Furnace Cycles

What is a "typical" cycle time for a furnace setup?
Our current setup (soon to exist replaced with HP and new furnace) is an 80k BTU (output) in a 2500 sq foot 25yo house. The thermostat (Lux TX500 located in hallway at center of house) shuts the furnace downwardly from 9am to 5pm. At 5pm the furnace (single phase) turns on to a setpoint of 19C which takes effectually 1 hour to accomplish. So from 6pm to 10pm the furnace does not come dorsum up. Exterior temp approx 4C-6C at 10pm.
Using the HVAC-Calc sw, the calculated loss is 54k BTU/h.
So I'm pretty sure our current furnace is style oversized. Is the culprit the furnace or peradventure the thermostat?

06:07 PM

Originally posted by pepper3245
Is the culprit the furnace or possibly the thermostat?

Either one or both. Non really enough info to say. Are you saying that later recovery is consummate, the furnace never comes dorsum on the residual of the night?

Are you certain it's not an 80k Btuh input?

Been asked that question many, many, many times when doing service calls. The answer: There is not one. Everyone'southward condolement zone ( temp to be comfy, estrus and cool) is differant. A departure in temp settings controls equals run time. More than run time( higher cost), lower run time( lower price) heat or cool. There is no constant. Now yous know why thermostat are adjustable.

Furnace is a 100K 80%. The furnace may come up dorsum on at 10:30pm simply the thermostat is programmed to turn information technology off at 11pm. The thermostat is programmed to fire the furnace from seven:30am-9am and 5pm-11pm. From what I see the furnace volition fire 1C beneath SP and turn off 1C (or was it 2C?) above SP.

are y'all concerned that the house is not to SP sooner?
what time do yous get home?

I would state that your furn is oversized --
at the normal everyman temp expected for your area, the furn should run all the time -- even at the recommended design temp -- [which is ___ ?]

seems like the t-stat doing its job ok

I'm dwelling around half-dozen-half dozen:30pm so the furnace may or may non be on. I'm comfortable with the ramp upward to the SP, I'm just not certain of a 80kBTU/lxxx% is more suitable (equally backup to the HP) for this house.
The temp did go into the -8C to -10C last month, subsequently reaching the SP it MAY have ran for 60-90mins (no more 20 mins/cycle) between 7 and 11pm.

The furnace was definitely replaced by the previous owner 6-seven years agone, perchance they replaced their 100k (40-60%?) with another 100k (lxxx%)?

I don't know what the design temp is.

my 1983 manN calls for 19F design at that place -- -7C

such should be shown on your heat load calc --

so, if your furn was sized for decent effeciency, it should have been running longer ea cycle --

A 80,000 input 80% furnace will output 64,000 btu'south, 10,000 above your load calc, so it would be advisable for your load calc.

Information technology will have a longer run time during recovery and so your current furnace.

But, get a real thermostat, for your new furnace.

Here nosotros go again ( lol)
as long every bit you are comfortable (heatwise) what would you rather have,....
a furnace that runs constantly?....
or i that runs well-nigh 6 or seven minutes a couple of times inside an hour..
Practice you think there is any comparing in fuel consumption?,.... lol..do the math.

Quote Originally Posted by deejoe View Post

Hither we go again ( lol)
as long as you are comfortable (heatwise) what would you rather take,....
a furnace that runs constantly?....
or one that runs near 6 or 7 minutes a couple of times within an hour..
Do you think there is whatsoever comparison in fuel consumption?,.... lol..do the math.

I take my oil furnace reduced from its ane GPH firing rate to .65 GPH.

It runs real long now. And uses alot less oil a year and so it did at i GPH.

I even switched back and forth between the nozzles or similar days.
And the reduced firing rate always uses less oil.
With the 1 GPH nozzle, I can heat my place to ninety when its - xx outside.
With the .65, most 73 at 0.

I did do the math. And over sizing doesn't save fuel.

Quote Originally Posted by beenthere View Post

I have my oil furnace reduced from its ane GPH firing charge per unit to .65 GPH.

Information technology runs real long now. And uses alot less oil a year and so it did at ane GPH.
I did do the math. And over sizing doesn't relieve fuel.

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duh! You are a real math whiz (lol)
how long did it take you to figure out that a .65 nozzle running for six minutes volition fire less fuel than a 1.0 nozzle running for half-dozen minutes.

Quote Originally Posted by deejoe View Post

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duh! You are a real math whiz (lol)
how long did information technology take you to figure out that a .65 nozzle running for half-dozen minutes volition burn less fuel than a one.0 nozzle running for half dozen minutes.

And where did I say information technology runs the same corporeality of time.

Learn to read.

My burner run time is about 25% longer with the ,65, then it was with the one gallion nozzle.

Yes, information technology runs longer, and uses less fuel.

Your wasting your time Beenthere. He knows manner more than than nosotros do

I mostly read these and don't postal service, but I'chiliad amazed that this guy all the same doesn't go it. Just for fun and because there's zero much doing, a .65 gph nozzle will take to run longer than the ane.0 gph nozzle to obtain the aforementioned amount of BTU.

It will bicycle less, and run longer, to obtain the aforementioned btus over time.

The savings comes from the more constant run and less startups. We're running our Thermopride with a .five gph nozzle and it's very economical over longer run times compared with a larger nozzle install.

Only equally trane just said, this ane can keep for days.

There is no doubt that staging a strong furnace (running at less than 100% total BTU Capacity), either artificially or as manuctured, will brand it consume less fuel over the aforementioned period of time to attain the same indoor temps, ceterus paribus.

I am about to get a 2-stage furnace. While I see the advantages, I am not ready to striking the Kool-Assistance as hard as some of y'all guys.

Yes, the furnace uses less gas. Even so, this relies on the blower running for longer. Doesn't this mean the system uses more electricity?

So, delight humor me a moment and tell me what the cost of running a blower motor in a furnace is compared to the cost of the saved fuel consumption.

Information technology depends, I did a little enquiry on the electricity question myself, I just replaced a older furnace with a mod. Checkout http://www.gamapower.org/
You lot tin compare specs from former to new. There are patently variables but it is a good reference. The new efficient motors apply and so much less it becomes virtually irrelevant though.
The betoken I think some are missing is that steady country efficiency is unlike than AFUE. If the furnace starts at twoscore% and reaches 80% in viii minutes then turns off the average eff. is 60%

Quote Originally Posted by lumberg View Post

I am about to get a 2-stage furnace. While I run across the advantages, I am not fix to hitting the Kool-Aid as hard as some of you lot guys.

Yes, the furnace uses less gas. However, this relies on the blower running for longer. Doesn't this mean the system uses more than electricity?

Your now bringing in a 2 phase furnace, which is not what we are talking about.

DJ wants everyone to put in a furnace twice the size information technology needs to relieve fuel.

two stage furnaces are for comfort, not fuel savings.

Although the fan will run longer, the electricity it uses volition generate heat, which will besides be put into your house.
And then the longer blower run fourth dimension is not a consummate lost of money.

Since my HX doesn't warm up as fast as with a 1.0 nozzle, the blower doesn't start every bit quick. It as well doesn't get as hot, and then information technology shuts off alittle sooner then it did with the 1 gallion nozzle. And so my blower run time is non a big money loser, for saving on the heating pecker.

Your gas furnace will operate slightly unlike since its desgned for 2 stages.

[QUOTE=dave davis;1377045]I generally read these and don't post, only I'm amazed that this guy notwithstanding doesn't get it. But for fun and considering in that location's nothing much doing, a .65 gph nozzle will have to run longer than the 1.0 gph nozzle to obtain the same amount of BTU
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oh, But I do get it.It would seem that you not only do non exceed at math , y'all do not read too well either. In my previous post I said that BOTH the .65 and 1.0 nozzles run for the SAME 6 minutes.The smaller nozzle runs the same fourth dimension, and so it uses LESS fuel.
Get information technology ,dude?
A note of interest for Dave the rave .Heat rise specifications take a lot to do with nozzle selection. could that be your reson to go the smaller nozzle.
I know so.

Quote Originally Posted by trane View Post

Your wasting your time Beenthere. He knows way more than than we practise

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at terminal, a correct statement by trane.
now yous are on the right track, trane

[QUOTE=beenthere;1377392]Your now bringing in a 2 phase furnace, which is not what we are talking about.

DJ wants everyone to put in a furnace twice the size it needs to salvage fuel.
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as usual, another wrong assumption by 'beenthere'(or is it.... not 'been anywhere')
]I,m but maxim to put in a furnace that is approx 15-20% over your rut loss calculations. You will be glad you did.

twice the size to salvage fuel ha ha.....lol.. ha, ha,... side by side joke pleeeezse

Neary Hapterk

Furnace Cycles

Typical Furnace Cycle Times

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