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Rheem 90 Plus Problems

10/20/07 4:05 am

I have a 14 yr old RHEEM IMPERIAL 90 plus furnace that is acting up! When it has set for (say over nite) it takes several tries to get the HSI (hot surface ignitor) to glow properly! Now after it warms up this failure goes away?

Resistance of HSI is ok,and 120 volts from IFC board is present at the HSI when it is required in the firing up squence.

Why would it take several tries to get glowing ok for the flame to start and to continue? This IFC board has 5 try lock out! Then it needs to be reset.

Need an answer/fix before the BUFFALO winter sets in?? lol

thx wayne

Re: Rheem 90 Plus Problems

Thank you Dwarfwytch; I have had a hvac specialist look at this furnace and they found that it was starved for fresh air; That problem is solved!
This HSI problem is there only on start up after setting for some time! (like over night) or for several hours durning the day. The HSI never glows on the first try! On the 2nd try it will begin to glow and on the 3rd try glows bright! Even tho the resistance is good of the HSI and 120 volts is present at the HSI on each of the tries! Then after that; every start that the thermostat calls for ; it will glow brightly and ignition will occur and furnace then runs all day good!

all the other suggestions you have given have been checked ok!

thx wayne :eek: :(

Re: Rheem 90 Plus Problems


Have you checked/swabbed the entire length of the exhaust pipe for obstructions? Sometimes just a spider web can cause very erractic behavior or completely prohibit ignition. Spiders like to build webs overnight.

(Or....if the wind is just wrong outside, it can swirl/backdraft just enough to prevent successful ignition.)

If you find nothing there (doesn't resolve the problem), I guess I'd next grab a new HSI and install that. A resistance test on a cold one doesn't tell the whole story. Even if it's not *the* problem right now, I like to keep one on hand anyway cause the dang things always seem to go sour when it's 3AM and -20F outside.

Yes, there are other potential problems that can cause what you're experiencing, but I'd try the above first....if you haven't already.

Re: Rheem 90 Plus Problems

well guys all that you have suggested has been done over the past month!except for the HSI being replaced as the HAVC tech said it was ok resistance wise and proper voltage at it durning the firing up sequence! looks like maybe I shall have to replace the HSI;;;as it was removed and cleaned as requested!

one other thing that I need to do is make sure the housing of the HSI is in good contact with the body of the heat exchanger!

as I have said this is a morning failure or after furnace has not been used for several hours;;;seems like a cold function!

well as of today will have more people in to look at it and also maybe install another Rheem as they will give me $375 if new one is installed b4 dec 31 of this year!

thanks guys/gals for ur input

wayne:confused: :eek: ;)

Re: Rheem 90 Plus Problems


Not sure if you'll stop back here, but in case you do.........

I'm not intimately familiar with your particular furnace.......so I don't know if it has a simple large HSI that glows the entire time ......or if it has a small HSI that ignites a small pilot flame which in turn ignites the burners. If it's the latter (flame-rod sensor type).....and replacing the HSI doesn't do the trick, then I would start suspecting the ignition/gas controls themselves. (Or if replacing the HSI only offers temporary remedy. More on that later.)

BTW..... On a flame-rod sensor system, the cleaniness of the flame rod sensor and the cleanliness of the metal base beneath the pilot flame doesn't even come into play until the HSI is glowing AND a pilot flame is established. So neither of those would be a potential culprit with the problem you describe .......if you have this type of ignition system.

Anecdotal info.....FWIW:

Installed a new Sterling unit heater in a client's shop about ten years back. These have Honeywell controls. It ran perfectly the first year. Guy is very pleased.

Second season rolled around and the unit worked fine for about half the winter. Then it started acting just as you've described.......for about two weeks. Reluctant starts in the morning, but once it did........ it ran fine for the rest of the day. Then things got worse about a week later. Eventually it wouldn't ignite at all because the HSI would be shut down before it could acquire some pilot gas. Unit would go into lock-out after several tries and that was that. Flip the switch to the unit and try again. Same old, same old. I then replaced the HSI and it ran perfectly for the rest of the winter. New HSI was free as warranty was still valid. Big deal. $18 bucks or so for that HSI. Nonetheless, I took the freebie part.

Next season, same deal. Heater runs fine for two or three weeks and then begins to act just like it had the year before. Grrrrrrrrrrrr. I acquired another free HSI and stuck that in. Ran fine for the rest of the winter.

Following year, it failed to start from the get-go. This is getting old in a hurry, says I. Stick in yet another freebie HSI and........ no-go. Glows for a bit, but never acquires any pilot gas, evidently. Unit locks out. (My teeth are kinda grinding about now) I reset and then check the output of the HSI for the required 5 milliamp (IIRC). It's there, but the unit shuts down anyway without ever acquiring pilot gas. Grrrrrrrrrrrrrr. I call Sterling tech and talk with a guy there. He confirms that the pilot should light if the 5 milliamps are there. Says they'll send out a new gas valve (Honeywell). No charge, although the unit is now off warranty. New valve is in my hand the next day. I install the thing and we're good to go the rest of that winter.

Next season......no pilot ignition right from the start. HSI glows a bit and then .....same old, same old. At that point I pick up the phone and call Honeywell. Talk to a guy there who says that they can't be held responsible for the trouble because they build the gas valves to Sterling's specs. IOW.....time to pass the buck. Surprise, surprise.......not. Nor would he offer any suggestions as to possible causes or remedies. Nuff said.

