Modifying controls on Viking Hood
MarineEngineer
| Posted in Energy, Heating & Insulation on
I’m helping out a friend who is an HVAC guy in NYC. We’ve installed ducting for a multifloor kitchen exhaust system, and today reinstalled the Viking Hoods with the fans removed. There is a fan on the roof that will do the sucking, and dampers that open or close (and start the fan) for each kitchen.
What my friend wants to do is to modify the existing hood controls, specifically the now no longer used fan rheostat, to generate a 2-10VDC signal to operate the motor (or a 4-20mA signal would be just as good). I’ve got the hood control module at home, tried googling the PCB but have come up empty. It’s a Worldtronics 20-22552.
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| Blackstone 21 Astor Place |
Here’s a link to the web album with pics from the job.
any ideas on how to proceed? Much thanks.
Jonathan
Replies
So the roof fan will suck open the dampers?
On the other side of it I would think that you could accomplish what you want with a low voltage relay.
"When the spirits are low, when the day appears dark, when work becomes monotonous, when hope hardly seems worth having, just mount a bicycle and go out for a spin down the road, without thought on anything but the ride you are taking." — Sherlock Holmes, 1896
no the roof fan will suck the cooking fumes. the dampers will open with a switch providing a 2-10VDC signal (proportional) or a 4-20mA signal to a 24VAC motor. We're trying to figure out how to generate this signal, hopefully using the existing controls. But I don't have a drawing for the existing controls, and don't know how to figure it out.fair winds and following seas
ME,
Put a 24v 2 position damper actuator on the damper, replace the rheostat with a similarly sized binary switch, mount the power supply in an accessible location. Put an end switch on the damper if there aren't proof of closure contacts on the actuator, to start the fan or to energize the fan start circuit and Bob's your Uncle.
Don't try to use a rheostat to run a 2 position actuator, you WILL have problems and the proper switch and actuator are cheaper and easier to put in now rather than later when you look (and feel) like an idiot.
If you need a multi-speed fan control the we can go there but it doesn't sound like it.
First of all the current fan speed is not controlled by a RHEOSTAT.
It uses a potentiometer with other electronics to operate a TRIAC. That is a an electronic switch that chops the power at each AC crossing to change the "average" voltage available. The same type of systems are what is used with light dimmers.
That board appears to be custom made for this application. World Tronics might just be the manufacture or the designer/manufacture. In any case you won't find any off the shelf replacement.
How "standard" do you want this change? That is anyone in the furture can figure out what was done and replace things.
You might get lucky and be able to connect a transform, rectifiers, capacitor, and a few resistors and in place of the current motor and get it to generate the 2-10. Actually it would probably end up 0-10, but that should be OK. But it also might only go down to a higher minimum because motor probably does not want to run below a certain minimum voltage. That may or may not end up a problem for you.
HOWEVER, unless there is special circuitry Triacs need minimal loads on them are they won't fire correctly and the output will be very eradic.
But if you can have a resistor (or light bulb) of 50 to 100 watts across it then it would probably work.
Any other solution would lose the timer features.
Looking at the construction of the board it would appear that it would not be easy to cut the connections to the potentiometer and use them to feed some other electronics.
Nor remove the pot and put a new one in it's place.
You can probably get a control relay that monitors the 2-10 (or 4-20) and use it to trigger the dampener at a selected point.
I have not been through these sites to see what all they have. But here are some sources of control modules and converters.
http://www.omega.com/ (looking under Process Controls and maybe Automation)
http://controlsignalconverter.com/
http://www.axiomatic.com/signal.html
And here is a forum on controls.
http://www.control.com/
William the Geezer, the sequel to Billy the Kid - Shoe
thanks for all the info. My friend was hoping he could reuse the "fan dial" on the existing controls for cosmetic reasons, but if he can't, he can't.The damper motors aren't two position, but variable position, with a 24VAC motor to open, and a spring to close.My role in the whole thing was to keep his mechanics on track, coordinated with each other and the other trades on the job, and to be the aggregator of information. We got all the ducting installed, hung the hoods yesterday, and are attending to details today.We're going to run test the system tomorrow, and just open the dampers by hand until he can figure out the controls. I told him I'd look into it, but it's beyond my skill set.I'm at a Cosi for lunch for the free wifi, thought I'd check in on BT and see the latest.I leave for sea in three weeks ... joining in Suez this time.thanks again for all your help.Jonathanfair winds and following seas
We bit the bullet and installed an additional potentiometer on the hood in each kitchen. Supplied it with 24VAC and configured it to output a 2-10VDC signal. This we sent to the Honeywell damper motors (also supplied with 24VAC for power) and installed a mercury switch clamped to the end of the damper shaft to send a signal up to the boiler to start and stop the fan.
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Jonathanfair winds and following seas