Where to check oil burner overdraft?

Reply

  #1  
Old 05-20-09, 03:40 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Where to check oil burner overdraft?

Hi all,
Can anyone tell me where to check the overdraft on an oil burning furnace using a manometer? The unit I'm trying to check is a 125,000 Btu ThermoPride model OT-16 horizontally mounted furnace, probably about 30 years old. This unit does have a round secondary air disk / inspection port . Thanks.
 
Sponsored Links
  #2  
Old 05-22-09, 04:57 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Thermopride

Somewhere near the burner is a bolt which looks out of place, like "what is that bolt holdling?". That is the overfire tap. The bolt will have a 9/16 or 5/8 head. If you can't find it, remove the plate covering the secondary air, cover the hole with foil tape & poke hole in the tape just large enough for the manometer probe.
 
  #3  
Old 05-27-09, 06:22 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Hi Grady,
I looked high and low and couldn't find an obvious tap, so I'll give your tape suggestion a try. Unfortunately, summer is here so I will have to wait until October. I'll let you know how it works as I'm sure I'll have more questions. Thank you for your reply.

Tom
 
  #4  
Old 05-27-09, 06:36 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Overfire Tap

The next time I service a Thermo-Pride horizontal I'll try to remember to either post the exact location of the overfire tap or send you a private message (PM) regarding same.
 
  #5  
Old 10-15-09, 07:37 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Overfire tap

Hi Grady,
Are you still there? Summer has passed and a chill is in the air, so I fired up the old girl, took a reading using a variation on your suggested tape method, and got almost nothing on the manometer. I think I'm looking in the wrong place. Any suggestions? Thanks.
 
  #6  
Old 10-16-09, 02:44 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Overfire draft

What is the scale on the manometer? You need to be able to read to 0.01" water column. Most manometers won't read that low.
 
  #7  
Old 10-16-09, 07:07 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Post

I'm using a Dwyer #460 Air Meter, which has a low reading of 0.01" water column, (actually less if the little ball doesn't make it that high).
 
  #8  
Old 10-17-09, 04:16 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Draft

You should get -0.02 to -0.04 at the breech & aprox. -0.02 overfire. If you can't get at least -0.02 at the breech you have some sort of venting problem.
 
  #9  
Old 10-21-09, 08:02 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Hi Grady,
Thanks for the reply, (BTW, hope you had a good summer). I think you have confirmed something I've suspected for a long time; that this furnace was improperly installed. I think the flue is too long and installed at the wrong angle. No matter what I did, the meter wouldn't measure more than a "bobble" at either end. On the bright side, this furnace has been working for over 30 years and still seems to be going strong. I would like to ask you more questions about this furnace and tune-ups in general. Please let me know if I should open a new thread.
 
  #10  
Old 10-22-09, 02:33 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Flue Pipe

The vent pipe should slope upward toward the chimney with a slope of at least 1/4" of rise per foot of run. If you have a draft regulator (barometric damper) in the vent pipe, adjust the weight to give you as much draft as possible, allow the furnace to run for 3-5 minutes & re-check your draft.

Regarding the other questions, I see no need to start a new thread, at least not at this point.
 
  #11  
Old 10-23-09, 07:31 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
The horizontal run of the flue and the height of the chimney seem to be about the same. The manual says the flue length should never be more than 50% of the chimney height. Both are about 15-17 feet. There is a damper but I could barely get a response from the meter no matter how I adjusted or played with it. There are some angles and slight inclines involved here, but most of the flue runs horizontally without any upward pitch. If I can figure out how to send pictures I will. They'll either make you laugh out loud or cry.
 
  #12  
Old 10-24-09, 04:24 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Pictures

The easiest way to do pictures is to open a free account on photobucket.com, post your pictures there, & provide a link here.
 
  #13  
Old 10-24-09, 07:25 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Thumbs up

Thanks Grady, I'll give that a try.
 
  #14  
Old 10-26-09, 01:30 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Pictures

Ok, let's see if I did this right. These pictures were taken with a low res cell phone in a photographically unfriendly location, but I think they'll give you an idea about what I dealing with here.

This first pic should be of the flue. After the second angle it travels horizontally (no rise) for another 12 or so feet before taking a 90 degree turn and entering the chimney. Notice the little bolt near the furnace. That's where I drilled a hole to take the manometer and temperature readings.



