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New oil furnance blowing cool air at first


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#1 toomanytoys84 OFFLINE  

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Posted November 07, 2015 - 08:03 PM

Maybe this is the way newer ones work...

My old furnace kicked on and ran for a few minutes then the blower kicked on and it was instantly hot air.

New furnace blows cool air then warm then hot.

I feel like plenum control is set wrong allowing the blower to kick on too soon. But then I wonder if it is normal operation for a new furnace. Like they don't want to waste any heat.

Going to call the guy who did the install Monday but I know a few of you are pretty familiar with HVAC stuff.

#2 pigsitter OFFLINE  

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Posted November 07, 2015 - 08:31 PM

I'm not very knowledgeable on oil furnaces as oil heat is rather rare in my area, but the blowers on most newer model gas furnaces are time on instead of temperature on,if your furnace is the same that would explain the cooler air on blower start up.


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#3 case442 OFFLINE  

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Posted November 07, 2015 - 08:32 PM

I'm no expert but I had the same issue. We have an outdoor wood burner and the oil furnace inside. last fall when i turned on the oil furnace it wouldnt stay running. The heat exchanger cracked and fell down. we had the furnace replaced at around 6400.00 which after looking at my cost of 4500-5000 for just the furnace we had it installed. At first I thought the same thing, blows cold air at first and runs much longer than the old one. I'm told its running properly. Once the temps drop steady into the low 30's over night I'll be starting the outdoor furnace. Its 72 F in the home at all times at that point.


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#4 Cat385B ONLINE  

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Posted November 07, 2015 - 08:50 PM

It's the nature of the beast, being a higher efficiency furnace. You might also notice it blows almost cool air at the end of it's cycle also, getting every last btu of heat pulled out.
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#5 CanadianHobbyFarmer OFFLINE  

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Posted November 07, 2015 - 10:28 PM

Exactly what Cat said. That is how all high efficiency furnaces work, regardless if they are gas, propane or oil. Get used to it is all you can do about it. Or burn wood.

 

Jim


Edited by CanadianHobbyFarmer, November 07, 2015 - 10:30 PM.

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#6 glgrumpy ONLINE  

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Posted November 07, 2015 - 10:48 PM

Lots of heaters now run a bit to kind of clear the area of any extra combustibles and also to allow air to run past sensors up by the exhausts to make sure all is open and safe, THEN, the blowers will kick in after the burner ignition. Also some have auto opening flue's which will take a moment to cycle open or closed and set the switches for off and on.  I have Boiler and it does similar but w/out the actual fan, instead is the pump for the water. Biggest issue I had with OIL was the newer nozzles and the blower fins that spin the incomimg air would always get clogged up and not work and I had to go and clean off the nozzle and the crud off the air fins to make it ignite and burn right again. Service man came many times and then he showed me how to do that and I fixed it myself to save the money. He did try diff tips too, and finally found a better one that lasted a little longer.  Hated that furnace. This was about 79 and a major brand too. Wasn't impressed at all, wished I had gone LP.


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#7 hamman ONLINE  

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Posted November 07, 2015 - 11:15 PM

Yup that's the efficiency part of the furnace. The blower ramps up until the heat is built up and then continues after the burner goes off and cools the heatexchanger. It actually is more efficient than the old ones.                                                                                                                             Roger


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#8 Arti ONLINE  

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Posted November 08, 2015 - 08:25 AM

Some have adjustments for Blower Time on and off.  Also you can check the temperature rise and sometimes the blower can be slowed down a bit to get warmer heat at the registers.

 

Also some newer furnaces use a variable drive blower that has a lot of adjustment, without a model number it is hard for me to tell what you have.


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#9 toomanytoys84 OFFLINE  

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Posted November 08, 2015 - 03:36 PM

Thanks,

 

You guys confirmed a lot of what I thought.  My old oil furnance would run for 5 minutes(or more) before the blower kicked on so the air was already hot when it came out.  Then at the end of the cycle the pump turned off the blower ran for a minute then shut off.

 

This one the pump kicks on, the fire starts, then 30 seconds to a minute(didn't time it exactly) the blower comes on. Then at the end of the cycle the pump shuts down and the blower runs for a good while before the blower shuts off.  So you end up with cool/warm/hot/warm/cool cycle.  Which I guess makes sense, because it is using every bit of heat.  Also I guess the air isn't so much "cool" as it is the same temperature as the house because its just recycling the air inside through the returns.

 

My only thoughts in the matter is if the blower coming on too soon it causes the chamber longer to reach temp and therefore it runs longer for a cycle.  I know on my wood stove if I kick the blower on before the fire chamber is hot, then it takes longer for the heat coming out to get hot.

 

I'm going to give him a call and confirm.


Edited by toomanytoys84, November 08, 2015 - 03:39 PM.

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#10 hamman ONLINE  

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Posted November 08, 2015 - 05:22 PM

Actually the way to maintain efficiency it is recommended on some models of high efficiency furnaces to run the blow constantly ! Most of these furnaces have DC variable speed blower motors on them so the amount of current being used is quite a bit less. We have a 90+ efficiency NG furnace, but I do not run the blower all the time. Just another thought.                                                                                                                                                                                            Roger


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#11 TAHOE ONLINE  

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Posted November 10, 2015 - 08:35 AM

our oil furnace does the same, runs for just a bit before burner kicks on. This furnace was installed in 2005.


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#12 toomanytoys84 OFFLINE  

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Posted November 10, 2015 - 09:14 AM

our oil furnace does the same, runs for just a bit before burner kicks on. This furnace was installed in 2005.

 

My old furnace was installed in 1984.  So it was probably 50% efficient...

 

Called the installer he said this is normal but he is going to stop out and watch it run.  It's covered under warranty.  He said he'd rather take a look and make sure everything is correct before he has to come out at 2AM to look at it.


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#13 toomanytoys84 OFFLINE  

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Posted November 22, 2015 - 11:03 AM

Little update. He came and made some tweaks probably just to make me feel better. It might wait another 30 seconds before kicking the blower on.

Didn't really notice any difference. But today and yesterday with temps in the low 20s and high in the 30s the cool air I felt before is now nice and warm. I wonder if it's because its easier to heat cool air than "warm" air.

I also have been paying attention to the pump. It runs very little. The furnance gets up to temp shuts off and the blower keeps cranking out heat for several minutes after wards.

I need to figure out how to hook up my hour meter to the blower and the pump like I had on my last furnace and compare.

My numbers on my old furnance were say 60 minutes of blower and 50 minutes of pump.

I'd say this one would be more like 20 pump 60 blower.

Probably use much less fuel this time around.

I also have several rolls of insulation to put up.

Edited by toomanytoys84, November 22, 2015 - 11:04 AM.

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