Variable Speed Air Handlers vs Multi speed air handlers?

mpire · Sep 19, 2011

Just as a learning exercise, I am trying to determine if the variable speed air handler is worth the added expense over a multi-speed air handler.

I picked out a couple Goodman units just for comparison numbers.

Goodman AVPTC426014 Variable Speed Air Handler 3 to 5 Ton Multi Position

$1180

Tonnage 3 - 5 Ton
Cooling Capacity (btu) 42,000 - 60,000 Btu
Electric Heat Capacity 10,15,20 Kw
Voltage -HZ / Phase 208-240/ 1 Phase
Min/Max Volts 197/253
Max Breaker Size 15 amps
CFM High/Medium 2,000/ 1,200
Unit Dimensions 22 W x 24 D x 53 1/4 H
Supply Plenum Dimensions 20 W x 11 D
Return Plenum Dimensions 19 5/8 W x 19 15/16D
Air Filter Dimensions (filter not included) 21 x 24 x 1
Suction Line Size 7/8"
Liquid Line Size 3/8"
Blower Motor HP 3/4
Blower Motor Speed Multi-Position, Variable-Speed
Refrigerant Type R410a
Shipping Weight 197 Lbs

ARUF486016 - 4 - 5 Ton Multi Position, 3 Speed, Standard Goodman Air Handler

$820

Tonnage 4 - 5 Ton
Cooling Capacity (btu) 48,000 - 60,000 Btu
Electric Heat Capacity 5,8,10,15,20 Kw
Voltage - HZ / Phase 208/240 / 1 Phase
Min/Max Volts 197/253
Max Breaker Size 15 amps
CFM High/Medium/Low 1,985/ 1,875/ 1,650
Unit Dimensions 22" W x 24" D x 53 1/4" H
Supply Plenum Dimensions 20 W x 11 D
Return Plenum Dimensions 19 5/8 W x 19 15/16 D
Air Filter Dimensions (filter not included) 22 W x 24 D x 1 H
Suction Line Size 7/8"
Liquid Line Size 3/8"
Blower Motor HP 3/4
Blower Motor Speed Multi Position - Multi Speed
Refrigerant Type R22, R410a
Shipping Weight 192 Lbs

phbsales · Sep 19, 2011

So what's your question?

mpire · Sep 19, 2011

phbsales said:
So what's your question?

I am trying to determine if the variable speed air handler is worth the added expense over a multi-speed air handler.

phbsales · Sep 19, 2011

That's fine, but what exactly are you looking for, ROI in dollars or are you looking to increase the overall comfort of your home?

Variable speed has the advantage for overall comfort over fixed speed units.

Fixed speed units have the advantage of lower cost.

So you need to ask more questions about how you want your home comfort system to perform.

phbsales · Sep 19, 2011

There are several advantages to using a variable speed air handler.
1. Variable speed motors cost less to operate because they usually run in low speed, unlike single speed systems which run in “high” 100% of the time.

2. Because variable speed air handlers gradually work their way from low speed to high speed, there is no blast of air from the vents.The transition when the machine turns on is very mild and it can be difficult to even tell when the machine actually turned on.

3. The noise level is much lower for variable speed air handlers because they usually run in low speed.

4. Variable speed air handlers make it much easier to create different zones in your home so that you can heat or cool one room differently than another room.

5. Variable speed air handlers do a much better job of removing humidity from the home, making you more comfortable in your home. Some systems can remove as much as 24 gallons per day from a home.

More comfortable, more efficient, and less noisy. Variable speed air handlers always trump single speed ones, IMO. Just make sure that your indoor and outdoor equipment are correctly matched by your HVAC sub. This will help your machine to run at its highest potential efficiency.

larry_g · Sep 19, 2011

It's also my understanding that the 3 speed air handler is only run at one speed selected at install. It does not change 'gears' as load changes..

lg
no neat sig line

phbsales · Sep 19, 2011

So now, based on the actual cost of the equipment with an increase in comfort level and a decrease in energy consumption, how long do you think it would take to recoup your added investment of $360? Less than 2 years.

phbsales · Sep 19, 2011

danski0224 said:
"Energy savings" materializes ONLY if the TESP is within specifications.

You and I both know that. Let's try to keep it simple for the OP........ :lol_hitti

phbsales · Sep 19, 2011

danski0224 said:
You have pointed out possible savings that the OP will never see if the existing installation is comparable to all of the other low bid residential hack work out there- "pro" or DIY.

