Suck-starting my Carrier furnace; for years . . .

Forrest McCanless

Thanks for your concern. The problem I'm having with this furnace is exactly why the class-action suit is being filed against Carrier (condensation and attendant problems caused by degradation of the secondary heat exchanger, because it's not SS). They have a long and well-documented history of ignoring specifically this problem with this specific condensing furnace.

I've had perhaps 20-30 service visits over the years, By the installing company, Carrier reps, and also the HVAC company I now use professionally. This is not really an issue of "fixing" in the sense of "returning the furnace to its original state" - it has to be modified. I simply want Carrier's advice or help in doing it.

As to the "suck-starting", typically after we fool with a while, it will run just long enough for the service techs to get away. I try the "suck start" technique occasionally to verify that yes, indeed, I have the same problem before I call a tech. I don't do it as a matter of normal running - it's just a technique that ALWAYS works.

I did talk to a new Atlanta-area Carrier rep this afternoon, and he has promised to get with my HVAC guy and come down next week. Since the class-action suit was just given the so-ahead by the Justice department, maybe Carrier is being more helpful!

Don't worry about my cheating on the safeties. I have another furnace, a big heat pump, and an even dozen working fireplaces in this big old house - we can stay warm.

Thanks again -

Forrest

Forrest McCanless

Suck-starting my Carrier furnace; for years . . .

Buddy from Fine homebuilding / Breaktime said maybe I could get help here. Here's my issue -

Older Carrier condensing gas furnace (Model 58EJA125-LC). Chimney fan won't generate enough vacuum to consistantly actuate the vacuum-diaphram on the "safe" switch that allows the burner to light. Been that way for years.

I can detach and suck on the tube, and the ignitor and burner start right up; I can even carefully re-attach the tube to the fan housing while everything is running, and if I pinch the tube until it's connected to the housing nipple, the furnace will continue to run until the thermostat setpoint is reached.

So, there is enough vacuum to maintain the switch diaphram, just not to engage it. If I pull off the hose, the burner immediately shuts off, as it believes there is a problem with the chimney draft - a nice safety.

Can't just jump out the switch; control board needs to see NO vacuum before anything will start.

Next cycle, I've got to suck on it again, or wait a while, and it MIGHT start. Many, many techs have looked at this; I've replaced the draft fan assembly and the vacuum diaphram switch, and it might work for a while, but not for long.

Carrier will not talk to me; I've had this damm tube sticking through the kitchen floor, to suck-start my furnace, for years.

I can think of two ways to bypass this - use a relay on the 120V draft fan power to trip the (formerly) vacuum switch, or restrict the inlet air to the draft fan to pull more vacuum.

I don't really like either idea. Anyone know a solution?

Forrest - lips are tired

bob_50

What is

the altitude (above sea level) of your home?

Forrest McCanless

~750 feet (Atlanta area). Interestingly. I think this problem is noticeably worse when it's cold and dry - less dense air?

Forrest

Mike D_7

Vacuum proving switch

Among other jobs, I was a ThermoKing (transport refrig) mechanic. Trailer refrigeration units had a defrost switch that was a pressure diferential switch to measure the loss of air flow through the evaporator coils as they iced up.
The switch is a microswitch mounted onto a small rectangular box containing a plastic diaphragm. there was a tube running from each side of the diaphragm out to a small plastic cup to "catch" the air pressure. This switch's sensitivity was adjustable.
Seems like a similar arrangement could replace the existing vacuum switch on your unit and provide a safe proof of draft. i.e. one cup on either side of the vent fan.

Opinions?

Robert O'Brien

Get

it fixed properly,it's a draft prover.If it's not proving,what does that tell you?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Big Ed

Intake

How long is the tubing on the outside intake ? Is there any plastic plugs in the furnace cabnet ? Try removing one of the plugs to let in more combustion air and see if it starts... Could be too long of a run or mice built a nest.ect.. You should take the intake pressure drop reading and compare it to what is needed..

Rich L.

Check your flue

Your living on the edge of moving enough air through this system. The fact that you can suck on the tube and make the switch tells you that the switch is doing what it's supposed to do, prove air flow. It's a safty switch, NEVER bypass a saftey, EVER!

I worked on a friends furnace that was doing what yours is but after a few tries it would eventually light. After checking the PVC intake and exhaust I removed approximatly 10 feet of bird nesting material from each horizontal run! Yes, a few dead birds as well. And his would still light! I also work on one customers every fall that gets a few mud daubber wasp nests every summer, blocks about a third of their flue and that restricts enough air flow to not make the switch. Clean them out and it takes right off.

