Boiler cycling

[MaxCoventry]

I have a Worcester Greenstar 24Ri boiler that was fitted a year ago. The installer told me that it has a test phase (which appears to take about 2 minutes and 15 seconds) every time the heating switches on, and a pump over-run (which appears to be for 3 minutes) every time the heating switches off.

The system also has a Honeywell CM51 programmable room thermostat. When the room temperature becomes close to the programmed temperature of the CM51, the heating switches on/off/on … at intervals of about one to two minutes. When the CM51 switches the heating on, the boiler does not usually complete its test phase before the CM51switches it off. The pump over-run means that the pump runs continuously while the boiler goes through part of its test phase repeatedly without getting as far as doing any heating for long periods, or sometimes it will heat for 5 to 10 seconds before the CM51 switches it off, and this has no real heating effect.

What can I do about this? Do I need a new room thermostat and, if so, are there thermostats designed for boilers with a test phase like the Worcester Greenstar? Responses from both Worcester and Honeywell Technical Support have been unhelpful.

 

[Agile]

I am not aware of any "test phase" and dont think its part of the normal operation.

During normal heating operation the boiler will turn off the burner off when the flow temperature reaches the set valve but the pump will continue to run.

The thermostat will turn off the boiler when it reaches the set twmperature but the pump will continue to run for the over run period.

It sounds to me as if-

1. The thermostat may be too close to radiators.

2. The anticycle delay is not set to the optimun setting.

Anticycle is usually set to around 5 minutes. It sounds as if yours is only at 1 minute.

Tony

 

[gas4you]

Are you sure he wasn't refering to the start up auto venting cylce that occurs when the boiler is powered back on after the fused outlet has been switched off, rather than just a heating deamnd?

 

[Boilerman2]

Is the Boiler wired correctly, i.e. perm Live & Sw L reversed?

 

[gas4you]

or indeed no permanent live at all, just switched

I've had a run of various makes installed like this lately and having to put the wiring right

 

[bengasman]

Easy answer this one, your boiler is still under warrantee. Call the installer to give him a chance to set it right.

 

[Deleted member 105431]

auto siphonfill program on start up is because no permanent live, only switched live as g4y has already said.