Furnace keeps running almost non-stop?

[oil pan 4]

You dont ever use a fuel burning heater or generator in the house . The Carbon Monoxide it gives off will kill you

Then I must have died sometime around 2011.

 

[oil pan 4]

but a gas stove top won't?

Yeah right? In our old house I installed a 20,000btu radiance hester with catalytic plates. Had 3 carbon monoxide alarms, one up high over by the heater, one on the other sides of the room and one in the bed room. Only time they goes off is when I shovel out the wood stove and leave a bucket of ash with some hot coals by the wood stove. So I know they work.

 

[oil pan 4]

A few things to know ....

As far as the thermostat goes, the power is typically taken from the 24VAC transformer in the furnace unit. If the T-stat indicates it's on (has power at face), then there's a high probability it's working right. If it has batteries, that's only for backup (unless it's a full "battery only" unit). Either way, if the display is working, the issue isn't with the t-stat most likely. T-stats either work or they don't; there's no in-between.


What most folks don't understand is that heating (and cooling) is a function of thermal transfer rates and capacity. Furnaces are rated in BTUs, but that's actually a nominal value as stated on the rating label. The house will gain or lose heat at a rate of "X" BTUs per hour, and the system has to be able to overcome that max rate of loss (or gain, when talking about cooling).

When the home is built, the HVAC guys are supposed to do a thermal load calculation (for heating and cooling, but we're only going to talk about heating for this thread). They will need to know a few things to properly size the equipment:
- the ductwork should be properly sized to serve the house (this is one of the constraints that often hinders HVAC performance)
- what is the thermal loss rate?
- what is the desired temp delta to hold? (that delta is simply the difference between the set temp inside and the temp outside)

As for the ductwork, there's not much one can do after the house is built; it's either sized properly or not. If it is undersized, it may not matter in moderate temps because the rest of the system can overcome the deficiency by simply running a bit longer. But at the extremes of temps (uber cold or stupid hot outside), then the undersized ductwork can hinder the ability of the equipment to do its job. Again; not much one can do after the fact. This is just for knowledge.

Regarding the thermal loss, this is where they calculate the loss/gain factors based on type of siding, type and number of windows, insulation value in walls and attic, etc. If the HVAC guy was good, he did a thorough calculation and didn't just wing it. This loss rate, and the info below, combine to tell you what size furnace is needed.

The delta T topic boils down to this ... What temp differential can the system maintain when at full run (operates non-stop)?
Examples:
- Let's assume your system can sustain a 70degF delta (inside to outside)
- Let's also assume you set the T-stat to 70F (you want it to maintain 70 deg in the house)
1) Now say it's 30 degF outside. That is a 40 degF delta (70-30=40); well within the max capacity 70F it can sustain at full-run (non-stop run). So the furnace will "cycle" on/off to maintain the 30 deg delta.
2) as it gets colder, let's say it drops to 10F outside (still t-stat at 70F inside). Now the furnace delta (70F-10F=60F) is larger; it needs to run a lot longer to maintain that same 70F inside; it's operating nearly at max capacity and will run "most" of the time per hour (maybe 55 of the 60 minutes).
3) once it gets to be -10F outside, the max that furnace can hold would be 70F(the max capacity delta it was sized for) above the outdoor ambient; hence it could hold the house at 60F inside with the furnace running non-stop.

If it's -10F outside and you want it to be 70F inside, it would take a system capacity "X" BTUS to hold that 80F delta, and still "maintain" that 70F inside. And that would only be true if the ductwork is right (which it probably isn't).


OP - I cannot tell you why your system isn't keeping up, but I suspect it's a function of all three issues. It's not uncommon when homes are built to have the ductwork undersized (the builders cheap out to save money ...). And I can't say if the transfer rate calc's are correct. Nor do we know what the dT value is when they did the capacity calcs. Sometimes you can over-cap a system a small bit to make up for a crappy ductwork system; but only maybe by 5% or so.

But the reality is that, unless you have a well engineered and fully capacitized system, your furnace will indeed run non-stop when it's really cold outside.

Mukanikal injenrering

 

[SHOZ]

You dont ever use a fuel burning heater or generator in the house . The Carbon Monoxide it gives off will kill you

They don't give off CO, rather CO2.

 

[Warstud]

They don't give off CO, rather CO2.

There are portable propane heaters specifically designed for temporary indoor use. When you are looking for a portable heater to use either outdoors or inside an enclosed space with air ventilation, it is vitally important that you read the packaging and the operating instructions. It could mean the difference between life and death from Carbon Monoxide (CO) poisoning . 3rd paragraph

Know the difference between indoor-safe and outdoor only propane heaters - Campsafe

Portable propane heaters have become a handy resource for taking the chill out of cool nights for campers, RV'ers and hunters. You'll also find them as a temporary heat source for a wide variety of other uses for heating chilly workspaces, garages, sheds and other ventilated spaces where...

campsafe.org

 

[Warstud]

but a gas stove top won't?

A Gas Stove isnt exactly safe either you need to worry about N02 with those . Los Angeles, Seattle, New York, and other progressive cities have already moved to ban most gas appliances in any new homes or apartments.

How Can I Keep My Family Safe While Cooking With Gas? Zephyr Range Hoods Have You Covered. | Zephyr Ventilation

Using Zephyr range hoods to ensure proper kitchen ventilation in your home will help keep your family safe when cooking with gas.

zephyronline.com

 

[eljefino]

As a side note, I went for a walk last night after dinner before the alleged storm and my neighbours A/C unit was on . I stopped in my tracks wondering to myself this can't be. I took three steps back and sure enough the condenser fan was on and a block of ice was protruding through the grille it had been running so long.

