laddomat header

Many wood burning or solid fuel appliances, such as biomass boilers or wood burning stoves require a minimum return temperature to the appliance to prevent condensing, as well as to work more efficiently.

A Laddomat loading valve is a device that by using a thermostat to control the water temperature, can help to supply a minimum return temperature to you stove, cooker or boiler or solid fuel appliance. It can also help in loading the accumulator tank or thermal store more effectively, by ‘layering’ in the heating water, and aiding the stratification within the tank.

Mibec have used and supplied the Laddomat 21 range of charging valves for many years, and can recommend them for use with these types of system. Laddomat come in two main types, the 21-60 unit for appliances up to 60kW heat output, and the 21-100 unit for larger boilers up to 100kW output.

Laddomat in your system prolongs the lifetime of your boiler. Because Laddomat cools the boiler with pre-warmed return water, the corrosion in the bottom half of the boiler is reduced drastically. Many boiler manufacturers also provide a longer boiler guarantee when Laddomat is fitted to the heating system.


Why Use a Laddomat System with an Accumulator Tank?

A tankless system has to be started several times a day to maintain heat which increases the consumption of fuels; a storage tank and Laddomat system reduces this requirement and can save you up to 50% in fuel costs.


laddomat graph

An accumulator tank acts as a buffer and intermediate store for water that is pumped around the system. The boiler heats the water in the tank, and the hot water is then supplied to the consumers.

The combination of a Laddomat unit and accumulator tank allows for more efficient use of a log fired biomass unit. Since biomas burners cannot be switched on and off at will the accumulator tank allows the hot water generated from the unit to be stored and then later retrieved for use. With an accumulator tank there will be long pauses between the times the boiler is fired which saves on fuel costs and helps to maintain a comfortable environment.

How does Laddomat Work?

laddomat diagram

Accumulator tanks work using a separation system – simple physics that hot water is lighter than cold water so the hot water stays at the top of the tank, and the cooler water at the bottom. If this process is to function as intended, the boundary between hot and cold water must be sharp. If hot water and cold water are continually mixed, the water temperature will be lower. The Laddomat system controls the flow of the water so as to maintain the difference between the water temperatures.

When the boiler starts to fire up, Laddomat circulates the water internally in the boiler, so that it rapidly achieves its working temperature and can begin to heat the tank. Laddomat then pumps the hot water into the top of the accumulator tank slowly and under full control, so that separation remains optimum. In addition, Laddomat cools the boiler with preheated return water – hot water from the top of the boiler is diluted with a little cold water from the bottom of the tank.

laddomat tank diagram



Laddomat 21 – 60

The Laddomat 21 is a complete unit and is simple to install. It ensures perfect charging of the tank. Thanks to efficient hot water control, Laddomat 21 has a higher opening temperature at high boiler output compared to other similar products.

  • Laddomat 21 enables the boiler to attain the right working temperature quickly and then charges with a slow flow and a high and even temperature. The vitally important boundary layer between hot and cold water is therefore optimal.
  • Laddomat 21 raises the return temperature to the bottom of the boiler. This prevents corrosion and tar formation, which extends the service life of the boiler.
  • During the final part of firing, Laddomat 21 charges the accumulator tank fully, thanks to the unique thermal valve, which closes the bypass port completely.
  • After firing, Laddomat 21 makes use of the residual heat in the boiler and embers by the self-circulation of hot water from the top of the boiler into the accumulator tank. Self-circulation also works in the event of a power failure.
  • Laddomat 21 has a simple design with generous sealing surfaces, for simple fitting.
  • Laddomat 21 is manufactured for maximum service life and problem free function.
  • Laddomat 21 is extremely easy to service, thanks to its ball valves with teflon pack box and heavy lever in metal. This means that maintenance can be carried out easily without draining the system.
  • Our ball valves have extra large openings to cope with the maximum flow demand at the end of the charging period and during self-circulation.
  • EPP insulation is standard.

Technical data 21-60

Pump: 6 m (non EU) (max 60 kW)
6 m ErP (max 80 kW)
Connections: Cu28, R32, R40, R50
Thermostat cartridge: 53°-55
Max. boiler output: 80 kW (see diagram above)


Additional information


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