Rheem Imperial drum 90 plus

Jmorris

I have read a million discussions on this particular furnace, and all not very favorable.
But I just need to know one question, and that is. On a Mod# REDG - 10ERAJS
When you change out the HSI control board with Protech's new board 62-25338-01 rev 05
You're faced with a addition of an amber flame sense light (led)
Since you cannot install a flame sense kit also made by Protech into this particular drum furnace, where in blazes does the new board get it's flame sense signal from?? And without the flame sense signal obviously the gas valve will shut off after 5 sec.

Thank you,

Jon

JUGHNE

Early Rheems used the HSI for the flame sensor, after that did not work out well they furnished retro FS kits that tied into the neutral (white) wire of the HSI.
The drum experiment didn't last that long. IIRC I thought maybe they were all recalled??
Are you the homeowner?

Tim McElwain

It should have a seperate flame sensor which was added as a kit.

Jmorris

I am a contractor.

Yes, they showed tieing into the neutral side of the HSI and then inserting that pin plug end into the molex connector on the control board. But where I stopped short was they still showed the thermocouple inserted in line with it. which again you cannot mount a thermocouple in a drum 90. Also on the neutral side of the side HSI wires until it fires, there is a potential of 90vac. which I don't think that control board will like that, but I may be wrong. And the reasoning is that the thermocouple only emits a few millivolts when heated in direct flame.

The new board did not come with an additional flame sense kit, and when purchased separately it is the one that requires that the thermocouple be mounted in the flame.

Perplexing.

Jmorris

One other thing is that I know the Rheem 90 was a mistake by Rheem, and they had a drum recall because of exchanger cracks.

But this one has no cracks (yet) and originally they did use the HSI as the sense for the CB. Which I do not know how, because on the original schematic there is no electrical connection between the HSI and asso. ckts to the main CB.

But when you order a new board, do to the old one having the charred resistors, you get the new board rev 05 that must have a sense signal to illuminate the amber light, therefore allowing the gas valve to stay open.

JUGHNE

Thermocouple???? Do you mean flame sensor rod?

Originally the HSI heated up red hot, powered off when gas valve opened and the gas was lit by the still glowing HSI which then became the flame sensor.

So the replacement board wants you to connect the white side of the HSI to where a normal FS would go?

That is what the retrofit Rheem FS kit did. The FS mounted on the opposite end of the burner manifold and the wire tied into that neutral. Back then they cautioned you to be sure that the white wire was actually the neutral of that 120 VAC feeding the HSI.

How old is this drum?

Jmorris

Yes, I mean FSR, I call it a thermocouple because the rod portion that is in the flame that sticks out from the porcelain insulator, is what creates the small millivolt current that tells the CB that everything is ok. Same as in a hot water heater, as long as that flame is present and the thermocouple is a working unit, then your gas valve will stay open. i.e. (safety device)

I understand the white wire needs to be the neutral. but in that retrofit kit, they also show the sense rod mounted on the flame burner in conjunction with the white wire then feeding the CB.

But in the case of a drum 90 there is no way you're going to mount the FSR inside that drum, not unless you want the wire leading from the FSR to burn up in less than a second.

So can you forget the FSR and just feed the neutral side of the HSI to the CB? and the CB will sense that the HSI is glowing and therefore keep the gas valve on. that just does not make sense to me.

I am not sure how old the drum is, since the customer purchased the home some 4 years ago, but I suspect the furnace is original and was placed there when the home was built.

Jmorris

One other thing that is puzzling to me, and that is on the original CB and HSI (they label it IE (igniter element) on the furnace schematic.
Since the IE is on the 110vac side and all that circuitry is independent of the 24vac side that feeds the CB. How is it that the CB sensed the IE still glowing that turned into a FS, since there is no electrical connection (according to the schematic) the only thing between the 110vac side and the 24vac side is the step down transformer.

Tim McElwain

If the HSI was used in the original to both light the burners and then was used as the sensor it would prove microamps (not millivolts) through the ground side (white wire) on the igniter. When a seperate sensor is required it must be placed in a position to insure the last burner getting gas has ignited. It must be 1/4" to 1/2" above the last burner and 3/4 to 1 inch into the flame. It can be tied into the ground leg (white wire) as microamps are proved through the ground connection to the system. If that is not working then you need to check and make sure your bare copper wire ground is continous or simply run a wire from the burners to the gas valve.

Jmorris

Ok microamps, But here is the rub. Had this been a four or five burner Rheem horizontal fired burner furnace, I would not even be asking any questions it would be operational long ago. Hence with this type of burner fired furnace, yes a very simple matter of attaching at retrofit FSR to the last burner, it would be working

But here we have the old style drum single burner inclosed within a drum, with a HSI attached to the side 5/16 in away from the internal burner, that is sealed within the heat exchanger.

So naturally there is no way to use the Protech retrofit FS kit.

So back to the original question. How to keep the gas valve open with the new Protech CB when you cannot get a FS signal to the CB via the HSI.

Is it possible that this Rheem mod# REDG-10ERAJS furnace, I have the wrong CB from Protech it's Mod No# is 62-25341-81

Thanks,

Jon

JUGHNE

You can double check the cross reference for the furnace/control board to be sure. If the instructions call for the jumper from white to the board I would install it. The CB people want their things to work properly and not have the smoke come out of it.

Once the HSI changes from a glow heater to a flame sensor, the CB switches its function internally. The FS does not rely upon heat for its function. It uses flame rectification (sends out AC and that signal returns as DC thru the ground path to CB) to insure that there is actually fire present and keep the gas valve open.

Jmorris

Finally some sense to all this..Thank you. I had completely forgotten about the ability for a dc component to ride on the ground ckt.

