230V rotary switch

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Rodinal

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Can anyone help out and give me an idea where I may be able to pick up a 230v rotary switch to replace the one in my dish heater. It needs to be suitable for use in a 10" x 24" B&W developer dish heater. The present one works, in as much it switches on and off, but won't provide the variable temperature I need to heat developer without going over the top, or constantly needing to monitor the thermometer. It also needs to be connected to the red light, telling me when it is off or on.
 
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It should be a variable resistor, also called a rheostat, possibly with an on-off switch at one end. You're going to need the spec for it, likely available online via Google from the model number etc in order to get an equivalent. I'd try someone like RS components, CPC Farnell or similar.
 
As per @ancient_mariner I'd be combing through RS Components, Premier Farnell or CPC (another Farnell brand)

On the heating front - is there a thermostat? (Again RS, Farnell, CPC are usually good for it)
 
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RS Components, I had forgotten about them!

Yes there is a thermostat - of sorts - it is a bi-metal strip that works when it warms up, then breaks the circuit and the power goes off. It is the two contacts are so burnt that it no longer works. They were originally adjustable but now the contacts are so badly burnt, all adjustment is out of the scope of the screw adjuster
 
It would be better to get a thermostat with a remote sensor,
Something like an underfloor heating controller will switch up to 16A without an additional relay, and the sensor can be mounted on the outside of the tank covered in styrofoam or similar
A red light could be connected across the heater element if you want to see when it is on.

Will hold it within +- 0.5C
 
The descriptions given on RS's 'on line' catalogue are a bit vague. The ones they have that are about the same size appear to be low voltage. I have to have one that is 230V and can handle 150w. I will speak to them on Monday. It's not urgent, just the large heating surface is ideal for a 12x16 dish. There is a red light already on the heater and there is a 'pigtail' connector with two wires and flat blade connectors (3mm) which will easily connect to a suitable switch.

Using something as large as an underfloor heating system switch will probably physically be too big to fit. The heater is not a 'tank'. it is a flatbed dish heater on which you place dishes containing paper developer, stop bath or fixer
 
Yes, it would probably be too big to fit in the original location. Mine was fitted to a small plastic box with a cable going to the heating device, which it would already have.

It was similar to this https://www.ebay.co.uk/itm/37452962...DchMPz5t8zGFSmruTCK7eZMuo=|tkp:Bk9SR_L1lt6HZA

I had another digital one that controlled a 2 kW fan heater in the conservatory. That one had a 13A socket in the box, so it could be used on anything up to 3kW

The only reason for a "underfloor heating thermostat" is that they switch a reasonable current, whereas a CH thermostat often can't.

Not actually certain what the original was, as a switch would require external control or resistors, and would only give a certain number of set options depending on the number of poles on the switch.
Someone mentioned it might be a rheostat, if so it will be hard to get at a reasonable price.
 
The possibility of a remote switch where there is liquid in an open dish is a non starter. It has to sit inside th heater itself where it is sealed away from liquid. More so when I will be working in reduced lighting I need to ensure it is safe. I will see what RS has when I speak to them.
 
Rodinal said:
The possibility of a remote switch where there is liquid in an open dish is a non starter. It has to sit inside th heater itself where it is sealed away from liquid. More so when I will be working in reduced lighting I need to ensure it is safe. I will see what RS has when I speak to them.
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How does power get to your heater?
 
Normal 13a x 3 pin plug into the outer casing via a sealed rubber grommet. It is the breaking the waterproof seal that I am VERY reluctant to do. Nor do I like the idea of cutting the cable and splicing in the new switch externally. It has to go into the same hole as the old one with anew silicone grommets. Believe me I have tried to think of about a way around it, but replacing 1 for 1 is the only safe way to go.

(sods law the RS website was down earlier today so cannot have another look at the switches they hold.)
 
Dont put the new switch in the heater then, add it to the power feed in and turn the heater switch to continous. The thermostat will just tunr the power on and off as needed. The switch can be anywhere then near the mains plug maybe.
 
Nope! That will leave a hole in the side of the heater about 15mm across. It is easier to follow the original design.
 
swanseamale47 said:
Dont put the new switch in the heater then, add it to the power feed in and turn the heater switch to continous. The thermostat will just tunr the power on and off as needed. The switch can be anywhere then near the mains plug maybe.
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Exactly, doesn't add any hazard at all!!!
 
Rodinal said:
Nope! That will leave a hole in the side of the heater about 15mm across. It is easier to follow the original design.
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Probably 5/8" hole, but a 15mm blanking plug will seal it effectively and neatly.

I'm afraid I done see any logical reason for your obsession for making it "original", which I am sure isn't going to be "easier", so leave you to it and say good luck :)
 
Sangoma said:
Probably 5/8" hole, but a 15mm blanking plug will seal it effectively and neatly.

I'm afraid I done see any logical reason for your obsession for making it "original", which I am sure isn't going to be "easier", so leave you to it and say good luck :)
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By having the switch remotely located, because of the nature of the beast, using it with open dishes there is always a bit if jiggling about to get the temp accurate every time it is used because it is largely dependant on the ambient temp of the room. (Have you actually ever used one?) and where the master switch is located away from the workbench, it will be very inconvenient to keep going over to check or alter it. I prefer to keep it as it was designed that way I know it will be electrically safe. Not an obsession.

P.S. It isn't a 5/8" hole, it is 15mm. Made by Kaiser in Germany is the clue! They didn't use imperial measurements.
 
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Rodinal said:
By having the switch remotely located, because of the nature of the beast, using it with open dishes there is always a bit if jiggling about to get the temp accurate every time it is used because it is largely dependant on the ambient temp of the room. (Have you actually ever used one?) and where the master switch is located away from the workbench, it will be very inconvenient to keep going over to check or alter it. I prefer to keep it as it was designed that way I know it will be electrically safe. Not an obsession.

P.S. It isn't a 5/8" hole, it is 15mm. Made by Kaiser in Germany is the clue! They didn't use imperial measurements.
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Yes, I have, and I have a home made one for film developing. Also used a very large version for litho negatives and plate making, which I modified for remote thermostat.

The sensor is either in the liquid or in close contact with the outside of the container, and if you only require one temperature, once you have found that on the dial (or display if you choose a digital version ) you don't need to change it again. Like any thermostat it will turn on slightly below the set temperature and turn off slightly above the set temperature (hysteresis)
A modern electronic thermostat is going to be better than an older mechanical one.

I think that one wire going into it will be as electrically safe as another wire going into it carrying the same voltage, as long as any wire is properly fitted.

My apologies for guessing it was made in the UK, I didn't notice where you had said "Made by Kaiser in Germany" before :)
 
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