There seems to be a few different ways of checking for a cracked heat exchanger and I was curious about which technique could be more effective than the other, asside from using a inspection camera, there very expensive and not everyone can carry one on there van, any input would be informative.
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.
Photo courtesy of the Baldloonie
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.
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.
9A. A flourescent dye spray and UV light test has been devloped by Visible Defects. The dye is sprayed on the exterior of the heat exchanger. The interior is then checked with the UV light. Picks up cracks, rust holes and faulty seams and welds. They also have a camera system. The lens head diameter is smaller than a dime. http://www.visibledefects.com
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.
10A. Smoke puffer test at the burner inlet and watching the smoke if it sprays away from the burner opening you may have a leak in the heat exchanger.
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%20Cam.htm
Abatement Technologies http://www.abatement.com/residential/hvac_video.htm
Visible Defects http://www.visibledefects.com
12. Optical boroscopes can also get you access to some narrow openings. Yet do not offer the ability to tape the inspected areas.
By supergluing a larger mirror to the Testo mirror you can improve the quality of the view.
Be sure to properly attach the mirror. The mirror support should be on the side of the head that has the large optical opening. The two smaller openings are the lights.
13. Pressure Testing - Lennox Pulse Furnaces using kit part number 74K96 available through Lennox.
This kit comes with the pressure gauge fixture, plugs, instructions and a furnace wall patch plate. Additional patch plates can be ordered through Lennox. The carrying case and inlay is something I did on my own. Cases available through Sears.
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/
15. According to the Timken Silent Automatic Oil Burner Serviceman's Guide, 1926 Edition:
A serviceman can easily check whether smoke is passing through the heat exchanger due to a crack is to shut off the burner and place a burning piece of TARPAPER in the combustion area. By then placing his nose next to a register if the smell of asphalt is detected in the home then there is probably a defective heat exchanger.
16. Here's a test used in the land of natural gas, Alberta, Canada. It's called a sulphur test. We bring the unit up to full operating temp. then a small amount of sulphur is placed on a tiny collectors spoon which is fastened to a piece of soft 1/4" copper tubing about 15 and 22" long (I made 2 for different applications) and then inserted into the burner area. I let it burn in each chamber for about 15 seconds, moving it slowly back & forth, side to side. The amount of sulphur should do 3 or 4 chambers.NOTE: if you need additional sulphur, make sure you cool off the spoon in some water, or you'll have one stinky fire on your hands!! And don't lay the hot spoon on a lino floor or something until it cools off.
The principle being... if the exchanger is good, the rotten egg smell will be taken out of the home via the chimney, if it has a hole or crack anywhere in it, the smell will be distributed into the living space via the heating ducts, just like CO would be. I still monitor for CO with a digital 4 gas detection unit as an addition back-up, but as you have already heard, there are many conditions that can cause false or no readings at all.
The test is very cost effective, quick to perform, and quite reliable. Most HVAC company's around here use it. The sulphur is available at Pharmacy Drug Co. and at some Veterinarian places. It's bright yellow in color, and can be in powder or pellet form. It's called Precipitated Sulphur and sells for ~$15. for a lb. which lasts a long time.
Hint: try and be quick if you have to pull the spoon completely out past the heat shield to get it into the next chamber, so you don't smell up the area your working in. It's pretty smelly stuff!
Want additional sources for heat exchanger testing and inspecting which include detailed methods and photographs of various heat exchangers showing locations of defects? Check the following.
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. If you want a copy call RSES http://www.rses.org
Contractor's Advantage http://4youradvantage.com/heatexch.htm
Furnace Safety Consultant's http://www.furnacesafetyconsultants....0635/index.htm
Heat Exchanger Experts http://www.heatexchangerexperts.com
Residential Furnace Heat Exchangers BOOK & CD-ROM
Also a good book source for combustion and carbon monoxide testing "Carbon Monoxide a Clear and Present Danger "
Kansas City Building Institute
Heat Exchanger Experts
For those that are concerned only about carbon monoxide from leaking furnaces check this site about the toxicity of natural gas http://www.geocities.com/RainForest/...port1.html#6.0
Dadgum ole furnace.
Aircraft Mechanical Accessories Technician. The Air Force changed the job title to Air Craft Environmental Systems Technician. But I've decided I'll always be a Mech Acc.
Kudos MechAcc. What a detailed answer. Appreciate the time input for that.
MechAcc thank you for all the information and it will all be used for future reference.
Great post mech, no wonder you find so many cracks
The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.
Dad gum furnaces.......................
Some Talk, Some Do
"keeping condensing pressures low and evaporator pressures high"
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