cracked heat exchangers

Alan_6

In the past, I have cut a hole in the back of furnace, to confirm that the cracks, go through the metal. Recently the company that I work for, made it policy that we have to pull heat exchangers to confirm cracks. Does anyone have another way to confirm cracks? We also cant use smoke sticks, or are investing into the camera's.

Gary Reecher

Check HVAC Talk for a detailed discussion.

Check the attached site thread

http://hvac-talk.com/vbb/showthread.php?threadid=52782


There are lots of links within this thread on different inspecting techniques. Plus some photos.

toearly_2

> In the past, I have cut a hole in the back of

> furnace, to confirm that the cracks, go through

> the metal. Recently the company that I work for,

> made it policy that we have to pull heat

> exchangers to confirm cracks. Does anyone have

> another way to confirm cracks? We also cant use

> smoke sticks, or are investing into the camera's.




We use many of the methods mentioned in the other post.
But my camera seems to on the job more and more.
There are many cameras out there to choose from. We use one called Snake Eye. I think I paid about 1600.00 for it.
Worth every penny

David

Mark Eatherton1

THE expert on cracked heat exchangers...

lives in Fort Collins Colorado.

http://www.heatexchangerexperts.com/photos.html


He uses water...

ME

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

dave connors

Salt water

If you spray salt water in the chamber then fire the unit. Have a helper at a register outlet with a torch that is lit. Turn on the blower. If there is a crack the flame of the torch will turn greenish blue.

Dale

Ellis Prach system

See ME's post below. Ellis of heat exchanger experts has the best system in my opinion to find cracks, he is as passionate about this topic as anyone on this site is about wet heat. His system uses detailed visual inspection with thin mirrors, a book of furnace brands showing where most cracks or defects are found and a water or WD 40 spray technique to confirm the crack. Ellis makes the case that most brands of a certain age crack in the same place ( like the Lennox dura curve) and if you know where to look and spray water with surfecant( a wetting agent for plant leaves) or enough water the crack will show up. He offers courses all over the country for about $300 where he demonstrates this, well worth the time. Sadly most attendees are home inspectors. His book of cracks by brand is only about $75 with yearly updates and he is great about helping tech schools.

Gary Reecher

For those that want one single never fail method for inspecting heat exchangers. There is none. Think about it. Would you inspect a Pulse heat exchanger the same way as a clamshell heat exchanger , a clamshell heat exchanger the same way as a tubular heat exchanger ? No you wouldn't nor should you. With equipment, knowledge and training you can become more proficient at inspecting heat exchangers.

Types of Heat Exchanger Failures
1. Cracks.
2. Rust perforations.
3. Leaking heat exchanger seams.
4. Loose or missing screws securing cells.
5. Broken crimped rings
6. Broken or leaking seals or gaskets, including cemented seals.
7. Missing factory welds on seams.


Inspecting Heat Exchangers

1. Flame deviation test. Watch the burner flame. Flame movement when the circulator blower comes on indicates leakage. If you do not locate a crack or perforation the heat exchanger the seams can be leaking or the metal may have pinholes rusted through.

2. Visual inspection of burner chamber area and exterior of heat exchanger using a flashlight with high candlepower such a rechargeable Mag Lite.

Use a variety of mirrors. Small round and oval mirrors that have long telescoping reach are available at most welding supply stores. A 2-1/4 inch round mirror that telescopes from 6-1/2 inch to 36-3/8 inch is also available through Sears.



For older heat exchangers have a mirror made at local glass shop 1/4" thick x 1-3/16" width x 24" length. A suitable carrying case can be made from 1-1/4" PVC pipe and fittings.

3. Water Spray Test.

Remove furnace blower assembly and the fan/ limit to prevent damage to these components. Spray the exterior of the heat exchanger with a water/soap solution 1 gallon water/ 1 tablespoon soap using a garden sprayer. Inspect the interior of heat exchanger with mirror and flashlight observing for evidence of water indicating a crack, rust perforation or crimp leak.

By shining a light on the outside or the inside of the heat exchanger area and examining the opposite side look for light penetration.

4. Measuring for CO in the plenum.

A CO detector cannot tell you if a heat exchanger is good. A CO detector can indicate a heat exchanger is cracked only if all of the following conditions occur simultaneously:

a. The flame generates enough CO (lack of oxygen, excess fuel, high temperature).

b. Enough exhaust gases are emitted from the heat exchanger crack or perforation.

c. The exhaust gases from the crack are not diluted too much before coming in contact with the sensor. A cracked heat exchanger may leak CO in a small stream. You may measure high concentrations only an inch away.

d. The heat exchanger is the only possible source for the CO detected.

