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Old 01-22-2013, 09:54 AM   #1
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Need help w univ control board on ruud furnace


After two days of a burning smell, our furnace failed. The control board was charred, and I picked up a universal board to replace it. ( our very unreliable HVAC guy called Sat morning and allowed to let me pick up the universal board.). The new board didn't have the correct wiring for our older furnace, but all the controls, etc, shown on the new diagram are on the old diagram. Since the univ board calls for separate Hi Limit Output (Hi Lim) and Roll out Switches(RO), and the original circuit had Hi Lim and RO in series, I separated them by making a new loop for RO and reconnected the Hi Lim to the original connector to mate with the 12 pin connector. (To do this I removed wires from the additional harnesses supplied w the kit and added splices to get all the components in their respective places.) I also added a univ. flame sensor to the circuit, positioned it to be in the flame, as well.

After troubleshooting the flashing codes - first polarity, then RO open, I verified connections, removed the RO wires, jumpered them, and, while the flashing light goes to solid, meaning Normal operation, still no joy. It appears everything is wired properly, but, hey, stuff happens, and I must be overlooking something. On my way to pick up two new RO sensors. BTW, the univ board is a White Rodgers 50M56U-843.

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Old 01-22-2013, 04:58 PM   #2
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Need help w univ control board on ruud furnace


how old is the furnace....I think if its before 1992 don't think that board will work....one of my techs had the same problem with a rheem furnace and he had to get another board...not sure though...ben sr

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Old 01-22-2013, 05:29 PM   #3
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Need help w univ control board on ruud furnace


Well, if you look at my previous post, you'll see that I had an older furnace and a new control board. Big problem turned out to be the Rollout switches, which I just finished replacing. Along with that, I formed a bracket and added a universal flame detector.

Doing it by myself probably saved me $400 or more, as the board alone from Ruud is about $220 plus tax.


As I'm an engineer, I've been around Molex connectors for years, and I knew how to remove the pins and plugs from the connector body. Doing so, I fashioned a hybrid harness to fit the Ruud furnace, which required me to break the series connected Hi Limit and Rollout switches into two separate circuits, which were then added to the harness. Also added a flame detector to the centrally located pin 14 on the board.


Yeah, it took me some 14 hours to troubleshoot and figure it all out, but once done, the furnace is running perfectly. If I were to do this again on a similar furnace, it would take an hour or less...


Let me know if any of you need a diagram of what the reworked harness looks like.
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Old 01-22-2013, 05:52 PM   #4
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Need help w univ control board on ruud furnace


You said you added a universal flame sensor. What did it have B4 or what was wrong with the original one. Hopefully you put it EXACTLY in the correct position or same positions as B4 as a flame sensor is a critical safety device and you cannot just stick it in the flame anywhere. It should be by the furthest away burner from the igniter and must respond with 2 seconds if there is no ignition or you could get one awful flashback/delayed ignition if it does not do its job properly and the gas pressure is low etc etc. Not somethng you want to fool around with for some serious liability and safety reasons. Post a closeup pic of it with good lighting and we may be able to see if it looks safe.
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Old 01-22-2013, 11:28 PM   #5
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Need help w univ control board on ruud furnace


Yuri,

Great point to make about the position of the flame sensor. After reading your post, I moved the sensor farther away from the igniter, actually as far as it will go.


The previous controller didn't use a flame sensor, and there were no instructions available with The one i picked up. Just the plastic bag it came in.


You are correct about the two seconds, as prior to having the sensor in the flame, the system would ignite, and immediately shut down. The position of the sensor has the tip roughly 1/4 in. Into the flame, and while it's doing its job, it's not getting red hot. Let me know if it needs to be red hot, and I can adjust the position. It's mounted to a 1/32 thk bracket made of 304 Stainless, and bolted to the sides of the flame unit. If I can get pics from the phone and post them I will.


The new board makes a world of difference in the house, as I now suspect several issues with soft failure of the RO switches or possibly an intermittent somewhere in the system.


Thanks for your help.
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Old 01-22-2013, 11:45 PM   #6
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Need help w univ control board on ruud furnace


Quote:
Originally Posted by TXN TOM View Post
Yuri,

Great point to make about the position of the flame sensor. After reading your post, I moved the sensor farther away from the igniter, actually as far as it will go.


The previous controller didn't use a flame sensor, and there were no instructions available with The one i picked up. Just the plastic bag it came in.


You are correct about the two seconds, as prior to having the sensor in the flame, the system would ignite, and immediately shut down. The position of the sensor has the tip roughly 1/4 in. Into the flame, and while it's doing its job, it's not getting red hot. Let me know if it needs to be red hot, and I can adjust the position. It's mounted to a 1/32 thk bracket made of 304 Stainless, and bolted to the sides of the flame unit. If I can get pics from the phone and post them I will.


