What happens if furnace is too small?

Author: Dangelo Waters  |  Last update: Thursday, March 27, 2025

A furnace that is too small for the house in which it is installed will put out too little heat to keep the home warm. So, the furnace will stay on for far longer than it is designed to do in an attempt to heat the home properly. This puts just as much stress on the system as if it were oversized, with the same result.

What happens if a furnace is undersized?

Having a furnace that is too small for your home means the system won't be able to keep up with the dropping temperatures outside. They simply can't make up the difference to heat your home properly.

How do you tell if your furnace is too small?

Before you go shopping, find out if your furnace is too small.
  1. The Furnace Runs Continuously. ...
  2. Your Furnace Struggles to Reach the Desired Temperature. ...
  3. There Are Cold Rooms in a Mostly Warm House. ...
  4. The Furnace Has a Premature Lifespan. ...
  5. There's Humidity in the Home. ...
  6. Ductwork Size Doesn't Match the Furnace.

Is it better to undersize or oversize a furnace?

it is best to have the right size furnace as oversize will cause too many on-off cycles. too small causes extended periods of running and the possibility that it won't handle extreme cold.

What happens if the furnace is too small for a house?

If a furnace is too small it won't keep the house warm in the winter while it runs continually. If the furnace is oversized there won't be enough airflow through the heat exchanger and the furnace will cycle on the high temperature limit control.

What happens when your furnace is oversized or undersized?

How do I know if my HVAC is too small?

4 Signs Your HVAC Unit Isn't Big Enough for Your Home's Needs
  1. Sign 1: Never the Right Temperature. Does your home always feel a little too warm in the summer and a little too cool in the winter? ...
  2. Sign 2: Inconsistent Temperatures. ...
  3. Sign 3: It Just Keeps Running. ...
  4. Sign 4: Your Energy Bills Are Sky-High.

What is the minimum size for a furnace room?

A general standard is to have at least 30 inches of space between the walls and a furnace's sides. When you hire a professional HVAC company near you, a pro will design the space according to your local area's codes and ensure that the room maximizes your furnace's performance and efficiency.

What is the correct size furnace for a 1500 square foot house?

A 1,500-square-foot home will require between 45,000 to 90,000 BTUs.

Can I put a bigger blower on my furnace?

No, you should not put a bigger blower motor in your furnace.

How much does a furnace cost for a 2000 sq ft home?

This can lead to a wide range of installation costs. The national average cost for installing a gas furnace in a 2,000 sq. ft. home is $4,000 to $8,000, with most people paying around $6,000 for a high-efficiency gas furnace installed with minor modifications to update the vent and drain.

What is the rule of thumb for furnace sizing?

A basic rule of thumb for furnace size calculation is that it takes 30 BTUs for every square foot of house. So, if you have a 1,000 square foot house, you need a furnace that has a 30,000 BTU output.

What is the most reliable gas furnace brand?

The 5 Best Furnace Brands
  • Carrier Furnace: Best Warranty.
  • Lennox Furnace: Best Company Reputation.
  • Bryant Furnace: Best for Durability.
  • Trane Furnace: Most Years of Experience.
  • Amana Furnace: Best for Efficiency.

How much does it cost to install a 60,000 BTU furnace?

Furnace Replacement Costs by Capacity

Here are the usual furnace capacities you will come across: 40,000 to 60,000 BTU furnaces: These are suitable for heating homes up to 1,200 square feet. Replacing such a furnace ranges between $2,000 and $3,000.

How do I know if my furnace is too small?

The most common (and in many cases only) sign that your furnace is undersized is that the device simply doesn't maintain the temperature in your home properly. This means that when turned on to full and left for a few hours, your furnace doesn't heat your home to the thermostat setting.

How long does it take to install a small furnace?

4-8 hours. Furnace installation in a residential home usually takes 4-8 hours, depending on the complexity of the job. Additional time may need to be added to account for ductwork, electrical, or gas line modifications to properly match the new equipment.

What happens if HVAC return is too small?

If the return duct is too small or there are an inadequate number of return grilles, your HVAC system won't be able to return enough air to recirculate into the system. Again, it's like if you were breathing in through a straw while jogging.

Is it a good idea to oversize a furnace?

An oversized furnace can also lead to a reduced lifespan and more frequent disrepair. This is because when a furnace is too large, it can put unnecessary stress on the components, leading to them wearing out more quickly. It can also lead to more frequent repairs and replacements.

Does furnace and AC use same blower?

Comfort Systems Rely On Each Other for Best Performance

Your air conditioner and furnace are dependent on each other in various ways, such as: Both AC and furnace use the same thermostat to activate and shut down. The AC and the furnace use the same blower to spread cool and warm air throughout your home.

Why is my furnace blower so weak?

Weak or Absent Airflow

The problem could be due to a clogged blower from accumulated dust or debris. It could also be due to leaky air ducts or a bad capacitor. Experts recommend that you schedule routine maintenance to diagnose the problem to determine if something needs repair or replacement.

Do you count the basement when sizing a furnace?

When sizing your furnace, you need to count all the square footage of rooms you want to heat. If you want to heat your basement, count it when sizing your furnace.

What size furnace for a 2000 sq ft house?

This size of home still needs a large furnace. If you want to evenly heat a 2,000 sq. ft. home, you'll need to look for furnaces rated between 60,000 and 125,000 BTUs, depending on the factors we discussed earlier.

How much does a furnace cost for a 1600 square foot house?

Replacing a furnace in a 1600 square foot house can vary significantly based on several factors, including the type of furnace, brand, installation complexity, and your location. On average, homeowners can expect to pay between $3,000 to $6,000 for a complete furnace replacement.

Can a furnace be too small for a house?

The size of your furnace is crucial. If you end up with a furnace that is too small for your home, you will have uneven heating and high energy bills. The furnace will also have a shorter lifespan because it is working harder to heat a larger space.

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