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What are the main reasons that condensing combi boiler and condensing boilers fail in short time.

bob eck
bob eck Member Posts: 930
Today there was a contractor that was saying a certain brand condensing boiler line does not last long.
He said they will only last 2-4 maybe 5 years at most.

From what is see there are a few reasons that can shorten ANY BRAND condensing gas boiler.
In no particular order.

1- over sizing of the boiler causing short cycling on and off of the unit to often.
2- wrong size primary pump not moving the correct GPM through the boiler heat exchanger.
3- Boiler was not piped in correctly. No P/S piping
4- not properly venting the boiler. Cross contamination bringing in exhaust gas instead of all fresh air.
5- water quality. No way to remove iron in the system especially on old cast iron radiator systems. This can clog the heat exchanger causing bad flow through the heat exchanger causing very hot spots in the heat exchanger stressing out the SS HX or Aluminum HX causing it to leak. This is NOT a manufacture problem. This is a installation problem.
6- not flushing the old system with chemicals to clean out all of the old crap in the system.
7- not adding chemicals after installation
8- home owner NOT doing yearly maintenance
9- contractors installing these boilers and not setting them up with testing equipment.

I am not pointing the finger at any contractor or home owner just giving my opinion on why some of the condensing gas boilers and combi boilers fail in a short period of time.

What type heat exchanger is better or more forgiving? SS Fire Tube, SS water tube, Aluminum heat exchangers?

Hot Rod and Ron Beck did I miss any major reasons why a condensing gas boiler will fail in a shot period of time. Other opinions welcome.

Mark Eatherton


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
    Ancient wiring with a bad ground or neutral could also cause some intermittent problems, as the electronics of these sophisticated new boilers are so sensitive.—NBC
    bob eck
  • j a_2
    j a_2 Member Posts: 1,801
    To sum it up, they fail early, due to the unskilled installers...and the home owners who trust them....most of them are pretty good products, at least that’s what there reps say...pretty sure I know what brand he was speaking of, they got a bad rap,in my opinion by selling the units online and to anyone that walked into homeowner friendly supply houses...

    bob eckRich_49
  • GW
    GW Member Posts: 4,701
    That contractor should take up sales in kitchen appliances
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
  • mow
    mow Member Posts: 12
    Well, sounds much easier and possibly cheaper? to just keep my old 80%er!!

  • Tom_133
    Tom_133 Member Posts: 888
    Im also curious what our expectations are with some of these rather inexpensive boilers. Some combi's are under 2k and becoming more and more plastic. My opinion is that product is a 10 year boiler at most. Thats typically what I tell my customer. There are others out there that you pay more for and may push the 10-15 year life span and longer. The old cast irons were 30 year and some of the newer cast irons are 20 year typically pretty trouble free.

    Expectations are something I discuss up front with them. If they want longevity and reliability I typically steer them a different direction than an inexpensive plastic filled 10 year boiler.

    Installation, water quality, and maintenance are the key to making anything last.
    It is odd that we spend big money on a car but typically own it less then 5 years. Where as a heating system is thought to be a bulletproof, efficient, and cheap accessory for the house.

    We need to train our customers, and be proactive in our service on the systems. No matter what we put in.
    Montpelier Vt
  • j a_2
    j a_2 Member Posts: 1,801
    Trouble I saw was people chased rebates, and low ball hacks...