Heating time for a 1100 liter hot tub using Vilpra Wood heater


The chart shows how the heating up of our model "HT150 prestige" works while using a Vilpra Wood heater. To warm up water of 1100 liter from 6 till 37°C takes about 3 hours. The chart shows also that water, which is rising towards the surface is warmer than the water on the bottom of the hot tub. This process is what we call "the thermosiphonsprinciple". Warm water rises towards the surface whereas cold water descends towards the bottom. In using this you obtain an effective self-circulation provided that the pipes, which go in and out are placed at the right spot.

Vilpra Wood has got a very good efficiency compared to other heaters which are placed on the inside of the hot tub, where the heat evaporates directly via the chimney pipe. Another problem with those types of heaters is that the temperature is concentrating around the heater itself. Our hot tubs including the Vilpra heaters, which are placed on the outside of the hot tub have been specially designed to heat up water quickly and equally.

Comments to the chart:

The metered measurements have been registered by a 4-channel HOBO logger and then compiled graphically in Excel. Each of the 4 lines represents its own measuring point. The red line shows the temperature of one of the spots, where warm water flows into the hot tub. Here it is also possible to see the burn-up effect (difference between the top and the bottom of the curve) and the fact that it is really important to fill up the heater with wood constantly. This and the quality of wood show the result of the total time for the heating up.
The green line shows the temperature of the second spot where warm water flows out.
The blue line demonstrates the temperature of 20 cm beneath the water surface.
The temperature on the bottom of the hot tub is indicated by the yellow line.

More details about heating effect of different heaters