The next two pics should be of the burner. That's a ruler propped in there in one picture. Yes, the burner is actually mounted 11 inches from the wall! And the access panel for the air filter - the part you're supposed to replace every three months - is on the other side of the burner.





Let me know if these make it and are any help. Thanks again.
 
  #15  
Old 10-26-09, 04:04 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Angry What A Mess

Anybody who would install a piece of equipment like that should be shot with s*** & hung for stinking.
Thermo-Pride makes (or made) that same furnace with the burner & flue on the same side.

About all I could suggest to improve the draft is to install a draft inducer. FIELD CONTROLS, LLC - CONTRACTOR PRODUCTS

The only other option I can think of is sidewall venting via a power venter like this: FIELD CONTROLS, LLC - CONTRACTOR PRODUCTS SWG and POWER VENTING SYSTEMS
 
  #16  
Old 10-26-09, 08:24 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Ouch

Jeez Grady, don't sugar coat it. Just tell me what you really think.

Before I make modifications to a system that has worked well for over 30 years, let's go back to square one. Were my manometer readings in the right place?

Also, I think you'll be interested in the stack temp.
 
  #17  
Old 10-27-09, 02:30 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Crude but effective test

Don't sweat the manometer. It looks like a hole in the pipe (white spot 6"? from the furnace). If that's where you checked the breech draft, that's fine.
After the burner has been running 3-5 minutes, remove the round flame observation door cover & gasket (left of the burner). Take a lighter, match, candle, incence stick, or heaven forbid, burning smoking material, & hold it up to the hole. If the smoke or flame is drawn in toward the oil burner flame, you have draft. Repeat the test after the fan goes off. If you still have draft, you're good as gold.
 
  #18  
Old 10-27-09, 07:37 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Crude draft test

I took the following measurements today using a punk and a candle. The furnace had been running and the firebox was warm.

Burner ON/Fan OFF: No draft. Candle blows out several inches from port.

Burner ON/Fan ON: Same as above.

Burner OFF/Fan ON: Draft. Candle and smoke go into furnace.

Just out of curiosity I played with the damper while doing these tests. I was always able to get a draft by pushing the damper slightly inward.
 
  #19  
Old 10-27-09, 07:42 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Strange

You should get maximum draft with the damper completely closed. Have you or anyone ever cleaned the heat exchanger using a brush & vacuum?
 
  #20  
Old 10-27-09, 08:39 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Heat exchanger

Me, no. I'm guessing it hasn't been done in a long time, if ever. When I mentioned getting a draft by playing with the damper, I meant at the damper. I was never able to get a draft at the burner port by playing with the damper. The only time I got a draft at the burner was when the burner was OFF, but the fan was ON.
 

Last edited by TtTankEngine; 10-27-09 at 09:08 PM.
  #21  
Old 10-28-09, 01:52 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Next Step

Well, the next step is to clean the heat exchanger or have it done. It would be fitting if you could find the jackarse who installed that thing & make him clean it.
 
  #22  
Old 10-28-09, 02:48 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
More questions

Ah, a little poetic justice, although I imagine he's long since retired or been drummed out of business.

Grady, I hate to admit it but I'm getting a little confused here. Was the burner port always supposed to have draft under the three conditions I listed? Is the reason I couldn't get decent manometer readings because of the poor installation (flue), or are we now considering something else (heat exchanger)?

Also, there is something else I should mention. When I tried taking manometer readings I also took a temp reading and got almost 700 degrees before adjusting for room temp. I know this is way too high. I'm currently using the largest rated nozzle for this unit (1.10 gph). Would going to a smaller nozzle help any of these problems?

Thanks again for your time and help Grady. I really do appreciate it.
 

Last edited by TtTankEngine; 10-28-09 at 03:15 PM.
  #23  
Old 10-28-09, 03:39 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Draft/Nozzle

Yes you should have draft under all conditions. The fact you were able to get draft at the breech is encouraging. Downsizing the nozzle might help but I also suspect there is a considerable amount of "junk" in the heat exchanger causing a restriction. I'm not sure if that furnace has the same design heat exchanger as those in the past 20 years or not. At a very minimum, remove the vent pipe and vacuum as much as possible thru the breech. A piece of flexible conduit such as greenfield or liquidtite adapted to your vacuum cleaner hose would be a big help. If you look at all the decals on the various panels you may find one which says something to the effect of "this panel is removable by a qualified servicer for acess to the heat exchanger". Such panel should be on the far side of the burner. You should also remove & disassemble the vent pipe to clean it & the chimney base.
 