So......I call the tech-fella back at Sterling yet again and after some conversation he says he'll send out yet another free gas valve. New valve is here the next morning and I install that an hour later. Haven't had a lick of trouble with that heater since. Runs perfectly every year.

I've installed maybe a dozen of those exact same heaters with the exact same gas valve/controls and that's the only one that ever gave me any grief at all. Go figure. They're very nice heaters, BTW.

Re: Rheem 90 Plus Problems


Thank you for the same story that I am going thru here and this unit has a HONEYWELL gas valve;;I do hear the gas flow when the HSI no glow bright! and I have 24 volts at the gas valve when it should be there!

This RHEEM has been running for 14 yrs with min. amount of problems! Just started late last year and now every morning same old same old [email protected]@T! but works great the rest of the day! I am going to try to have some heat on the gas valve in the morning to see if that is my problem;;;;;its in a warm/dry basement

This HSI ia a large unit that sets into the combustion chamber along side of the circular burner! very easy to remove and to check resistance and or voltage to it! The price I got on line for this HSI is about 87$'s with out S/H! IT IS THE ORGINAL HSI (14YRS) OLD ;;;SO IT OWES ME NOTHING;;BUT IT ACTS SO WEIRED! LIKE VERY LITE GLOW WHEN FIRST USED IN THE MORNING! USUALLY ON THE 2ND OR 3RD TRY IT GLOWS BRIGHT AND NOW THE FLOW OF GAS IGNITES AND RUNS GREAT! oops sorry did not realize I was in CAPS! Also this funace has the 5 step lock out {has not locked out so far this year) meaning by the 3rd cycle it lites and runs great! But as things go here; looks like it may start to take more cycles! or not light at all! :mad: :D :eek:

thnaks again byeeeeeeee

Re: Rheem 90 Plus Problems
Re: Rheem 90 Plus Problems

Wayne... here is some information.

Hot Surface Ignition
The hot surface ignitor is the most commonly used electronic ignition system used today. The reason is they are reliable, inexpensive and the electronic controls they require are also less expensive. All they require is a flame sensor to detect the ignitor glow and open the main burner valve.
The hot surface ignitor works like a light bulb filament, except here, we want the heat from the element, not the light. The hot surface ignitor is usually made from a material like silicon carbide or nitride and as electricity passes through the ignitor, it will glow red hot.

Under normal conditions the ignitor should last for 3-5 years. However, it will eventually crack and need to be replaced, quicker if the oils from your skin get on the element by improper handling.
These hot surface ignitors are between $25 to $100 depending upon the model of furnace you have.[COLOR=#000000] Just like a light bulb, the filament does not last forever and these ignitors fail[/COLOR].

[COLOR=#000000]Possible Reasons for HSI Failure [/COLOR]

  • Dirty or corrosion covering ignitor
  • Premature failure due to improper handling (oil from skin got onto element)
  • Improper ignitor
  • End of normal usage life cycle (keep replacement on hand)
  • Electric current in the home is too high (over 125 VAC)
  • Dirty filter or squirrel cage.
  • Loose connections to/from control module
  • Damaged spark electrode
  • Faulty control module

Here is a simple procedure for cleaning the ignitor.

  • Turn off power and gas to the furnace
  • Remove flame sensor from it's bracket. Lightly clean the surface with fine emery cloth and replace.
  • [*]If this does not work, replace with new flame sensor.

Re: Rheem 90 Plus Problems

Hello ALL; thanks so much for all your replies/suggestions;;

http://americanhvacparts.com/Merchant2/merchant.mvc? this is the place that wants $87.88 for the HSI for my Rheem furnace!

pn HSI622266 says it is an upgraded used in RHEEM,RUUD,NORDYNE,MILLER AND INTERTHERM!




WAYNE/JUDY:eek: ;) :D :confused: :cool:

Re: Rheem 90 Plus Problems

Dwarf,, the IDM runs great, no slow downs or noisey! and does come on when called for and causes the NPC to close to show that it has correct neg pressure ctrl(meaning no obstruction) in the exhaust pipe!

The service flow chart does do the 30 sec. prepurge>yes igniter warms up and glows red(36 secs) now the answer to this is NO;;;on the first cycle;;2nd or 3rd cycle it will now be cherry red and then I can answer YES;;;main burner lites now and all is well for the day! so I have been up and down this service flow chart;;

the failure is first start up after it has been setting for any lenght of time;;;;just takes too long for the HSI to get cherry red;;;lol even tho it has 120 volts and its at the right time in the firing up sequence!

ok off i go and work on somehting else;;as long as the weather in "WESTERN NEW YORK" STAYS at what it is today bright sun and temp now at 74 degrees! We have no problem! ;) :D :) :cool:

later you all

best regards wayne/judy

Re: Rheem 90 Plus Problems


No flame sensor on this model! A write up in the manual says this::This furnace hasa hot surface ignition system which features direct ignition of the main burner. The ignitor also ACTS as a sensor for proving main burner ignition??

well now; nothing shows how this occurs;;as the ignitor has only 2 wires running to it and that is at 120 volts when it suppose to be! well this problem never gets to the gas BEING lit! as the HSI never gets red hot on the first to third try;;;

but once the main burner fires it goes well ;;;so however its sensing the flame is working?? many surprises with this furnace!

SOME MAGIC IS OCCURING?? LOL :confused: :eek:




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