These manufactured home AC units barely meet minimum standards

If you’re considering Intertherm air conditioners, you probably have a manufactured home, because the Intertherm brand is marketed specifically to the prefab home market. And while Intertherm air conditioning may be economical in terms of up-front price tag, in the long run higher operating costs may eat away at those savings.

There are a number of factors that determine the total annual operating cost of an air conditioner over its lifetime: Purchase price, installation costs (typically included in the purchase price), financing costs if you buy on credit, energy used over the unit’s lifetime, amount of cooling required each year, and maintenance costs. US electricity prices are generally in the $0.09 to $0.15 range through most of the Continental states. These low prices can make it hard to justify a more energy efficient unit from a purely economic point of view, unless you live in an area with a combination of high energy prices and a long cooling season.

Intertherm single-unit air conditioner

Intertherm single-unit air conditioner

For example, consider two three-ton air conditioners, the Intertherm air conditioner model P5RD-036K with a minimal SEER (Seasonal Energy Efficiency Rating) of 13, and a competitor model with a much higher SEER of 21, of which several brands are available that are actually made by the same company that makes Intertherm air conditioners (more on brands later). The annual savings in energy costs for the more efficient unit vary substantially by state. This table shows a list of states, and for each set of states, estimated electricity costs per year for a 3-ton unit at SEER 13 and SEER 21, assuming the unit runs for the typical heating hours of that region. I also show annual energy cost savings from buying the more efficient unit:

State SEER 13 SEER 21 Annual Savings
Florida, Texas $995 $617 $378
California, Louisiana, Arizona, Alabama, Georgia $654 $406 $248
South Carolina, Mississipi, North Carolina, New York, Illinois $444 $276 $168
Pennsylvania, Connecticut, Ohio, New Jersey, New Hampshire $343 $213 $130
Michigan, Oregon, Minnesota $200 $124 $76

As you can see, if you own a manufactured home in Florida or south Texas, you’ll save almost $400 a year on the more energy efficient unit at today’s electricity prices, compared to the lower efficiency Intertherm air conditioners. And if you ask me, electricity prices are more likely to go up than down in coming years, given ever greater demands for energy from developing countries, and ever dwindling supplies of conventional fossil fuels. So annual savings are likely to be higher in 5 years than they are today, in any region of the US.

Thus suggests that, over the next ten years, you would be saving a minimum of $1,000 in operating cost savings from the most efficient 3-ton unit available, compared to SEER 13 Intertherm air conditioners, and up to $4,000 if you live in one of the hottest regions of the US.

Now let’s compare the sticker price of 3-ton Intertherm air conditioners, estimated at $3,500, with a 3-ton SEER-21 air conditioner, which you can find for around $5,500. That’s a $2,000 price difference. If you live in Michigan that $2,000 will take about 26 years to earn back from the energy savings of the more efficient unit at today’s energy prices – longer than any air conditioner is likely to last. If you live in Florida or Texas, the higher efficiency unit will pay for itself in a little over 5 years. Again, the actual payback times are almost certainly shorter than this because electricity prices will rise, but unless the price increase is drastic, it’s still very hard to justify the higher efficiency unit on purely economic grounds if you live in a relatively cool part of the country.

Intertherm air conditioner features

Intertherm air conditioners are designed, as I said, for the manufactured home market. They are single-package units, which means the compressor and coils are all in a single unit, designed to be mounted on a slab directly beside your manufactured home. Unlike split units, which have an outdoor condenser unit and indoor coils that cool air running through your central heating and cooling ductwork, Intertherm air conditioners connect directly to your ductwork through an opening in an outside wall (actually, two openings, a cold air supply and a warm air return). These openings should be just above ground level.

Intertherm air conditioners can be purchased with an electric heating strip as well, which gives you heating capability in cooler weather. These heating strips have a capacity of 5 kilowatts to 20 kilowatts, which should be sufficient for heating a modestly sized manufactured home in mild (5 kilowatt) to colder (20 kilowatt) climates, where temperatures don’t often dip down below 15F.

For comparison, a 2 kilowatt heater is typically enough to heat a single bedroom on a mild winter day. So in climates where you don’t get a deep freeze – say the Caroliners or further south – a 20 kilowatt heater should be adequate to keep you warm in winter in a moderately sized manufactured home.

However, you will save considerably on electricity costs in a manufactured home that lacks a central heating system, if you instead buy an air conditioner/heat pump that provides both cooling and heating using the compressor loop, since in mild climates it is much cheaper to heat with a heat pump than with resistance based electric heating.

When the heat dips below 20F, electric heat starts to become more efficient than heat pump heating, but the higher above this temperature, the more efficient heat pump heating is. On mild days where you need just a little heat, a heat pump can use a third the energy of electric resistance heating to provide the same amount of heat.

Not only are heat pumps more efficient than resistance electric heating at milder temperatures, but many brands of heat pump also work as air conditioners, operating with SEER ratings well above the SEER 13 of Intertherm air conditioners.

You can find Intertherm air conditioners in 2- to 5-ton capacities (24,000 to 55,500 BTU). Make sure your installer sizes your unit according to your local climate, building insulation levels, and square footage area. Ask to see the sizing sheet he/she uses. If they just eyeball the sizing, you might want to look for another installer. Buying an undersized unit means the unit will be running constantly in hot weather, which will wear out components faster. Buying an oversized unit might seem like a good idea but in fact the unit is likely to start and stop frequently, as the significant cooling capacity of oversized units tend to cause your thermostat to flip the unit off almost as soon as it goes on. Again, this wears out components faster because of the constant starting and stopping of the unit.

Intertherm air conditioners come with a very modest 1 year parts and labor warranty, and a 10 year limited compressor warranty. This level of warranty doesn’t really give me a lot of confidence in the brand. Make sure you buy a service contract from the HVAC company that does the installation (and make sure they’re a reputable HVAC outfit), otherwise you could find yourself paying for a lot of maintenance down the road. With a general decline in the quality of central air conditioners across the board in the last 15 years, you’re really tossing the dice if you buy an air conditioner without a service contract.

What’s in a name? Intertherm and related brands

Intertherm air conditioners are made by Nordyne, a company that has done an outstanding job designing and building highly efficient and extremely quiet central air conditioners based on their iQ Drive technology. Other companies (and perhaps Nordyne itself) repackage the Nordyne iQ Drive system and sell the units under popular brand names like Frigidaire, Westinghouse, and Maytag, and lesser known brands like Broan (a Nordyne-owned brand) and Tappan.

In the case of the Intertherm air conditioners made by Nordyne, they are sold under the brand names Miller, Intertherm and Broan. Intertherm air conditioners are limited to SEER 13 models, while some of the Miller branded units designed for manufactured home use are available in SEER 15, a roughly 15% increase in efficiency for an average of about 50% more on price. This is one case where the payback period for the more efficient model will extend past the expected life of either unit in all but the sultriest climates.

Intertherm claims to have unique testing methods. Here’s a quote from one of their product brochures:

Intertherm’s product quality [is] made possible through Demand Flow Technology™. While other companies test products at random, we use 100% computer-automated testing on every Intertherm product to eliminate human error in the final analysis of product quality. We are the only heating and cooling manufacturer to be DFT certified

I’m not sure what you think of that statement, but my BS-meter is trending to the right here. If Demand Flow Technology is trademarked, that suggests that Nordyne owns the process and so no other manufacturer would even have the opportunity to be DFT certified. Do you really believe other manufacturers test products at random? And how do we know that Demand Flow Technology does anything to guaranty quality or durability in air conditioners?

Quality and reliability

It’s likely that Intertherm air conditioners are not particularly less reliable than other brands, because the biggest consideration, by far, in any air conditioner installation, is the quality of the installation job. You may find reviews on other websites of Intertherm air conditioners, and you might conclude from those reviews that Intertherm air conditioners are quite unreliable. But one thing to bear in mind is that the people who write Intertherm air conditioner reviews tend to be disgruntled consumers whose air conditioner stopped working. The owners of thousands of properly running Intertherm air conditioners aren’t going to bother to write a review of their unit while it’s still purring along.

If you don’t believe me, try searching for reviews of other popular brands of air conditioners like Lennox, Trane, York and Nordyne. You’ll find similar rants there from unhappy customers. An interesting aside here is that in many cases the rants include complaints about rude or price-gauging or inept staff at the HVAC company, all of which usually indicate that the installers either didn’t know what they were doing when they installed the unit, or didn’t care whether it was installed properly.

If you’re looking for Intertherm air conditioners and you want quality and reliability, here are the installation factors you need to consider:

Choosing the type of unit: A good installer needs to determine what type of system is best suited for the application based on well-explained criteria. For example, does it make more sense to have a combined unit (where the entire aparatus is out-of-doors)? A split unit, with an outdoor condenser and indoor coils? A ductless mini split, with small indoor units inside each room and a single outdoor wall-mounted condenser? For manufactured housing a split unit air conditioner might be your best bet, as they are relatively inexpensive, you can install them yourself if you’re handy, and they come with SEER ratings of up to 21.

Proper sizing: A good installer needs to properly size the BTU output of the system based on the home size, local climate, and home efficiency factors such as insulation, solar exposure, windows etc. If your installer doesn’t properly size the unit, it will either run continuously if undersized, wearing out components more quickly, or it will short-cycle, wearing out the motor due to frequent starts and stops.

Installer knowledge of the brand: A good installer will specialize in a small number of brands they are familiar with. While it’s true that an HVAC installer will try to sell you the brand he has in stock, that’s not just because it’s easy for him; it’s because he installs many such units and knows how to install them properly. He also has parts in stock in case something goes wrong during or after the installation.

Installer professionalism: Finding an installer who is reliable, has a solid reputation, and many strong references, should be your number one priority when choosing who will sell you an air conditioning system. Your local Better Business Bureau, your neighbors, or local “Consumers Choice” or “Readers Choice” awards are good sources of information on what installers are dependable. Usually your phone and face-to-face conversations with the sales rep and installer will give you some indication of where the company as a whole sits on the “Cheap price” to “Customer excellence” scale. If you get a bad feeling talking to one of the staff, stay away from the company!

Energy efficiency is the bottom line

If you ask me, Intertherm is no better or worse than any other brand in terms of quality, but I wouldn’t buy one myself simply because they are so very inefficient. This might sound odd given that their product literature boasts that they are efficient, but that claim is hard to justify when their only advertised units have an SEER of 13 which is the bare minimum that central air conditioning manufacturers are allowed to sell.

If you own a manufactured home that is already set up for a single packaged air conditioner with the ductwork connections built right into the unit, your options are fairly limited unless you want to redo substantial parts of your ductwork (or switch to a ductless mini split system). In that case, you might want to look at the Miller or Broan lines of packaged systems also made by Nordyne; they are essentially the same as the Intertherm air conditionres, but come in a slightly higher SEER 15 rating, which not only saves you a little energy, but gets them ENERGY STAR certification and therefore might qualify you for tax credits, utility or municipal rebates, or other financial incentives for buying an energy efficient air conditioner.

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