Honeywell evohome boiler parameters

jon1981

Hi there,


I installed the honeywell evohome system myself. 9 radiator trvs, hot water kit and the control panel. It's all working great, some tweaking here and there.

I have a question regarding the boiler cycle rates. i have a Baxi megaflo boiler, about 6 yrs old. The honeywell system is set up for a max of 6 cycles in and hour and a minimum on time of 1min. These are defaults.

I can't find any details in the boiler manual about cycle times and recommendations. Wondering if anyone on here can offer advice on a recommended setting?

J

jeffk

Just found this thread via Google search

Wondering the same myself, different boiler,but curious should I change the settings

I know optimised start is great and that wasn't set by the installers, so maybe there's more they didn't do that is good

Dardania

If you look at page 9 of this:

https://www.baxi.co.uk/-/media/websites/baxiuk/files/product-literature/baxi-megaflo-system/baxi_megaflo_system_installation_and_service_manual.pdf?la=en

you'll see that the boiler runs for 3 minutes minimum (or at least, after the return temperature is satisfied, the pump runs on for 3 minutes, to prevent the heat exchange from having too hot water in it, and also to spot if the return temperature drops and so re-fire the boiler)

I would be inclined, in your position, to leave it as it is. While you don't want to short cycle your boiler by firing it too frequently, the advantage of having the potentially 9 minute delay between firings allows the residual heat to dissipate to the rooms without burning any gas, and should give you a stable environment.
Just to check, when you wired it, the honeywell controls the enable signal for the boiler, and not the power to the boiler (e.g. if honeywell isn't calling for heat, there's still power to the boiler even if it isn't running?) Reason I ask, I've encountered boilers with their power wired directly from the thermostat, and it can cause issues like distortion int he heat exchanges if there is hot water not dissipated away - in those cases, like with an il boiler, you'd need to have a longer minimum run time, to keep the pump circulating.

jon1981

Dardania wrote: »

Just to check, when you wired it, the honeywell controls the enable signal for the boiler, and not the power to the boiler (e.g. if honeywell isn't calling for heat, there's still power to the boiler even if it isn't running?) Reason I ask, I've encountered boilers with their power wired directly from the thermostat, and it can cause issues like distortion int he heat exchanges if there is hot water not dissipated away - in those cases, like with an il boiler, you'd need to have a longer minimum run time, to keep the pump circulating.

Thanks for responding.

Yes I've wired it to the switched live i think it's called. The boiler still has power even when the thermostat is not calling for heat i.e. the boiler is powered up but not running.