Brewfridge heater recommendations
- Thread starter Martybhoy
- Start date
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ericmark
Regular.
8W bulb.
The problem is the heavier the heater the more heat it retains after being switched off, so you want something light, also as the heater gets larger so hysteresis increases, so needs to be a low wattage, putting the heater inside the brew like with a aquarium heater ensures fast transfer, but in the main transfer is slow.
So I did an experiment, heart of Winter I put an Energy meter on the supply to my heater at that time a demo underfloor heating tile 18W and by using the time and total kWh used I calculated it needed 5W to maintain temperature of 20 degs with ambient of zero degs so to ensure a little leeway 8W seems reasonable.
I used the freezer compartment of a fridge/freezer to start the brew, because of the motor I leave the bottom draw in place with a tray to stop any spot heat from bulb and simply have an 8W bulb in a bulb holder which sits under the fermenter. Actually a compact fluorescent bulb and it is ample. I never get a cycle between heating and cooling, and the sensor is held to side of the fermenter with sponge so monitoring actual fermenter temperature not air temperature.
Although I still use the 18W tile in the fridge, it is really both too big and holds too much heat, if as with me the fermenter is moved from the freezer to fridge after first 8 days the tile works well as at the correct temperature to start with, and no longer is the brewing producing heat, plus it is acting direct on the fermenter not just heating the air.
Oddly on cooling the over shoot is not a problem, however I am using a frost free freezer, this means when on cool there is a circulation fan running, putting in a fermenter which is around 4 degs too warm will normally cause the freezer to run three times, monitoring air temperature when the thermostat is set to get fermenter to 19 degs the air temperature will drop to 8 degs, on first run, and it showed me how really you need to measure fermenter temperature not air, I did experiment with sensor in the brew and pressed against side of fermenter under a sponge so sponge stopped it reading air temperature and the difference was only one deg so I felt not worth the chance of contamination having the sensor in brew, it is just pressed hard against side of fermenter under a sponge.
Clearly from what I have said if you also have a fan running inside the fridge or freezer than you could use a larger heater and you could also measure air temperature without such a massive difference between to air and fermenter temperature, with chest freezers with two fermenters in the unit it may be better measuring air temperature, however the sensor needs putting on a heat sink so the fridge/freezer motor runs for at least 10 minutes each time it starts, to switch on the fridge/freezer with less than 5 minutes between each run and damage it, hence using the fermenter as that heat sink is a good idea.
Although a 60W heater in the brew is OK, outside the fermenter it is far too big, I would say even my 18W heater which the fermenter is sitting on so in good contact is too big.
The problem is the heavier the heater the more heat it retains after being switched off, so you want something light, also as the heater gets larger so hysteresis increases, so needs to be a low wattage, putting the heater inside the brew like with a aquarium heater ensures fast transfer, but in the main transfer is slow.
So I did an experiment, heart of Winter I put an Energy meter on the supply to my heater at that time a demo underfloor heating tile 18W and by using the time and total kWh used I calculated it needed 5W to maintain temperature of 20 degs with ambient of zero degs so to ensure a little leeway 8W seems reasonable.
I used the freezer compartment of a fridge/freezer to start the brew, because of the motor I leave the bottom draw in place with a tray to stop any spot heat from bulb and simply have an 8W bulb in a bulb holder which sits under the fermenter. Actually a compact fluorescent bulb and it is ample. I never get a cycle between heating and cooling, and the sensor is held to side of the fermenter with sponge so monitoring actual fermenter temperature not air temperature.
Although I still use the 18W tile in the fridge, it is really both too big and holds too much heat, if as with me the fermenter is moved from the freezer to fridge after first 8 days the tile works well as at the correct temperature to start with, and no longer is the brewing producing heat, plus it is acting direct on the fermenter not just heating the air.
Oddly on cooling the over shoot is not a problem, however I am using a frost free freezer, this means when on cool there is a circulation fan running, putting in a fermenter which is around 4 degs too warm will normally cause the freezer to run three times, monitoring air temperature when the thermostat is set to get fermenter to 19 degs the air temperature will drop to 8 degs, on first run, and it showed me how really you need to measure fermenter temperature not air, I did experiment with sensor in the brew and pressed against side of fermenter under a sponge so sponge stopped it reading air temperature and the difference was only one deg so I felt not worth the chance of contamination having the sensor in brew, it is just pressed hard against side of fermenter under a sponge.
Clearly from what I have said if you also have a fan running inside the fridge or freezer than you could use a larger heater and you could also measure air temperature without such a massive difference between to air and fermenter temperature, with chest freezers with two fermenters in the unit it may be better measuring air temperature, however the sensor needs putting on a heat sink so the fridge/freezer motor runs for at least 10 minutes each time it starts, to switch on the fridge/freezer with less than 5 minutes between each run and damage it, hence using the fermenter as that heat sink is a good idea.
Although a 60W heater in the brew is OK, outside the fermenter it is far too big, I would say even my 18W heater which the fermenter is sitting on so in good contact is too big.
