Boiler taking random amount of time to fire up (programmer problem?) All aspects of plumbing questions and answers, help, tips and information

[DIYAmateur]

Hi,
I'm trying to diagnose a problem where it seems to take a while for the boiler to kick in and fire up (works fine once it does - it's a new Worcester Bosch one bought this year and installed professionally). It takes something like 10-15 minutes normally before it fires up.

The programmer is a Potterton EP2 and the thermostat an old gold-coloured Honeywell effort with just a temp dial.

I've tried turning the thermostat from high to low (and back/forth a bit to see if that gets the boiler to kick in but doesn't seem to make any difference, and I can hear a click when passing the current temperature, so it's left on a high temp now).

The EP2 programmer has a half/third full battery indicator, which I can see from google may indicate an internal battery needs replacing, but can't see any easy way to do this. Regardless - I don't think that would cause the strange boiler firing up late issue would it?

Is there an obvious problem this might be, or anything simple to check/try, to work out what the problem is, or fix it?

Thanks in advance,
Rich

[stoneyboy]

Hi diyamateur,
Most likely cause is a sluggish motorised valve in the system- find it and see how easily it operates.
Regards S

[DIYAmateur]

Thanks for the tip Stoney,
I've had a look and found the motorized valve. Lever seems pretty firm (but does move - and can hear pump kick in after moving it) so perhaps this is the issue (or part of it). Also a far bit of blue copper residue buildup above the nearby recently replaced grundfos pump so perhaps an issue there with something needing tightening there (too).
Have contacted my local plumber now (who did the boiler and pump previously) as the combination of both probably should be looked at by someone who knows what they're doing!

[stoneyboy]

Hi diyamateur
You now know how far the MV lever has to be moved to get the pump running. Try turning on the heating and feel the MV lever so you can judge how long it takes to start the pump.
Regards S