any electricans about?

Discussion in 'Shop Talk' started by 65284, Apr 11, 2005.

  1. 65284

    65284 Well-Known Member Supporter

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    Location:
    Missouri
    I have a problem I can't solve on my own. I have tried to hire several persons but it isn't a lucrative enough job and no one is interested.

    Problem, I have an older incubator with the wafer and snap switch type controls and the snap switch went bad.

    I wanted to upgrade from this type of controls anyway so I bought controls from the Petersime Incubator Company. I hope this description is understandable to someone.

    These consist of a box with a face plate made of some sort of composite material. The plate has 2 clips, similar to the old automobile type fuse block clips. There is a glass "thermometer" a tube that contains mercury and has 2 metal bands around it and a wire that go through the tube and these bands, the bands snap into the clips. When the temp rises to the proper level the mercury expands and contacts the wire and shuts off the heating element.

    There are also 3 terminals on the front side of this face plate, Red, White, and Black that extend through to the back side. There is a brass bar from the white terminal to one of the thermometer clips. It came with a moveable jumper wire attached between the black and white terminals. I have no idea if this is relevant or not.


    Screwed onto the back side if the faceplate is a block that says "Douglas Randall solid state relay, model a25a nc". There are 4 screw down terminals (at least that's what I think they are called) numbered 1,2,3,4, there is a line drawn between 1 & 2 with what appears to be a switch symbol in it, on the left side of the "switch" it says 120 vac on the right side of the "switch" it says 25 amperes. There is a line between 3 & 4 with a circle in the center, on the left side it says 90-260, on the right side it says vac. There is a red wire from the bottom of the plate (the red terminal) to # 1 on the relay. There is a black wire from the black terminal to #2 on the relay. There is a yellow wire from the clip where the metal band on the thermometer snaps in to #3 on the relay. There is a brass bar between relay terminals 1 & 4.

    On the old controls there were 2 wires 1 white and 1 black. The new seems to need 3 wires. How do I proceed from here?

    Any help will be appreciated.
     
  2. PezzoNovante

    PezzoNovante Well-Known Member

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    Jun 10, 2002
    Location:
    Texas
    An educated guess is that it is wired for make on temperature rise (cooling) and make on temperature drop (heating) and uses a different mercury bulb for each function.

    The "nc" probably means "normally closed" - temperture below setpoint = closed contact (heating)

    I suggest you take the controls to an electrical supply house and humbly ask someone behind the counter to explain how to connect it. Visit after 9AM when they aren't busy loading out contractors.

     

  3. Runners

    Runners A real Quack!

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    Nov 6, 2003
    Location:
    Near Callands, Virginia
    Please tell me where I can get those bulbs!!!!

    I'm just finishing building a large incubator, and I've been looking for those thermostatic bulbs for months!

    Hooking this up should be pretty straight forward, you'll need a volt ohm meter.

    You're right, as the temp rises, the bulb will close the contacts (or in this case, energize the relay). Your heating element would tie into the control relays common and normally closed contacts. It should call for "heat" when the relay is de-energized with this thermostatic bulb system.

    Using your VOM (volt-ohm-meter) find the NC, C, NO terminals on the relay (or sets of them, depending on the number of poles it has).

    Keep in mind, it's best to have a fail safe, wafer or something as a backup, because your heating control relay will continue to energize the heating element until it becomes energized. (does that make sense?)

    OK that's how it should work.

    "Screwed onto the back side if the faceplate is a block that says "Douglas Randall solid state relay, model a25a nc". There are 4 screw down terminals (at least that's what I think they are called) numbered 1,2,3,4, there is a line drawn between 1 & 2 with what appears to be a switch symbol in it, on the left side of the "switch" it says 120 vac on the right side of the "switch" it says 25 amperes."

    Sounds like th relay is rated for 25 amps @ 120 volts AC. The line between 1&2, if it has a little perpendicular bar or arrow on the end of it, that IS the switch to your heating circuit that the relay controls. What ever end has the little arrow, or is touching a "contact", dot or whatever, that is your NC (normally closed) contact. The other end is the common. Those are the terminals you want to wire your heating element to - AFTER you confirm this with the VOM (zero ohms).

    " There is a line between 3 & 4 with a circle in the center, on the left side it says 90-260, on the right side it says vac. There is a red wire from the bottom of the plate (the red terminal) to # 1 on the relay. There is a black wire from the black terminal to #2 on the relay. There is a yellow wire from the clip where the metal band on the thermometer snaps in to #3 on the relay. There is a brass bar between relay terminals 1 & 4. "

    Sounds like the bulb is rated for line voltage, 90-260vac, and the terminals 3&4 are the actual thermostatic bulb in your schematic. The brass bar is forming a common between the relay coil and the common on the relay's switch side (terminals 1 sounds like the relay's common, #4 sounds like the bulb)

    Power (the scarey part) .... confirm it all with a VOM before you do ANYTHING else. If they have a web site (place where you bought this), post it, 'cause I'll buy one and tell you how to wire it up.


    If that sounds like a pain to figure out, you can buy those micro switches for $10-20 and most electronic stores.
     
  4. 65284

    65284 Well-Known Member Supporter

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    Hey, thanks guys. Runner I bought these controls several years ago from the Petersime Incubator Co, 303 N. Bridge Street, Gettysburg, Ohio 45328. The phone # is 937-447-2151.

    There is a Petersime Incubator Co. website but it isn't this company it is some Dutch outfit and entirely unrelated. I doubt there is a computer anywhere in the Ohio based Petersime Co.

    They are sort of hard to get a hold of, I think there is 1 older lady that IS the office staff. Just keep trying, once you do get someone they are very helpful and very nice. I have dealt with them for many years.

    I had been trying, without success, for a couple of days to reach them when I decided to try here, about a dozen busy signals and then the "leave a message" recording.

    If you do buy something from them and get it set up please let me know how to do it. I do appreciate your attempt at explaining things to me but I am ignorant of electrical terminology. My knowlege is so limited, I need to know where do I put the black wire and where do I put the white one. I do know how to changing light bulbs and turning switches off and on, and that is about the extent of my expertise in this field.
     
  5. Timber

    Timber Well-Known Member

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    Jun 15, 2003
    Location:
    NE Ohio
    On your SS relay from what you're saying, terminals 1 and 2 are your contacts load side. Terminals 3 and 4 are the control side, the control voltage can be anywhere from 90 volts to 260 volts AC to turn on the relay. 1 and 2 are the load (heater) high current circuit and 3 and 4 are your low current control circuit.

    Maybe I could render some help, few questions. What is the switch symbol between terminals 1 and 2? Does it appears to be open or closed switch? Also the face plate composite material are you saying this is just some insulated material not some form of a heater with internal wiring (like a hot plate) to the 3 terminals?

    Looking at this at a safety stand point using NC contacts are not too safe. If the function of the bulb to check temperature raise to energize the relay to shut off the heaters. Then if a mishap the bulb breaks or bad connection on control wiring will leave the heaters on unprotected, cooked eggs or worst.

    Timber