[PAX]

Working on an old carrier unit commercial rooftop approx 25 yrs old.... Received the standard no heat call... Upon arrival found burned up wiring near roll out- fired up unit and identified unit was ok at first when 2nd valve came into play unit experience bad roll out.... I checked the heat exchanger by visually looking to both access points.... and into each tube...was definit rust present (unit was not taken care of) in the tubes but I could not see any crakes or holes....

Talked to tech support they told me to do a cumbustion analysis and see if the co levels changed constantly.... If they did change frequently he would say it was cracked....

Any feed back would help!

 

[simplyrollin]

Well, I would make an absolutely positive verification that it was cracked or did need replacing before any shooting down.

 

[mike3]

Working on an old carrier unit commercial rooftop approx 25 yrs old.... Received the standard no heat call... Upon arrival found burned up wiring near roll out- fired up unit and identified unit was ok at first when 2nd valve came into play unit experience bad roll out.... I checked the heat exchanger by visually looking to both access points.... and into each tube...was definit rust present (unit was not taken care of) in the tubes but I could not see any crakes or holes....

Talked to tech support they told me to do a cumbustion analysis and see if the co levels changed constantly.... If they did change frequently he would say it was cracked....

Any feed back would help!

What do you mean "second valve came into play"?

You have roll-out, you have to do something and that does not include leaving unit in operation. Also you say rust is present, try cleaning heat exchanger?

 

[yellowirenut]

my fist though is "rust" has fallen and partially blocked HX...clean that thing out and do a proper inspection. open the other side and look in.

 

[airproguyrick]

Working on an old carrier unit commercial rooftop approx 25 yrs old.... Received the standard no heat call... Upon arrival found burned up wiring near roll out- fired up unit and identified unit was ok at first when 2nd valve came into play unit experience bad roll out.... I checked the heat exchanger by visually looking to both access points.... and into each tube...was definit rust present (unit was not taken care of) in the tubes but I could not see any crakes or holes....

Talked to tech support they told me to do a cumbustion analysis and see if the co levels changed constantly.... If they did change frequently he would say it was cracked....

Any feed back would help!

Hx is probably restricted internally with rust and soot.There are baffles or turbulaters in the heat exchanger near the flue connection. That's whats usually plugged. 25 years can be pretty old for a RTU. Most of them are pretty well trashed at that age around here.

 

[PAX]

The unit runs ok when only the first gas valve is activated. When the 2nd gas valve is activated...the roll out begins. As far as the rust I did clean it out but same result. Would you recommend any other tests on the exchanger?

 

[hvactech98]

Do a visual inspection of the heat xchngr. I don't know which model you are working on but, I know there is a panel that can be removed to expose the heat xchngr. The roll out is most likely happening when the blower is running in which case yes the heat xchngr has failed. They usually rust through the seams of the tubes.

 

[yellowirenut]

how are u inspecting it? is the fan blowing when the second valve engages?

have u removed the side panels to get a look at the back side of the HX?
what is the gas pressures? is the fire ball right away or does it seem to build up gas then poof? like a delay from the gas valve to ignition?

 

[the dangling wrangler]

It's 25 years old. I'll condemn it from here.

 

[timebuilder]

If it's mint green, it's an old Weathermaker.

If you have rollout like that, I'd say don't replace the exchanger, quote a new unit.

 

[the dangling wrangler]

If it's mint green, it's an old Weathermaker.

If you have rollout like that, I'd say don't replace the exchanger, quote a new unit.

Yep. I can't remember ever seeing one near ten years old.
It's well past replacement time.

 

[madhat]

Are you going to fix it under the Warranty ? :argue: We Never had a problem with it in Twenty-five years, till you touched it.


Had a Beauty Salon, did a double take, when I looked at the unit, and there was NO heat exchanger, just a pile of rust. Of course we got a call from her brother, the Lawyer. Oldest trick in the book, needed to turn the gas back on, and we had better not have punched a hole in the unit, unless we were prepared to give her a new unit.