One thing you can try, disconnect the intake and exhaust from the furnace and see if it will light normally. Of course shut it down as soon as it does, and if it does that tells you there is a restriction in those lines. I have ran across bad pressure switches but the vast majority of the time it's a blockage.

Good luck, Rich L

Forrest McCanless

Intake is about 22' of 3" PVC; one 90. Same for the exhaust. Both are horizontal, once the 2' rise up from the furnace.

Interesting about letting in more combustion air. I could try temporarily disconnecting the intake and/or exhaust at the furnace to eliminate those variables.

Another thought - perhaps air is leaking in under the squirrel-cage impeller along the motor shaft seal (the motor cage is open)? The vacuum tap at issue is under the impeller, very near the motor shaft. I've just had the blower unit out to check that it wasn't cracked, but I couldn't swear to the condition and/or correct positioning of the shaft seal.

I have a great pic of the impeller and tap, but was unable to attach a .bmp - any tips?

Thanks for your time.

Forrest

Forrest McCanless

Okay - pulled off both the intake and exhaust. Furnace fired right up the first time, raising all kinds of excitement, but cut itself off even before the air-handler blower came on (30-40 seconds). Never got it to do even that, again.

Ran a snake through both PVC pipes; clean.

Suck-started it, fired off instantly; it's running now. Once it reaches thermostat temp, though, it won't restart with that switch tripped.

Tried putting little bits off paper over the draft fan vacuum tap (it comes out horizonally); it would hold a 2x2" bit of manilla envelope paper against itself, but not one bit bigger.

Another thing - this is a differential pressure switch; the tube from the other side of the switch disappears into the furnace. If I disconnect it, I can suck and blow through it, seemingly without restriction.

Forrest - confused

Steve Ebels_3

Forrest

Have any of the technicians ever tested the draft to see what is actually being developed? This would give a definite indication as to where the cause of the failure might be. All furnaces designed with a draft inducer, such as yours, are made to run in a very narrow range of operation. Most of the time the pressure differential is less than 2" of water column and often less than 1". That's around an ounce or less of air pressure. A tech will tee in a draft gauge that is capable of measuring 1/10 W.C." and determine if wht your furnace needs is actually being developed. Without laying eyes on it anything else I'd say would be guessing.

Forrest McCanless

(from the house computer)

No one has tested the draft, AFAIK. I just drilled out and raiused the vacuum tap slightly, to see if that made a diff - no. Plus, Carrier won't tell me the desired depression H2O" for the switch.

Do you have any idea what the other side of the diaphram might be hooked to? If tempted to try to tap into the exhaust to get that extra bit of pressure on the other side of the diaphram.

Forrest

seabee570

switch

everbody has given good advice
1-NEVER EVER ATTEMPT TO JUMP OUT SAFETY
2-NEED TO GET A DRAFT READING AS WAS SUGGESTED BEFORE
3-YOU NEED TO FIND THE MAXIMUN ALLOWABLE LENGTH FOR VENTING,ADDING ELLS,TEES,AND 45'S,PLUS LENGTH OF PIPE.YOU CAN PROBABLY GET THIS INFO FROM A SEARCH.YOU MIGHT NEED TO INCREASE PIPE SIZE,OR MOVE THE FURNACE,OR LOCATE A SHORTER ROUTE FOR THE VENT PIPING.IF YOU ARE BOARDERLINE ON THE VENT PIPE DISTANCE YOU WILL ALWAYS HAVE PROBLEMS

Scott Larabee

I'm not familiar with this unit, but if that is a differential switch as you said, it could be that you have a cracked heat exchanger. Regardless of what the problem is, you are quite literaly taking your families lives into your hands everytime you "fool" the saftey!

You either need to find a tech. that knows what they are doing, or replace the furnace. No matter what you choose, you should choose to be cold until the issue is resolved.

Cold is much better than DEAD!

Scott

Forrest McCanless

Interesting about the cracked heat exchanger. Like I said, there seems to be no restriction when I suck on that tube. I'm sure there's a fairly large volume in there, but I guess I could seal and vacuum it to test?

Rest assured, I don't really "suck-start" it except to diagnose it! Sometimes it works fine - just not today.

Forrest

Tony_23

Scott's right

What is the serial # ? That will tell us the age.

You're well within the vent requirements for a 125,000 furnace.

You need a GOOD tech, not a parts changer or an installer who plays serviceman.

