How To Size A Two Stage Furnace

Unmarried-Stage, Two-Stage and Variable-Speed Furnaces: Differences and Benefits

Single-Stage, Two-Stage and Modulating Furnaces: Differences and Benefits

I lead the Burn down & Ice sales team and meet with homeowners to hash out and solve their comfort problems.

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What'south the departure between a single-stage, two-phase and variable-speed furnace? And which is best for yous equally y'all search for a new furnace?

You need a furnace, but what kind? 1 that heats, correct? Joking bated, sometimes homeowners are unsure of what the best type of furnace is for them. At that place are a lot of options out at that place!

One of the biggest decisions volition be about whether to go a unmarried-phase, two-phase (sometimes called dual-phase), or modulating furnace.

The differences between those types can be huge, and it can be the difference betwixt having an absurdly comfortable home and one that'southward but sometimes the temperature y'all'd like information technology to be.

If you're convinced that you lot need to larn more, we're here to assist you figure out which type is for you.

And no, we're not going to conclude that you should just get the nigh expensive one. That'south non what our business is nigh. It's in our best interest to keep your best interests in mind. And sometimes that means each of the 3 options described above. With that said, permit'due south get into it!

Single-stage vs. Ii-Stage Furnaces

The archetype furnace unit of measurement has two settings: ON or OFF. This is a single-stage furnace, because information technology has only one heat setting. Two-stage furnaces will have a secondary setting that's normally 60 or seventy% of the maximum heating output (measured in BTUs, or British Thermal Units).

Why does this matter? After all, will i additional setting actually brand a ton of deviation? As it turns out, yes.

The commencement is that it can reduce the number of times your furnace has to start and finish. This creates clothing and tear on diverse parts. Over many years, this tin add up, and tin can consequence in needing repairs or having a noisier furnace.

2nd, do y'all always need 100% heating chapters? For nigh of us, the answer is no. For example, a typical fall evening hither in Ohio could dip down to xl degrees, and you might want to rut your home. However, the amount of heat needed to stay comfortable will be a lot less than during a 10 caste February common cold snap.

These are the perfect times for that lower stage. The other upside is that fewer BTUs means less money spent on your monthly heating costs.

To exist clear, single-stage furnaces are the right option for some homes (which we'll talk about shortly), but dual-stage has certain advantages over it.

Modulating Furnaces

Modulating (occasionally chosen variable-speed) furnaces have multiple heating stages, from 100% chapters to as low as around 40%. They modulate between these stages to provide optimal comfort to a home. The exact number of heating stages volition vary depending on brand and model.

If ii stages of heating are a noticeable improvement over single-phase in a few areas, the same is true of two stages vs. multiple stages. The same benefits, lowered free energy costs, increased condolement and less starting and stopping, will be true here as well.

Additionally, the lower rut settings oft allow modulating furnace units to more evenly heat a home. Let'due south say you lot have a multi-level home, and the 2d floor is consistently less comfy (in the wintertime, this would mean it'southward colder). In one case the primary floor is sufficiently heated, depression-stage operation from your heater tin keep that temperature steady while also allowing the heat to spread throughout the habitation.

The event is a home without hot and cold spots, or wild spikes in hot or cold every bit the furnace kicks on and off.

Divergence Between Modulating Furnaces and Efficiency

In that location'south lots of jargon and terminology in HVAC, so I desire to exist articulate about what modulating ways, and just as importantly what it isn't.

When the furnace changes from, say, 100% BTUs to lxx% BTUs in a modulating system, it's doing two things:

Adjusting the amount of fuel or energy that'southward being used (natural gas, electric, propane, etc.)
Adjusting the blower fan inside the furnace, which is what actually moves the air through your ductwork and into your home

This is part of what makes a furnace efficient, but not the entirety of it.

You might hear the term "loftier-efficiency furnace," and this relates to the percentage of fuel or energy that's going direct toward heating your habitation. For example, a standard new furnace unit will be 80% efficient, meaning that lxxx% of heat generated will be pumped into your home. The rest volition be vented, usually through a chimney flue or PVC pipe.

The virtually efficient home furnaces can be up to 98% efficient. This means that very little oestrus is vented, while nearly is going to your home.

So those are two separate ideas, simply both are related to efficiency.

In practise, you lot can get an 80% efficiency furnace that is unmarried-phase, dual-stage or modulating, or ones that are 90% or higher of all three types. This will increase your options. Understanding what each choice represents can make your determination less intimidating.