The new board makes a world of difference in the house, as I now suspect several issues with soft failure of the RO switches or possibly an intermittent somewhere in the system.


Thanks for your help.
So you're saying your furnace had an ignitor but didn't have aflame sensor? I've never seen that before. Not sure how that could safely do that.

As for the flames sensor I'm sure it's a "flame rectification" system. It basically passes ac voltage through the flame causing it to switch to dc voltage. The board senses dc voltage off the case and is it sees dc voltage it knows a flame is present.

The temperature of the sensor doesn't matter. Just that the voltage passes through the flame and into the burner.
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Old 01-23-2013, 04:41 AM   #7
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Need help w univ control board on ruud furnace


Old board used the HSI as the flame sensor.
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Old 01-23-2013, 08:27 AM   #8
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Need help w univ control board on ruud furnace


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Old board used the HSI as the flame sensor.
Ahh I've never ran into one of those, but I have heard of them.

I must say I'm pretty impressed, that sounds like it would've been a difficult install even for a pro. Well played TXN TOM
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Old 01-23-2013, 08:31 AM   #9
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A pro would not ever re-wire a board to accommodate it not being the correct one. You void any and all warranty as well as assume all financial responsibility for when that home burns to the ground.

Not saying what he did was not intriguing, just not smart.
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Old 01-23-2013, 08:38 AM   #10
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Need help w univ control board on ruud furnace


Ruud/Rheem and Coleman had that system of using the HSI as a flame sensor and it is pretty much obsolete. Both of them have a factory approved conversion kit with the board and sensor and bracket which is what the Pros use.
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Old 01-23-2013, 08:42 AM   #11
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Need help w univ control board on ruud furnace


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Originally Posted by Doc Holliday View Post
A pro would not ever re-wire a board to accommodate it not being the correct one. You void any and all warranty as well as assume all financial responsibility for when that home burns to the ground.

Not saying what he did was not intriguing, just not smart.
It's not the wrong board it's a universal board. And I work in the field and we install universal boards sometimes. Granted I'd check to make sure all the limits actually work etc, but it's not unsafe to use a part that isn't a direct manufacturers replacement.
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Old 01-23-2013, 08:46 AM   #12
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are you kidding me? I've worked in the field for going on 13 years now, yuri for who knows how many hundreds of years . The conversion kit design specific for his unit is the only one that should have been used but alas, the HO was wanting cheap.

Your belief of one single board being universal to every furnace out there is corrupt and dead wrong. If you think, which apparently you do, that re-wiring a universal board to makeshift the conversion kit is correct than I need your companies phone number, you need to find a different field to work in.

so what's that number?
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Old 01-23-2013, 08:56 AM   #13
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Chill Doc.

We do use universal boards and they are NOT universal. They cover about 80% of the models and Lennox especially is not a good candidate for them. The main issue being that a Pro knows the sequence of operation and how to properly test the safety controls but a DIYer does not. I avoid universal boards like the plague as they have all kinds of quirks and the manufacturers OEM board is always much better. In a pinch they are useful but you need to carefully read the cross reference chart that WR and HWell supplies and even with a S86U universal control some rewiring needs to be done. Just get a experienced Pro to do it.
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Old 01-23-2013, 08:59 AM   #14
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Need help w univ control board on ruud furnace


Quote:
Originally Posted by Doc Holliday View Post
are you kidding me? I've worked in the field for going on 13 years now, yuri for who knows how man hundreds of years . The conversion kit design specific for his unit is the only one that should have been used but alas, the HO was wanting cheap.

Your belief of one single board being universal to every furnace out there is corrupt and dead wrong. If you think, which apparently you do, that re-wiring a universal board to makeshift the conversion kit is correct than I need your companies phone number, you need to find a different field to work in.

so what's that number?
Whatever you say chief. I've got 9 years experience myself along with my father being in the business for over 40 and we've successfully installed universal boards with no problems. Do we do it all the time? No, but sometimes you can't get a direct replacement & you have to do what it takes to get heat to your customer. Universal boards are not dangerous as long as you read the instructions & install them properly.
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Old 01-23-2013, 09:07 AM   #15
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Need help w univ control board on ruud furnace


Young Skywalker,

I never said universal boards won't work, I've installed hundreds of them, but one is not universal to every unit out there. You need the correct replacement, not supposed to have to re-wire the roll outs and high limits or whatever else. The plug in adapters that come with the new universal replacements take care of that.

No sane and educated insurable heating company would ever have their techs do that.

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Last edited by beenthere; 01-23-2013 at 05:06 PM. Reason: Removed un-needed comment
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