Do boilers produce less heat output as they age?


Old 02-19-16, 08:45 PM
Thread Starter
Join Date: Feb 2010
Location: USA
Posts: 19
Received 0 Votes on 0 Posts
Do boilers produce less heat output as they age?

I have a 1987 Vaillant gas boiler (80,000 BTU input) with cast iron heat exchanger. Would this boiler have used less gas than now to produce the same amount of hot water or heat (just house heating)? Recently, I attended the local home improvement show. At a heating contractor's booth, I was told that gas boilers lose about 1% efficiency each year. Can this be true, or is it "liar, liar, pants on fire"? Thanks for any response.
Sponsored Links
Old 02-19-16, 10:24 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 53,567
Received 410 Votes on 385 Posts
When it comes to boilers...... efficiency isn't everything. Design build/quality is more important.

I'm not real familiar with your almost thirty year old wall mounted gas boiler. It would be nice to know how much life it has left. It doesn't appear that parts are easy to get for them as the company has been sold out.

Name:  vuvuw05-3072int01-38668-format-16-9@1704@desktop.jpg
Views: 107
Size:  10.6 KB
Old 02-20-16, 05:51 PM
Join Date: Oct 2015
Location: Ct.,USA
Posts: 1,245
Received 36 Votes on 31 Posts
You could do your own little investigation by checking your annual gas usage and dividing by the degree days for that year. If its increasing by about 1 % each year, the contractor is correct. Also remember his job is to sell you a new boiler. Will he guarantee the new boiler will not have the same degradation and put it in writing?
Old 02-20-16, 08:04 PM
Join Date: Apr 2014
Location: us
Posts: 641
Received 9 Votes on 9 Posts
The 1% per year is b... s... Find the specified stack temp for your unit, may be on the label. Then measure it. If it is much higher than spec then cleaning will lower it.

The basic degrading issue with boilers is dirty chamber walls. One problem with new ones is that they are harder to clean.
Old 02-21-16, 03:15 AM
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,493
Received 33 Votes on 25 Posts
I agree with doug. The factors that will cause the loss of efficiency are the cleanliness of the firesides and water sides. Keep it clean and it will NOT drop off in efficiency.

Now it IS possible the combustion efficiency will change due to changers in the fuel make-up consistency but this is out of the user's control.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes
Ask a Question
Question Title:
Your question will be posted in: