[Fix'n it]

i have a HUNTER stat that used to be in use, about 3+ years ago. i took it off thinking it was a problem. till then, it would turn the furnace on for 20 mins and off about 40 mins @ 32deg outside temp.
i installed a basic new ( about 4 years old now)honeywell stat. it turned the furnce on for 8 mins and off about 20ish mins @ 32deg outside temp.
i think this is to much cycling. so, i put the HUNTER stat back on. house was cooled off a few deg when i turned it on. furnace ran for 8 mins, shut off, even though the stat temp was not reached and was calling for heat. then the furnace stated right up immediately .

this 8 minute thing. i thought it was the honeywell stat. but it "seems" not.
now, i'm confused. can a basic furnace have a setting for this 8 minute thing ?
its a 06 nordyne gas.

 

[Fix'n it]

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[user_12345a]

What's the problem?

The honeywell out of the box doesn't allow for much of a swing. You can cut the cycle rate to get a larger swing, 3 cph should be okay. check the advanced portion of the install manual. The factory setting is often 5 or 6 - hard on the furnace.

The honeywell has heat anticipation and make take a few hours to "learn" the house and get the right heat anticipation for your system. The lower cph rate will allow for some more overshooting if you adjust it.

till then, it would turn the furnace on for 20 mins and off about 40 mins @ 32deg outside temp.

Were you not comfortable?

The long cycles are better for the furnace and to an extent the gas bill. may get a little chilly after 40 minutes off though.

 

[Fix'n it]

What's the problem?


Were you not comfortable?

The long cycles are better for the furnace and to an extent the gas bill. may get a little chilly after 40 minutes off though.

the 8 minute thing. i thought it was the stat.

no, not at all.


yeah, thats what i am after. 40 minutes is not an issue, could go even longer.
i am trying what i can to make my furnace last.


i know the honeywell stats are programed for "comfort" and to hell with the longevity of the furnace.

 

[Fix'n it]

no, not at all.

ooops. should say = yes, very comfortable. not an issue.

 

[user_12345a]

reduce the cph setting to 2 or 3, maybe even 1. experiment and see what works best.

From the factory the honeywells cycle the hell out of the equipment. i've also seen them cycle when recovering from setback periods.

solution is to cut the cph and disable smart recovery.

otherwise they're very good stats.

 

[Fix'n it]

i can do that with the HUNTER stat. but not with the 2 honeywell stats i have. thats why i switched back to the HUNTER.

 

[Yodaman]

imo - 8 mins run x 20 off sounds about right. Gives you a 40% run time where 20 on x 40 off is 50% run time. You will also be more comfortable.
Its possible but not likely you are running hot and hitting the high limit switch. Filter clean?

 

[user_12345a]

what's the model number of the honeywell.

 

[Fix'n it]

what's the model number of the honeywell.

this is the one i was using
http://www.lowes.com/pd_356348-74493-RTHL111B1001_0__?productId=3464344

but i also have a rth6300b1005. works the same, but its programable.

 

[Fix'n it]

filter is clean

 

[Fix'n it]

Its possible but not likely you are running hot and hitting the high limit switch.

is there a way for a diy'r to check this ?

 

[user_12345a]

function 5, heating cycle rate, page 20 of the install manual.

Drop it to 3, if that's too high try 1.

 

[Yodaman]

is there a way for a diy'r to check this ?

if your stat is still calling for heat and the furnace shuts down then you may have hit the high limit

 

[Fix'n it]

my bad, this is the one i was using.
RTH111B1016

 

[Fix'n it]

if your stat is still calling for heat and the furnace shuts down then you may have hit the high limit

it did this with the HUNTER. but not with the honeywell.
and, its been warm for several days now, 60deg days. so the stat is not being tested well. actually, the hunter stat. the heat has not been on for hours now. and its not cold in here at all. the honeywell stat, it would have been on MANY times.

 

[Yodaman]

imo - your concern is much about nothing. 8 on, 20 off is not short cycling. 2 run times per hour would not be considered short or rapid cycling. If you were on and off 5 to 6 or more times per hour it would be considered short cycling. (IMHO)

 

[Fix'n it]

imo - your concern is much about nothing. 8 on, 20 off is not short cycling. 2 run times per hour would not be considered short or rapid cycling. If you were on and off 5 to 6 or more times per hour it would be considered short cycling. (IMHO)

yeah, i know its basicly normal. but its not what i want.

 

[user_12345a]

Check page 15 of your installation manual.

The furnace should never be cycling on limit; if it does you must correct that. either an airflow problem, overfired or both. it should be able to run constantly without tripping anything.

The overheating shortens the life of the heat exchanger and raises gas consumption.

 

[Yodaman]

Also keep in mind that your cycle times will change when temps go down closer to design temp, which should be 0 to 10F for Chicago. Your runs times will increase and your down time will decrease.
Might want to check your cold to hot air plenum temp rise. Simple test, Google it for instructions. It will tell you if its running too hot or cold. The temp rise spec for your furnace should also be printed inside the unit.