changing speed on direct drive blower

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  #1  
Old 12-03-12, 06:42 PM
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changing speed on direct drive blower

I have a Nordyne furnace made by Metzger Machine Corp. Heat only no AC. The blower is a direct drive 3 speed. My question is how do I know what the blower is set at, I think its set to hi. The furnace when recycling turns on for 15 seconds and then off until it heats back up and then it repeats.

There is a small wiring panel on the blower. There is a green (ground) wire a white wire a black wire connected to a prong labeled red. A red wire connected to a prong labeled blu. On the bottom there is a purple wire (com) red wire (lo) blue wire (med) and black wire (hi).

Please help...
 
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  #2  
Old 12-03-12, 07:22 PM
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Nordyne is not made by Metzger. We will need a wiring diagram (usually located on the inside of the blower door) to help you,
 
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Old 12-03-12, 10:19 PM
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It would be much easier if we could read all the designations on the terminals but if I had to take an educated guess I'd say that the piece of 3 wire is feeding the blower. It's wired in 3 wire because it's set up for two speeds. White is neutral, black is low speed and red is medium speed. The fan is not set up right now to even run in high speed.

Now with the wiring diagram you have to determine which function powers red and which function powers the black.
 
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Old 12-04-12, 10:03 AM
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The blower speed may not be too high.

If your furnace is 15+ years old, it may have a adjustable fan/limit switch which controls the fan. A small adjustment may be needed.

Post a picture of the inside of the furnace.
 
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Old 12-04-12, 06:17 PM
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here is the picture of the wiring diagram and also a picture of serial number.
 
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Old 12-04-12, 06:43 PM
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Your furnace does have a fan/limit switch.

Does it look like this?

 
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Old 12-04-12, 06:45 PM
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I stand corrected. Darn, that crow tastes awful. I wonder if MM makes all of Nordyne's stuff. I always thought they made their own. Nordyne sells HVAC equipment under many brands including Maytag, Frigidaire, Tappan, Ammana, Miller, Intertherm, Broan, Nordyne & probably a few I've forgotten.

I believe Muggle nailed it with the fan/limit thought. Most fan/limit controls are adjustable. If yours has adjustable pointers, set the lowest one (fan off) at 100, and the middle pointer (fan on) at 140. DO NOT mess with the highest setting (limit). If it is of the type in Muggle's picture, make sure you hold the dial still while moving the pointers.
If that doesn't solve your problem, get back to us.
 
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Old 12-04-12, 09:12 PM
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Yes. It has a fan limit switch. The switch for off is at 90 and on at 140. Im trying to figure out if the furnace is set to blow on hi med or low. The reason being because when the furnace is recycling the blower turns on and off every 15 seconds until it totay cools down. This only happens when the thermostat is trying to maintain temp in ths house not when its raising the temp to a higher one. Is this normal?
 
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Old 12-04-12, 09:45 PM
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Normally at those settings, the fan shouldn't cycle like that.

You can try changing the fan off setting to 85F; if that doesn't work change the fan on setting to 145F. (don't go higher than that) Hold the dial when changing settings as stated by Grady.

It's possible that the fan limit/switch is worn out and needs to be replaced.
 
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Old 12-04-12, 09:58 PM
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To answer your exact question:

When the furnace heats up and the thermal fan/ limit switch turns on the blower....it's on medium
When you put thermostat to FAN ON.....it's on high

Those guys have a good point with the fan switch. Try this....put your thermostat up to call for heat and put the AUTO/FAN ON switch to fan on and see if blower runs normally then.
 
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Old 12-04-12, 10:16 PM
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In looking at your first pic it appears that those taps may be in-correctly set. They don't appear to match the schematic. In my post # 10 I listed the fan speeds based on your schematic.

When I look at the fan terminals:

The red wire is the AC or FAN ON speed which is currently set at medium.
The black wire is the fan thermostat line and it looks like it's on low.

That could be your problem. If you don't have AC you can switch the red and black wires and the blower will run on medium.
 
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Old 12-04-12, 10:24 PM
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The heating blower speed was probably set by the installer to get proper temperature rise. Every duct system is different.
 
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Old 12-05-12, 07:44 AM
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Fan speeds should not be changed willie nilly, as Muggle suggests. They need to be set to keep the air flow at the proper level to strip heat away from the furnace and to heat the air conditioning coil properly or it will freeze up.

I would not make changes in the fan speed unless you have the skill to perform the proper tests to verify that the fan speed is correctly set.

Maintenance and repair such as cleaning of the fan blades, lubricating the fan motor and inspecting and cleaning the air conditioning coil which might be plugged should be done before modifying the fan speed in any case.
 
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Old 12-05-12, 08:34 AM
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You all make great points. My heating system (NO AC) was recently updated with more returns. My house was built in the 1950's and I just bought it back in March. There were a total of 12 supply vents and 2 tiny (2.5 in x 9 in) returns for the whole house (1300sqft). The blower was working overt time to push out a little bit of air to heat the house not to mention trying to suck in as much cold air a possible to not overheat the furnace.

We now have 2 more returns one large ceiling return 14in x 14in and another floor return 9in x 6in.

