 'stratification' in large cylinders so cylinder sensor location is key, but typically all cylinders will be hotter than the set point due to this. Very difficult to be accurate here in my opinion.

[DBMandrake]

To test the Hot Water function, I started with a cool cylinder of water 30 Celsius.
The system had been installed 48 hours earlier so everything was at equilibrium temperatures.
The boiler is set to operate at 65 Celsius.
The hot water temperature for this test was set at 50 Celsius.

It took the boiler only 25 minutes to raise the cylinder of water from 30 to 50 Celsius.

My questions is about the temperatures that were displayed on the Evohome controller during this process.
The Evohome controller started out displaying a hot water temperature of 30 Celsius.
This displayed temperature did not update for 8 minutes whereupon it jumped to 36 Celsius.
This displayed temperature did not update for 10 minutes whereupon it jumped to 45 Celsius.
Thereafter the display updated in individual degrees until the temperature of 50 was reached and the boiler duly switched off.

Does anyone know how often the Evohome receives updates from the CS92 (or how often it polls for an update if it acts by polling the CS92)?

Has anyone observed this pattern of infrequent and large temperature jumps when the HW temperature is a long way short of the target temperature followed by frequent but small jumps as the target temperature is approached?

Can anyone explain how the HW temperature display should update?

Sounds like normal behaviour to me - mine has always behaved this way.

When the temperature is in the differential range (above setpoint-differential, and below set point) the temperature updates are frequent, typically every 1-2 degrees. However when the temperature is below the differential range it only updates once an hour, or if the temperature changes by several degrees in a short time.

As long as it reliably stops heating at the set point temperature and the temperature updates frequently in the differential range I don't think you have anything to worry about.