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

 
Proposed new building regulations requires the pump does not have any uncontrolled gravity circulation pass through it when it is not running. In order to future proof our control systems we feel it is has been prudent introduce a modification for the gravity circuit to bypass the pump on all our new panels.

Whilst introducing a pump bypass loop is relatively straight forward it is still a major modification for us requiring new jigs etc, so we have taken this opportunity to make several improvements to the panel to further increase performance.

 

 1. First objective for the gravity circuit to bypass the pump allowing unrestricted flow to the heat leak circuit.

 

Status.

Solid fuel appliance is firing in slumber mode with gravity circuit functioning.

Heat Leak Loop Valve  - Normal position sprung open allowing unrestricted flow to heat leak circuit.

Gravity circulation to

  1.  hot water cylinder. 
  2.  heat leak circuit. (unrestricted)

 
 

 

2. To gradually wean the heating system up to the circulating pressure when the pump when it initially starts. In some installations, when the header tank was installed fairly close to the H2 panel it sometimes pulled a small amount of air into the system when the pump first switched on.

Slowly closing the heat link loop valve over a period 3 minutes greatly reduces the shock of the initial pump start up.

 

Status.

Solid fuel appliance is firing and the flow has reached 58°C, activating the pump.

Heat Leak Loop Valve  - begins to close, loop recycles and gradually reduces to nil over approximately 3 minutes.

When the water leaving the solid fuel appliance reaches 58°C, a dry well thermostat (aquastat) will switch to "make on rise" and send a switched live to the H2 panel and the pump will switch on.

The heat leak link valve begins to close, taking around 3 minutes to fully shut

For the first three minutes, the new heat leak loop will recycle back through the heat leak loop valve into the pump supply pipe reducing the full pull of the pump on the heating system. This 'soft start' when the pump is initially activated very much reduces the sudden pull exerted on the open vent. which in certain cases could pull a small amount of air down the open vent into the heating system each time the pump is switched on.

Pumped circulation to

  1.  hot water cylinder. 
  2.  heat leak circuit.

The heat leak loop recycles and gradually reduces to nil over approximately 3 minutes.

 
 

 
3. On the original H2 panel the gravity heat leak connection is fitted onto the pipework downstream from the pump, when the H2 system is in slumber mode, the gravity heat leak flow had to pass through the static centrifugal impeller of the pump on its way to the heat leak circuit.

In slumber mode (pump not working) the principal worked fine but when the H2 panel was in pumped mode the heat leak gravity circuit was force-fed by the pump. This created a problem with too much heat being pushed into the gravity circuit which proved difficult to adjust and get the right balance on the actual radiator/s.

If the circuit was to be restricted in pumped mode, (by the installer of the H2 panel) then it would also be restricted in gravity mode and reduce the gravity circulation, which would defeat the object of having the gravity heat leak circuit.

To reduce the effect of to heat leak circuit robbing the rest of the system of energy we have diverted the heat leak flow through a smaller pipe when the system is fully pumped.

Status.

Solid fuel appliance is firing and the flow has reached 58°C, activating the pump.

Heat Leak Loop Valve  - Electronically closed to shut off the recycling circuit around the heat leak loop.

The heat leak diverter valve is fully shut, the pumped heat leak flow is now diverted through a small bore pipe controlling the flow rate to the heat leak radiator.

Pumped circulation to

  1.  hot water cylinder. 
  2.  heat leak circuit. (restricted)

The heat leak loop ceased to recycle.

 

4. When the H2 panel was first designed cylinders were expected to be heated in an hour and that was what the H2 was based upon. Modern day system design requires the hot water cylinder to be heated in half that time and the upgraded H2 panel has been modified to do that by simply increasing the size of the supply pipe on the panel.

 

Contact Mill Cottage Plumbing & Heating Ltd

Technical Support and Sales

Telephone 01354 653854