Ah, useful information - didn't know about the modulating controller,
The Gledhill pcb has labeled screw terminals on it and connections for a time clock...and even room stat terminals to switch in the boiler/CH pump. It can be easily fitted in a vented metal box. A Google says the pcb's are £240 inc VAT plus sensors at approx £28. You need the modulating Grundfos pump, not a normal off the shelf job.
No flow switch or TMV is needed, or the two cylinder stats and relay, saving money there to offset costs. No need to set up the stats and the pcb does all.
You may as well use the Gledhill pcb as most, if not all the functionality you need the pcb offers. Heat the cylinder switching in the boiler, using one sensor in a pocket. It has three temperature sensors. One sensing the cylinder temp, one sensing the plate temp in the pipe after the plate on the primary side, one sensing the DHW temp just after the plate in the pipe.
It has the built-in anti-cycle functionality that two cylinder stats gives. Once up to temperature the boiler does not cut in until the thermal store temperature drops substantially. Below 60C cylinder temperature the CH pump will be held off to give a swift reheat of the cylinder, if you wire in the CH part. All quite simple. The pcb "learns" the boilers maximum temperature and heat up time. It will run from 70C minimum to 80C learning the boilers ways.
Using the Gledhill PCB is the cheapest way when building a custom store with rich functionality and economy. All parts are there readily available and cheap enough, and simple to implement. One pcb, three temp sensors and a modulating Gundfoss pump. All simple and all done for you. Just connect up. It even gives temperatures of the sensors on a display on the pcb.
Gledhill should have made stainless versions of their thermal stores with PHX's inside the cylinder with the CH taken off an internal coil to prevent sludge build up. Then they would have sold like widfire and given few problems improving the reputation of thermal storage. Gledhill had the right idea of all in one highly insulated neat box, but the mechanical design and/or materials left a lot to be desired in some points. The pcb was/is superb with superb functionality simplifying some of the mechanical aspects and improving efficiency.
Because of the Credit Crunch Gledhill have "temporarily" dropped the advanced thermal stores, reverting to coiled DHW stores. All parts are available for all previous models. The pcb was made in Czechoslovakia for Gledhill. There is no reason why Gledhill cannot sell these pcbs to other thermal store makers, unless they seriously intended to resume manufacture of the older products, or have a newer product on line using the same pcb.
Other makers using this pcb would make thermal stores much more efficient and cheaper all around. Then thermal store pcbs would be generic and interchangeable.
The maker. A quality company..
It may now be a general pcb available to any makers. This is the pcb used by Gledhill, from the Czech web site and appears to be generally available to other makers....
The Czechs have two pcbs on their catalog. The pcb shown above....
The unit is designed for controlling thermal stores. It controls the temperature of the water in the store and the preparation of domestic hot water. The unit can be expanded in order to control thermal systems with condensing boilers, solar panels. Also the unit can transmit data by means of GSM.