  #24  
Old 10-28-09, 07:43 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
A bit of good news

Several years ago I removed that long stretch of horizontal flue from the chimney and cleaned it out. I got about one and a half 5 gallon buckets of soot out of the chimney before I started pulling sand. The flue had almost no soot at all. I think that's pretty good for a flue that might have been there since the early 1950's. When I re-installed it I made sure not to push the flue in too far and resealed the joint with mortar. Maybe that's why there's some draft today ? ?

The literature says this furnace has an "Octatherm" heat exchanger that's made of 13 gauge steel. From what I've read, that's supposed to be top notch. The access panel, unfortunately, is on the burner side - the one closest to the wall. I'll remove the vent pipe tomorrow and start cleaning from there. Thanks again for your help. I'll keep you posted.
 
  #25  
Old 10-29-09, 07:09 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Octatherm

That's the same design heat exchanger they use today & they are still made of 13 gauge steel. The finest oil fired warm air equipment made.

If you can get to & remove that access panel, behind it should be two cleanout ports, each covered with a plate similar to the observation hole cover. If you got a lot of sand from the bottom of the chimney it could be coming from the mortar, especially if there is no liner in the chimney.

Please do keep me up to speed on your progress.
 
  #26  
Old 10-30-09, 07:26 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
More info

Hi Grady:
I was able to pull off the flue tonight and take a look, but first let me tell you about the chimney. It does have a liner and the sand I think - (guess) - was put there at the time of construction. When I got the flue apart I found about 3/4" of soot in the horizontal run, so I think that "several years ago" I mentioned about cleaning it might actually have been more around 10-15. However, when I put my arm in it to pull the soot out, I could see the dust rising back into the flue. I think the chimney is OK.

Now the breech: What a mess. Crud up to the pipe. Here are a couple of pics.





I was able to vacuum out this side down to the flat of the octagon before I had to button it all up for the night. I ran a test and still couldn't get a draft at the burner port. The stack temp did drop to 500 degrees. That's a 200 degree drop! Then I remembered to put the secondary air / inspection port cover back on and it was more around 625 degrees. Still, that is a drop in temp.

Tomorrow I'll remove the inspection cover from the burner side. Please let me know what you think about what I've done so far. Thanks
 
  #27  
Old 10-30-09, 07:51 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Good Job

So far you've done very well. We really need to get into that heat exchanger. After seeing what was at the breech, I'd bet further back in the heat exchanger (especially at the bottom) is a real mess. Keep up the good work.
 
  #28  
Old 10-31-09, 05:27 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Unhappy From bad to ... the worst

Hi Grady:

I pulled off the inspection cover from the burner side today, and when I did my heart dropped. I didn't even try to open the clean-out port.




I'm going to pour myself a stiff drink and weigh my options.
 
  #29  
Old 10-31-09, 05:42 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Unhappy Worst indeed

I don't know if Thermo-Prides of that vintage had the lifetime warranty on the heat exchanger or not but it's worth a call to them to find out. (800) 348-5130
If there is an upside to this, at least you found the problem before serious damage to your life & home. GOOD WORK

I would wager serious money that furnace is WAY oversized for your house & climate. Maybe Thermo-Pride will give you an allowance toward a properly sized furnace instead of a new heat exchanger. Certainly worth a try if the heat exchanger is still under warranty.

Pour one for me too. Or at least a few of these: Beer 4U2
 
  #30  
Old 10-31-09, 09:22 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Cause?

I know, poor maintenance. What I mean is, can you explain how so much pressure built-up that the exchanger burst? Or did it implode? I've only been able to find two diagrams of this exchanger on the internet and they weren't really helpful. If you could send me a reference or two that would be great.
 
  #31  
Old 11-01-09, 12:14 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Not pressure

It wasn't pressure but heat & moisture. Crawl spaces are terrible places due to their normally moist environments. The moisture mixes with the residual sulfur from burning fuel oil & creates sulfuric acid which over time eats the metal of the heat exchanger. Obviously the best preventitive measures are a thorough cleaning right after the heating season & keeping the crawl as dry as possible.

About all I could find was this PDF on Thermo-Pride's web site.
http://www.thermopride.com/pdf/OilFiredFurnace.pdf
Page 12 of the document (Pg.16 in the PDF) shows a couple of drawings.
 
  #32  
Old 11-01-09, 08:53 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Keep cleaning?