Sounds like it was in heat pump mode, moving heat from outside to the inside. Which is why it attracted ice to the coils. Hopefully the owner had a backup heat source as well.

 

[XB_Fan]

I have a Lux thermometer, one of the only brands that enables you to have a .25 degree to 2.5 degree swing setting on them.

Mine runs 21-23 minutes and shuts off for about 1 hour 10 minutes because of the swing setting.

I keep house colder than you guys though at 65F.

It is currently -51F here where I live.

 

[02SE]

Let us know if it's still running in July...

 

[SHOZ]

There are portable propane heaters specifically designed for temporary indoor use. When you are looking for a portable heater to use either outdoors or inside an enclosed space with air ventilation, it is vitally important that you read the packaging and the operating instructions. It could mean the difference between life and death from Carbon Monoxide (CO) poisoning . 3rd paragraph

Know the difference between indoor-safe and outdoor only propane heaters - Campsafe

Portable propane heaters have become a handy resource for taking the chill out of cool nights for campers, RV'ers and hunters. You'll also find them as a temporary heat source for a wide variety of other uses for heating chilly workspaces, garages, sheds and other ventilated spaces where...

campsafe.org

Propane heaters do not emit CO until the ambient O2 content is way below normal. If they do the CO2 content of the air would be a near intolerable though not fatal level leading to discomfort unless unconscious. So use ventilation.

 

[bobdoo]

I have a CO Meter by Forensics | Sensitive 0.1ppm Resolution . This is a fast-response meter (seconds). Your typical plugged-in meter won't respond until maybe 30ish ppm that maintains for an hour or more. This is very unhealthy, especially for older folks.

Running our natural gas stove top or oven will take the meter from 0.0 to 1.0 in about an hour.
With the meter in an attached garage, with the large and service entrance doors open, and starting up a lawn mower, or 2000 watt genny, or a car, the meter will be screaming a warning in 10 seconds or so, and be at 15 ppm and rising.

Everything that burns creates CO.

The Canadian forest fires had my meter at 5-7 ppm for a week. I thought the meter had failed. Took me a while to figure that one out.

 

[SHOZ]

CO is 1% with your gas stove? Never in the 8 years that I've had a CO meter has it ever let out a peep.

Do you have ventilation in your house? What's the CO2 level? A tight house will cause elevated CO2 without any combustion and is much more of an issue with open flame gas.

 

[vavavroom]

Seems like it almost never shuts off! Had it serviced less than a month ago. Cleaned, tested and new filter.

Worked great until a few days ago. Now that it got below zero, when i need it most, it keeps running!
-2F now and falling to predicted low of -20F tonight by 7 PM. Should I be concerned?

Be concerned if it stops running.

 

[dishdude]

Does anyone still use one of those kerosene heaters that were so popular in the 80's?

 

[GSCJR]

Sounds like it was in heat pump mode, moving heat from outside to the inside. Which is why it attracted ice to the coils. Hopefully the owner had a backup heat source as well.

If that were the case, why the ice build up? Is this normal for a heat pump to build up with ice? I'm trying to learn more about heat pumps, they seem to be pushing them around here as of late. The houses in my neighbourhood were all fitted with forced air natural gas HE furnaces.

 

[eljefino]

If that were the case, why the ice build up? Is this normal for a heat pump to build up with ice? I'm trying to learn more about heat pumps, they seem to be pushing them around here as of late. The houses in my neighbourhood were all fitted with forced air natural gas HE furnaces.

On an air conditioner you have a condenser and evaporator. The condenser gets warm and the evaporator gets cold. You blow a fan over the condenser to make the freon inside ambient temperature again, the heat goes away, and then when the freon "evaporates" it gets colder than ambient. It then goes back through the compressor, gaining heat.

A heat pump is versatile and can pump the freon either way, so either side can be warm while the other is cold. That thing outside (you inaccurately described as a condenser, because it's presently the evaporator) will be plenty warm next summer when it's cooling off the house.

You get ice from condensation, when you have a cold thing lower than the dew point of the air around it.

 

[RhondaHonda]

Does anyone still use one of those kerosene heaters that were so popular in the 80's?

I sold a couple I bought off of Craigslist a few years back to some guy. We had a real cold stretch in the forecast and his furnace died. I sold them cheap and hoped they didn’t die of CO poisoning.

 

[Jetronic]

A Gas Stove isnt exactly safe either you need to worry about N02 with those . Los Angeles, Seattle, New York, and other progressive cities have already moved to ban most gas appliances in any new homes or apartments.

How Can I Keep My Family Safe While Cooking With Gas? Zephyr Range Hoods Have You Covered. | Zephyr Ventilation

Using Zephyr range hoods to ensure proper kitchen ventilation in your home will help keep your family safe when cooking with gas.

zephyronline.com

I know they aren't exactly safe, but they're not instant death either. stuff in disrepair orused without care is an issue though

 

[Jetronic]

Does anyone still use one of those kerosene heaters that were so popular in the 80's?

No but I know they are still on sale, every winter.

 

[Jetronic]

I have a Lux thermometer, one of the only brands that enables you to have a .25 degree to 2.5 degree swing setting on them.

Mine runs 21-23 minutes and shuts off for about 1 hour 10 minutes because of the swing setting.

I keep house colder than you guys though at 65F.

It is currently -51F here where I live.

I went down to 65F this year aswell and it's fine provided there's a constant influx of a little heat. That's why I keep the radiator temps so low. I like it better than 70F and on/off cycles