Gas furnace heating question

CS8161

I keep the thermostat set at 60 degrees, to save money on my heating bill. It seems like the furnace still cycles frequently to maintain that temperature. If I had the thermostat set at say, 65 degrees, would there be any difference in the furnace cycles? I mean, once the house was heated to 65 degrees, wouldn't the furnace cycle about the same amount of times to maintain 65 degrees as it would to maintain 60 degrees? Thanks for any input.

slipgate

I think your house is losing a lot of heat. We just reinsulated our house and got new siding and our heater almost never cycles on. We keep the heat at around 68. We have 3 levels and @3000 sq ft to heat.

We also run the furnace fan continuously at night.

We also have gas. It will take more heat to maintain 65 than 60 as your heater is measured in degrees difference from outside air.

HandLoad

Thermodynamics Laws say that heat flow is dependent on a variety of factors, one of which is the difference between the hot side and the cooler side. the higher the difference in the two temperatures, the faster the heat is lost. You MIGHT be able to sense the difference in outflow/cycling, but it would probably only show in your bill. And since any trial period is gonna have a unique set of outside temps for you to heat the house against, you really can't make two runs in identical conditions to prove it. Just set the temp where you can just stand it. Dress well.

All bets are off, however, if you have a Female Sensing unit present. Then, in the interests of Connubial Harmony, it is best if you just stay in the Garage as much as possible.

Daddie_Tom

Your thermostat should have a Heat Anticipator on it. Which means you can adjust the length of the cycles.http://home.howstuffworks.com/home-thermostat2.htm http://homerepair.about.com/od/heatingcoolingrepair/ss/adj_anticipator.htm

tomh.

What does running the fan continuously do?
Just to circulate air?
Seems like you'd lose heat to the cool duct work?
My thermostat has a fan switch but I never really thought there was a benefit with the "ON" position.
Just curious.

HandLoad

Running the fan continuously makes noise, wastes power, and probably makes your house lose heat faster.

HandLoad

Keeping the fan on will cover small outside noises, and will make the contactor have less wear, and will cover the firing up of the burners. It may also contribute to smoke propogation, so your smoke alarms will get the message sooner, if the smoke is not too diluted by the air motion. Some people like the soothing sound of the air rushing.

1911a1-fan

yes the fan switch is just that, it turns the fan on, automatic is where it should be

chris

depending on what type of furnace you have, btu/location of thermostat size of home will dictate how your furnace cycles, assuming when it was installed correctly {settings on the furnace}it works like this

for gas the thermostat turns on the burner, when it reaches temperature in the heat exchanger {preset temp varies 175-200}, the fan will turn on, blowing the heat, then when it hits another temperature the burners turn off, fan will continue until it hits a 3rd temperature stage, this completes one cycle


now depending on what these 3 settings are on can also dictate how long this cycle will run in junction to your thermostat, they should be at factory settings on the limit switch, but if set incorrectly can cost you tons in heating bill, if you know what type of furnace you have you can look up the setting for your "limit switch"

HandLoad

The "anticipator" is to prevent short cycling of the system. It needs to be adjusted so that the system only fires about four times an hour at maximum. If your system is too small, or if it is too cold outside, your system will run nearly continuously.

Too many starts in an hour reduce the life of your blower motor, and excessively wear the ignitor and the main contactor.

slipgate

Mostly I run the fan at night for the white noise.

We also frequently leave it on for days - sometimes weeks - at a time in the summer as it makes the house more evenly cooled.

The A/C was replaced 2 years ago but my heater (including fan) is about 23 years old and still going strong.

Sperry

An oversized furnace will also do exactly what you describe .. short cycle.


Next time you buy a heater, get one with a variable speed blower - runs on DC power.

CS8161

I got out my instruction manual for the thermostat, it is a digital and there is nothing in the manual about an anticipator? It seems as if the heater cyles on and off every ten minutes. It will cycle on, run for about four minutes, shut down for about ten minutes and then kick back on. It has done this since new last year and from what people here have said, there is something wrong with the system. I better give the company that installed the furnace a call.

HandLoad

There is a couple of things you can do first: Basically the Thermostat is "seeing" the heat too quickly. You can open the registers further from the thermostat, and close a little more the ones near the thermostat. In an attempt to save energy, you may have closed off the registers (and/or doors) on rooms/areas you don't want to heat - this has the effect of making the remaining space smaller, and as noted above, when the heating plant is "Oversized" it tends to short-cycle.

Some systems have the "Anticipator" (Hysteresis) control in the furnace unit itself. If located there, you can adjust it there, but you will have to have the access cover(s) off. Don't do this if you are not totally familiar with working on LIVE machinery.

Sometimes, the homeowner has furniture or other obstacles to the air movement that make just-heated air from the furnace "lane" or move quickly to the thermostat area, and this can also make the system go nuts. You can make the thermostat less sensitive by restricting airflow around it, but this will result in longer runs with wider swings of temperature.

Yet another cause of short-cycling is if you have an access door open to unheated spaces in your house, or holes in the roof, crawlspaces, or chimney. Another place houses lose heat is through the chimney - the flue should only be open if the fire is burning. Still another is if you have single pane windows, or if the double or triple glazed ones you have have lost their seal. One or two big picture windows with a failed seal can significantly change the heat balance of the house. Windows with busted seals look a little foggy/or smoky. Look around. Birds tore open my siding just where I couldn't see the damage, and cost me for all winter till I found the damage.

A good heating company will adjust the system after careful analysis, and get you the best performance. A bad company will just blow you off, saying "It is supposed to do that".

select-fire

If it is running for 4 minutes and off for 10 the cycle is 14 min. Is the thermostat near a heating vent? If the airflow is contacting it directly it will sure affect the cycle time.

Tailgunner1954

Not sure which furnace you have, but the older style would kick on and overtemp the house than wait for things to go undertemp before starting again IE with the stat set at 65, the furnace would fire at 61 and heat the house to 70 than wait for it to drop back down to 61. This led to a lot of room temp swing, caused long "burn" times but kept the # of cycles/hour down. The newer "high efficency" furnaces tend to fire closer to the stat setting, and to also turn off sooner IE kick on at 63 and off at 67. This leads to more cycles, but of a shorter duration and the temp stays more consistant.

slipgate

One more thing to check - Our programmable thermostat needs to be told what type of furnace you have. Perhaps yours is set wrong like on "Heat Pump". Ours has several choices to choose.