Forrest McCanless

Serial is 2292V00526. Installed Nov '93, I recall. It's always done something like this - for a while we thought it was the overtemp sensor, then Carrier had us move it outside the air handler - no change.

Forrest

Jason_25

the condensate drain trap may be patially pluged you could pull a drain hose off and pour water in it with a funnel but as said before the heat ex needs to be checked - very common problem with carrier, have a tech remove blower and lay in the blower compartment to visualy inspect. Is there any wetness in blower area under heat ex?

Forrest McCanless

I have checked the condensate drain - it's clear - the (3) tubes - from from the furnace, the draft fan housing, and the chimney pipe drip leg.

Do you mean remove the large air-handler blower to check the HeatEx?? Just for a visual check?

Is there any way I can pull a vacuum (got a little auto hand vacuum pump with gage) in the heat exchanger and check for a leakdown? Am I correct in thinking the HeatEx should be sealed except for intake, exhaust, gas in, and two pressure tap tubes?

Also - do you mean look for wetness inside the air handler under the heat ex? This is the first I've run the furnace since last May, so I wouldn't think so - total run time of my experimenting today has probably been less than ten minutes.

I've replaced the big air-handler motor years ago, but haven't had the side cover off lately. Looks like that may be the next step.

My tech, who owns the company that does my HVAC installs (I'm a residential GC) can't figure it out either.

Thanks much for your time.

Forrest

Unknown

Class action suit...

There was/is a class action suit involving cracked Carrier heat exchangers! I'll see if I can find more...

Here you go:

http://www.lieffcabraser.com/furnace.htm

Unknown

Forrest, a good way to prove if your air intake and exhaust

are the problem is to disconnect them from the furnace. If the furnace fires okay with them disconnected then your problem is the vent and air intake.

If that is so then increasing the size of intake most often will solve the problem.

Forrest McCanless

I've done some Internet research on Carrier secondary heat exchangers, and the lawsuits tonight. Some of the posted stories of consumer's experiences both with their furnaces and with Carrier, have been so similar to my own I could have written them!

I wonder if this has always been my problem? I have another Carrier furnace (smaller) for the front part of the downstairs, and a 4Ton Carrier heat pump upstairs in this same house, and they've both been fine.

Have to get this heat exchanger checked!

Forrest

jim lockard

Mag gauge

How about we measure the the air pressure at the switch as any number of things could be wrong both inside and outside of the furnace. Any troubleshot on this furnace involves knowing what the air pressure is at the switch and why. J.Lockard

big willy

Have to agree

With Jim. That is always the first step with preshure switch problems for me. A switch will either have the setting on the tag, or the manufacturer can tell you what it is. It will look like .65 in. w.c. That means .65 inches of water collum. This should be checked by the service tech. One thing I have seen with alot of carrier furnaces is the preshure switch tube comes of the bottom off the heat exchanger manifold. The other tube that size is a equilizer for the p-trap. This one comes of high. Quite a few times I have had to switch the tubes position to get the switch to work. This is because of water getting into the tube. So if the Magnahelic guage showes the preshure it is designed for and inspection shows no heat exchanger cracks, the switch is probably bad. I see alot of them pick up the moisture from the heat exchanger and this ruins the switch. Also they are a very sensitive switch to begin with and Carrier got it from the lowest bidder so its very possible its bad. Because you disconected the flue pipe and intake and the problem still happened I think you can rule that out. Just be very sure of the heat exchanger condition and the pressure. Also remove the fan assembaly it takes four 5/16" screws and ten minuts but their may be debris in it or the impeller may be worped. Good luck.

Forrest McCanless

Thanks for the reply. I'll pull the switches off today and look at them for markings or adjustments.

Yesterday, I noticed this - There are two vacuum switches on the exterior - the first, on the left, is a single-acting diaphram, connected to one clear flex tube that goes into the furnace cabinet. But, the heavy yellow short wire with connectors on either end is just dangling, only one side connected.

The second vacuum switch, on the right, is double acting. The left-hand side goes to the vacuum tap on the draft fan housing; the right side is attached to a second tube that goes into the cabinet, below the first tube coming from the other switch. This switch has two heavy yellow wires that connect to the control board.

Clearly, at some point in the past, one yellow wire came from the control board to one switch, the short yellow connected the two switches, and the second yellow wire returned to the control board.

I have no way to check the original configuration of this - Carrier manuals don't seem to exist online.

Any idea about this 'til my tech guy can come with a sensitive pressure gauge tomorrow?

Thanks again -

Forrest

Rich L.

Schematic?

