Safe, waterproof, low voltage greenhouse heating

Although it’s possible to grow all year round in an unheated greenhouse, adding greenhouse heating makes a huge difference in the winter months. Plants grow much better with in a greenhouse with heating, and you can start growing much earlier in the season than you would be able to in an unheated greenhouse.

Harvst 4-season mini greenhouses can be fitted with heating to help you grow more, all year round:

Both heated seed trays and the heater cable are only compatible with the Harvst smart control system, and should not be connected to any other power source.

The control units in our 4-season greenhouses can power up to 6 heated seed trays to germinate faster, 3 heated seed trays and a 4m low voltage heater cable for general greenhouse warming, or two heater cables.

Heated seed trays

heated seed tray
Heated seed tray

Harvst heated seed trays have holes to drain off excess water and unlike other heated seed trays they are designed for a damp, irrigated space.

They are standard deep seed tray size (38 x 24cm), with a heater pad set between two layers.

The heated seed trays are designed to be used with Harvst soil moisture and temperature sensors, which in conjunction with the Harvst control app, will let you set any temperature you like.

Soil heater cable

Heater cable in greenhouse
12v heater cable

Harvst 12v heating cable / soil warming cable is suitable for laying around the inside of the greenhouse frame to warm up the interior, or for laying in the soil under the greenhouse.

Supplied as a 4m length, it’s strong, waterproof and reliable.

The heater cable is self-regulating, which means it stays at a constant temperature regardless of the ambient temperature. On a colder day, it will use more power to stay warm, and on a warmer day, it will use less. The target temperature is approximately 50 degrees. Ensure it doesn’t come into contact with roots or plants.

How warm can the Sprout mini greenhouse get?

In the mild climate of the UK, keeping the interior of the greenhouse above zero degrees isn’t a problem in most areas for most years. For much of the UK winter, you can expect greenhouse temperatures well above 10 degrees C, especially if you’re combining your space heating with grow lights, which also give off a lot of warmth. The heated seed trays have a maximum temperature of 40 degrees (indoors), and because the heat is being delivered more directly to the plants, can get warmer than the surrounding air. You do need to ensure you have a soil/temperature sensor in the soil of the tray so your plants don’t overheat.

Can I run heaters with a Solar Sprout greenhouse?

No, unfortunately there’s just not enough energy from a reasonably sized solar panel and battery to provide the power that a heater needs.

How many heaters can I power?

The Harvst control unit and mains power supply has a maximum capacity of 150 Watts. Each heated seed tray is approximately 20W, which means you could run six at once, with a little safety margin.

Each heated cable is approximately 60W at max (this changes significantly based on how hard it’s self regulating). If you’re just running heater cables, then two is the maximum.

The control unit is smart enough to make the most of power, and also factors that you might be running hot grow lights too. If lights are off, both heater outputs can be run. If lights are on, then only the top heater output will be run.

Can I control mains powered heaters?

Not at the moment. In the future we may release a remote switch, controlled by the Harvst system. The inside of a Sprout mini greenhouse is a wet environment and non waterproof mains heaters should never be used.