lockout on 90+ furnaces

RichW

I have a little magic box that can monitor nine inputs. They can be high or low voltage- AC or DC. When the unit calls for heat or cool the box instantly records the condition of all nine inputs then goes to sleep for one minute. It continues this cycle until all inputs are low. At that time it will sleep until one of the inputs goes high again ( maybe an inducer getting power without a call for heat-problem solved-bad board ).
When I return I can playback the exact sequence of operation and pinpoint the failure in the chain of operation. Though it's too late to make a long story short, I have found what may be your trouble. Remove the pressure switches and use tubing to puff on the inlets and outlets. I am amazed how often they have condensation inside, even if you don't see liquid in the tubing. This gets them going until I can return with a new Pr.Sw. Hope that helps Robert.

RichW

robert norton

i have a question that id like to bang off the wall i worked for a large heating company for 15 yrs my toughest job is fixing a 90+ furnace that has gone into lockout and the cust has shutoff the unit ,when i arrive and reset power the unit fires only to lockout several days later again ive tried cleaning flamesensor or cycle several times what do you guys ever run in this problem.ive tried to tell cust to leave running till i get there but that never works

Dale

The intermittent

Sure, probably the most difficult thing to troubleshoot. It's getting a little better with diagnostic LED's being more common. This is where Timmies trouble shooting steps need to be followed. First when you're stumped, round up all the usual suspects, check gas pressure at the manifold, amp the ignitor, check and add another ground wire. One suggestion I have is to take all the necessary readings on a given brand of newly installed and set up furnace that works perfectly and write them down. For instance at what negative pressure does the vent switch close at? At what pressure does the inlet pressure switch open at? What is the exhaust blower giving us for total negative pressure for this vent run? What are the microamps of the new ignitor, what is the heat rise? And, you try things and remember what happened last and try it again. I call the tech line as soon as possible, Ruud water heaters had an ignition module that was one try and then lockout. I have put on several and the techs about 100 of the 3 try for ignition replacements and that usually fixes the no hot water call. Yet, you could test the old version, find nothing out of spec, and it would go for weeks without problems then lock out. Trane furnaces the old xl90 had a fenwall box that was like this. If the factory has a "suggestion" I try it. We had a new range that stopped ignitting and found out the home owner unplugged it only at Christmass to put in an ungrounded adapter for the window lights. Still, there are an infinite number of variables in life and in furnaces and sometimes you just need to eliminate the most likely problems and hope for the best. The best odds for a fix is to really understand the products exact and detailed sequence of operation and be open to the out of the box problems.

steve_26

90 plus

what make and model?

JimmyJam

Lockout

I have seen numerous lockout problems due to doorbell transformers. Yes it sounds goofy but listen to this. In the old days (and even today) electricians loved to mount the low voltage transformer on the furnace circuit to power doorbell, if the furnace is running at time someone activates doorbell it can cause a voltage spike that the control board does not care for thus locks out,or there is no actual grounding wire to furnace from breaker panel. Check the ground from the panel to the furnace and make sure proper ground has been obtained and if so, rewire transformerto alternate circuit and see if that helps.Good Luck!

Unknown

Robert

If you e-mail me your postal address I will mail you for FREE a complete step by step procedure for troubleshooting such a problem.

It really does not matter if they leave it on off or otherwise the checks I recommend will find the problem most of the time.

RichW

Steve Thomas (Foley Mechanical)

90+

Robert,

You should check your ground. I've worked in alot of old homes with 90+ gas furnaces. If BX cable was used for your power feed you may have to run a new ground. Also check the burner head in front of the flame sensor. It also may need to be cleaned. The flame sensor reads ground from the burner head through the flame to the sensor.

Hope this helps

Flag

Ben_3

It,s a ghost

It's a ghost, yep there is nothing else it could be, or maybe it's possessed. I've been there your not alone. I find a lot of "phantom" lockout occurs through the backup of condensate, dirty traps or whatever the mfger is using to get rid of it, sagging pvc which builds up a water seal only after extended operation. These are the ones you pull out all the toys and check everything and if possible check against the install instructions to make sure it was done correctly. Many of these problems are created because of improper sizing and/or installations. Good Luck

BillW@honeywell

This is a pet peeve of mine...

I have posted this before, but for what it's worth, here it is again. PLEASE use NEMA rated transformers on all your installations. The electronics in todays high efficiency products don't like off-spec voltages, spikes or surges. The couple dollars you save using a cheesy transformer is lost in the first callback and the angry customer. NEMA rated transformers provide consistent voltages. Another problem with hi-tech heating equipment is grounding. Proper gounding is essential, and is the second most common cause of those maddening intermittent problems. Protect the entire house with a whole-house surge supressor. If it's ghosts, well, who ya gonna call??? Ghostbusters!

Dale

Ground wire

Reading the good thoughts on the other posts I thought I say something about grounding too. If you have a lockout problem and the house is BX or conduit take the time to run a separate green wire from the main ground at the service entrance to the furnace ground screw. You can wire tie this to the outside of the conduit as from the electral code NFPA 70 this is a bond wire not the legal ground which is provided by the conduit. I know dealers who do this on all old wiring systems to lessen the problems you mention. Also, if you ever find a furnace fed off a sub panel not the entrance panel make sure the neutral wires in the sub panel are SEPARATE from the ground wires and NOT connected electrically to the sub panel. This means that the neutral bus bar in the sub panel MUST be insulated from the panel steel. I have fixed many lockouts and shorts to the shower head ect by checking this whenever I see a sub panel.

Glenn Harrison

Little magic box?

Is this "little magic box" made by OnWatch or somebody else. I assume by your description that it works vey well and has helped eliminate some of those dreaded ghosts we encounter. Id be interested in more info.

Thanks, Glenn.