There should be a wiring schematic inside of one of the access panels you're pulling off to get to the "insides of the unit. Look for the pressure switch(s) on there to see if 1 or 2 are shown wired in.

Good luck, Rich L

bob_50

I heard about

a gal that could suck start a Harley but I've never heard about suck starting a furnace!

Forrest McCanless

Ya' know, it's all about a good title to bring folks in!

F

Unknown

Hmmm,,,

Not to be a party pooper but I'm a little concerned as to why someone with little or no experience is fiddling around with a very complicated and potentially hazardous control problem. My suggestion is to have your local service co bring in the Carrier tech rep for your area and nail this thing down. The thought that you have been "suck starting" your furnace "for years" is pretty troubling to me. First I'd find a Carrier authorized dealer and take it from there. If they can't figure it out they need to get the factory rep in on it.

Unknown

Good,,,

I feel better now! My next suggestion is to get that POS out of your house, preferably at some expense to Carrier.

Rich W

Trap

Maybe I missed it in one of the replies. My apologies if I did. Have you cleaned the trap. That's the thing that is connected to the pipe going to the floor drain. There should be several tubes entering the top and one on the side or bottom going to the drain. It could be in the blower compartment or on the side of the furnace. It needs to be removed and flushed. Force water through the drain connection while plugging all but one of the other holes until the water runs clear. Repeat until all are clear. A plugged trap causes your exact symptoms. Good luck.

Rich W

Unknown

This is a very good

example of what happens when complete annual maintainenance is not conducted on equipment. One of the things that must be done once a year is to flush the secondary heat exchanger and also the condensate line , pump and all traps. If this is not done it will come back to haunt you.

It is also important on boilers with condensate lines they must be back flushed and cleaned once a year. It is also a good idea to pull the burners out and check the combustion chamber on all condensing units once a year.

A little cooking oil used very sparingly into the small hole (use an eye dropper) on the pressure switches will prolong the life of the diaphragm in those switches also replace the condensate tubing lines and the plastic tubing lines to the pressure switches every other year. REmove the combustion blower assembly and make sure the squirell cage is clean and not damaged, spray a little WD-40 sparingly on it to keep it free moving. Smell the motor if it has a burned smell it should be replaced even though it may still be working. If it slows down it can affect the ability to pull in the pressure switch by not creating sufficient differential or suction pressure.

If you do not maintain and test you do not know what the equipment is doing. That includes combustion testing and checking the heat exchanger for damage when doing the combustion test.

rich pickering

Don't forget to tell the rep about the brass wire around the draft fan.

jim lockard

you are not understanding

If the switches were defective the furnace would not light when you sucked on the hose. You need a good service tech to go thru your furnace and solve the problem or replace the furnace. J. Lockard

tom_49

Forrest,

I recently had an older Carrier unit giving me a similar problem. Turned out to be a slight crack in the sec. HX drain tube, causing the suction pressure in the fan housing and pr. sw. to drop, something to check.It took 3 hrs. of watching this thing run w/ magnahelic hooked up, but I got it!

You need to take magnahelic readings and compare to manuf. specs.

You might want to pull it out and install a Carrier Infinty 2 stage , variable spped unit and save some $$ on your heat bill.

Good luck.

Unknown

Afterthought...

Don't be afraid to contact those lawyers at that website I linked you to. They are actively searching for people with the heat exchanger problem. Just the mention of their names to the right people at Carrier might get results too.

Forrest McCanless

FINAL #$%^& RESOLUTION!!!

OKAY - Y'ALL AREN"T GONNA BELIEVE THIS!!!!!!



I'm sorry, was I shouting?

Finally, after 15 years and who knows how many service visits and cold mornings and teeth-gnashing, a Carrier rep or two came out Wednesday. Along with my HVAC guy, they completely disassembled the heat exchanger. First time it had ever been apart.

My guy tells me today, "one of the reps looks at the two clear pressure tap tubes connected to different places on the HE that feed the draft safety switches - "Hey, this isn't right!""

THE PRESSURE TAPS HAD BEEN CONNECTED WRONG (reversed), INSIDE THE HEAT EXCHANGER, AT THE FACTORY, FIFTEEN FREAKIN" YEARS AGO!!!!!!!!!!

Okay, I sat down. 1 2 3 4 5 6 7 8 9 10.

They simply swapped the tube positions. Been fine ever since.

God, I hate counting on other people.

Forrest

Plumdog_2

I believe it

I don't think very many of these products get tested at the factory. Testing should be mandatory. Probably costs too much.