Thanks for the file. I'm still trying to figure out exactly what the inside of this exchanger looks like, specifically where the inner and outer chambers meet. I can tell the hole in the outer chamber has been there for a long time.

I guess what I'd really like to know is if I should continue cleaning at the clean-out ports, so I can get draft at the burner, or is the crud in there the only thing keeping us from certain death?
 
  #33  
Old 11-02-09, 06:50 AM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Heat Exchanger

If I were to see a heat exchanger like that, the furnace would be taken out of service RIGHT NOW. No way, no how should you continue to use it without replacing the heat exchanger or the entire furnace.

If memory serves me correctly, the interconnection of the inner & outer parts of the heat exchanger is on the opposite side & opposite end of the heat exchanger from the vent pipe.
 
  #34  
Old 11-03-09, 10:22 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
A brief update

Spent several hours tonight cleaning out exchanger from burner side. You've seen the pictures so you know what I was dealing with. Started furnace and still couldn't get draft at burner port. If I can stand up straight or bend at the knee tomorrow will fully inform.
 
  #35  
Old 11-05-09, 04:30 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Improvement

I spent more time last night cleaning the exchanger. Don't know why. I guess if I can't use it I may as well learn something, right? I pulled off the flue and opened the clean-out at the burner. They're on opposite sides, remember? Here's a little tip. I discovered if I couldn't pull something out from the port I could push it over to the breech and vacuum it out from there. Push me, pull you. Lot's of bending and straining. I've been popping aspirin like Pez all day.

You were certainly right about the exchanger. Huge difference in stack temp. Down to 425 or so degrees before adjusting for ambient temp. But, for some reason I still can't get draft at the burner port. Any thoughts?
 
  #36  
Old 11-06-09, 07:03 AM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Draft

Some of the exhaust instead of going thru the heat exchanger is coming out that rust hole.

Have you called Thermo-Pride yet? You will probably need the "furnace number" which is on the data plate, I think.
 
  #37  
Old 11-06-09, 08:48 AM
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 8,629
Originally Posted by TtTankEngine View Post
I've been popping aspirin like Pez all day.
I think you are only allowed 8 per day, if I'm not mistaken.
 
  #38  
Old 11-06-09, 06:21 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Thank you

Thanks for the concern ecman51. I was joking. Although, I am now considering picking up a wicked heroin habit. Have you been following this thread?
 
  #39  
Old 11-06-09, 07:57 PM
TtTankEngine's Avatar
Member
Thread Starter
Join Date: May 2009
Location: State of confusion
Posts: 76
Ok to ask more questions?

Hi Grady. Haven't seen you post in a few. Everything alright?

Here's where things stand at this end. The heat exchanger should be under warranty. Unfortunately, the warranty also contains a clause about "reasonable and necessary maintenance". I think that ship has long since sailed. It also mentions the owner pays for shipping and installation costs for a new one and possibly shipping costs for returning the old one for inspection. I think your suggestion about asking for an allowance on a new furnace is a good idea and I will look into it.

Since we have now entered the land of the theoretical, I hope you don't mind if I ask a few more questions.

1) If I plugged the hole in the heat exchanger with a rag (FOR TEST PURPOSES ONLY) and still couldn't get draft at the burner port, where should I look next?

2) I got lucky, if you can call it that, when I removed the inspection cover and immediately found a hole. I know from all the time I spent cleaning the exchanger that some areas are completely inaccessible. How would a tech search for a hole?

Thanks again for your time and help. I plan to start working on the second furnace tomorrow. Wish me luck.
 
  #40  
Old 11-07-09, 06:57 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,928
Missed Post

I posted yesterday, short post, probably easy to miss.

With you and Thermo-Pride both being in NC, shipping shouldn't be too bad. I can't remember exactly where their factory is (Denton comes to mind) but maybe you could pick up the heat exchanger. Just checked, the old memory bank isn't completely broke. They are indeed in Denton.

I wouldn't use a rag but you might try foil tape. Strictly for testing purposes. If you still can't get draft, there are a few possibilities. (1) There is another hole. (2) The heat exchanger is still plugged. (3) With that long horizontal run, you may need a draft inducer.

Horizontal furnaces present special problems when looking for a defect in the heat exchanger. Often it involves virtually un-installing & disassembly. Sometimes a swivel head mirror with a long handle will help us find a defect other times not.

Second furnace??? Must be a BIG house.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes