Short Cycling Janitrol

Bud_14

are home inspectors obligated to inspect a furnace and it's efficiency or operation, they are only required to make sure the unit comes on amd turns off...this is true with central air, most home inspectors haven't a clue to the proper operation of any of these units other than, it comes on and turns off...both parties should be calling in a contractor for a complete operation and safety inspection...


Bud (thesheetmetalshop.com)

Jim Katen

Short Cycling Janitrol

Greetings. I'm a home inspector in Oregon and I'm hoping that someone here can help me with a question.

I inspected a home with a 1998, 90% Janitrol furnace (gmcgmpn100-4). In addition to several other small problems (condensate leaking and dripping onto the burner plates, no dirt leg on the gas supply piping and no filter compartment cover in this garage installation. . .) the furnace was short cycling about every 90 seconds. The filter was moderately dirty, so I removed it -- no change. It would still fire for only about 90 seconds at a time.

The tech who came out to look at it to do the repairs said that the short cycling wasn't a problem because, "the honeywell thermostat has a built in energy mind that cycles the furnace for better comfort."

I've never run into a thermostat that behaves like this before. The only control wiring I saw was between the furnace and the stat. There was no outdoor thermometer. If this thing is cycling for efficiency, how does it know what to do without an outdoor sensor? It was 51 degrees outside on the day of the inspection. Seems a bit cool to be modulating the furnace to that degree.

I've tried to call the tech to speak with him directly, but haven't been able to hook up with him yet.

Can anyone here shed some light on this for me?

- Jim Katen

lchmb

never heard of that

I have never heard of cycling a warm air furnace in that manor. Not saying it's not out there, just I have never heard of it. Are you sure it was the t-stat cycling the unit on and off and not the high limit? I would be checking the blower and the plenum sizes myself..Along with a few other things..

Jim Katen

lchmb,

Like you, I never heard of a stat that worked quite like that. In my report, I said that it was cycling on high limit, though I didn't actually check the output of the limit switches. (my bad)

This was a replacement furnace and the installer re-used the existing plenums though they looked, if anything, generously sized.

I was thinking along your line of reasoning; blower speed, poor ductwork, etc. I didn't expect the tech to come back with "Fancy Stat."

With luck, he'll return my call on Monday and I can learn about this stat that no one else seems to have heard of.

In the meantime, if anyone on this board has heard of this, please let me know.

- Jim Katen

jim lockard

wonder

If you were to remove the blower door will the furnace run longer?
If so maybe a return side restriction. If you jump the stat at the furnace red and white wire on a goodman board will the furnace continue to run or shut off on hi limit?
On the drip leg for the gas some inspectors do not like them in unconditioned spaces like garages, because they may freeze (a local thing).
Do not fret about the tech he's blowing smoke.

Sweet_2

Jim

Has anyone checked flame sense? Possible build up on rod.

hvac64

Jim, I'd start w/ jumping out the tstat at the board ( usually on these furnaces they are hanging out the side).Jump the red and white. If the furnace runs right, the problem is external from the furnace. If it doesn't run right I'd check the flame sensor, clean it with some sand cloth. also check the wires from the flame sensor to make sure the connections are tight( on some janitrols they have a molex connector in between the burner compartment and the blower compartment make sure that is tight ).
Another thing ive found on those units is moisture will build up in the pressure switch tube. Take the tube off the pressure switch to check for moisture. Those furnaces have had lots of problems, though lots of the problems i see are installer error ( the most popular is OVERSIZING the unit in regards to the duct system and house size ).
Good luck Tom

jim lockard

flame sense

Most flame sensor problems are righjt now not after the fffffurnace has run for 90 seconds. But would not hurt to clean it just for grins

jim bannister_2

Short Cycling Janitrol

Before you condemn the tech, check the thermostat. Most of your newer series, especially the Honeywell line, have dip switches which are set for cycle rate per hour. This will bring on the unit before there is a large disparity in the set point. The thermostat may be set for electric heat which cycles at approximately six times per hour. It the cycle rate is too fast, I personnally would move up timing to the next level.

S Ebels

My guess

It's shutting down on the high limit safety. Easiest way to check is to stick a thermometer probe into the plenum and see what the temp is. Most of these shut down at about 160* if I'm not mistaken.

