Gledhill Electramate 2000, filling a cupboard
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 its way to the hot tap.
How does the ElectraMate work?
The water in the unit is heated by pumping it through a 9kW or 12kW 'flow boiler'. The flow boiler is a copper canister containing either a pair or a set of three immersion heater elements. 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.
Firstly I feel obliged point out the Electramate tends to be rather unreliable, so users tend to experience a series of breakdowns over several years of ownership so my best advice to any Electramate owner is replace it rather than embark on repairing possibly the first of a long series of expensive breakdowns. They can be awkward things to fix too, with lots of service valves in particular that leak when you operate them during repair. The Electramate 9kW is generally fixable but the Electramate 12kW can be so troublesome I have decided (as of now, March 2017) to stop attending 12kW versions. I am also reluctant to travel long distances from here in Reading to fix even the 9kW version as repeat failures are not uncommon and I feel an obligation to go back should this happen, even though a further failure a few days later is usually unrelated to the original repair.
I will ask you which version you have should you call me, and the identity of yours can be obtained from the little data label on the front, right at the top on the left. The label on the 9kW version bears the model number AEC2020 or AEC2041, while the 12kW version label says AEC2040. I will ask you to look at the label and tell me which model number it states before booking a visit. Here is a photo of the identifying label, which is usually attached to the outside of the case of the appliance, right at the top:
Anyway to the faults... The vast majority of ElectroMate 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’ (three in the larger, 12kW version). One will commonly one fail and the user generally does not notice. When the second (or third in the case of the 12 kW) fails, the unit goes stone cold and all services are lost and a repair becomes urgent! I always carry Electramate heater elements in stock for the more common 9kW Electramate so I can promptly repair this failure. The very rare 12kW version, I would have to order.
2) Relay (or contactor) 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 overheat, burning out the wiring and one or both relays. New relays and wiring are needed to repair.
3) Store overheat thermostat(s) tripping
The heat store overheat protection thermostat trips, as the appliance has overheated. The usual cause of this is the power relays above both sticking or jamming in the ‘on’ condition. The PCB withdraws energising power from one contactor to disconnect the heater elements but the contacts inside stay closed, continuing to power the heaters. One of both of the overheat thermostats trips which withdraws energising power from the other contactor, shutting the unit down safely. Re-setting the protection thermostats temporarily fixes the problem until the next time the contactor sticks. A new pair of relays (contactors) usually fixes the problem properly.
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.
5) 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.
There is an additional overheat protection thermostat attached to the side of the heater element cartridge on later heater cartridges, which can trip. This is easily rectified by pressing the reset button but the reason for the tripping needs to be investigated, and this can be 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.
7) Leaking pump 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.
As you can see, there is a pretty long list of failures Electramates suffer from so I suggest you consider replacing yours rather than repairing it. If however you'd still prefer me to fix your ElectraMate, feel free to contact me on 07866 766364.
Mike Bryant, AKA Mike the Boilerman.
The store overheat protection thermostat
Copyright Michael Bryant 2020
Site first created 31st December 2006
Last updated 2nd February 2020
Gas Safe Register 197499, CIPHE registration number 56207