Carrier 48SS018-060 shuts down when cold out - pics included

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Old 02-13-11, 09:07 PM
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Carrier 48SS018-060 shuts down when cold out - pics included

(I live in TN and the unit uses natural gas.)

I have a Carrier model 48SS018-060. It got down to 16 degrees F the night it went out. I did the reset procedure and it worked fine for 4 days and cut off again, LED is flashing 8 times = internal control fault according to the manual. I reset it again and its working so far. The fan does NOT blow cold air when it goes out. The orange ignitor wire was touching the yellow flame sensor wire so I took care of that with a quick reroute. The guy who came out last year when my mom lived here told her that the burner was rusting and would need replacing soon. Of course that is what he told a woman so I take that with a grain of salt. It didn't look too rusted to me (pics included) but I didn't remove it and look inside of it. Besides, the burners are only $15/each and I only have two so not a big deal. Here are some pics. Any help is greatly appreciated!

http://i839.photobucket.com/albums/z...o/overview.jpg
http://i839.photobucket.com/albums/z...ercloseup1.jpg
http://i839.photobucket.com/albums/z...ercloseup2.jpg
http://i839.photobucket.com/albums/z...cuitboard1.jpg
http://i839.photobucket.com/albums/z...cuitboard2.jpg
 
  #2  
Old 02-13-11, 10:38 PM
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Mmmmmm.


The manual on your unit is at:

http://xpedio.carrier.com/idc/groups...t/48ss-4pd.pdf


Those burners are pretty rusted. More importantly, this is an outdoor unit. Usually you could wire brush off the rust and get additional years of use from them. But these are exposed to moisture condensing on them all year. They are going to rust up more rapidly and worse now that the corrosion resistant coating is gone.

Replacing the burners would be a good idea, in my view. But that's a job for this summer, probably.

What were you doing for a "reset" procedure?

The sequence of operation of the furnace is described on page 25 of the manual. You need to carefully observe the sequence of events that occurs when the thermostat is turned up and describe that here.
 
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Old 02-14-11, 12:47 AM
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Your link is for the "Product Data" sheet. I have the physical "Installation, start-up and service instructions" and "A guide to operating and maintaining your gas heating/electric cooling unit" in hand. According to the latter the procedure I followed was referred to as "To Light Unit" and is as follows:

1. set temp on room thermostat to lowest temp setting and set system switch to HEAT
2. close the external manual shutoff valve.
3. turn off electrical supply
4. remove burner access panel
5. turn control dial on internal gas valve counterclockwise to off position, wait 5 mins
6. turn internal gas valve clockwise to the on position
7. replace burner access panel
8. turn on electric supply
9. open external manual shutoff valve
10. set temp selector on room therostat to slightly above room temp to start unit

It started and heated properly but went off again 2 days later (correction). You refer to the "Sequence of operation" below.

Sequence of operation-
Heating—On a call for heating, terminal ‘‘W’’ of the ther-
mostat is energized, starting the induced-draft motor. When
the hall-effect sensor on the induced-draft motor senses that
it has reached the required speed, the burner sequence be-
gins. This function is performed by the integrated control
board (IGC). The indoor-fan motor is energized 45 seconds
after flame is established. When the thermostat is satisfied
and ‘‘W’’ is deenergized, the indoor-fan motor stops after a
45-second time-off delay.

What exactly am I supposed to be looking for? The only thing in question is the 45 second delays, the rest of the sequence must go as above because it then works. If I time the delays will that help anything?

The only observations I made were (with corrections):

1. It went off overnight when it got down to 10F (2/10), I did the light procedure in the AM.

2. That night it went down to 6F (2/11), worked fine.

3. The next night it went down to 21F (2/13), it shut off.

4. In the AM of 2/13 I removed the burner access panel, the LED was blinking 8 times, internal control fault according to the manuals stated above. There seemed to be sort of an electrical humming coming from the ignition control panel. I decided to lookaround and take pics after I cut the gas and electricity. Then I vacuumed the entire area behind the burner access panel with a shop vac. I got in every nook and cranny, even vacuumed the holes the burners were firing into. I vacuumed the flue hood screen, it had a small amount of debris on it. The LED was blinking 8 times, internal control fault according to the manuals stated above.