A clue would be if the inducer continues to run when the burner goes off. That would indicate a call for heat from the thermostat is still present.

Some newer stat's have a cycle per hour setting but I've never seen one even remotely close to every 90 seconds. Most function as a limit to the number of cycles, like 3 or 6 per hour.

Jim Katen

Thanks everyone

Thanks everyone. Your responses were thoughtful and helpful.

Just to clarify:

I have no interest in condemning the tech. The furnace was short cycling every 90 seconds when I was there, but I don’t know what it was doing when he was there. It might have been behaving in a different manner that he found to be acceptable.

The draft inducer continued to run when the flame quit.

The flame sensor was clean – heat discolored of course, but no carbon build-up.

I hadn’t thought about moisture in the pressure switch tube. That’s a handy thing to know. I can imagine a tech going absolutely nuts with that one.

It’s interesting that hvac64 should mention the wiring connections. I mentioned before that condensate was leaking onto the burner plate. It now occurs to me that the flame rollout switches are right there getting dripped on. I wonder if acidic condensate has any effect on the wiring connections to these suckers?

- Jim Katen

Boiler Guy

A flame rod should NEVER be \"cleaned\" with sand cloth!!

You did not mention wether the blower was opersting or not, during your inspection. If the failure is consistently happening @ 90 secs, I too suspect the flame proving circuit.

John Taylor_2

Sounds like it's in the ignition control circuit somewhere. If it where the t-stat the combustion blower would drop out as I believe it would with the high limit. You could try jumping across the safety that is getting wet to see if it being affected (don't let it run like that for very long though). Has anyone checked gas pressure? Sounds like you should get qualified tech out there.

Empire_2

Limit

I'll bet ya the secondary Heat exchanger seeing that the blower door was left off...

Empire_2

Limit

I'll bet ya the secondary Heat exchanger seeing that the blower door was left off...

hvac64

boiler guy,

Why not clean the rod w/ cloth?

Kevin__Flynn

Sand cloth

It is not a good idea to clean a flame rod with sand-cloth because sand-cloth is made from sand. When sand is heated it turns to glass and glass is an insulator. This will stop the ground circuit from being completed and cause nuisance lock-outs.

Steel wool is probably a better idea.

If you do use sand cloth, make sure that you use a clean rag to wipe off any sand left behind.


Kevin Flynn

hvac64

sand cloth

Thanks kevin...never thought about the glass thing. I'll put that one in the vault.Thanks, Tom

Boiler Guy

Another reason is

If you get too aggressive with the sand cloth, you will leave deep scratches in the rod which will permit an easier, quicker build up of particulates on the rod, requiring more frequent cleaning.
I have never heard of the sand/glass/insulator scenario before.... but I guess it does make a little sense .... if you don't wipe the rod off afterward.

hvac64

Guys, I think next time I'll just change out the $4.00 sensor.

Rely_2

Just a though

what if it is a goodman stat it maybe, they still have mercuy bulb in them could be heat setting on stat have seen it many times.If it is electronic stat than it is air floww across the heat exchanger and if it is that old they used a ring type seal to assemble the exchanger and it toast check for CO in outlet of furnace!

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jim lockard

Flame sensor

If I scrape it with my pen knife are you ok? J.Lockard

hvac64

Thats why you jump out the tstat 1st . Start there, then move on.

S Ebels

\"Draft inducer continued to run\"

AHA! That fact pretty much eliminates any t-stat issues as it indicates that you are obviously not losing the call for heat from the stat.

Someone mentioned condensate buildup in the pressure switch tube and that is a good possibilty. Usually though, if it's a plugged tube or trap issue, it will take a matter of several minutes at least before the trap or tube will clear itself and allow the furnace to recycle the burner.

I'd still check on the discharge air temp. If it's within nominal operating range, then replace the high limit.

hvac64

1 more thing , check to see if the condensate trap is cloged. I had a call recently where the trap was clogged causing a backup w/ the condensate and causing a pressure switch fault. I fix these things all the time, theres only 1 furnace thats worse , their Gmp, 1993 in particular.
"Janijunk", you dont get nick-names, you earn them.

Boiler Guy

Any scratch is a potential problem

I have found some of the early sensors crystalized from the constant heat quite prematurely. Give 'em a little pull and they snap right off.

