What IS a SysteMate?:
The Gledhill SysteMate is a thermal store, in other words a tank full of water heated by an ordinary central heating boiler. The water never changes. It is used purely to store heat energy from the boiler. The stored hot water is pumped around the radiators to heat the house, and is used to heat domestic tap water before it arrives at the hot taps. This allows hot water to taps and showers at full mains pressure for high performance showering and faster bath filling.
The SysteMate is an enhanced version of the BoilerMate, and the two are easily confused. The difference is that the BoilerMate has to be fitted with it's expansion tank at a higher level than the boiler and all the radiators (because the BoilerMate fills the radiators and boiler with thermal store water directly, and boilers/radiators fitted higher than the BoilerMate could not fill up with water), while the SysteMate can be fitted anywhere in the property. The SysteMate achieves this by separates the central heating water from the thermal store water using a copper heating coil inside to transfer heat from the boiler primary into the thermal store water, and making this and the radiator/boiler circuits into a separate sealed system.
How does the SysteMate III work?
A conventional central heating boiler heats the water in the SysteMate III in directly. The radiator/boiler pipework is a sealed system with an expansion vessel built into the SysteMate. The boiler is fired and it heats the store by pumping boiler water through a coiled-pipe heat exchanger inside the store. A three port diverter valve switches the pump flow on CH demand to the radiators from either the boiler or the heat store, depending on the temperature of the heat store. When it falls below design temperature the boiler is fired to add heat energy to both rads and heat store.
The SysteMate III delivers hot water to the hot taps by using an external plate heat exchanger and a further pump. The pump starts when a hot tap is turned on and pumps hot store water through the plate heat exchanger, thus heating the cold mains water very effectively on it's way to the hot taps or showers.
Faults known to occur in the SysteMate III:
1) Circulating pump failure
Even SysteMate IIIs are all quite old now, and many of those without corrosion inhibitor in the circulating water are suffering from advanced radiator and system corrosion. The corrosion deposits cause the circulating pumps to seize up and burn out. Fitting a new pump gets the system working again but doesn't address the cause of the original failure. A system cleanse is usually necessary (a 'powerflush').
2) Water scale-contamination of the plate heat exchanger.
The plate heat exchanger was hailed my manufacturers as the answer to water scaling, but this has proved not to be the case. Hard water in certain areas still seems capable of blocking a plate heat exchanger with calcium deposits causing restricted hot water flow from the taps and warm (instead of hot) temperatures. The answer now is to fit a repalcement plate heat exchanger, which takes around an hour instead of several hours to descale the previous copper coil heat exchanger.
3) Blender valve failure.
The thermostatic blender valve is prone to damage from accumulated water scale. This results in the water taps only ever being slightly warm. A new blender valve is necessary.
4) Heat sensor failure.
Hot water temperature from the taps and/or shower becomes unreliable and unpredictable. The hot water temperature sensor delivers a signal to the PSC board and this controls the pump speed. They seem to fail with age (after three or four years) and replacement restores reliable hot water performance. I believe they are thermistors but there is more to them than that as there are three conductors in the leads. Their true nature is shrouded in secrecy. No-one at Gledhill gives anything away when I ask questions... quite frustrating really but I'll get to the bottom of them eventually....!
