Honeywell TR4 | Worth upgrading?

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I have a Vaillant Ecotech 835 boiler controlled by a Honeywell TR4.

The boiler was previously set to automatic partial load and I tried dropping the flow temperature. The boiler kept turning off before the flow temperature was reached. I've now changed the partial load to 18kW and flow temp to 60°C.

Things are working fairly well, but I think I'm probably missing out on the boiler's more advanced features - e.g. automatic load and flow temperature control. I suspect the boiler and the thermostat might be working at crossed purposes - hence the issues when set to automatic partial load and a lower flow temperature.

Is there a 'recommended' thermostat for this boiler?

It's it worth upgrading/changing the thermostat or will it just be money down the drain?
 
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First things fittest, how many radiators do you have or more precisely, what is the total output of all your radiators. No point in pushing buttons without educated reasoning. Now this is what the CH output should be set at.

Next. Boiler when it goes to heating the rads, will not fire at 35 kw or 28 but at the output matching your setting.

Now, if you set the heating control to 65, boiler will start up and boiler will self regulate to maintain 65 degrees. If the flow temperature exceeds 65, burner will extinguish, pump will continue to run. Predetermined time setting later, burner will relight.

Boiler will stay on line until the thermostat set temperature has been reached whereupon boiler demand will removed by T4. If you set the T4 to say 30 and radiator has a TRV on it or is undersized or has poor flow through it, boiler will keep cycling.

Nothing wrong with T4
 
Radiators
4x 180cm X 50cm double panel, double convector (DPDC).
1 x 200cm X 60cm DPDC.
1 x 60 cm X 200cm double column.
3 x 60 cm X 60cm DPDC.

According to specifications on Screwfix, these total about 17kW. We would like to do quite a large extension, which could double the existing floor area, hence the large boiler.

TRV in room with thermostat is already set to max to avoid issues.

Young kids in the house and I work from home, so heating set to 18-21°C, 24x7.

With partial load @18kW and flow at 60°C the boiler self regulates okay and does short, low power top up burns. The radiators barely get warm.

With partial load set to auto and flow set to 55°C, things go pear shaped - flow doesn't get above 35°C and anti cycling kicks in. I think this may be a known issue for 'auto'.

Given we heat 24x7 and have big radiators, I'm wondering if a more advanced controller (rather than on/off) might work better - e.g. it might automatically drop the flow to 45°C and do longer, very low power burns?
 
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[Bump]

Does anybody have experience with 'smart' ebus controllers and Vaillant Ecotech Plus boilers?
 

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