The Craftmans Shop > New from Old
Puma / Dorman 6LE / MacFarlane B46B / 110 kVA Generator Resurrection
awemawson:
It's a point to consider but it doesn't overly concern me considering the intermittent use this is going to see occasionally driving my induction furnace for maybe an hour or so.
Without managing to source a suitable sensor with a curve opposite to this one I don't really see any other option, and this one was the only one I could find on the correct 'root stock' ie 1/2" BSP. My preference would have been an on/off switch operating at about 100 deg C - this would have avoided all the faffing about with electronics, but I couldn't find a suitable one!
I could get really fancy and use another controller input to sense that the sensor is passing current but that is getting over complicated even for me
RussellT:
It's too late now but here are a couple of links. I had to look as I was surprised you couldn't find one. Mind you at that price I'd probably be mucking about with electronics anyway.
https://www.asap-supplies.com/high-temperature-warning-switch-95-degrees-1-2-bsp
https://pressurevacuumlevel.co.uk/product/ts-tsp-temperature-switch/
Russell
awemawson:
Russell thanks for the links - yes I admit I'd found one or two at very silly prices!
John's comments set me thinking - I'd thought that the Deep Sea controller would only take a closed contact as an error signal, but closer reading of the manual, if I'm interpreting it correctly, is that the error state can be defined as open or closed, the open obviously being safer as John points out.
Now over temperature switches intended for surface mounting are readily available - in deed I've just bought a 70 deg C one to put in the relay box to cut off the fuel and starter relay feeds in case of fire. If I could somehow use the body of the original sensor to mount one of these all would be well.
I decided to eviscerate the device - I used an old 1/2" end mill naughtily in the tail stock chuck, and chomped out all the filling gunge and eventually the sensor itself emerged on the end of the end mill!.
Then I turned a slug of brass to fit inside, along with a platform to fit on top to take the actual switch - all a bit crude but it should work.
Then ONCE MORE ! I managed to melt it all while brazing it together. I've run out of proper silver solder and have been using Harris Phoson which has a melting point of 732 to 815 degrees C which is obviously too high for the brasses that I've been using. (It's excellent with copper and needs no flux - beloved of the Heating and Ventilating Engineers!)
So - what to do? Well stop being so miserly, dig out that nice big bar of silicon bronze (I think) that's been in my stash for years, and make one from fresh.
So into the Beaver CNC mill to have a hex put on one end (just using the machine as a dividing head) then make the rest in the lathe. Came out OK - no brazing required so no more oops moments.
Now the switch is obviously not in the water but gets it's heat by conduction through the bronze bar which IS immersed in the cooling water, so there may be a degree or so difference actually at the switch, but these switches are available in a whole range of trip temperatures so if necessary I can put a 95 in rather than a 100 for example.
mc:
I was just going to suggest those temperature switches, as I happened to replace one at work this morning on a driveline compressor, with a new modified sealed switch unit. It's only taken this supplier about 15years to finally come up with something that might last longer than a couple years on the underside of a vehicle!
I'd like to know where they got the new switch, but it had been bonded into a bit brass/bronze (I'd guess about 3/4" thread, but it's an Italian compressor so it could quite easily be metric..), with no obvious information.
I'd guess the switch came with flyleads, as it had very flexible wiring in a high temperature sheath, with a superseal connector heatshrunk on the end.
Whatever it is, they must be available cheap from somewhere, as the whole assembly only cost about £60, whereas the old unit which was a brass/bronze plug with one of those surface mounted switches attached with some heat transfer compound, used to cost about £80.
mc:
Just done a bit googling, and I'd guess what I fitted today was something like this - https://cpc.farnell.com/microtherm/t11a10005u112l310100/thermal-switch-nc-100-c/dp/SN36221 stuck in the fitting, then held in with resin/epoxy.
The price would certainly explain why it was cheaper than the old surface mount switch.
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