5. I took off the blower access door, vacuumed it out. I spun it around, it spun freely and quietly. It did have some build up on the fins inside the squirrel cage. I could not clean it thoroughly without removing it so I did the best I could. Didn't notice any rust. Replaced cover

6. The orange ignitor wire was touching the yellow flame sensor wire (as in the bottom of this pic: http://i839.photobucket.com/albums/z...o/overview.jpg ) so I took care of that with a quick reroute. I read that if these wires cross it is a bad thing.

7. I noticed that the ignition control board had 2 white rectangle things that appeared heat damaged on the bottom as in this pic:
http://i839.photobucket.com/albums/z...cuitboard2.jpg

8. Put the burner access panel on, did the "to light" procedure. Hot air began to come out of the inside vents.

9. Went outside to the unit, smelled gas. Went back inside for about 30 mins.

10. Back to the unit, no gas smell. The unit was running, hot air was coming out the flue hood and I removed the burner access panel. Noticed 2 blue flames shooting out of the burners, seemed normal. Replaced cover.

11. Remembered I had recently (date uncertain but before there were any problems) replaced the indoor filter. Checked it to make sure I didn't put in in backwards, it wasn't so I put it back in. The filter it replaced was about 5 months old yet only slightly dirty. The replacement was the same brand etc as the previous filter.

I can shut it off during the day so I will watch it go through its "Sequence of Operations" and report what I see later today.
 
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Old 02-14-11, 04:47 AM
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Some of these unit appear to have a hot surface ignitor that glows white hot to light the gas. Yours looks like it may have direct spark ignition ---- a spark that turns on to light the gas.

Which method do you see lighting the gas?


I might expect you to report that:

1. thermostat turns on

2. inducer motor comes up to speed

3. HSI glows (or spark turns on

4. Main burner gas turns on and lights

5. Fan to circulate air around the house starts up.



You appear to have an intermittent problem with thye furnace not lighting. You probably need to become familiar with the lighting and operating sequence of the furnace and then cycle it through the ignition process repeatedly until you can observe it to fail to light and report at what point in the ignition sequence it is failing to light.
 
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Old 02-14-11, 05:32 AM
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Indeed, it says it is "equipped with a direct spark ignition 100% lockout system". And that if the unit fails to light possible causes:

"misaligned spark electrodes", adjust as necessary
"burned out heat anticipator in thermostat", replace thermostat
etc

This should be fun, thanks for the help.
 
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Old 02-14-11, 02:20 PM
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I removed and cleaned the ignitor and flame sensor, reinstalled. Watched it startup a couple times. It lit no problem but I noticed that there appears to be a small flame between the 2 burners, yellow/blue then blue. I can't see back there but it would seem that there is a (rust?) hole/crack back there and/or the burner(s) are separating at that point where the sheets are welded together in the back. When they cool down I will get my handy extension mirror with LED attached and inspect it. But my question is would this cause the burners to not light occasionally? Or could I have installed the ignitor and/or flame sensor in such a manner that they interfere with the flow and cause this? They were just put in with screws, not like they were precision aligned or anything. Oh, and I vacuumed out the area where I removed the ignitor and flame sensor. Thoughts?
 
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Old 02-14-11, 06:56 PM
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Two White Rectangles

Those appear to be resistors. If so, it wouldn't surprise me if they got quite warm. What do you think SP?
 
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Old 02-15-11, 02:47 AM
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The corroded burners are a likely cause of the ignition failure. Cleaning that up may have solved the problem.


If not, you will need to cycle the furnace on until you observe the ignition failure often enough to determine the cause. That might require cycling the furnace on 40-50 times or more.

I think it's not especially likely that the ignition control is the problem in this case. Much more likely a problem with the burners or spark electrode. But I could be wrong.

Careful observation is needed. Guessing on probabilities isn't the same as identifying the problem.
 
 

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