clogging condensing furnace trap

tim smith

> I have a customer with a Carrier 58mxa100-12 92% <BR>
> condensing furnace that within the last 3 years <BR>
> needs trap cleaned 2 times each season.The <BR>
> customer is getting frustrated because he has a <BR>
> fall pm done and a service call each year.The <BR>
> first 8 years this was not an issue but now it <BR>
> is.The trap is becoming blocked with a mud like <BR>
> substance not like a typical algae type block.The <BR>
> intake and exhaust pipes are about 6 1/2 feet <BR>
> above ground and not by shrubs or anything <BR>
> else.vent pipes approx. 20 feet each and slope <BR>
> back to furnace. section of trap that becomes <BR>
> blocked is from the secondary and I flush with <BR>
> hot water and bleach on pm. Please help dont want <BR>
> to lose a customer. thank you <BR>
<BR>

Mike Altman

clogging condensing furnace trap

I have a customer with a Carrier 58mxa100-12 92% condensing furnace that within the last 3 years needs trap cleaned 2 times each season.The customer is getting frustrated because he has a fall pm done and a service call each year.The first 8 years this was not an issue but now it is.The trap is becoming blocked with a mud like substance not like a typical algae type block.The intake and exhaust pipes are about 6 1/2 feet above ground and not by shrubs or anything else.vent pipes approx. 20 feet each and slope back to furnace. section of trap that becomes blocked is from the secondary and I flush with hot water and bleach on pm. Please help dont want to lose a customer. thank you

Paul Mitchell_3

I think it must be algae. I would replace the trap and piping. Then see. REMEMBER this is not your problem. YOU ARE TRYING TO HELP. It is hard to remember...but we know what we are doing and doing it right. If he gets someone else it will happen to them...or they will replace the parts...bill him and they will be the hero.
Good Luck

Glenn Harrison_2

Two thoughts

1. what ever is plugging it up is probably growing in the secondary heat exchanger. you will need to flush the entire secondary heat exchanger with bleach (easier said than done )

2. The propylene coating in the secondary heat exchanger has failed and you are getting corrosion of the metal. The combination of degraing propylene coating and corrosion residue is plugging the trap.

Either way it is in the secondary, based on your description.

S Ebels

Carrier problems

Although condensate traps are a yearly maintenance item, what's going on there is definitely not normal. We have replaced tqo MCA models furnaces with bad/plugged secondaries this winter. In each case they were on LP gas and Carrier says that some LP gas companies are not real careful with the amount of sulpher they allow in their fuel. This sulpher when burned forms sulphuric acid which attacks the HX and causes failure due to flaking of the HX coating. This is what happened with both of the furnaces I'm refering to here. Carrier stood behind them with an offer to replace the HX at no charge or to replace the whole furnace if the HO pays the labor.

There have also been a couple that just failed due to other circumstances. Airflow is critical on any 90% furnace and a lot of times temp rise across the HX is too high due to inadequate duct size/design, causing overheating of the secondary. In Carrier's furnace, this is lined with "plastic" as refered to in a previous post.

At any rate, I'd bet that your customer has a HX that is in the process of failing or has failed. Industry average life for a high efficiency furnace is only 11 years or something like that. They shouldn't be surprised.

tim smith

Carrier, Trane, Bryant, Tempstar etc

All these condensing furnaces will have heat exchanger problems along the way. We have found a need to tear the units down for thorough inspection, or cleaning as needed appx every 10 years or so. In 05 we probably have rebuilt 15 to 20 furnaces that either some or all of the primary heat xs had failed, holes or cracks. And most of the Secondary stainless heat exchangers inspected had small pin hole corroded out areas. To the customers benefit they are usually in warranty by the mfr and all they have to pay is labor, we do it all in one day including the exchange of parts with the supplier. Just FYI. It still ends up being less than a 1/4 the cost of a new furnace installed.