It'll fire to 75% of its rated heating output. At the moment, if it hasn't been adjusted that'll be fro 24kw. Down rate the heating max output to a lower figure, 10kw for example, and it'll fire at 75% of 10kw.
Short cycling at lower flow temperature
- Thread starter ntl142
- Start date
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Many uk properties leak heat although the home owner will think their property does not leak heat but they do,the boiler and its bespoke installation could just be doing its best
edit-just to mention on your original post,you had found a higher boiler thermostat heat setting will prevent more frequent on/off cycling but you have edited your original post.
happy heating
Sorry to cause confusion by editing - it was just a minor typo. This bit is there now and always has been: "If I increase the flow to 75 it behaves correctly, with no cycling. The downside of this is roasting hot radiators (unsafe for child) and high return tempertures (not condensing). Maybe ok in winter to heat up quickly after work, but not now in warmer conditions when I want a constant 18/19 degrees inside. I want the flow temperature to be around 55 or 60 degrees."
I've got it on 70 at the moment and that seems ok from a cycling point of view. Not great from a condensing or radiator temperature point of view though. Also, happy to admit my house leaks heat like a seive! 1900 miners cottage, with the only addition being decent loft insulation, double glazing and draught proofing. It's not too bad though.
Understand that bit now, thanks. I'll ask the Vokera guy about de-rating it, once I'm happy it provides more than enough heat in winter in it's current format. I think it does.
Also, to answer my own question - when it fires up after a short cycle, it definitely modulates. However, it takes about 10 seconds to react and wind down the flame, so if the flow temp goes over the setpoint + hysteresis before the modulation can catch it, then it cuts out. If it has enough time to catch it then it will modulate successfully.
Came to the boiler just now and saw the two dashes on the display, showing it was off/standby. Odd, as the selector dial was still on the snowflake for heating + DHW. Rather than spin the dial to off and back to on, I gave it a tap and it fired up again. Does anyone know if the selector dials are known to occasionally fail/wear? Thanks.
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As @vulcancontinental says get your engineer to down rate the maximum heat load to 10KW and that should solve your problems, what you are not thinking about is that when the radiators are at temp if any of the TRVs are closing down then your heat dump is less, and your worry about when it is cold you will need more heat , but you say that you only have 7.3 KW of heat load so even with allowances for heat loss on pipework 10KW will be more than enough, the range rating is all done electronically and not as you suggested changing injectors
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