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upon replacement of both exchangers there was no signs of rust or sludge build up on the socondary, also no restrictions or considerable lint or debris found on the AC coil the rings from the clam shells had busted suspect the draft inducer was pulling air from the conditioned space rather than from the intake causing the flame to run slower down the exchanger therefore heating the burner box.
Originally Posted by frustraded tech the "saga" continues, received the secondary yesterday, so we proceeded to change it today when I pulled it out I found 2 rings from the clam shell of the primary and proceeded to pull that out and visually inspected found a total of 6 rings busted out, so the primary will have to be replaced. Then I needed to make sure the secondary is in fact cracked or leaking and the only thing I could think of doing was to stand it with the bends towards the bottom and fill the tubes with water and let it sit for a while and had no water leakeage at all now the dillema is where was the water coming from? and obviusly why wasn't my combustion analizer registering CO in the conditioned air dam thing is brand new and for $2K you'd think it be calibrated.......... Please don't rely on CO in the supply air as your determining factor for a breached heat exchanger, you will miss the ones that are. The blower is forcing are across the chambers(read: positive pressure), that's why it's protected by roll-out limits.
Originally Posted by Juan Madera CO rots steel! Any CO. If you have pulled a water heater burner covered with flakes of rust, you have seen CO at work. I concur with the flakes in the secondary. ALSO; you mentioned the Delta T being high. Perhaps a restricted duct? What is the External static on the system? Rust is from the acidic flue gases condensing on metal surfaces, it has nothing to do with CO. Rust is always a sign of a venting problem. It is a sign that the flue gases are not venting out of the appliance properly at the end of each cycle.
Originally Posted by Juan Madera CO rots steel! Any CO. If you have pulled a water heater burner covered with flakes of rust, you have seen CO at work. The acidic condensate during cold opperation rusts the steel, not CO. Before the discovery of natural gas, CO from coal gasification was delivered through the same steel gas lines for lighting coal burners and it did not rot them out.
CO rots steel! Any CO. If you have pulled a water heater burner covered with flakes of rust, you have seen CO at work. I concur with the flakes in the secondary. ALSO; you mentioned the Delta T being high. Perhaps a restricted duct? What is the External static on the system? Originally Posted by frustraded tech sorry, forgot to mention that has been done the flue readings where about 89% efficiency 122F & 6.2 CO
Originally Posted by frustraded tech the "saga" continues, received the secondary yesterday, so we proceeded to change it today when I pulled it out I found 2 rings from the clam shell of the primary and proceeded to pull that out and visually inspected found a total of 6 rings busted out, so the primary will have to be replaced. Then I needed to make sure the secondary is in fact cracked or leaking and the only thing I could think of doing was to stand it with the bends towards the bottom and fill the tubes with water and let it sit for a while and had no water leakeage at all now the dillema is where was the water coming from? and obviusly why wasn't my combustion analizer registering CO in the conditioned air dam thing is brand new and for $2K you'd think it be calibrated.......... Just cause you have a crack doesn't mean co in condition space
this particular unit did not have any sludge what so ever!
upon inspection this exchanger was very clean small buildup @ the bottom where the transfer box to the secondary bolts on.
we found 6 rings busted out, plus first post explained that we switched the roll-outs and the unit kept tripping on the same spot not the switch.
Roll out switch tripping on the H9mpd series furnaces is usually the result of a problem with the secondary heat exchanger. There was a problem with the oil used when the heat exchanger was formed. It would react with acid from the flue gases and form a thick sludge that pluged the tubes in the exchanger. It required removal of the cold header box and the turbulators and then working a wire with a rag attached thru each tube till they were clear. A messy and time consuming job but it would get the furnace working. Worse case would be a cracked secondary heat exchanger although I have not found one yet.
Try measuring the temps at the roll out It shouldnt be even close to the trip temp
Just a thought...I have seen faulty roll out switches. I had a 90plus furnace kick my butt for a week, changed the switch and never had another issue with it. Luckily it was a friends system.
it's not like i didn't test for it, that has been my diagnosis from the begining but I frustrated because could not prove or document it!
it always did in the past same analizer model, has a screen for flue and conditioned air. selection for gas type etc...
6 busted rings and it wasn't noticed on the first visit, this is why when I go to a new customer they get upset when I find stuff like that and they say it gets checked every year. Thank you for all the loyal customers they're the ones that don't get estimates from other companies and they stay with us forever.
Originally Posted by frustraded tech the "saga" continues, received the secondary yesterday, so we proceeded to change it today when I pulled it out I found 2 rings from the clam shell of the primary and proceeded to pull that out and visually inspected found a total of 6 rings busted out, so the primary will have to be replaced. Then I needed to make sure the secondary is in fact cracked or leaking and the only thing I could think of doing was to stand it with the bends towards the bottom and fill the tubes with water and let it sit for a while and had no water leakeage at all now the dillema is where was the water coming from? and obviusly why wasn't my combustion analizer registering CO in the conditioned air dam thing is brand new and for $2K you'd think it be calibrated.......... An analyzer will not pick up CO in the supply air when the heat exchanger is cracked. There is nothing wrong with the analyzer, don't bother testing the supply air for CO, it doesn't tell you anything about how safe the furnace is.
the "saga" continues, received the secondary yesterday, so we proceeded to change it today when I pulled it out I found 2 rings from the clam shell of the primary and proceeded to pull that out and visually inspected found a total of 6 rings busted out, so the primary will have to be replaced. Then I needed to make sure the secondary is in fact cracked or leaking and the only thing I could think of doing was to stand it with the bends towards the bottom and fill the tubes with water and let it sit for a while and had no water leakeage at all now the dillema is where was the water coming from? and obviusly why wasn't my combustion analizer registering CO in the conditioned air dam thing is brand new and for $2K you'd think it be calibrated..........
Secondary HE will be replaced customer is debating about primary since it might not be under warranty.
plastic? you mean collector box? that was inspected and look fine at the time. why would it be dry on top if that was leaking. I have also taken the blower and looked at the secondary (before the leak) and could see much but I was actually cheching that it was no plugged not for cracks.
Originally Posted by frustraded tech follow up...........first of all thank you to all for your feedback it has helped me a lot. so customer called today saying he found water on the floor near the furnace and water heater, the water heater is only 2 year old and I told them I would be right over (even though its my bday) hehe, because of course I assumed that I had forgoten to tighten a clam or to put back a hose or whatever but the top of the cabinet was bone dry and the water is dripping from the rail for the blower motor and I am assuming is carrying on the rail from just under the exchanger then to the front, now could the of been a hairline crack that just open up in the secondary HE I was not able to put my Combustion analizer on it but if water is leaking the exchanger its a no brainer right?? Stop assuming, and check the secondary with a good mirror and flashlight. Pull that blower motor and get your head right in there. The plastic secondary connection always cracks on these.
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