Variable speed Amana seems to run only one speed

14 days ago

I had a new heat/AC system installed in January and opted for the most expensive option offered with variable speed compressor, condenser and blower motor. In addition to energy savings, I hoped to see a substantial difference in the amount of on/off cycles and have the system run at quieter lower speeds when possible.

This new system replaced an older 1-speed Trane furnace with no AC (swamp cooler instead), and the first thing I noticed in January was that the new blower in heat mode was not at all quieter. Now that it has been used in heat and cool modes I can say that there is never a time when I can detect a noticeable difference in fan speed or noise level, so I'm unsure if the fan is really varying speed. It seems to me that it jumps on and off as suddenly as the previous system and no better than any other I've had in the past.

I shared these thoughts with the person who sold and installed the system and was told over email, "the system runs as promised, there is no way you would know the fan speed unless you were into the diagnostic side of the controls". Am I wrong in thinking that the fan speed change should be noticeable just by its force and noise level?

I don't want to be a whiner or pretend to know more than I do, but I'm unhappy with the real-world results of the system, and am trying to decide whether and how to pursue the issue. Here is more technical detail on the system:

NLP 5025 AVXC20-36-V

Amana® brand 3 Ton, AVXC20 vertical A/C system with variable speed furnace, mounted on roof

Amana AVXC200361, CAPF3743C6, AMVC80805CX

I believe the middle one is the heat pump and blower unit? Showing my ignorance here ;) -- just pulled these codes from the project quote.

The Thermostat is an EcoBee 3 lite. I have access to the logs and as an example, on a recent day with an outside high of 88 and thermostat set to 72 it turned on/off 36 times (18 cycles). The longest run-time was a solid stretch of 150 minutes where it kept indoor temp nice and stable with outside temp at 88. But at other times it cycles much more and does not noticeably turn down the fan to adjust.

The logs always show the state 'compressorCoolStage1On' when on -- so there is no info there on what speed the fan is running at and I do not know if the thermostat is controlling the fan or if that is happening elsewhere in the system if at all.

I'm hoping someone far more knowledgeable than myself can weigh in on whether this all seems reasonable or if there is something wrong and this system is not performing properly. I would love to trust my local rep, but his attitude when I posed the question was overly defensive and did not help to clear anything up.

Thanks!

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Comments (6)

PRO
Austin Air Companie
13 days ago
Amana AVXC200361, CAPF3743C6, AMVC80805CX

I believe the middle one is the heat pump and blower unit? Showing my ignorance here ;) -- just pulled these codes from the project quote.

Nope, none of these are a heat pump. The middle one is a 3 ton - 3 1/2 ton upflow coil. The last one is 80% gas furnace 4 ton.

I shared these thoughts with the person who sold and installed the system and was told over email, "the system runs as promised, there is no way you would know the fan speed unless you were into the diagnostic side of the controls". Am I wrong in thinking that the fan speed change should be noticeable just by its force and noise level?

Varible speed blowers when ramped can generate air noise, especially if there are issues with the duct system. Was the duct system replaced with this install or just equipment?

The more air you push pull thru a system? Variable speed are quieter, but only if your duct system is capable of handling the air these can generate. The algorithm to the blower can be adjusted. But the better approach is to design a proper duct system to handle the air flow.

Because you came from a swamp cooler before, heating loads tend to be lighter and so the duct system for those is likely inadequate for AC.

If the duct work was replaced with this job, he should at least try to change the algorithm to the blower.

The logs always show the state 'compressorCoolStage1On' when on -- so there is no info there on what speed the fan is running at and I do not know if the thermostat is controlling the fan or if that is happening elsewhere in the system if at all.

These systems are communicating, but Amana as well as Daikin and Goodman brands moved the communication part to the furnace. They claim you can use any thermostat with them.

The signal from the thermostat merely gets the cycle started. From there the communication aspects of this system take over.

However, smart thermostats like the ecobee (nest are often worst offenders) can disrupt the lengthy run times of varible speed / inverter type systems.

Disrupt means the signal from the thermostat tells the system to shut off. When that happens / the new start up the process begins again it could take up to 20 minutes of run time for the inverter to find it's bearings. Because the way these run is to mostly keep on running. That is the most efficient form for these.

These machines are mostly looking for nirvana or the load of the structure to minimize off cycles. So when you see long run times along with adequate comfort --- that is what you want. That is how they are designed to operate.

There are other things that could cause stop / restart outside that of the thermostat. A test would be to buy a cheap run of the mill thermostat / remove the ecobee and use the cheap thermostat for awhile if you believe your ecobee might be part of the problem.

I have a customer that uses an ecobee with Bosch inverter with no issues for over 2 years now. But Bosch advises against using smart thermostat because the thermostat will sometimes try to think it knows best how to run the system. I don't know if that is an issue or not, merely a guess of something to pay attention to.

--------------

Does the unit cool properly? Are you comfortable except for the blower noise?

