Problem after new circulating pump fitted

[HughPugh]

Problem: Circulating pump failed - new pump fitted - now the boiler seems to randomly fire up regardless of requests for heat. i.e. can turn controls to "Off" but boiler keeps firing.

I have an elderly but usually reliable heating system. It has evolved over the years and now consists of: Ideal Mexico Super 2 CF-60, new circulating pump just fitted, ST699 that only controls hot water, CM61 for the CH, V4043 motorised zone valve, copper hot water cylinder in the airing cupboard with L641A stat, F & E tank in the loft.

The pump was replaced because I came home to find nothing working. The 3amp fuse in the spur had blown. Diagnosed the old pump was U/S. Went to close isolator valves and they leaked. So, drained system, replaced pump plus new isolators. Connected up, turned on and everything immediated sprang to life. Job done or so I thought.

Any help / advice greatly appreciated.

 

[Agile]

I am going to guess that the pump took an excessive current and that one of the controls has been damaged by welding relay contacts closed.

To find out what needs electrical testing, or just possibly removing each control in turn and see what prevents the problem.

Tony

 

[HughPugh]

Hi Tony
Good call. Looks like it's the CM67 (not CM61) that's the culprit. They're discontinued I believe so I'm now on the hunt for a direct replacement or somebody with old stock as I also have the auto time setting module and it would be good to reuse it.

Thanks for your help.

 

[Agile]

The CM907 is the maker's replacement but I don't know how compatible the fixings are. But not much trouble to change.

You might find a new or used CM67 on Ebay!

http://www.ebay.co.uk/itm/Honeywell...474107?hash=item211f2587fb:g:F1IAAOSwImRYh0oZ

 

[HughPugh]

Hello again.
OK. Got a CM907 (physical fittings identical spacing wise, by the way), connected it up same way as the CM67 and it now seems to be fine.

Thanks again.

 

[snb]

there was nothing wrong with the old unit most likely. it just needed to be paired again as it had gone into fail safe which keeps the heating on 20% of the time and off 80%

 

[HughPugh]

Mine is hard wired not wireless so I don't think that would apply. Thanks anyway.