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RandyM1911
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Posted: Fri Oct 3rd, 2008 03:01 |
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Snyder General Model # GUF075A012AN Mfr. Date 9/88
Blue wire to gas valve came off it's connection and I can't tell where it goes.
Here is a description of the wiring:
From Thermostat:
Green - to brown to coil on relay
Yellow - to white to A/C unit
Red - to pink to (thermostat in heat chamber?)
White (greyish) - to white to gas valve + to humidifier
Orange (not connected to thermostat) - to red to A/C unit + ground + blue to coil on relay + blue to 24 vac secondary on transformer
Does anyone have a wiring diagram of this unit or can someone tell me where the blue wire from the gas valve lands?
Thanks in advance.
Randy
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dkpd1581
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Posted: Tue Oct 14th, 2008 02:26 |
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Grab your meter, set it to volts, attach one end to the blue wire, the other end to a common or ground. Turn the t-stat to a call for heat.
If you have an induced draft motor in your furnace section, it will spin up and clear the burner chamber of any possible gas and prove the flue is clear for about 45 seconds. Around the 45 second mark you should see 24 VAC register for about 3-5 seconds. If so and the gas valve does not click or try to open, you are holding the +24VAC and it needs to go on the gas valve opposite the common or grounded side of the gas valve's magnetic coil.
If there is no signs of 24VAC you may be holding the common side. Repeat the same sequence above except take the one meter lead off of the blue wire and touch the now unhooked meter lead to the other side of the gas valve and hold it there (one lead to the opposite of the gas valve and the other lead left on a common or ground - on the board, transformer or even metal case of the unit). If you now see +24 VAC your blue wire hanging in space right now is most likely the common terminal to the gas valve.
If you have no inducer draft motor you will perform the same two tests only you will not notice the 45 second time delay on a standing pilot or spark to light system. If you have a Hot Surface Ignitor, there will be a minor delay for the ignitor to come up to heat and you will notice the voltage from the above tests on your meter as the glowing comes to its brightest and begins to dim just a bit.
Let us know
1*
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RandyM1911
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Posted: Wed Oct 15th, 2008 20:51 |
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I'm sure my original post was less than clear so here is an attempt to make things more understandable. The blue wire that's loose is connected to the gas valve and has come loose where it had been attached at the control wiring area. Hopefully the photos will make things clear to someone with knowledge of this system. If anyone has a wiring diagram of this unit I would be much obliged. There is none attached to the inside of the lower cover as there should be. What I really need to know is where the loose end of the blue wire connects. Thanks.
Thermostat Wiring
Thermostat to controls
Controls wiring
Thermo-Switch and Gas Valve
Furnace Label
Gas Valve
General View of Furnace
Last edited on Wed Oct 15th, 2008 20:55 by RandyM1911
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dkpd1581
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Posted: Wed Oct 15th, 2008 22:40 |
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Follow your wire pairs from the back of the T-stat to the inside of your furnace unit. You will find the white wire (W terminal from T-stat sub base) bundled in the brown sheathing connected to whats left of your low voltage terminal board (brown thing with screw connections on the front and spade connectors on the back).
Find where the white wire is spade connected to the back and then attach the blue wire to the front using the screw connection. Put the T-stat in a call for heat and check for proper operation. That should get you going.
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RandyM1911
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Posted: Thu Oct 16th, 2008 19:11 |
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Thanks for the advice. The white wire from the thermostat is already connected to the white wire that is connected to the gas valve via the screw connector on (what's left of) the low voltage terminal board. There are no other wires attached at this terminal point, either at the screw terminal or spade terminal connections.
I ASSUME from your first reply that the blue wire connected to the gas valve (the wire that has become dis-connected at the low voltage terminal board end) should land on the common/ground terminal of (what's left of) the low voltage terminal board. I would prefer not to guess at this so if you can confirm I would appreciate it.
There is no inducer draft motor or hot surface ignitor in this system. There is a standing pilot light with a thermo-couple, both of which are connected to the gas valve. The pilot is presently out. It's not clear to me if voltage needs to be present at the gas valve in order for the pilot to operate. It would appear not, as the only time there would be voltage at the gas valve would be when the T-Stat calls for heat, if wired as I assume above.
OBTW, the low voltage terminal board was like that when I opened up the cabinet. The mounting plate that it was attached to was mounted in front of the blower motor with the wires poking through the slot where the terminal strip had been fastened. I took the mounting plate off of the blower and pulled the wires back through the slot so I could see what was going on. Once I have a solid understanding of where everything gets connected I'll clean up the connections and make a new terminal strip.
Why is it so difficult to find a wiring diagram for this unit?
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dkpd1581
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Posted: Fri Oct 17th, 2008 01:34 |
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One reason that a wire diagram is hard to come by is that your unit is 20 years and one month old and is obsolete by industry standards. This is not to say its bad or to be derogatory, it has met its service life expectations and Manufacturers have a cut off time for certain products, information, and support.
The second reason that I think its hard is the fact that Snyder General has been out of business since the early 90's. Comfortmaker is a division of ICP and ICP does not publicly disseminate its literature. This supports the Authorized Dealer/Contractors - builds in brand loyalty where you must use X to get Y information/support/repair.
As to your gas valve, the pilot MUST be on first and the thermocouple MUST be sending a rectified DC voltage to the gas valve second or else nothing will happen to energize/open the gas valve on a 24VAC call from the T-stat - a safety feature of the valve. Pilot first, T-stat voltage after.
Unfortunately, without sitting there applying fudamental knowledge of orders of operation it will be hard to give you the spot on answer. Pictures do help but do not replace the actual eyes on. Your unit is not complicated at all, the problem lays in communicating technical information without having the full thing there for basic examination. That blue wire will serve either:
1 Send 24VAC to or from the Low Volt Terminal Board
2 Carry 24VAC to or through an over limit safety
3 Carry 24VAC to a relay coil to change fan speed from Cooling to Heating speed
4 Carry 24VAC to a redunant coil on the primary gas valve (safety feature of valve)
5 Carry 24VAC to the Common or Ground circuit
You will have to grab a multimeter and start checking by voltage with the unit energized (light the pilot, put in a heat call from the T-stat) and see where you loose 24VAC or use the meter with the unit in an unenergized state and see where continuity is lost from the W terminal on the T-stat through the entire sequence. There again a solid understanding of fundamental circuitry, orders of operation, and some fundamental instruments (a meter) are necessary.
Best of luck...let us know.
Attachment: Basic Wire Diagram Low Volt.jpg (Downloaded 16 times)
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RandyM1911
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Posted: Mon Oct 20th, 2008 17:30 |
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Thanks for the help and patient explanations. I understand the lack of support for such old equipment on the manufacturer level but one would think that over the years someone would have scanned in wire diagrams for all sorts of appiances and uploaded them to the net. Since the diagram was supposed to be affixed to the inside of the lower door of the furnace, it would appear that the installer must have removed it in an attempt to prevent anyone but an "authorized" Comfortmaker dealer from servicing the equipment. That's just wrong in my opinion and the manufacturers should be responsible for providing this information to any consumer who requests it.
At any rate, your basic wiring diagram confirmed my assumption that the loose wire should be connected to the ground. I did call a local heating contractor that I have done business with before and had him stop by today to take a look at the system and verify the wiring prior to start up. All is well and the furnace is working fine.
Thanks for the help and advice. I always appreciate the good folks here at the forum.
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