Note: I have not tried this but have heard of some that will spray WD-40 or Gunk penetrating oil into the burner chambers (not the outside) of heat exchangers of furnaces with inshot burners to generate CO to see if CO will leak to the outside of the heat exchanger.

5. Combustion meter measuring undiluted flue gases.
One sign of a cracked heat exchanger is a change of oxygen concentration in the flue gases of greater than 1 / 2 % oxygen, or a change in the carbon monoxide level greater than 25 ppm. This change is measured by comparing readings before and after the circulation blower has turned on. For this test to be valid , CO levels must be present in the flue gas.

Check Bacharach's site Checking for Cracked Heat Exchangers
http://www.bacharach-training.com/Tips/Cracked.htm

6. The American Gas Association developed FURNACE HEAT EXCHANGER LEAKAGE TEST injecting a nitrogen and methane gas mixture into the burner chamber. The heat exchanger outlet of the heat exchanger is plugged and a combustible gas detector is used to check for gas leakage on the exterior. A detailed fact sheet on the AGA test procedure is available at
http://www.aga.org/pdf/publicinfo/codesstandards/twfacts8612b.pdf

Test Products International advertises the J&N Associates H.E.T. Kit and HXG-2 Combustible Gas Detector on their web site which does the above AGA test.
http://www.testproductsintl.com/gas.html


7. Magnehelic gauge test. Tape shut burner chamber openings and flue outlet. Connect magnehelic gauge to inducer pressure sensing port. Operate circulator blower. Movement of gauge needle indicates leakage into chamber.


8. Vapco H.E.A.T. Spray catalog number HT-1Q. Sprayed into the blower compartment on opposite side of motor. If burner flame changes color there is a leak in the heat exchanger.
Vapco http://www.vapcoproducts.com/catalogPDF/P19-outline.pdf

9. Magna Flux dye penetrant test. Using cleaner then penetrant and then cleaner over suspected area developer is then sprayed. Penetrant which has seeped into cracks, perforations or pinholes is pulled out by the developer agent. Full length of crack is seen not just what may be seen without theis test. Magna Flux cleaner, developer , red penetrant and zyglo fluoroescent penetrant is available through welding supply stores.



10. Smoke Bomb test. Smoke bomb is placed inside burner chamber and lit. Evidence of smoke on the exterior of the heat exchanger indicates leakage.

11. Camera systems can gain you access to some narrow openings and the inspection can also be taped for viewing by the home owner or for training. A couple sources for cameras are:

The Inspector http://www.shamrockindustries.com/home.html

IC Cam http://www.rotobrush.net/IC Cam.htm

Abatement Technologies http://www.abatement.com/residential/hvac_video.htm


12. Optical boroscopes can also get you access to some narrow openings. Yet do not offer the ability to tape the inspected areas. You can also order extra polished metal mirrors cut glass mirror material and superglue them to the polished metal.

Testoview http://www.testo.com/testoview.htm


13. Pressure Testing - Lennox Pulse Furnaces using kit part number 74K96.
Most failures on the Pulse occur at the solder joints at the condenser (secondary hx) outlet tube. However failures can occur at other areas as the following photo shows.


14. Global Leak Detection Corporation--- LeakChek Hawk pressure test kit. It can record and report using new industry standards in testing procedures as developed by Alberta Mechanical Officials Society . Click on products link. http://www.gldcorp.com/


There are additional sources for heat exchanger testing and inspecting? They include detailed methods and photographs of various heat exchangers showing locations of defects. Check the following sites.

RSES Members check your SAM manual "Residential Gas Furnace Heat Exchanger Testing" Douglas DeWerth, P.E. American Gas Association Laboratories manual number 630-92 9/86


Contractor's Advantage http://4youradvantage.com/heatexch.htm

Furnace Safety Consultant's http://www.furnacesafetyconsultants.com/pages/710635/index.htm

Heat Exchanger Experts http://www.heatexchangerexperts.com

Residential Furnace Heat Exchangers BOOK & CD-ROM

http://store.homeinspection.com/script/merchant/merchant.mv?Screen=PROD&Store_Code=ITA&Product_Code=KB5471

http://store.homeinspection.com/script/merchant/merchant.mv?Screen=PROD&Store_Code=ITA&Product_Code=B547CD&Category_Code=BOOKS-INSPECTION

A good book "Carbon Monoxide a Clear and Present Danger "
http://www.escoinst.com

Training Classes

Kansas City Building Institute
http://www.kansasbuildingscience.com/inspect.htm

Heat Exchanger Experts
http://www.heatexchangerexperts.com/photos.html

For those that are only concerned about carbon monoxide from leaking furnaces check this site about the toxicity of natural gas http://www.geocities.com/RainForest/6847/report1.html#6.0