Try this test: Clip a lead from a multi meter to the plug end and slide the other probe up and down the flame rod. If it is questionable you will see the meter flutter (analog meter is best) No flutter - rod good <> Flutter - rod no good. It is cheaper and simpler to just replace with new. No more PIA

Craig Bergman

Sand cloth??

You NEVER clean a flame rod with Sand Cloth!
The silica residue can turn to glass and ruin the flame rod!

Sweet_2

I've always used steel wool

any potential problems with this that anyone can see??

Dave Yates (PAH)

Question

Why is someone who is not qualified sticking their fingers into the controls side of high efficiency equipment and why jump out the TT terminals without disconnecting/isolating the stat?

From what I've read & learned, home inspectors are not obligated to test appliances.

Too much potential for liability and bad advice.

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jim lockard

never tried that

Boiler guy, I tend to find a few flame sensors that are carbonized after the 1st year of service in new homes. I blame drywall dust and carpet fibers for this 1st year loading so scraping it seems to solve the problem for a sensor with very little age on it. J.Lockard

Jim Katen

> Why is someone who is not qualified sticking

> their fingers into the controls side of high

> efficiency equipment and why jump out the TT

> terminals without disconnecting/isolating the

> stat?

>

> From what I've read & learned, home

> inspectors are not obligated to test

> appliances.

>

> Too much potential for liability

> and bad advice.

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 98&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Jim Katen

Dave Yates writes: Why is someone who is not qualified sticking their fingers into the controls side of high efficiency equipment and why jump out the TT terminals without disconnecting/isolating the stat?

Don't know where you got that from. I never said that I stuck my fingers into the controls or jumped the terminals. You may be confusing what I did with what some folks here suggested that someone do to troubleshoot the problem.

Dave Yates writes:From what I've read & learned, home inspectors are not obligated to test appliances. Too much potential for liability and bad advice.

You've heard wrong. Home inspectors are, indeed obliged to test permanently installed appliances such as furnaces. The liability comes from not testing them. As for bad advice, that depends on the education and knowlege of the one giving the advice. I'm trying to improve my education and knowlege by seeking to understand an unusual phenomenon.

- Jim Katen

Jim Katen

Gets more interesting

Today I spoke with the tech who looked at the furnace. He said that when he was there it was cycling every 5 minutes, not every 90 seconds as it was when I was there (though he says he didn't actually time it with a watch -- it just 'seemed' like about 5 minutes). He first assumed it was a bad high limit sensor, but when he tested the leads from the stat, found that power from there had shut off. Since he wasn't familiar with that particular Honeywell stat, he searched through the instructions for it and found a statement to the effect that, for efficiency and comfort, this stat would cycle the furnace on and off. He was vague about exactly what the instructions said.

Throughout his visit, the homeowner, (the lady who's selling the house to my client) kept telling him that the furnace was fine and had never given her a day's trouble since 1998 when she had it put in. (I guess not, since she never felt the need to have it serviced) At that point, he figured, "what the heck," wrote her a letter saying that the furnace was behaving normally and left.

Now he's concerned that he missed something. So am I.

- Jim Katen

Boiler Guy

Actually ... steel wool is recommended

by most flame rod manufacturers.
Jim > the meter test works quite well on larger diameter flame rods, but I'm not sure about the small ones found in residential furnaces. Gotta use the most sensitive ohm scale on the meter though.
Old service guys tip(myth?)I still remember: Use a dollar bill to wipe the rod >>apparently something in the make up of the paper or ink does a good job of cleaning it<< If you want to do a "real good" job >> use a $100 bill !?!? I think he was jerking my chain though.

I do know this trick used to work well on the old Fireye and Honeywell burner programers for cleaning the contacts.

Point of interest: Not sure if it makes a difference if the bills are CDN or US :-)

Dale

Garage

To me the big one here is no filter cover in a garage, fortunately we don't have too many garage furnaces in Wisc. but given the monoxide risk all the return side needs to be really well sealed, tape and mastic. I too think the inlet side of the secondary is causing high limit trip, putting a tattle tale on the limit would show this, if the computer won't go with that then watch the limit with a voltmeter and monitor discharge temp. I have my differences with home inspectors but in some places the more eyes the better safety.

jim lockard

Boiler guy

Have seen furniture refinishers use brown paper bags to "knock the snits off" just a little abrasion without too much damage. Best Wishes J.Lockard

Dave Yates (PAH)

interesting reply

Jim,

Don't mean to be a fly in the ointment, but you'll need to direct me to the code of ethics and list of what's included that's governed by your licensing organization. The ones I've studied specifically exempt appliances and do not even mention CO testing.