I will tie in the neutral side of the HSI that turns FS into the appropriate pin on the molex plug on the CB and see what happens.

Tim McElwain

Let us know how you make out.

Jmorris

This is the report, by hooking a wire from the neutral side of the HSI and connecting it to the pin 7 on the CB it allowed the flame to remain on for about ten sec. I suspect not enough current as would be from a actual flame sense rod.

Final conclusion, this Rheem furnace which by all accounts was a mistake by Rheem. And the mod# of REDG-10ERAJS does not exist anywhere on the web, nor does Rheem even acknowledge it, nor can one find the original control board made by Honeywell. to fit it. Because all other boards need the flame sense kit, which will absolutely not work on this furnace.

So I give up, and it's new furnace time!

JUGHNE

I think the drums came out in mid 90's. And IIRC many recalls.
At that time the recall info went out to the dealer/installers, not necessarily home owners.
Probably time for change out at 20+ years of questionable product design.

However, did you change the HSI? They can work well as igniter but fail as FS. They use 120 VAC to get hot, that is brute force of voltage pushing thru. But for flame sensor they have to conduct micro amps of AC, a fairly delicate signal. This issue has come up on the wall before. The HSI works to light so it seems like it should work as FS......not necessarily so. New HSI make the flame sensor function again sometimes.

Also the other part of that micro amp circuit is the return ground path and it must be pristine in conductivity. It may depend upon the burner piping etc. Corrosion may have set in and the best fix is to run a ground wire from burners to control board. Even the ground wire on the 120 power supply must be solid for some ignition systems to operate.

There are other systems that use the HSI for FS. So all this is good to be aware of. JMO

Jmorris

Thank you JMO, for your input it is greatly appreciated. And you are correct the grounds in this particular furnace are extremely important. I thought they were good for I done a ohm check to chassis ground from several points and it showed .01 or less. But a physical inspection I need to go back and look .

I did install a brand new HSI, to no avail. Only to find out that the customer had installed one of those replacement CB and it will not work in this furnace because there is no way of attaching a FS kit.

The main issue was that this furnace utilizes the Honeywell S9201 CB, which uses the HSI as the FS. problem being that this board after x number of years, with the high wattage resistors mounted on the PCB, discolor and burn the PCB and break away from the solder joints. Yet one more design flaw in this Rheem furnace. and with Honeywell.

And there is no other CB that will work in this furnace. And the Honeywell S9210 seems to be all but extinct and not available. Everyone want's to sell the replacement CB, which will not work because the replacement boards all need the FS kit to operate. Of which of course will not work with this furnace.

It's a crazy deal!! But with this furnace design flaws and all, which was produced back in the 90's, I do believe it's time for new.

Was just trying to get this guy up and running, for he sold the home and did not want to plunk out 8K for a new furnace when he is not not going to live there anymore. But isn't that the way it always works...?

Jmorris

NEW THREAD.

As it turns out the replacement board 62-25341-81 will work in place of the Honeywell S9201A

But here is the catch. NO ONE will explain how to transfer the FS signal from the neutral side of the HSI to the new board so it can see the microamp signal from the HSI so it will keep the gas valve on.

And as everyone should know, in a Rheem imperial drum 90 plus furnace there is no such thing as mounting a flame sense rod in the burner.

Jon

John Mills_5

One of them still in existence and the customer wants to put a new board in it? Wow. Bet if someone looked a bit they'd find a crack. I don't think we have any left kicking out there.

Yea, go with the 62-25341-81 board.
It's a UTEC board not a Hokeywell and it is meant for the DrUM furnace. Looking at the instructions, you shouldn't need a flame sense rod since that is a drum only board.

Tim McElwain

The new Silicon Nitride Igniters from Kyocera (Distributed by Robertshaw) can not be used as a sensor they are only to be used as an Igniter. They are the ones from Robertshaw with an "N" after the basic number such a 406N. They are also listed as Universal replacements. The old Norton Igniters (now Koors Tek) are still available, those are silicon carbide which was the original material used on igniters.

Tim McElwain

All the Honeywell S9201 and S9301 are replaced by the 1012 or 1013 series of United Technology Boards. The igniter plugs directly into the board and works as a igniter and also a sensor. Just make sure you have the correct igniter.

Tim McElwain

By the way the Honeywell S9200U-1000 also can be used to replace that board. That is their Universal Replacement Integrated Furnace Control.

Jmorris

WOW!! finally some insight!! for which explains everything!!

I cannot thank you all enough!!

Yes believe it or not there is still a few of the (dreaded) drum 90's out there. should have all been put quietly into the metal salvage yard long ago. Believe it or not this one has no cracks in the exchange....

But with needed info on this subject I think will be able to get this poor soul up and running. So he will not have to plunk out 8+grand for a new furnace, that he can never enjoy since he sold his house.

Thanks, again.

Jon

Jmorris

One quick question Tim,

On the Honeywell S9200U-100 they show on the schematic a place for the flame sense rod in two connections on that board. Since the HSI plugs directly into the board, does one just disregard the two connections for the FSR since they cannot be used in a drum furnace?

Thanks,

Jon

Tim McElwain

I would imagine it would be okay as it will still prove through the ground on the board. I have never tried it however. I many times will add a separate sensor just to be positive as I do not trust some of these igniters now days.

Jmorris

Understood, but in the case of a drum Rheem furnace you can not install an additional flame sense rod. I just hope that it can see the microamp signal via the ground connection. I just never have heard of a difference of potential on a ground ckt if it is truly a chassis ground.

Tim McElwain

One of the things we do when we suspect a poor electronic ground is simply run a wire from the burner or pilot and connect it to the gas valve. It works everytime provided the third wire bare copper wire has been run to the equipment.

Jmorris

I will give this a try. and report back

Thank you!!