Thermostat Span/TPI settings

Can anyone shed any light on what these mean and explain them in laymen’s terms?

There are two dip switches on the back of the wireless thermostat, and the upshot is that I can have it on either

– a ‘Span’ setting, with a tolerance of +/-0.25 DegC
– a ‘TPI’ setting, with a choice of 6 or 9 cycles per hour

What’s the best, i.e. most economical, way to set it up?

Wild guess, but I’d say that Span would fire up the boiler any time the temp dropped by >0.25c whilst a TPI of 6 would mean that it would ignore small variations and fire up every 10 minutes if the temperature had dropped.

No idea though!!

Edit: nearly right-ish.
https://youlearn.honeywellhome.com/uploads/documents/FAQ_-_TPI_functionality.pdf

(I’d go with TPI I think)

Ah, that makes sense.

I’m still a bit confused though as it was set to TPI/6cph, with a threshold temp of 20degC, but it was showing 20.5degC and the boiler was still firing.

Maybe I should just leave it alone and let it do it’s thing.