I service the Katy, Texas area.
mike_home
13 days ago
Now that it has been used in heat and cool modes I can say that there is never a time when I can detect a noticeable difference in fan speed or noise level, so I'm unsure if the fan is really varying speed.

The AMVC80805CX is a 80K BTU 2-stage furnace with 80% efficiency. You should be able to hear and feel the difference between the low and high stages heating stages. If you don't then I suspect a bad installation. You are not getting the performance from the expensive equipment you purchased.

I shared these thoughts with the person who sold and installed the system and was told over email, "the system runs as promised, there is no way you would know the fan speed unless you were into the diagnostic side of the controls".

This is an unacceptable response from the installer in my opinion. You don't need to know the fan speed. You want to feel the comfort and quietness the 2-speed equipment provides. You should ask the installer to come back and demonstrate to you how the 2-speed operation works. Typically a the equipment should start up in low speed when cycling on and off to maintain the thermostat set point. If the thermostat can't satisfied in a set amount of time, or if there is a big difference in room temperature and thermostat set point, the equipment should switch to the high stage.
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sktn77a
13 days ago
"the system runs as promised, there is no way you would know the fan speed unless you were into the diagnostic side of the controls".

What utter drivel! How does he know what the issue might be without coming out and checking it. Tell him you need him to come out and demonstrate to you that the system is modulating and why it is so noisy at the lowest speeds.
wdccruise
12 days ago
last modified: 12 days ago
If I'm undersanding it correctly, the Amana AMVC8 furnace supports two types of thermostats. The first type is the so-called ComfortNet thermostat. The second type is a conventional thermostat such as the ecobee.

Take a look at the diagram on page 22 of the AMVC8 installation instructions. Find the section labeled "24 V Thermostat Connections".
- If you had a ComfortNet thermostat, you'd wire that thermostat to the 1, 2, R, and C connectors as shown in the section, "Installing ComfortNet" of the ComfortNet CTK04 Instruction book.
- If you had a conventional thermostat, you'd wire it to the appropriate subset of the R, C, G, W1, W2, Y1, Y2, and O connectors.*
Ecobee Support: What do my thermostat's wire labels mean?

It's certainly possible that your furnace installers only wired your thermostat for single-stage operation. (The company that installed my two-stage packaged heat pump did that.) I would:
- Using the document linked above as a guide, look at the ecobee wiring to see whether there are any second-stage wires connected to the thermostat,
- Make sure that the ecobee is configured for two-stage operation. I had to change a setting in my Honeywell thermostat for that.
-- amateur

*The diagram shows dip switches labeled T-STAT which may control the type of thermostat connected to the furnace. Dunno.
PRO
Austin Air Companie
12 days ago
Amana AMVC8 furnace supports two types of thermostats. The first type is the so-called ComfortNet thermostat.

That comfort net t-stat was the old way years ago. With the introduction of comfort bridge technology it did away with the need for the comfort net thermostat. Those were discontinued, they still have some of them for installs that use the older communicating design.

While these systems are still communicating the thermostat is ommitted from it -- the furnace relays the info to the outdoor unit.

I don't believe you even need a two stage thermostat with these as the furnace uses an algorithm for operation, there is likely at least 4 different algorithms to choose from. Could be more than that now.
wdccruise
12 days ago
@Austin Air Companie: "I don't believe you even need a two stage thermostat with these as the furnace uses an algorithm for operation..."

From the ADVC8/AMVC8 Technical Manual:

"Single Stage Thermostat

"A single-stage thermostat with only one heating stage may be used to control this furnace. The application of a single-stage thermostat offers a timed transition from low to high fire. The furnace will run on low stage for a fixed period of time before stepping up to high stage to satisfy the thermostat’s call for heat. The delay period prior to stepping up can be set at either a fixed 5 minute time delay or a load based variable time between 1 and 12 minutes (AUTO mode). If the AUTO mode is selected, the control averages the cycle times of the previous three cycles and uses the average to determine the time to transition from low stage to high stage. To use a single-stage thermostat, turn off power to the furnace, move the thermostat selection DIP switch to the OFF position. Set the desired transition time by setting the transition delay DIP switch to the desired ON/OFF position. Turn power back on. Refer to the following figure."

[figure in original]

So a single-stage thermostat is supported and his ecobee could be wired and configured that way. But given the choice, I'd rather have the thermostat control stage-1 and stage-2 based on the actual temperature of the room.

Also, that is for heating. The ecobee supports two-stage cooling as well and the Amana AVXC20 wiring diagrams show thermostat connectors "Y1" for stage-1 cooling and "Y2" for stage-2 cooling. I'll take a wild guess that connectors "1 BK" and "2 GY" labeled "to indoor unit" turn on the blower when the AC unit is switched on by the thermostat.*

-- amateur

*This is based upon working with my own heat pump and thermostat. I don't know this.

Variable speed Amana seems to run only one speed

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Austin Air Companie

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