The OP got pricing on Goodman equipment. Do you think he's really concerned about quality?

And let's face it. 90% of the duct systems we see out in the field that are more than 35 years old are improperly sized or sized for heating only. No way I'm selling a VS furnace without verifying airflow and TESP, as well as DELIVERED efficiency of the entire system.

mpire · Sep 19, 2011

larry_g said:
It's also my understanding that the 3 speed air handler is only run at one speed selected at install. It does not change 'gears' as load changes..

This appears to be the most helpful information in the thread so far. Thanks Larry! This tells me that its either variable or fixed.

I am not buying anything at the moment.

As I stated in the original post, I was curious what the differences between the two was and how much value, and if it was recommended.

I have a 10 year old system that isn't dead yet, probably because I have a twice yearly clean and service from a good HVAC service company. Its the only one left on the block. I also have all flex ducting throughout the house, nothing else. Cheap contractors!

I am hoping to build a new house/garage in the next 5 years, and this board is chock full of people with knowledge who are generally willing to share a little bit.

That being said, eventually I will have to buy another AC system for this house or the new house, so I am researching the voodoo that is HVAC.

From what I can tell so far, the payoff for buying anything but the minimum would most likely take longer than I plan to own the house.

Goodman units were listed for reference and comparison only, I have a 4 ton Carrier system at the moment, I added a mini-split in the master bedroom, and am currently installing another mini-split in the garage.

Mini-splits don't have all these fancy options.

Just doing some research. Thanks to everyone who chimes in, its all informative.

phbsales · Sep 19, 2011

Flex duct also increases TESP on a duct system. With respect to TESP (total external static pressure), the higher the TESP, the more inefficient the system becomes, and the harder the blower has to work to try to maintain airflow. The harder it works, the more electricity it will consume, and the quicker it will be in need of repairs.

If the duct work is in an attic, it is definitely the cheapest and fastest installation. However, the BEST installation would be rigid, insulated (on the outside) metal duct with the branch ducts also being round metal and sleeved.

Trey T · Sep 19, 2011

You would have to get more info from Goodman. But here's my take on it:

I don't see the benefit or advantage during cooling because you need to have a minimal speed to keep the thermodynamic steady. Another word, if the system was installed to have amt of refrigerant at a certain air flow, then you need to keep the speed at that minimum speed. If you slow down the air flow, you will risk of freezing up the evap coil.

For fan-only, variable speed make sense.

I wonder if they use Variable Frequency Drive. VFD is the only real way of controlling the speed of the motor on AC.

phbsales · Sep 19, 2011

danski0224 said:
Keep the ductwork within the conditioned space, size it properly and seal it.

I agree with this statement completely. ^^^

*edit*
If the ductwork has to be located in a crawl space, I would find a way to seal it up and condition that space as well.

mpire · Sep 19, 2011

Umm, danski0224, aren't you just agreeing with me that Flex ducting is cheap?

I clearly don't know the answers, I am just learning what to look for.

I don't intend to install a damned thing in the next house, but I will probably run extra speaker/network/cable/etc wiring before the drywall goes up.

The agreement is that the house will be 100% done and the garage will be a bare shell.

mpire · Sep 19, 2011

danski0224 said:
Yes, but you pointed the finger at the "cheap contractors" when the problem rests squarely upon the shoulders of the builder.

The contractors work within the limits set by the builder.

When I said cheap contractors, I was referring to the contractor who built the tract housing I currently reside in.

phbsales · Sep 19, 2011

Trey T said:
I don't see the benefit or advantage during cooling because you need to have a minimal speed to keep the thermodynamic steady. Another word, if the system was installed to have amt of refrigerant at a certain air flow, then you need to keep the speed at that minimum speed. If you slow down the air flow, you will risk of freezing up the evap coil.

The idea behind V/S and cooling is that the blower comes on very slowly at the start of the cycle, allowing the evaporator to get very cold for "quick cooling". After about 90 seconds, the fan will ramp up to about 65% airflow for maximum dehumidification. This part of the cycle will be around 7 minutes. If there is still a call for cooling, the fan will ramp up to 100% until the call for cooling ends. The circuit board handles the timing and the percentage of airflow that it needs to satisfy the thermostat. No danger in freezing the coil unless you haven't changed your filters in a couple of years........LOL

Trey T · Sep 19, 2011

I see what you mean. So a system like this just operates on its own w/o messing around with the variable speed.

