Furnace Stops prematurely while in recovery mode

[Zephyr]

Hey all,

My furnace seems to be running all right, but, one thing has me curious. I've got a Honeywell stat that is supposed to have "smart recovery" that learns the amount of time necessary to re heat in the morning. It takes the furnace about an hr to get back up from 57 to the 69 I ask for in the morning with the outside temp in the single to teen digits (Michigan)

In the mornings the heat will turn on around 6 to have the house warm by 7. The odd thing is that the furnace will run for about 30 minutes or more, then it will then stop for about a minute or 2 then turn back on continuing to heat. At the time the furnace turns off it might have raised the temp from 57 to 65 or so, on its way to 69.

The stat has a "heat" indicator on the display and while it is blinking "recovery" indicating that the system is trying to re heat the house, the "heat" indicator will turn off.

The fan will run for a few minutes after the heat indicator turns off, then the whole system will sit for a minute or too, then it will turn back on, and work its way back up to the desired temp.

Is this normal? should the furnace not run straight thru up until it reaches the desired temp?

I've got an older (17 yrs??) furnace Thermo Pride Furnace which I believe has an 80% efficiency (based on btu IN/OUT calcs on the stickers. The house is about 30 yrs old 2200 sq/ft.

Thanks for any and all comments / info

Dave

[Tony Hwang]

Hi, You can peruse service option menu relating to this.

[Zephyr]

sorry, I don't follow. what service menu are you referring to?

Dave

[Joseph Meehan]

I would not call it normal (Maybe for a heat pump, they often have a few special tricks to reduce heating cost).

There may be a problem with the furnace (sounds like a gas furnace). Maybe it is detecting a overheat situation at the burner. That could be a bad sensor.

In all fairness, I am making a lot of guesses here, but I suspect you will need to have someone check out the furnace. If it needs repair, I would consider a newer high efficiency furnace as it may not pay to repair that lower efficiency one in the long run.

[trader4]

It isn't a problem with the furnace, because he said that when this happens, the "heat" indicator on the thermostat goes out and the recovery indicator stays on. If it were the furnace, the heat indicator on the thermostat would not change.

I think the service menu that Tony is referring to is the advanced settings menu in the thermostat. Some of the HW thermostats, like the LCD touchscreeen (8600?) ones have a zillion settings. It's possible something in there controls this. Like maybe it's set for some dual fuel system option, where it uses one fuel to get most of the way, then switches.

If you can't find a setting, I'd contact HW or look on their FAQ page, etc. My vote is this isn't right, and it's either a setting or a software bug, but it's not a failure in the thermostat.

[David Martel]

Dave,

What you describe may be normal. My furnace comes on in the morning and runs for about half an hour. This raises the air temp in the house to 68, the setpoint. The furnace shuts off. The walls, floors, ceilings et c. are still cold. The thermostat is mounted next to a wall. Until the wall is heated up the furnace keeps cycling quickly. It seems to take slightly more than an hour and a half to heat up the interior walls. So the furnace does run a lot first thing in the morning

Dave M.

[trader4]

His doesn;t get to the setpoint. It stops prematurely at 65, when the setpoint is 69, waits a bit, then resumes. That is not normal.

[scott21230]

In your case I would also be suspicious of the thermostat. Having said that, mine was doing the exact same thing and it turned out to be the fan limit switch.

[Zephyr]

I should have provided some more info,

it is a gas furnace, I have a gas water heater, and gas stove. The furnace had the exhaust fan and ignitor unit replaced earlier this year under home warrenty. I have a few vents closed currently to prevent heating of unused rooms.

That was my thinking too, that if the heat indicator went off on the stat, that it was not the furnace that was at fault, it was the stat. A friend of mine (who had not looked at it) suggested that maybe the furnace was overheating, but, given the situation with the stat, I was skeptical of that possibility. Unless the funace had some overheating sensor that fed to the stat that turned of the stat, instead of just stopping the furnace leaving the stat still calling for heat.

That all said, I do have a few vents closed in spare bedrooms and all the vents in the unfinished basement.

I will look into the stats menu settings, it doesn't seem like there is a lot there, this is a lower end model, it doesn't even record the run times for the past day/week/period.

Thanks for all your help

Dave

[Zephyr]

I should have also added that I never see this happening when the furnace is just maintaining the temp,