LK 810 ThermoMat G load unit

The LK load units consist essentially of a pump, a 3-way valve controlled by a thermostat, and a thermosyphon bypass. A flue thermostat detects when the stove is running and starts the pump in the load unit. We recommend a flue thermostat as opposed to a pipe stat because the temperature of the flue pipe is a much better indicator as to whether the stove is going or not: the water in a system can stay hot long after the stove has gone out.

While the water in the stove is below 55ºC the valve remains closed and the water is only pumped through the backboiler in the stove. This volume of water is very small and so quickly heats up. The thermostat in the unit begins to open the valve when the water reaches 55 ºC, allowing water from the stove out into the heating system. The valve is fully open at 65 ºC which means that all the water is then allowed out into the heating system.

This means that only hot water is allowed into the heating system which is especially important if you are using an accumulator tank as you only want to allow hot water into the tank, otherwise you risk cooling your tank. Whilst the water is being heated from 55ºC to 65ºC the valve is gradually opening so the flow into the system increases gradually as the temperature does - again this reduces potential cooling of the tank through mixing.

If the power fails or the pump fails then the LK load unit still allows for thermosyphoning which is very important as it means that the water in the boiler should not overheat, and your system may even continue to provide heating and hot water as long as you designed it with thermosyphoning in mind.

An LK load unit comes with 3 thermostat dials which show the temperature of the water flowing through the unit. This allows you to see that the load unit is working as it should. In many smaller installations the load unit would be hidden, but it is a good idea to incorporate an inspection hatch as part of the design so you can access, inspect and service (not that the LK unit should really need servicing).