aquarium heater only 36 deg c

[unibonded]

I've been looking at aquarium heaters to use with my Jobo CPP-A as the heater element isn't working (in case I can't get it fixed). Trouble is, after much searching I can't find one that goes up to 38 deg c, 36 is as hot as it gets. For colour is this going to be a major problem, Obviously colour film processing is temperature critical, is processing at 36 deg c going to mess things up??

 

[amuderick]

There is a solution! Find a cheap aquarium heater with a dial on the top. You don't want anything digital or anything 'precise'. Inside the unit, the dial turns a screw which levers a bimetallic strip. As the temperature increases, the strip warps until 'click'...it makes contact and shuts off. Upon cooling, it de-warps and 'click'...it breaks contact and turns the heater back on. All you have to do is turn the dial to its hottest setting, pop it off and put it back on facing the lowest setting. Bingo. You just reset the temperature range of the dial. Now, turn it up towards hot again until you reach your desired temperature. Does this make sense?

 

[Mike Wilde]

Like he said - bi-metallic is the way to go. I picked up 2- 300W ones on close out from Super Pet when they changed the packaging. My theory on two was that the day would come when the first one would break just when I needed to do a batch of c-41. Sure enough, that day happened about a month ago. I'm on the look out for a new spare. I use mine to temper chems and film tanks in a water filled picnic cooler.

I take the little stop tabs and break them off to let me wind the temp setting higher than what fish are comfortable at. Once I get it set to the temp I want, I cover the top of the unit with a stcky goo called duct seal which is meant for sealing electrcial wires in conduits to exclude moisture ingress. Then I can stick the lid on the cooler to cut heat loss and not worry about condensation getting into the part of the heater that the manufacturer considers as normally operating in a low moisture environment.

In the interest of safety you do power the thing on a GFCI/RCD protected power outlet, right?

 

[unibonded]

Great stuff, thanks for the advice, I'll see if I can get hold of a dial bi-metallic heater. Well actually I'm hoping I can get the heater in the CPP-2 working again, it's off on a trip to Germany for repairs. If all else fails though I now know what I can do. Good advice about the RCD too Mike.

 

[darkroom_rookie]

Find a cheap aquarium heater with a dial on the top. You don't want anything digital or anything 'precise'. Inside the unit, the dial turns a screw which levers a bimetallic strip. As the temperature increases, the strip warps until 'click'...it makes contact and shuts off. Upon cooling, it de-warps and 'click'...it breaks contact and turns the heater back on. All you have to do is turn the dial to its hottest setting, pop it off and put it back on facing the lowest setting. Bingo. You just reset the temperature range of the dial. Now, turn it up towards hot again until you reach your desired temperature.

Could the heater shown in the picures work for keeping 38 degrees C?

 

[Mike Wilde]

Good chance. Hard to tell from the photo. I like the stainless steel cover. Mine is glass. It does show me that the thermostat contact is quite low in the body, which is handy when the water bath level drops when you remove a bottle to use it. This one from the low and normal working levels suggests that the temperature sensor is up higher.