Equipment Matching Furnaces

With all those options, information technology should come as no surprise that non all HVAC equipment is uniform with all other types of equipment. This is important when picking a furnace.

This is virtually important when matching air conditioners or heat pumps with furnaces. If your existing air conditioner is two-stage, for example, it makes sense to try to match the furnace to this level of operation (or vice versa).

To exist articulate, you tin can have a single-stage or two-phase A/C with a modulating furnace, or vice-versa. Merely occasionally this is where y'all'll start to run into trouble.

Let's say yous installed a unmarried-stage A/C final year, and now you'd like a modulating furnace. Did you replace the thermostat at the same time? If so, it may not have the necessary complexity to handle modulating, or you may have to run extra wiring into the thermostat to let for it to communicate with the furnace properly.

This is a problem that can normally be solved with a couple extra installation steps. Other times, though, at that place is no simple solution.

For example, installing different brands of HVAC equipment can be catchy. Even matching modulating with like variable-speed technology can be problematic when it'south carve up brands. The reason for this is the sophistication of the equipment, which actively communicates with the thermostat and other HVAC equipment. It tin be difficult to find compatible equipment that utilizes all the functionality of your heating and cooling units, and hard to find a thermostat capable of communicating with both.

Most times, matching "like with similar" both in terms of efficiency and brand is the simplest solution. But if you're only replacing a furnace, but not the air conditioner, it may be something you demand to keep in mind.

RELATED: One-Stage, 2-Stage & Variable-Speed ACs: Differences & Benefits

Furnace Installation Considerations

For the most office, installation of a unmarried-stage, dual-stage, or modulating furnace is the same. The biggest differences will be in the thermostat needed to run them properly, and possibly some extra wiring to the thermostat (though this is rare).

That'south not to say that at that place won't be installation considerations across the furnace itself. You may need to consider things like ductwork or gas lines. But the equipment type volition exist largely the same.

RELATED: Furnace Installation Process From Start to Finish

Of course, price will differ likewise. It volition come as no surprise that modulating units will be the most expensive, but they also come with the most potential benefits. We'll talk a petty bit more below well-nigh when this actress cost can exist worth it for a home.

Choosing the Right Furnace for You lot

At present the important office: which of these is best for you, and why?

I can't give i respond that will be right for everyone reading this. But I can give yous some tools to figure out the answer for yourself.

Asking the Right Questions - What Problems Need Solving?

Here are some questions you can inquire yourself, which are also ones that a skillful HVAC contractor should be discussing with you when they visit for an in-domicile approximate. I've likewise included some considerations depending on what your answer is.

How long do I expect to be in this home? If you lot plan on selling in the next few years, yous're probably not going to run across the long-term benefits of a modulating system. Conversely, if y'all're planning on 10+ years in your current home, that's when upgrading to more comfy, higher-efficiency equipment can pay long-term dividends, both for you and your family's condolement and your utility costs.
Are you planning on replacing both the furnace and A/C, or just one? Some people are surprised to learn how financially beneficial it tin can be to do both at once. The large reason is saving on labor costs. Only if y'all're simply doing one, that's where equipment compatibility comes into play, and may limit your options.
How many levels is my home? While whatever home can benefit from any of these furnace types, a unmarried-level or more meaty habitation is sometimes less likely to accept large jumps in temperature betwixt areas. In these homes, modulating technology will be used less. Conversely, temperature variance in multi-level homes can often be solved by that same equipment.
Are there hot and cold spots in the habitation? Like to the previous question, this can sometimes relate to issues similar windows or ductwork, just dual-stage or variable-speed equipment is at to the lowest degree worth checking out before you make a decision.
Do I use my furnace in the fall and leap? If you look until the coldest wintertime months to plow on your furnace, you won't become equally much benefit out of modulating equipment. But if you lot're having to plough on the furnace for boosted fall and bound months, two-stage or modulating becomes a much better choice.

At that place will exist exceptions to each of those, and also other questions that might exist particular to your home. Only hopefully that gives you a good sense of how to start determining what'south right for y'all.

Choosing the best home furnace

Take the Next Steps

Your money is your own, and your dwelling is your own, which is why the ultimate decision on a new furnace should be yours alone. Notwithstanding, an experienced HVAC partner - one that's interested in presenting options and educating you on each, rather than just making a auction - tin assistance y'all in that decision.

RELATED: The Complete Guide to Dwelling Furnaces

If y'all're fix to sit down down and accept that talk, we'd love to be invited to the table with you. If you're in or well-nigh Columbus, OH, fill up out the service surface area checker below to get started!

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