Winter Heater

[Sour Kraut]

OK, as someone who deals with electronics daily (safety first), and as someone whose job it is to anticipate worst-case failure modes (broadcast station reliability and the ability of the hired help employed there to destroy absolutely anything with nothing), and as a beekeeper last:

Forget light bulbs

Forget running whatever you use on 120 (240 in Europe) volts; my preference would be a 12-volt system.

Here's my thoughts

Make up a bottom board that is about an inch deeper than normal

Place 4 25-ohm, 10 watt resistors in a square pattern, 1/3 and 2/3 of the distance lengthwise and widthwise from the edges

Wire them in parallel and bring wires out the rear, then pour the board full of epoxy resin to cover resistors and wires.

Set a 2-pole male connector in a recess in the rear of the bottom board (NOT a 'standard' plug !!!) and you can then run a master power cord, with mating receptacles, across behind a row of hives.

A 'metering cable' could be made up that can be inserted between the master cord and each individual bottom board periodically, to make sure current is being drawn and thus heat produced.

I calculate the heating power of the proposed bottom board to be as follows: 
12V / 25 ohms = 0.48 amps per resistor

0.48 x 0.48 x 25 = 5.76 watts per resistor.    Times 4 = 23 watts approximately

Further refinement would be a master controller that adjusts voltage to the common power cord as outdoor temperatures change.

Just my $ 0.02..................

[ScituateMA]

We may need to wait on Finland for the definitive winter expert :laugh:….. but I’ll take a stab at it in the mean time.  :)  

First off, what are these “bulbs” you’re talking about?  Incandescent light bulbs?  We do know incandescents will generate a lot of heat since they’re so inefficient (but this is another story).  They will work, but I can see some issues with them.  

Maybe a mini DFMEA is in order?

If anything drips on a hot incandescent bulb, poof and the bees freeze.
Light does stimulate the bees.  There is a risk you will get them too active.
How are you going to regulate the hive temp?  Power cycling bulbs is hard on them.  You could put them on a dimmer (TRIAC), but you would still need some way of controlling the TRIAC as a function of temp.
How are you going to avoid electrocution?  An exposed broken 120VAC bulb in a wet location is a quick way to go.  

I’m not trying to be negative; just pointing out some issues to consider.  What I have done over two separate winters is heat some nucs and hives with 12VDC and 24VAC power sources.  Those are low voltage circuits and are considered safer than 120VAC because your skin is an insulator at low voltages; provided you’re not dripping wet.  If you do use 120VAC, at least have it on a GFCI circuit breaker!

Personally I think there are probably better heat sources than a light bulb.  Finski has used aquarium heaters and I have used heaters I built from power resistors (2W resistors in series).  I think another relatively safe option would be the use of plumbing heat tape which are probably hitting the shelves in MN about now.  Lots of people use those outside in the winter, they are low cost,
they have a temperature regulator around 40F, and they are pretty well insulated/safe.  I bought some to keep some CU pipes warm last winter for about $25.

You’ll have to provide more detail about your hive design before I can visualize what it looks like.  I think a simple pancake shaped heater (potted in cement) would work fine to just slip into the hives bottom entrance.  No special bottom system needed.  Slip it in, plug it in, and you’re good to go.  

My experience would suggest not to overheat the bees in the winter, but the right amount of heat really does wonders!

hi I just bought 1/4 watt resistors to make a 15 watt heat mat for bees.60 resistors per mat and size like 10x15 inches.
 I was thinking to wire them in parallel not in series as you .did. Can you pls tell me if series would be
and how did you cover the resistors?
better?