HVAC Decisions: To Repair or Replace a Boiler

Jun 18, 2023

Boilers are complex machines, which in turn means there are a number of things that can go wrong with them and cause them to stop working. Sometimes the issue is easily fixed and a little repair is all it needs. Sometimes the issue is bigger and is happening on an older boiler, so replacing the system is the only option.

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• Boilers & Hydronics

• Service & Maintenance

• Boiler Maintenance

Some of the most common boiler issues are poor combustion and dirty burners, which stem from either poor preventative maintenance or no preventative maintenance. When a gas fired burner on a hydronic boiler is dirty and has poor combustion, it could result in plugging up the heat exchanger, the system running very inefficiently, unsafe operating conditions, and costly repairs.

Another common issue of poor hydronic boiler operations is low flow or plugged (with debris) make up water piping.

“We should always be checking the makeup water system on all hydronic heating systems. Many people forget this step when performing maintenance on these systems,” said Steve Blazina, service operations manager at Atomatic Mechanical Services Inc. in Arlington Heights, Illinois. “With a poor water makeup system you also run the risk of pump seal failure, system pressure loss causing areas in a building not to heat, and running the system dry which can be catastrophic.”

Air in a hydronic system is terrible. So when tending to the water makeup of the boiler, it’s vital to check on the expansion tank. That expansion pressure buildup that happens when the water in the system is heated has to go somewhere.

“You have to have an operating expansion tank,” Blazina said.

In light of preventive maintenance, Blazina said make sure to check the safety relief valve for correct relief pressure, just another system component that often is forgotten.

“I strongly recommend performing preventive maintenance on hydronic heating systems annually to verify proper running operation. Preferably in early fall.”

Leaks are another common issues with boilers. These can be detected by taking a look at the boiler pressure indicator. According to Design Swan, “If it continues to drop even after you’ve topped up your machine, then chances are it is caused by a leak somewhere around the system.”

Technicians can find those leaks by evaluating, examining, and inspecting the boiler’s pipework thoroughly.

Arguably the best way to tell if a boiler should be replaced or repaired is by its age. Boilers are more efficient today than they once were, and if they are old and having problems, it’s probably not worth a repair.

“If the boiler is 20-30 years old and you notice a water leak in the heat-exchanger, the recommendation would be to replace it with a more efficient boiler,” Blazina said.

However, if the boiler is only 10 years old and has a heat-exchanger leak, a repair might be just what it needs.

If there’s a crack on a cast-iron sectional boiler, those can sometimes be sealed for a temporary fix.

“Although the State Fire Marshal doesn’t approve of any leak repair sealant, it will buy you time in most cases until a permanent repair can be made,” Blazina said.

Replacing just sections of the boiler, rather than replacing the entire system, used to be way more common at one point in the industry. It’s still done today — just not as much. Again, the age of the system has a lot to do with whether or not it warrants an entire replacement.

“If the boiler is 15 years or younger and there’s a section crack, I might recommend just replacing the section. If it’s 20-30 years old and there’s a section crack, I would recommend replacing the boiler,” Blazina said.

Another way to tell whether a boiler warrants a repair or a replacement is the immediacy of the problem. A lot of this will have to do with during what season the boiler has an issue.

“Like if it’s a really cold day in the middle of the winter and there’s a crack in the boiler, and it takes days to replace a boiler, versus trying to temporarily repair the crack to get you through the rest of the winter,” Blazina said. “Usually the urgency and weather condition will dictate whether to repair or replace … most boilers can’t be installed in one day. So you’d be without heat for multiple days. But if that boiler can be replaced in a day, then I’d recommend replacing it and not trying to make that repair.”