What I'm concerned about is that the idiots before me might have changed the blower settings to try and get more air out of the inadequate ducts. Now that I have them properly set up for heat and cooling I'm wondering if the blower is blowing to hard and cooling the furnace down to quickly.

During a normal heat up of the house the furnace behaves normally. It is only when the thermostat calls for more heat to keep the house at temperature where the problem comes in. If the thermostat is set for 67 and the furnace kicks on to keep it at 67 it performs a weird recycling cycle. It will heat up to its 140 temp turn off then the blower will start and run for about 15 seconds and then kick off. It will heat up again from residual heat left over and turn on the blower and then turn off quickly again.

i just want to make sure this is OK for the blower to be doing, cycling on and off so rapidly.
 
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Old 12-05-12, 12:39 PM
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So the fan cycles a few times before it stays on? Example - hits 140 and turns on, drops back to 90 and shuts off a few times until the furnace warms up.

Does the oil burner stay on when the problem occurs?

How warm is the air coming out of the vents?

Does the rating plate have a listed temperature rise range?
 
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Old 12-05-12, 06:56 PM
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I believe the 4 wires at the bottom of the terminal strip are the blower wires since they conform to the "standard" for color vs speed. Red is low, blue is medium, & black is high. A picture from farther back might help us see where the wires go since they don't agree with the color code on the diagram. I'd be willing to wager the fan is on high to prevent or reduce high limit shut downs with the old ducts. Lacking any labeling regarding temperature rise, I'd shoot for around 60*.
 
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Old 12-05-12, 08:18 PM
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Nothing is connected to black on the terminal board so the fan is never running on high.

From left to right:

Violet = com
Red = lo
Blue = med
Black = hi
 
  #18  
Old 12-07-12, 06:26 AM
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Have you tried the red on Hi as it shows on the print? It would seem that on Med. you may not be moving enough air and the Hi limit is opening,you could prove that by putting a meter across the limit terminals and see if that is the case.
 
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Old 12-07-12, 12:02 PM
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Don't change the speed without checking the temperature rise.
 
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Old 12-07-12, 06:44 PM
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It seems we've lost or OP.
 
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Old 12-10-12, 11:52 AM
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not sure if the previous pictures are viewable. Here are some additional ones.
 
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  #23  
Old 12-10-12, 02:09 PM
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With the furnace running, measure voltage from the red then black on the top of the terminal strip to white. Report your findings & we can tell you on which speed the blower is running.
 
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Old 12-10-12, 07:27 PM
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Won't work Grady....all fan speeds share common neutral. Checking with a voltmeter between any of the fan wires will all show the same thing.

I think I answered your question twice in this thread
 
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Old 12-10-12, 07:36 PM
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PJMax, no disrespect intended but it will work if the wires to the blower are disconnected so you are only reading the input side.
 
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Old 12-12-12, 12:05 PM
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So I changed the wires around to put the blower on med. I swaped the red and black wires and obvisously left the white where it was. I didnt touch the four wires on the bottom (blue, red purple and black).

Did I do this right. I just want to make sure I dont burn out the motor or break the furnace?
 
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Old 12-12-12, 01:25 PM
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You were advised not to change blower speeds without checking temperatures. To do so can cause damage to the furnace.
 
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Old 12-12-12, 06:27 PM
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What temperatures do you want me to check?
 
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Old 12-12-12, 06:36 PM
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After the burner has been running for at least 5 minutes, you need to check the temperature of the air in both the supply & return duct within a couple of feet of the furnace.
 
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Old 12-12-12, 07:04 PM
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Grady,

You seem to be leaving out some details. What temperatures should they be reading? I don't have anything to measure the temperature with. With the wiring diagram that I posted and the photos that show where the wires currently are can you or PJmax or both of you agree that the furnace is currently wired or needs to be changed. If so was changing the black and red wires the right thing to do to current the wiring?
 
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Old 12-13-12, 04:02 AM
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You can get an inexpensive (probably less than $5) dial type thermometer with a probe at nearly any hardware store.

The absolute temperatures are not as important as is the difference. Every installation is different & many things infuence temperature rise. No one can tell you if it is wired correctly or not without knowing the temperatures & the manufacturer's specified temperature rise.
 
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Old 12-13-12, 10:36 PM
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Normally modern gas furnace should have a temperature rise of 40-60F.

Oil units might put out hotter air - shoot for no higher (rise) than 70F if there's no temp rise range printed on the rating plate.

If your furnace is old, it may be rated at 70-100f.

Don't measure the supply air temperature directly above the furnace - do it in the trunk line.
 
  #33  
Old 12-17-12, 04:10 PM
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Here are the temperatures from a digital thermometer.

From a supply access panel 5 ft from the furnace in the truck line: 128 f

From an return access panel 5 ft from the furnace in the truck line: 69f

Vent right above furnace: 125
Vent furthest from furnace : 115
 
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Old 12-17-12, 04:25 PM
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That's a 58F rise, which is okay but a little high.

50F is optimal for a modern furnace.

Anything lower than 45F would feel drafty.

I think anything lower than 40F could cause condensation to form in the heat exchanger.

Disregard this post if the furnace has a temperature rise rating.
 
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Old 12-17-12, 06:26 PM
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If you fan isn't short cycling as it was, I'd leave it alone.
 
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