Immersion Heater/Overheat Rod

Hi Mike,

A few months ago my Pulsacoil 2000 boiler broke down (again!). The guy came out and changed the overheat rod at the base of the boiler (green base, metal rod, item 1 in the gledhill manual) as well as the sensor (think it was the PHE sensor).

Anyway my boiler was running fantastic then broke down on Saturday. I've become quite familiar with them so I investigated. I noticed the pin at the base of the rod had popped out. So I switched off the heater, using a nail I pushed the pin back in and powered up. Hot water!!

Unfortunately the pin popped again yesterday. I powered down for 4 hours, pushed pin back in and restarted. Everything is hunky dory so far today (touch wood). Have you any idea why this is happening??? Overflow tank is fine and LED flashes in intervals of two.

Thanks,

MICK

Hi Mick,

This pin you are pressing back into place is the new overheat thermostat. It is built into the primary thermostat on yours. They should be the same in each heater, and the old 're-set button' should have been removed and bridged out.

The fact that your overheat 'stat keeps tripping tells us that either the appliance is genuinely overheating (i.e. the primary thermostat has failed) or the overheat protection thermostat has failed. Either way, the fix is to replace the thermostat that keeps tripping.

Sometimes the reason for the failure is a water leak. A 'known problem' with Pulsacoils is corrosion of the pocket the thermostat fits into, leaking store water out into the electrical connection box and thermostat housing of the immersion heater and making the thermostats wet. This could be the reason yours has failed so soon. New heater elements will be necessary if this is the case.

Cheers, Mike

Hi
One of the causes of this problem that Mike has not mentioned yet is element restriction.
As an approved Gledhill Service Agent like Mike, I have had this symptom on many occassions. It is often associated with either hard water areas or where the water quality in the thermal store is very poor.
The scale formation around the element pocket in the tank causes a lack of heat loss from the area around the head of the immersion heater resulting in local overheating.
The rectification required for this problem is to drain the unit and clean/replace the elements.

Regards
Dave Hickey
service@midlandboilercare.co.uk
07973 624179