Fermentation Fridge Heater - Power Rating?

[Fil]

the tube heater may arrive with a heavy flex fitted as its a 45w device its will be perfectly safe to run it with lighting/lamp flex which is much thinner

[Kev888]

Need to see what I can fit through the drainport - I can get my temperature probe through but I imagine it'll be close getting that and the heater flex. A fan as well? Quite unlikely. I'll consider a fan but I think I'll see what the performance is like first - The fact this fridge is quite so small means I think the heat will be pretty uniform without a fan but I'll keep an eye on it!

You can use very thin bellwire for the fan if its a 12v PC type of thing. Its not just about even-ness, but also heat transfer; air is pants at conducting heat but if you can circulate it even modestly (to supplement the convection currents) things can improve noticably, especially if/when crash cooling.

[TempTest]

Where would you locate the fan? Where should it be moving the air from/to? Position infront of heater? Some distance away from heater? How to ensure it also aids with cooling? Etc. I have such limited space in the fridge due to the small size I'm not sure it'll fit but if I know where it should be positioned I can have a look... Thanks!

[Kev888]

It depends on your setup and (as you say) where you can fit it. But it isn't critical, you really just want to encourage a gentle breeze around the fridge and especially over the cooling and heating surfaces, to stop (a) the cold air pooling at the bottom and the hot air at the top, and (b) to spread the heat to/from the cooling and heating surfaces rather than having to rely on convection alone.

It will still work without a fan if you wanted to leave it initially, its just one of those small improvements thats generally worth the effort. PC fans are good because their low voltage is safe around liquids and also they are very low powered so won't add any meaningful amounts of heat whilst you're trying to cool.

[Doingatun]

I've got a 40 watt in my under counter fridge, it works great

[TempTest]

to spread the heat to/from the cooling and heating surfaces

So should the fan run constantly? Or just when the fridge *or* heater (or either?) are on?

Thanks!

[sbond10]

I use a 25w ceramic heat bulb

[Kev888]

So should the fan run constantly? Or just when the fridge *or* heater (or either?) are on?
Thanks!

Assuming it is very low wattage than I'd have it running constantly. Its most important when the cooling/heating are running so you could stop it at other times, but theres no harm in keeping the air even/mixed at other times. If you decide to have the sensor in the air its also a good idea to keep the fan running so that the sensor gives a more representative reading.

[McMullan]

A 50W reptile heat cable is more than adequate for my beast of a fermentation chamber:

[TempTest]

the tube heater may arrive with a heavy flex fitted as its a 45w device its will be perfectly safe to run it with lighting/lamp flex which is much thinner

Hello,

My heater has arrived with a heavy flex fitting. Can you please give me a link to something suitable on eBay where I can buy a meter or two? I was going to head to B&Q but looking online I'd need to buy a whole reel which I don't need! Can you link me to/recommend something that is as thin (and flexible!) was possible while still being completely safe for a 45W heater? Thank you!

[Fil]

'0.5mm sq 3 core flex' should return results if used to search ebay etc..
http://www.ebay.co.uk/sch/i.html?_sacat ... lex&_frs=1

edit while im no electrician...

cable capacities are rated in amps, to give plenty of headroom lets assume your heater is 100w so how many amps is that??
http://www.rapidtables.com/convert/elec ... to-amp.htm
tells us 100 / (0.8 x 250) = 0.5A for an inductive load
or 100 / (1x 250) = 0.4A for a non inductive load,

if your ac supply is a little weaker
100w / (0.8 x 220V) = 0.56A for an inductive load
or 100w / (1x 220V) = 0.45A for a non inductive load,

and a quick google lookup confirms 0.5mm sq flex is good upto 3A/720w

http://www.diynot.com/pages/el/el003.php

**edit thought it best to show my working out as i am not a qualified electrician,

[TempTest]

'0.5mm sq 3 core flex' should return results if used to search ebay etc..
http://www.ebay.co.uk/sch/i.html?_sacat ... lex&_frs=1

Nothing seems smaller than 5.6mm outside diameter though which is not much smaller than what the header already has (and fits but without allowing me to squeeze other cables through, too). Even 0.5mm sq is still good for 3A at least but this heater at 45W is still a fraction of that.