Let's see what's to be included and what's excluded. How extensive was your training? Schooling and exams or was this an on-line un-proctored exam to become a Nationally Certified Home Inspector? What's your background?

The reference to jumping out the wires wasn't meant to imply you, but rather to test knowledge regarding potential damage that can cause. But, if you don't know the answer, you shouldn't be twisting wires together to "test" the system.

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lchmb

Just curious

But wouldn't it be well worth your client's time and money to have a complete inspection by their own service company? That way they have a pro that they are comfortable with check what may soon be their own?

S Ebels

Finding the Pro is the hard part

Case and Point:

This past January I received a call from a customer we had installed a ThermoPride furnace for several years ago. He wanted it serviced before he left for Florida. Like that afternoon. We were swamped with no heat calls and I told him I would not be able to get to him that day. He said he'd just get someone else because it had to done before he left. I reminded him that his burner (Riello F-3) was not what most service people around our locale were familar with before we hung up.

Long story short; his furnace takes a .50 60* W Hago nozzle and the "tech" that serviced it replaced it with a .75 80* B Delavan. I have no idea what he was thinking (or not thinking). Incredibly, the Riello ran through the duration of their vacation, 6 weeks, but they returned home to find a house covered in soot and about a 7 spot spewing from the chimney.

This work was done by a local heating company that has been around a lot longer than my company has. Their name is known far and wide around here when discussion turns to furnaces and other heating appliances. The third generation is now running the business so people automatically assume they know what they are doing.

And THAT my friends, is the problem. Just how does Joe Homeowner qualify who's good and who's not. As a general rule, 9 out of 10 homeowners wouldn't know what questions to ask or what to look for that would enable them to say, "this is (is not) the guy I want.

Jim Katen

Dave,

My professional association is ASHI, the American Society of Home Inspectors. Their standards of practice are here: http://www.ashi.org/inspectors/standards/standards.asp

In Oregon, the state licenses home inspectors and requires them to perform to the standards here:
http://arcweb.sos.state.or.us/rules/OARS_800/OAR_812/812_008.html
(Scroll down till you come to heating.)

There are lots of home inspector organizations out there. Some are very good. Some are downright sleazy. However, every one that I'm familiar with requires their members to do a visual inspection of the furnace and venting and to operate the furnace using the thermostat. Most of them require us to open the cabinet.

All of these standards define the minimum that a home inspector is expected to do. Inspectors may exceed the standards.

In the context of a home inspection, the point of this examination is to determine whether or not there are any fundamental flaws in the installation or performance of the furnace. If there are, or even if there appear to be any, we pass the ball to you guys to analyze the problem and correct it.

As for my training, I'll be the first to admit it's weak. Twelve years ago, I took three 6-month classes at a local community college. One on gas furnaces, one on oil furnaces and one on heat pumps. I know, I know, pretty much everything I learned in those classes is outdated. But Oregon requires me to have 15 hours of continuing education each year and ASHI requires 20. Last year I got just under 50 hours. About 20 of them were HVAC related. But some of the best training I've had is from 3 local HVAC techs who've patiently answered my questions and explained things whenever I've encountered something that's new to me. They've been good, patient teachers.

I've been a home inspector for 13 years now and I'm proud to be Oregon Certified Home Inspector #15. I hope that I can continue learning from the folks on this board and I promise to try to avoid asking questions that are too terribly dumb.

Oh yes, as to your test question. I suppose that the danger of jumping out wires is that you could fry the stat or the transformer, or at the very least blow a fuse. I suppose if you tried really hard, you could fry the board.

- Jim Katen

Jim Katen

Lchmb writes: But wouldn't it be well worth your client's time and money to have a complete inspection by their own service company? That way they have a pro that they are comfortable with check what may soon be their own?

Absolutely. I always tell my clients to hire their own contractors directly. If they twist my arm, I even give them names and numbers of people that I trust.

In this case, they wanted the seller to cover it.

You can give people good advice, but they don't have to follow it.

- Jim Katen