rheem over temp limit error

[stuff350]

I have a rheem 90 plus series model number rgfd07emcks over temp limit error 33, right when the unit starts up cold it flashes code 33 over temp limit. I have used the volt meter took it all the way to the board. I could not find an open anywhere. I then jumpered the whole circuit at the board still got the same code. I figured it was a bad logic board so I changed out the board however still have the same error code. '
Does anyone have any ideas

[TriWorksInc]

Are you the service tech, or the homeowner??????

[qwerty hvac]

Could be a lot of things. Is is a two pipe setup?


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[ga-hvac-tech]

Hmmm... RGFD... that is a MOD furnace (modulating). You really need to get a RHEEM guy out there... this furnace is unique... not an average unit and not easy to service unless one understands the unit.

Furnaces are not DIY products... folks can cause a lot of damage and potentially create an unsafe condition if they try.

[qwerty hvac]

I have a rheem 90 plus series model number rgfd07emcks over temp limit error 33, right when the unit starts up cold it flashes code 33 over temp limit. I have used the volt meter took it all the way to the board. I could not find an open anywhere. I then jumpered the whole circuit at the board still got the same code. I figured it was a bad logic board so I changed out the board however still have the same error code. '
Does anyone have any ideas

Jumping things out on that board can screw the board up.


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[TriWorksInc]

Hmmm... RGFD... that is a MOD furnace (modulating). You really need to get a RHEEM guy out there... this furnace is unique... not an average unit and not easy to service unless one understands the unit.

Furnaces are not DIY products... folks can cause a lot of damage and potentially create an unsafe condition if they try.

Thats what I was getting at, just from the post theres a possible drowning situation there.

[ga-hvac-tech]

Thats what I was getting at, just from the post theres a possible drowning situation there.

Yeah... If this guy is trying to DIY this furnace problem... he may spend a LOT more $$$ on his learning curve than calling a Rheem person and paying them to do the work properly... not to mention all the time, aggravation, and possibly nights on the couch 'cause mama is cold and irritated...

[stuff350]

Sorry, I was not specific when I said jumped it at the board, I'm an OSU -it student in the HVAC program and am working on this project for extra credit. I jumped it from the back side of the plug before it goes into the board .

[TriWorksInc]

What I do is work with the tech manual right in front if me? There are too many mistakes that can be made with electrical troubleshooting and you need to follow protocol while troubleshooting and don't use jumpers in the wrong places, good luck.

[qwerty hvac]

Check for three things:
Faulty limit control
Insufficient combustion air
Unstable flame pattern


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[stuff350]

The burner don't fire off at all right away it gives off that high limit error

[ga-hvac-tech]

Might clear the board... then start over... sometimes codes get 'stuck' in a board... power off and count to 10... then power back on.

If you are in school and doing a project... I would go through the entire troubleshooting chart in the IOM manual (I assume they gave you the manual)... sooner or later you will find something of interest.

Then when you KNOW what was related and what was not... you can explain the WHY's of what was wrong and how to fix it.

Knowing the WHY's is the key to this industry... otherwise... one becomes a parts changing hack.

[stuff350]

I like that point you made with the parts changing hack, there isn't much of a manual that came with the unit and yes I did clear the board even changed the board.

[ga-hvac-tech]

The WHY's are the key to being successful (technically) in this business.

I suspect if you approached the faculty at your school... they could find you a current IOM (installation and operations manual) manual for that furnace. Give them the model and serial... and see if they can get it for you.

[hurtinhvac]

It's cold. It flashes an open limit before it fires. You've replaced the board and still get an open limt error before ignition. And you could not find any open safeties?

How exactly did you confirm the limit was closed?

[stuff350]

I checked with a volt meter

[hurtinhvac]

I checked with a volt meter

Seems to me you've caught the extremely rare impossibility.

Please let us know the resolution. And be very cautious when jumping around safeties. Especially if anyone you care for is living upstairs.

[Joehvac25]

I like that point you made with the parts changing hack, there isn't much of a manual that came with the unit and yes I did clear the board even changed the board.

It's a school project and they don't have a manual?

[ga-hvac-tech]

It's a school project and they don't have a manual?

Sounds like a couple of other schools I attended decades back...

[stuff350]

Waiting iom manual, to come in ill let you guys know what's wrong with it when I find out. Just also found out students have been trying to trouble shoot this unit for a year now to try to figure out what's wrong with it