Contractor Talk - Professional Construction and Remodeling Forum banner

1 - 16 of 16 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter #1
ok so i do commercial hvac and well inspecting commercial equipment is fairly easy...dont do alot of resi work but the old furnaces was a visual inspection of the heat exchanger...how do you check the new heat exchangers when you cant even see in the new ones...no one can give me a clear this is how you tell if their cracked....so how are you guys doing it?
 

·
Thom
Joined
·
4,137 Posts
turn on the furnace, let it run for a few minutes, and test for CO at a register.
 

·
Registered
Joined
·
9 Posts
They have what are called smoke bombs. You put them in the firebox on your furnace and turn on your blower. If smoke comes up through your registers you have a cracked heat exchanger, if not you are generally good.
 

·
Registered
Joined
·
2,477 Posts
You can use an inspection snake. Run it through the cells.
Or, you can open the plenum and inspect from the top down.

Ridgid has a model you might like. SeeSnake
 

·
Registered
Joined
·
86 Posts
as beenthere said,there are alot of different inspection cameras to choose from,pull the blower for a visual of outside of heat exchanger, and a combustion analysis of the flue gas also....these are methods i use along with observing flame after blower comes on,.....there are other methods also,but these are the ones that i use the most it seems like.
 

·
Registered
Joined
·
3,920 Posts
How often do you use the combustion analysis gear?

If I am to do an official inspection of the h.e., I would at least pull the blower and/or open the evaporator coil. Since I have a sea snake, and an impact drill, I will pull out the burner assembly as well. The s.s. is an investment, but it's worthwhile.

I you want to keep it simple, you can pull out the limit switch and use the sea snake there, and take a peak through the burner ports, but I wouldn't declare that as an official inspection of the he.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #8
again i am asking about new furnaces...where the heat exchanger is not at all visable...inaccessible to put a smoke bomb...without taking the whole thing appart what are you looking for in the results of the co test if it were cracked?
 

·
Registered
Joined
·
2,477 Posts
again i am asking about new furnaces...where the heat exchanger is not at all visable...inaccessible to put a smoke bomb...without taking the whole thing appart what are you looking for in the results of the co test if it were cracked?
Watch for the CO to go down(sometimes it will go up)when the blower comes on. Also watch for the O2 to go up when the blower comes on.

These are indications of a crack or hole. But not a 100% there is one.
 

·
Registered
Joined
·
86 Posts
i use the comustion analysis on every furnace i touch,even brand new ones and print the results..............took me along time to beat that in my head;),there are certain parameters that the co level must fall under....
 

·
Registered
Joined
·
3,920 Posts
My supply house has a kit which they want to get rid of. They offered me a good price, but at this time I can't pull the trigger. None of the outfits I used to work at ever used them or hadone for that matter. I certainly wasn't ready to shell out my money. However, now it's Flash time. Do you think they are a "must have" tool?. I primarily work on nat gas and electric equipment.
 

·
Registered
Joined
·
2,477 Posts
Only way you can tell if a gas fired or oil fired appliance is operating correctly.

Contrary to popular belief. Just because a gas flame is blue. It doesn't mean its burning as clean as it should. Or without producing excess CO.
 

·
Registered
Joined
·
186 Posts
Only way you can tell if a gas fired or oil fired appliance is operating correctly.

Contrary to popular belief. Just because a gas flame is blue. It doesn't mean its burning as clean as it should. Or without producing excess CO.
Absolutely TRUE. CO burns blue. You cannot tell if you have CO by looking at the color of the flame.

Dr. Thomas Greiner, Iowa University, would display lots of photos during his CO seminars. Some with monoport burners with yellow flames, less than 10 PPM. Some linear burners with doctored orifices and only one unaltered one. The burners were numbered and he would ask people to raise there hand for the burner that was burning the least amount of CO. He said the results would run less than 10 percent of the attendees would guess the correct burner. And that is why you need testing equipment. Period
 

·
Registered
Joined
·
142 Posts
primarys you basically have to look at,cut hole in plenum and inspect.or if rollout switch tripped its a good indication of trouble..now secondary x changers can pretty accurately be diagnosed by inserting co probe in exhaust vent outside,anything over 100 ppm i'd be pulling vestibule plate off for a closer inspection ..
 
1 - 16 of 16 Posts
Top