Oil Furnace Burner/Fan routine


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Old 02-11-07, 08:25 PM
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Oil Furnace Burner/Fan routine

Our new ThermoPride OC2-56 with a Beckett Burner comes on when the furnace (55000 BTU) receives a call from our thermostat.

The furnace is a downdraft model. The return air plenum (on top of the furnace) gets warm, then the blower fan comes on.

Shortly after the blower comes on, I'll notice the Beckett Burner stops for several minutes. Yet, the thermostat demand isn't met. Air coming out of the registers is only around 105 F--and that's 5 feet away from the furnace.

It's as if some high limit switch is signaling the burner off.

This general cycle will repeat itself.

On our old oil furnace, the burner would come on. Then when things go hot enough, the blower would come on. The only time I noticed the burner stopping, was when the thermostat demand signal had been reached.

Is it common for new oil furnaces to have their Beckett Burners cycle on and off several times before the themostat call is satisfied?
 
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Old 02-12-07, 04:53 PM
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If it is NEW...who put it in? If this was me, I'd be talking to the person who installed it as to what it could be.

Has this behaved this way from the get go? How new is NEW?
 
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Old 02-12-07, 05:07 PM
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Sounds like the blower is not right. Not fast enough. Duct work not the right size. Blower controls on counter flow furnace have to be time on temp off. Sounds like the blower dont come on when it should. You say new . Get them back on it now
 
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Old 02-12-07, 11:16 PM
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Here's tonight's numbers for our OC2-56:Inlet filter in ceiling 16" X 25"., 14 inch dia flex duct 10 feet long in attic, drop to furnace is short four foot long 10" X 17" plenum and widens to 17" X 17" at furnace inlet. House has 9 to 10 six inch dia ducts serving 9 to 10 normal rectangular floor registers.

Tonight:
(Room temp appx 66 F. Outside Seattle air 41 F)

Demand from thermostat: 68 F

Room temp demand 68 F. Room temp:around 68 F. Seattle weather 41 F

Time:
9:23 Burner ON
9:27 Blower ON
9:27 Burner OFF
9:28 Burner ON
9:31 Burner OFF (Duct temp 109 F)
9:33 Burner ON (Duct temp 103 F)
9:35 Burner OFF (Duct temp 110 F)
9:36 Burner ON (Duct temp 106 F)
9:38 Burner OFF (Duct temp 110F)
9:40 Burner ON (Duct temp 109 F)
9:42 Burner OFF (Duct temp 111 F)
9:53 Blower OFF (Duct temp 83 F)

Demand satisfied.Finally after 5 burner cycles.

As you can see, moving the anticipator up did nothing. Slightly lowering fan speed did not increase duct temp.

Ed-What do you mean by time on temp off for downdraft furnaces?
DaVe-Furnace is less than one week old.
 
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Old 02-13-07, 12:02 AM
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On most down flow furnaces. The fan on is a time on temp off. Then also we have some where the tstat turns the blower on like it does for the AC.

Slightly lowering fan speed did not increase duct temp.

If you kick up the fan speed .Will the burner stay on???

Is this the tstat that came with the furnace????
Id call the guys back that put it in.
 
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Old 02-13-07, 01:09 AM
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Since you are in the Seattle area I was going to offer to come look at the silly thing. However, since it is only a week old I strongly urge you to get the installing company out immediately to fix it. You paid good money for a new furnace and you certainly deserve MUCH better than this.
 
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Old 02-13-07, 08:04 PM
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Ed. DaVe and Furd:

Problem looks solved.

1. I took the air filter (a medium density 1" filtrete) out of the duct and put back the lighter one the installer used.

2. I set the Blower Fan to "HIGH."

3. I set the Blower Fan "ON" temperature to 130 F (down from 150 F).

Looking at the position of Fan Control temp setting disc (on the furnace) operating plenum temperatures outside the Heat Exchanger seem to be in the neighborhood of 170 F.

Duct temps at the air registers seem to be around 120 F after a few minutes. I'm sure with the unit running much longer (like on a cold day), they might go higher.

Thanks for your comments (and continued comments--if any)
 
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Old 02-13-07, 08:38 PM
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Yes push the fan to on about 115 off at 95. lets get that fan on soon

Try it there
 
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Old 02-13-07, 11:06 PM
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Unhappy Whoops.. Happened again !

Well almost.

Burner started tonight. Fan kicked on at 130F. Good duct flows as usual. Then limit temp increased to 200F and burner cycled OFF.

Glad the tech is coming next week.

The only air shutter on the Beckett is MAX open, points to "0." We are running a .50/80A nozzle. Maybe the burner is overfired?

Very disappointing.

Ed, like you said, I'll try to push the fan on at 115 F.
 
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Old 02-13-07, 11:12 PM
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How big is the home in sq ft???? Thats only a 1/2gal nozzle
Get the fan on sooner.
 
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Old 02-14-07, 08:27 AM
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Ed,

Home is 1400 sq ft. 9 ducts.
Years ago, I had to remove one duct from under the house when I put in a half bath with electric wall heat. I will reinstall a 6-in duct and cut a new hole in the floor. That will give 10 ducts.

Air is very forceful out of all ducts. Fan motor selection "High"

Temp at Furnace Limit switch ramps up nice and slow to 115 F. Blower comes on then Temp at Limit switch climbs reasonably slow to 170 and stays there until trip OFF a few minutes later. Out of duct temps still 110 F.

Like I said, we have a professional coming over next week. By then I should be finished putting in an extra heat duct.

My wife and I have noticed some fresh soot--now this is not a large amount, but appears very fresh-- coming out of two of the registers in the few days the furnace has been operating. There is the possibility that the new fan speed dislodged older soot accumulations in the nooks of the ducting, but this looked fresh to me.

I do not smell anything in the house, nor do I see CO indications.
 
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Old 02-14-07, 06:26 PM
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Smile Reason for Shortcycling found ! You won't believe !

Reason for Short Cycling discovered !!!

Overheat cycling of our brand new furnace is being caused by the top of the heat exchanger being blocked by the foil insulation that should be attached to the underside of the blower pan.

I pulled the heat exchanger access plate and used a flashlight and a mirror to make the discovery.

This forum made me think. Thank you.

-Hank, Edgewood, Washington
 

Last edited by Therm Enjoy; 02-15-07 at 12:07 PM. Reason: No need to ask for what next step should be. Thx
 

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