What's the Problem With Oversized Boilers?

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If you're installing a new boiler in your home, there's a good chance you're replacing one that may be too large for the heating system in your house. Many people choose large heating systems under the mistaken belief that more power will mean faster, better heat. Unfortunately, oversized HVAC equipment often leads to less efficiency and higher utility bills.

The modern approach to HVAC system design is to choose gear that meets your family's needs without adding extra capacity. For a new boiler installation, taking this approach is the best way to save money and build a more reliable heating system for your home.

Why Shouldn't You Go With a Bigger System?

Like any other piece of HVAC equipment, your boiler can work best to provide you with comfortable, reliable heat if it's appropriate for the application. All boilers attempt to heat water to roughly the same temperature, but the unit's capacity accounts for heat loss through your home's radiators or baseboard heaters. A larger home with more radiators will dissipate heat more quickly. 

Unfortunately, an oversized boiler will reach this temperature more quickly before the radiators and heaters in the house can dissipate the heat. As a result, the water temperature may rise, producing uncomfortably hot temperatures in your home and stressing the components of your boiler. In other words, you'll waste energy, be less comfortable, and ultimately wear out your boiler faster.

What Should You Do?

You may be used to installing new HVAC equipment that matches the old equipment already in your home. This approach can be useful when dealing with relatively modern air conditioners or water heaters. However, you should avoid replacing like-with-like when installing a new boiler to replace a much older unit.

Instead, your installer will need to perform a load calculation for your house. For hydronic heating systems, load calculations are more complex than forced-air systems. Your installer will need to account for the amount of heat your home losses through walls, windows, etc. Additionally, they will determine the total amount of heat dissipated by the radiators and other heaters in your home.

This calculation allows installers to come up with a relatively accurate estimate for the size of your new boiler. You'll most likely discover that your old boiler was drastically oversized for your home, especially if it was more than a few decades old. Moving up to a correctly-sized boiler will help reduce your utility bills and extend the life of your system.

You may also want to consider upgrading to a high-efficiency or modulating boiler. Modulating boilers can adjust their heat output, allowing them to avoid some of the downsides of being too large for an application. Along with an appropriate heat calculation, these steps will help save you money while also bringing your home's hydronic heating system into the 21st century.

If you would like to know about residential boiler installation, be sure to contact an HVAC professional.