Furnace DIY » Furnace Repair » Barnstead Thermolyne Muffle Furnace
Barnstead Thermolyne Muffle Furnace
Question
I’ve got a little Thermolyne oven (Thermolyne F-A1730, 1093C, 9″x8″x13,” 240v) that was built way back. The controller consists of a contactor (relay) that drives the elements and is switched on/off by a rheostat (labeled 0% to 100% time on) that drives a coil wrapped around a bi-metal strip that pushes a momentary contact switch when sufficiently heated. A meter (connected directly to the oven sensor and not part of the control circuit) shows the oven temperature (0C – 1200C) and reaches full scale with 70ma. I’d like to replace this with something a bit more up-to-date. I could probably duplicate its function with a timer circuit with variable on/off, but it would be nice
to have a thermostat mode that used the sensor to keep a constant temperature.
Anyone designed and built something like this? I’d love to get pointers to schematics, books, web sites, etc.
Answers
There are tons of fairly cheap, exceedingly reliable devices (many
multifunction/ramp ones under $500, some much cheaper, less than $200,
depending on the desired functionality). There are on/off controllers
for even less. The Omega company sells slightly overpriced products
using a very well written set of catalogs that explain things very
well. There are many other vendors selling the same sort of things
(Dwyer is a pretty good discount vendor). Surf over to
www.thomasregister.com and check out the listings under “controllers:
temperature” (don’t hesitate to register with them, Thomas Register is
_the_ industrial yellow pages, very well respected, and found in every
library.) After the initial page of listings comes up, you can narrow
to your state using the selector on the bottom of the page.
You can also check out your local phonebook under “thermocouple”.
Those companies will probably send out a rep to your site to see your
set-up and recommend an item. What you want to do is standard fair.
Basic controllers (<$150) just check the temperature and turn their
relay either on or off. Middle range controllers ($200-$600) can hook
up to anything that gives them thermocouple or any other sensor
feedback and then control virtually anything through either built in
relays or proportioned outputs. High end controllers (>$600) can put
your furnace through controlled ramp schedules, remember multiple
schedules, and interface with a computer for datalogging if you want.
It’s pretty much determined by the price you want to pay.
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