Maintenance and working with a heatbead

Hi folks,

some time ago i built my own little heatbed:

First of all some facts about the heatbead. It is filled with regular filter sand. The first layer of sand is about 4cm (1.6 inch) then comes a layer of thin metal mesh together with the heating cable and on top of that again 3cm (1.2 inch) of sand. The temperature is controlled via a computer with a thermostat which measures the temperature in a depth of approximately 2cm (0.8 inch).
The temperature is hold at 22°C to 26°C depending on the outdoor temperature.

Till now i am very happy how everything works but i am wondering how often do you water the heatbead? At the moment i water it every 1-2 weeks with one liter. The surface is abotu 2 square meter. Do you think this is fine or would you water more/less?

Thanks for your opinions and experiences.

to my understanding the heated works by having heat in the roots while the plant is cold. It seems your’s is sitting inside, defeating the above purpose (or is it a non heated ver cold annex)?

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@antelion is correct. Cold air, warm roots.

I know. That’s no problem. The room is non-heated with an open window all the time. The temperature is just one degree warmer compared to the outside (2-9°C most of the time). So the temperature is all fine but i just don’t really know how fast the water in the heatbed evaporates and how often i should water the heatbed to have a moist atmosphere in the roots.

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I’m experimenting with yamadori heat beds this year and the watering issues are a worry for me in the uk so far this year, Its a struggle to keep the temperatures below 10c in the garden let alone in the greenhouses, I’m finding the bed heat is causing a lot of humidity under the pot for the first week and not drying the soil in the container, I use my good old finger poked down in the soil as a guide to moisture and it will depend on your soil mix and the amount of roots so each tree is treated as an individual regarding water and misting. I can’t see keeping your bed damp a problem as water is a great insulator of heat.

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Yeah, that’s my experience so far too. Watering the bed every week a little bit seems to be perfectly fine to keep it damp. The temperature problem is really annoying. Especially when the sun is shining. I try to regulate it with opening the window, closing the window and opening it again depending on the weather.

I bought a heat/cool thermostat system (looks the same as yours) but it will only work around at 1 fixed temperature setting, so this is running a huge extracter fan and keeps it under 10C/32F for dormancy, I have another outdoor fan heat to keep the temperature above freezing also I have some heat mats to complicate things a little more. the weather has been all over the place in the Uk it’s been above 32C this week,it’s tough to know what to try and replicate weather wise anymore.