HELP Please - myson economist cutting out

[petecbr]

Can anyone help please.......

I have a 17 yr old myson ecomomist which keeps cutting the pilot light out. As soon as the boiler reaches any kind of temperature and cycles off the boiler thermostat out goes the pilot light. Seems to be the limit stat which is turning off at the thermo coupler as you can hear it clunk off.

The only way to run the boiler is to turn the boiler stat down to next to nothing and then it seems to limp along... as soon as the boiler stat is turned up to get reasonable heat off she goes.

I had a new limit stat in summer when it went.

I've had an engineer replace the thermocoupler but the problem remains.

Only way an engineer can get the pilot light going is to temporary bypass the limit stat to get it lit and off it goes again.

Also just fitted a new pump after draining the sytem. This seemed to be knackered for quite some time.

Everything points to the limit stat but the manual fault chart indicates gas valve !

Is it possible to get faulty limit stats ? engineer says they only cycle off a couple of times then may not work properly again.

The boiler is fitted with an elmwood 2455r limit stat. Anyone know where i can get one possibly.

Sorry to go on a bit but i haven't got the cash for a new boiler right now

Pete
( a very cold Pete ! )

 

[namsag]

When demand for heat has gone and boiler turns off the pump should carry on running for about ten mins to get rid of excess heat if it doesn`t it will trip limit stat
If the pump does not keep running then you have a faulty pump over run stat .
Pump should be wired back to the boiler for this to work

Also as boiler stats get older they go out of sync and on high it may be shutting off higher than the limit stat trips..#

Boiler stat and pump over run stat are built into the one stat on this boiler part number 68/2021/42