Is something like this OK?

http://www.ebay.co.uk/itm/351211405229

Let's say, 3 core 26 AWG which should be ( http://www.powerstream.com/Wire_Size.htm ) suitable for 0.361A 'Maximum amps for power transmission'. 45W / 240V = 0.1875A. Should be much thinner. But safe? Or perhaps on the safer side 20 AWG (1.5A) and then fuse the plug with a 1A fuse? Any reason not to go this route?

EDIT:

Perhaps this, http://cpc.farnell.com/alpha-wire/1173l ... dp/CB16238 ? 3 core CSA 0.35mm², outer diameter 4.3mm which could be a big difference...

[Fil]

Im at my level of comfort looking up ratings for uk standard sized flex and going from there...

have you opened up the electrical connection end of the heater yet, Iirc mine when opened revealed a redundant earth wire, not grounded within the heater, either capped off or secured to a synthetic insulating post.. And i ended up using 2 core flat lamp flex as a result.
though im doubting my recall on this as it was a few years ago and the original length of 2 core flex has been butchered for a number of lil tasks... and my own fridge build is with an ex bottle fridge with an easy access top port into the chill cabinet resealed with putty. my need was for a longer length of flex to snake neatly to my connection block.
there are a number of options however,

Most fridges today have an single cold radiator clearly identifiable by the ice/condensation pattern that reveals it.. so the risk of putting a hole through the top or side and hitting a pipe is very low, and a hot screwdriver can be used to melt the shell and probe from the inside before any drilling takes place to be on the safe side too. and the wires for light thermostat etc will only be on the one side where they bulb etc are visible as a rule..

all the cables , heater flex, probe wire, and bell wire for fan, are flexible and could possibly be squeezed through with careful taping,

thread the 2 thinner wires through first, then sandwich the last flex between the 2 and tape spirally down using thin brown packing tape or similar, gaffer tape for example may add too much girth.. ensure the tape is all sticky down and as smooth as possible, and start the spiral inches above the point the 3rd flex is added so taped flex comes through the hole before the full 3 flex bulk .. it can be fiddly setting up, but its worth taking the time for a neat job,
Also dont cut the large flex off bluntly.

lube the flex, w/up liquid n water, tho a 'dry' grease may be better, vaseline, butter or marge even..
a 2nd pair of eyes/hands on the feed at the back to ensure it faces in straight will help as you pull through the fle combo.

OR ? strip off the flex coating sleeve either fully or partially the individual wires are coated with insulation and a handful of diddy cable ties can re bunch them together..

OR you can also consider opening up the drain hole, If doing this leave the bottom half of the smooth moulded drain hole alone and focus on enlarging the top half +, so that the drain exit path remains intact for any condensation rather than saturating the insulation/insides of the fridge through a corrupted/enlarged shell hole.

[BenB]

Well I'd be happy with 3 core 26AWG. The stated power rating for a cable is usually in free air rather than being stuck up the chuff of a fridge which will insulate it quite nicely. Can't see a cable producing much heat though at 50% of it's max rating though.... The outer insulation looks good and thick which would be my main worry with a cable without a specified maximum voltage..... Run on a supply with a RCD I wouldn't bat an eyelid.

We can approximate things using P=(I*I)R. Obviously we're talking AC here and so really need AC impedence not DC resistance etc etc. Anyway...

The resistance of 26awg cable is 0.245 ohms per 6 foot (on the basis of 40.81 ohms per 1000 foot). So passing 45W/240V = 0.18A through that you're looking at tiny amounts of heat production in the cable itself. 0.007938W from a six foot length. I think that won't be a problem!

[themadhippy]

personally i wouldnt use any of those cables linked to,the farnell cpc states its suitable for upto 300v,is that AC or DC? if its DC then its only suitable for 150v AC. Much better to use proper 0.5mm mains rated flex with a 3A fuse in the plug,leave a 13A fuse in there and you'll need a bigger cable.