ElectraMates are thermal stores, rather than hot water cylinders. Like conventional hot water cylinders, a thermal store is a container filled with hot water but here the similarity ends. Once filled, the water in a thermal store never changes. Instead, the heat stored in it is used to heat conventional wet central heating radiators to give electric-powered central heating, and to heat the tap water using a heat exchanger. This allows the hot tap water to be delivered at full mains pressure, and is one of the primary benefits of installing a thermal store instead of a conventional hot water cylinder.

The Gledhill ElectraMate transfers heat into the tap water using a pump and an external 'plate heat exchanger'. A plate heat exchanger is a block of very thin stainless steel plates arranged so that cold mains water can flow through one set of spaces between the plates, and hot water from the thermal store core can flow through an alternate spaces. Heat transfers through the plates and heats the cold mains water on it's way to the hot tap.

How does the ElectraMate 2000 work?

The water in the unit is heated by pumping it through a 9kW or 12kW 'flow boiler'. The flow boiler is a copper cannister containing a pair of 4.5kW or 6kW immersion heaters. The pump needs to run whenever the immersion heaters are powered up to distribute the heat energy. There is a thermistor (heat sensor) inside the water store and this tells the circuit board the temperature of the stored water. Overnight the board runs the pump and flow boiler to heat the unit up to 80 degrees Celsius on cheap-rate electricity. If during the day the core temperature falls below 55 degrees C, the board turns the heat on again and warms it to about 60 degrees using day-rate electricity, to avoid the user losing heating and hot water services completely.

A thermistor (heat sensor) is attached to the domestic hot water outlet from the plate heat exchanger. When a hot tap is turned on the thermistor records a fall in temperature, and the circuit board runs the hot water pump. The pump circulates stored hot water through the plate heat exchanger, heating it, and the circuit board turns it off again when the thermistor reports a temperature rise. This system is proportional. The bigger the temperature fall seen by the thermistor, the faster the circuit board runs the pump. This way the designed flow temperature (of 52 degrees Celsius, I think) can be maintained at almost any flow rate when a hot tap is turned on.

Common problems:

The vast majority of ElectrMate 2000 breakdowns to which I am called out fall into one of the following categories:

1) Heating element failure in the flow boiler. 

The ElectraMate 2000 has two immersion heater elements in the flow boiler, and commonly one will fail and the user does not notice. When the second fails, the unit goes stone cold and all services are lost. It becomes urgent to fit a new flow boiler! I always carry them as spare parts in stock so I can promptly repair a flow boiler failure.

2) Relay failure.

The flow boiler and the heat store are both protected from overheating by overheat thermostats. These thermostats operate relays that isolate the power from the flow boiler should either thermostat trip out. The problem is that the wiring connections to these relays sometimes overheats, burling out the wiring and one or both relays. New relays and wiring are needed to repair.  

3) Thermistor failure.

The hot water service heat sensors (there are actually two) can become unreliable with age. This usually presents as unpredictable hot water performance or unstable hot water temperature. The thermal store will be hot, but the pump will not run fast enough (or at all) when the hot tap is open. A new hot water flow sensor is needed.

4) Circuit board failure.

Failure of any of the circuit board functions means a new board is required. 

Control board failure can also be caused by pump failure or water ingress from a leak into a (still working) pump motor. In this situation fitting a new board without replacing the pump motor usually results in the new board failing too. The best defence for an engineer is to measure the input resistance of the three pumps and to visually inspect each of them for any evidence of water contamination. If any pump has a resistance of less than 160 Ohms or has any sign of water marks or corrosion around the connection box on the motor, I strongly advise replacing it even if the pump still works. 

5) Tripped immersion heater overheat protection thermostat. 

This is easily rectified by pressing the reset button on the overheat thermostat (located on the right hand side of the unit, under the front cover, and near the floor). The reason for the tripping needs to be investigated though and this can be very difficult to trace. Usual reason is a stuck boiler pump (lowest of the three). If the boiler pump is not seized then possibly the pump is intermittently sticking, or the overheat thermostat itself has lost its calibration and needs replacing. Another possibility is the right-hand power relay at the top of the unit is sticking ON when the board withdraws energising power from it.  Best thing to do in my view is replace all three components together (relay, pump and overheat thermostat) as a speculative repair. 

6) Tripped store overheat protection thermostat.

As above, this is easily rectified by pressing the reset button, but the reason for the trip still needs to be investigated. (This thermostat tripping is usually accompanied by the heater element overheat thermostat tripping at the same time because it stops the boiler pump while the immersion heaters are running, causing a genuine overheat of the heater element cartridge.) The usual reason for the store thermostat tripping is loss of calibration of the thermostat itself, so a replacement thermostat will fix it. Diagnosis is more likely to be correct if the store thermostat stops tripping when the summer/winter switch on the unit is set to 'summer', and/or the problem is worse when the switch is set to 'winter'. Replacing the thermostat is the first thing to try regardless, as it is by far the most likely cause. If the problem persists then the store is likely to be genuinely overheating, usually caused by control board failure. 

7) Leaking isolator valves.

ElectraMates have several 'ball' type isolator valves. These are fitted for the purpose of allowing replacement of circulating pumps (and a few other components) without draining the whole thermal store. Sadly these isolator valves have a tendency to leak water through the seals around  the operating spindles after being used. Surprisingly these leaks generally 'self-heal' after ten or fifteen minutes as microscopic debris in the water gets caught up, slowly blocking up the water path causing the leak. Unfortunately this is not always the case, and the consequences can be bad. If the water continues to leak from an isolating valve it is not unusual for it to eventually corrode though the metal of the pump motor body and enter the motor windings causing the pump to fail. Pump failure often causes control board failure at the same time, and water in the pump motor windings sometimes causes control board failure even if the pump motor still works.

If there is evidence of isolator valves leaking I advise replacing them. This is very time-consuming as the unit need to be drained and all three pumps removed first, but unless this is done there is a continuing risk of pump and control board failure.

 An alternative course of action is to purchase the manufacturer's extended warranty plan. This is available to all owners of Gledhill appliances, even if the original warranty has long expired. Contact Gledhill for more information.

If you'd like me to fix your ElectraMate 2000, contact me

Mike Bryant, AKA Mike the Boilerman. 

This page last updated 29th August 2008.