Originally Posted By: slong This post was automatically imported from our archived forum.
Hey guys.
Is it normal operation for a gas fired furnace less than ten years old to cycle on and off for about 30 min before it stays on continually? The ac was previously on, is it sensing the condensate or something? There are a lot of safety sensors and I’m suspecting that one is faulty.
The owner says it does that when you switch over. What do you think?
Originally Posted By: nlewis This post was automatically imported from our archived forum.
Stewart,
Do you mean that the burners cycled on and off or the blower fan, or the whole unit , or what? Do you really run a warm air furnace for 30 minutes, or was this a special circumstance?
Originally Posted By: slong This post was automatically imported from our archived forum.
Hey Neal
I didn’t clarify. The burners cycle off/on every 10-20 seconds or so. Actually I didn’t run it for 30 min. That’s what the owner said it takes before it stops. It was 75 degrees outside and getting pretty warm so I told the buyer they should have it verified.
Originally Posted By: rsummers This post was automatically imported from our archived forum.
If the unit is induced or forced draft it could be cycling off its pressure switch. More modern units would go in to a lock-out if this was happening. I’ve seen units with flue vents to small or to long not operate properly until the flues heated up. How was the flame?Some units prove ignition with a flame sensor rod. If not fully engulfed in flame or if its to corroded it will shut the burners down. Some of then old 3 wire pilots with the pick and hold circuit will do this until the hold side of the control snaps into place. It really could be a lot of things depending on the brand of furnace that’s installed ,good thing we don’t have to trouble shoot just pass or fail it.
Originally Posted By: dvalley This post was automatically imported from our archived forum.
Rolland,
I personally don't go around passing or failing anything on a home inspection.
There are times where I get asked that dreaded question "Does it pass or fail"? I just look them in the eyes and say "I just report what I see, to my client, and nothing in this house is considered to pass or fail". I don't make judgements on anything I see defective. Reporting the defects and recommending corrections by particular professionals is the best way to go.
If you pass or fail something and a particular expert is called to evaluate your decision, and he/she then finds out that you were wrong... OH OH. Not a good situation to be in, based on your evaluation.
Do yourself a favor. Observe And Report to stay out of court.
Originally Posted By: Blaine Wiley This post was automatically imported from our archived forum.
David,
Observe and report to stay out of court. That has been my mindset since I got into this business, but not in those exact words. Can I steal your line 
Originally Posted By: Blaine Wiley This post was automatically imported from our archived forum.
or
How long will the (insert item here) last? Well, I'm not sure, is your crystal ball working? I left mine at home. 
Originally Posted By: slong This post was automatically imported from our archived forum.
Is this where I was waiting for an answer from the HVAC experts such as, “no don’t tell them to call a service man it’s perfectly normal for the burners to cycle off and on?”
Originally Posted By: Blaine Wiley This post was automatically imported from our archived forum.
Stewart,
I thought I read the answer to your question in a previous post, before we got off topic. The answer is NO. The burners in any gas furnace aren't meant to short cycle.