Interesting on the DC motor w/ variable speed, first time hearing about it on HVAC. Are all high efficiency air handler uses DC variable speed now?

phbsales · Sep 19, 2011

Trey T said:
I see what you mean. So a system like this just operates on its own w/o messing around with the variable speed.

Interesting on the DC motor w/ variable speed, first time hearing about it on HVAC. Are all high efficiency air handler uses DC variable speed now?

No, you can still get high efficiency with fixed speed blowers.

mrobins297aaa · Sep 19, 2011

mpire one more thing to consider that no one has mentioned..........find out the cost to replace that var speed motor if it fails................that'll make your mind up quick.

mpire · Sep 19, 2011

I am still trying to wrap my mind around all the new features other than "off" and "on" when it comes to air conditioning.

brewchief · Sep 20, 2011

phbsales said:
No, you can still get high efficiency with fixed speed blowers.

We are finding very few AHRI matches on the higher seer units, 13 seer with PSC blower is easy but 17 seer can be tough.

Almost all of the variable speed air handlers/furnaces have the ability to lower blower speed for increased dehumidification, it takes a thermostat with that capability but works much better then the built in 7 min program in my experience.

Builders will put in cheap HVAC systems because nobody wants to pay more for stuff that doesn't show on the surface, joe homeowner wants granite counter-tops before he wants a better more efficient HVAC system.

Flex duct, metal duct and ductboard all can make up a good duct system if they are sized correctly, unfortunately even a lot of pros can't handle that job. I've twice looked a job that has 5 tons of A/C, is zoned and has 3 trunklines of 18x8, cheapest zone control and no bypass and they don't under stand why it doesn't work well.

mpire, if your current home needs a system and you will be moving in a few years go with a basic, standard blower system.

New house go with variable blower, returns in all rooms, thermostat with dehumidification and a good quality media filter that is at least a merv 10.

I've installed a lot of variable blower furnaces over the past 10-12 years, to this day I haven't had a customer say they wish they had saved a buck and went with the cheaper system.

theoldwizard1 · Sep 20, 2011

phbsales said:
5. Variable speed air handlers do a much better job of removing humidity from the home, making you more comfortable in your home. Some systems can remove as much as 24 gallons per day from a home.

Can you explain why a variable speed air handlers works better than a fixed speed air handler for removing humidity.

theoldwizard1 · Sep 20, 2011

mpire said:
larry_g said:

It's also my understanding that the 3 speed air handler is only run at one speed selected at install. It does not change 'gears' as load changes.

Click to expand...

This appears to be the most helpful information in the thread so far. Thanks Larry! This tells me that its either variable or fixed.

The speed CAN be changed by moving some wires on the motor. I believe that some still may have an adjustable pulley.

My son just went through this decision process recently. He went with a 95% efficient, single stage burner, multi-speed blower, Amana, based on recommendations from a friend in the business. I believe Amana and Goodman are owned by the same company.

phbsales · Sep 20, 2011

theoldwizard1 said:
Can you explain why a variable speed air handlers works better than a fixed speed air handler for removing humidity.

I believe I already have. See below....

phbsales said:
The idea behind V/S and cooling is that the blower comes on very slowly at the start of the cycle, allowing the evaporator to get very cold for "quick cooling". After about 90 seconds, the fan will ramp up to about 65% airflow for maximum dehumidification. This part of the cycle will be around 7 minutes. If there is still a call for cooling, the fan will ramp up to 100% until the call for cooling ends. The circuit board handles the timing and the percentage of airflow that it needs to satisfy the thermostat. No danger in freezing the coil unless you haven't changed your filters in a couple of years........LOL

brewchief · Sep 20, 2011

theoldwizard1 said:
Can you explain why a variable speed air handlers works better than a fixed speed air handler for removing humidity.

Variable speed units are able to slow the blower speed on command, slowing the blower will make the A/C coil run colder, a colder coil will remove more moisture because it's further below the dewpoint of the air. You do lose some cooling capacity however so it's ideal to only run in dehumidify mode as needed.

theoldwizard1 said:
The speed CAN be changed by moving some wires on the motor. I believe that some still may have an adjustable pulley.

My son just went through this decision process recently. He went with a 95% efficient, single stage burner, multi-speed blower, Amana, based on recommendations from a friend in the business. I believe Amana and Goodman are owned by the same company.

