Boiler cycling

[Gert_Lush]

I have a Glow Worm Ultimate 40 conventional boiler and a standard vented heating system.
When the house is cold and the CH is switched on, the boiler will run as normal for about 20 mins, then cycle on for about 1 min then off for about 3 mins until eventually the room stat cuts the boiler off when the house is up to temp - but this take about 5 hours or so.
The boiler stat is set to about three quarters, the room stat set to 22 C, and the TRVs opened up all the way.
The circ pump is only on setting one (the slowest) so my guess is the pump isn't shifting the water away from the boiler fast enough, causing it to cut out as it should. (if i have the pump set any faster, i get overpump (and a noisy CH system) and overflow from the F+E tank). Is this actually whats happening? If so, is turning down the output of the boiler the answer?

Cheers

 

[chrishutt]

if i have the pump set any faster, i get overpump (and a noisy CH system) and overflow from the F+E tank).

Sounds from this as if you have some blockage in the feed pipework. This is quite common as you will see if you search the forum. Blockage is usually near the connection to the flow pipe.

 

[Gert_Lush]

That's job two...
Any ideas on why its cycling though?

 

[JPC]

poor circulation i think is what chris is saying.

if not , the cycling problem may be something to do with a boiler fault. check manual for fault finding
__________________

 

[Gert_Lush]

You are probably right - although can the output of a boiler to reduced (by a corgi tech or course)?

 

[chrishutt]

No substitute for cleaning out the system - it's gong to get worse.