When to Replace the Boiler - Circulating Pump Done

[Chefwong]

Circulator Pump just went bad on new years Bad bearings or something sheared. It just fired up with loud screeching metal/metal noise heard 1 floor above.

Anyhow, I know the pump is bad.
And of course, it's winter...

I can use hvac for heat, but we prefer the hot water..
It's a old 70 year boiler that just runs.
How efficient might be a different answer....

At what point does one replace a boiler ?
When it's broke or no parts available ?
This old dinosaur of a boiler just keeps on going.
Not sure whether to replace the pump or go all in with boiler replacement...

 

[Dana]

A boiler that's old enough to be required to be making withdrawals from it's 401K is well past retirement age, even if it still "... just runs...".

Replace the pump with a "smart" ECM drive version that can be programmed to different speeds, and it would probably still be useful with a newer/better/different boiler behind the system.

If you haven't already, run a fuel use based load calculation using the antique beast as the measuring instrument, which will be valuable information to guide the replacement process. Odds are pretty good than it's 3x+ oversized for the space heating load, and running at well below it's steady state nameplate efficiency.

Another shaggy-dog story:

My biz partner owns a 2-family rental property, where one of the units still has a boiler first installed in 1922. A year or so ago the gas company had turned off the gas to service the lines, and the techs for the gas company couldn't figure out how to re-light the pilot. They mis-diagnosed that the gas valve was shot, installed an inappropriate valve an ignition replacement that worked, but had NOT replaced the actual antique pilot assembly, which was still sending a steady stream of gas. Dozens of gas explosions later an independent contractor figured out how to plug old pilot assembly, but neglected to re-align all of the cast iron burner assemblies that had been jostled around by the explosions.

More than a month after the initial "service" the tenant called to report they had no heat. My biz partner inspected the boiler- took a bunch of photos of the burners, and then shoddy work with the hacked-in new gas valve, determined that there were in fact gas leaks at the connections to that valve, and made an irate call to both the gas company and the independent contractor for having failed to detect the gas leak or fix the burner assembly alignments. It took filing a complaint against the gas company to the state Attorney General and a threat to challenge the contractor's gasfitter licence to get it put back together (fortunately before the house burned down or people were injured.)

But with all that behind it the boiler "...just runs..." at whatever atrociously low combustion efficiency it still musters after nearly a century of service.

 

[Sponsor]

 

[Chefwong]

Thx Dana. I shoehorned a grundfos today, and decided to just doing the bid work come spring. I'm sure this time of the year, most boiler shops are working round the clock on break/fix/ad-hoc repairs

 

[Dana]

Thx Dana. I shoehorned a grundfos today, and decided to just doing the bid work come spring. I'm sure this time of the year, most boiler shops are working round the clock on break/fix/ad-hoc repairs

It's definitely better to do a boiler swap when it can be done with deliberate speed rather than rushing before the house freezes up. Boiler replacement time is a once in a generation opportunity to get it right from both an efficiency and comfort point of view. Don't count on HVAC contractors to spec the right equipment- the industry track record on that is pretty abyssmal.

It's worth running both the load estimates (based on fuel-use, Manual-J, or I=B=R methods) as well as a rudimentary radiation analysis well prior to soliciting bids. Most boilers that old are LUDICROUSLY oversized for the design heat load, and most boiler installers don't seem capable or willing to do a legitimate heat load analysis. Figure out how much boiler you need, figure out a few boiler models that fill the bill, then solicit bids on something that would be reasonably right sized for your loads, that can still operate at low, comfortable & efficient water temperatures without short-cycling itself into low efficiency or an early grave.

If installing another cast iron boiler it's still important to right size it for the space heating load to get reasonable efficiency out of it, but may require setting up a system bypass or primary/secondary configuration to protect the boiler from destructive condensation, particularly if you have high-mass radiation such as bulky cast iron radiators rather than fin-tube baseboard, etc.