On a standard unit you can adjust speeds, most units have 3 or 4 to chose from, on a furnace you often will run the A/C on high and heat on low or med low, some furnaces have a separate speed for continuous fan that will normally be your lowest speed. This really doesn't give many choices, in the variable equipment I am most familiar with(Lennox) you have 4 choices for heat, 4 choices for cooling and you can adjust each of those choices up or down 10% by selecting dip switches on the circuit board, that's 12 choices for each. Continuous fan is based on a % of cooling speed. The new modulating furnaces have even more choices.

Yes Goodman owns Amana, some of there products are the same and some are different.

I haven't seen a belt drive blower on any new residential unit or rooftop package unit 5 tons or less in a very long time, Thermopride oil furnaces may still have it as an option but I don't see many of those any more.

7echo · Sep 20, 2011

I had a VS air handler and 2 stage outdoor unit installed a few years ago. The system was more expensive than the typical single speed units but I have been very pleased. The humidity level was much higher before, now I can run it down to around 43% to 45% even without using the dehum mode. Much more comfortable. But, I also changed out the duct work and had it properly sized. If you want to learn a lot about hvac you should check out hvac-talk.com You can search and read, but be wary of posting there. I haven't visited there in a while, but when I was researching a few years ago they were really tough on homeowners posting, mostly I think because the HO was usually diy. Several of the guys posting in this thread are obviously hvac smart, good information to digest.
BTW, if you really want to learn about proper sizing and how the build quality of the house matters do a heat load calc, hvac-calc is one to check out.

mrobins297aaa · Sep 20, 2011

danski0224 said:
If the ductwork is sized right and TESP is within the rated limits, that VS motor is more durable than the typical three/four speed PSC motor with sleeve bearings.

Given proper TESP, the electrical savings will more than cover the cost of a new motor.

Unfortunately, there are sensitive electronics inside.

Fortunately, (1) prices are coming down and (2) repair kits are coming out.

There are also non-variable speed ECM motor replacements for standard PSC motors.

What is the cost of one of those motors today?

If I remember right when they first showed up I think that motor was around 6-700 dollars wholesale which turns into a $900 job to the home owner.
I'm sure your right that over the life span it probably saves enough to pay for a new motor............It just seems like a tough sell telling the home owner that he needs a new motor for $900 and he's already saved enough money to pay for the new motor and on top of that I doubt he would even notice a difference in his bill between the two. Plus he paid more for that motor to begin with.

phbsales · Sep 21, 2011

A side note on VS blowers being expensive........

I have never seen one fail in my 17 years running service. The failure 90% of the time is the VS module, which is a $200.00 part, and a 30 minute replacement.

green.bubbly · Sep 21, 2011

mpire said:
Mini-splits don't have all these fancy options.

There are variable speed dc motor mini-splits units available.

z3bram3n · Jul 23, 2013

Well the thermostat can switch speeds of the blower. At least on the unit I have.

I think if you use a variable speed motor you will need a TXV instead of an orifice. This device will attempt to maintain the subcooling across the evaporator. The increase in dehumidification results from longer running periods at slower speeds. When a fixed speed device runs, with or without txv, it moves the air faster and reaches set point and shuts off the unit.

If you use an orifice with a variable speed blower your subcooling will be off since the orifice is a constant. Some variation of refrigerant flow will occur but it won't be desirable.

A variable speed air handler will also require a more expensive thermostat. It's probably a good idea to get a variable compressor too since running on low fan speeds will likely shorten the condenser on-off cycle. With variable capacity scroll pump (Ultrascroll) you have two modes that are again controlled by the thermostat, either by explicit demand or built in algoritm.

I rushed through this so I am sure I made some errors if not only by omission but I think generally, the slower speeds get the moisture out because they run longer not because the coil is colder.

pseudorealityx · Jul 24, 2013

Good first post...

Too bad it's for a thread from September of 2011.

GGB · Jul 24, 2013

I'm not an HVAC tech, just a homeowner (although I did work for an HVAC contractor in high school and college). From a comfort standpoint, i'm much happier with a variable speed air handler because it reduces the temperature swings of a single speed system.

To my way of thinking, a multiple speed fan should be a selling point for a home simply from a comfort point. And as utility costs increase, if a multiple speed fan allows the HVAC system to run more efficiently, it should make a home easier to sell.

I'm betting that lenders will soon factor in utility costs when determining how much to loan on a house.

GGB

Variable Speed Air Handlers vs Multi speed air handlers?

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