Mill Hill Cottage Plumbing & Heating Ltd

(Previously Heating Innovations)

Home Up heat link loop 15mm By-pass Position Dry Well Themostat pre 2011 Pipestat H2 Control Box

Control Box

The H2 control system is fully automatic, once commissioned by your heating engineer the settings should only be altered in exceptional circumstances. 


 'Pump' indicates that the motorized valve No 9 and the circulating pump are energised, it continues so long as the pump is running.  Motorized valve No 9 converts the H2 Panel from a gravity, into a fully pumped system.

 'Auto Boiler' indicates that the motorized valve No 8. and the automatic boiler are energised. Motorized valve No 8 opens to let the heat from the automatic boiler flow into the H2 Panel.

  'Link-up mode' indicates that the motorized valve No 22. is de-energised to to allow the valve to fall naturally open. Motorized valve No 22 when open, puts the H2 panel into linkup mode. The heat from the solid fuel appliance is fed into the return of the automatic boiler.

  'Radiators on' indicates that the motorized valve No 10/17. should be motored to mid position. Motorized valve No 10/17, when in mid position opens the radiator circuit to share with the hot water recharge primaries.

Bias Stat Dial

Mounted on the control box the bias thermostat has three functions and operates within the efficient temperature range of solid fuel boilers, approx between 60 and 70 deg. C, the solid fuel stop post is at the lower end of the range. When the Bias stat temperature is reached it opens the radiator motorized valve port.

Function 1  With only the solid fuel boiler operating, the boiler primary flow pipe temperature rises and heats the domestic hot water. The closer the pointer is to the automatic stop, the hotter the primaries get and will heat the water quicker, before the heat is shared with the radiators.

Function 2 With the solid fuel boiler in slumber mode, the primaries circulate by gravity. The Bias Stat becomes the high limit safety stat and switches on the pump as well as opening the radiator port.

Function 3 With both boilers firing, the Bias Stat setting determines at which Temperature the automatic boiler is no longer required.



Top Toggle Switch 'Solid Fuel Run Option Switch'

'S/F 58 DEG ON' With the switch to the back, the pump will run whenever the dry well thermostat is satisfied at 58 degrees Celsius. 

'S/F TIMED' With the switch to the front, even with the dry well thermostat satisfied the pump will only run if the hot water channel on the programmer is timed to be 'on' or the bias stat temperature is satisfied. 

This function is occasionally used ensure the pump will not run at night if the noise disturbs your sleep. Most systems are run with the switch to the back 

Bottom Toggle Switch 'Automatic Boiler Option Switch'

'NORMAL RUNNING' With the switch to the back, the automatic boiler will function as per normal 
'S/F BOILER ONLY' With the switch to the front, the automatic boiler is prevented from functioning.

Again most systems are run with the switch to the back. 


Contact Mill Hill Cottage Plumbing & Heating Ltd

Technical Support and Sales

Telephone 01354 653854