ECM Motor but not Variable Speed

[rChris]

Not looking like Rheem makes a VS furney, just a 2 stage that has a ECM motor.

So if that's the case, could someone esplain what's so great about these motors. Looked at the lit' not really seeing it.

TIA for any help

Chris

[damedi07]

not too familiar with rheem since i haven't put many in....especially recently. but why do you feel that they can't be both 2-stage heat with a variable speed blower?

[ga-hvac-tech]

If I am reading your post correctly, I think you are referring to the Rheem RGPR furnace. It is an 80% 2-stage (2 stages of heat, usually the lower one is around 65% of the higher one), and it has an ECM motor. In the RUUD like (same product, and the product I install), this is called an LXE furnace.

But you might also be thinking of the RGFD furnace, which is 90+% efficient, and truely has variable heat as well as a variable speed blower (ECM motor). In GA, the 90+ VS furnace (Rheem or Ruud) is not stocked, as this is an A/C market and there is not much call for 90+ VS furnaces.

The two stage is for quieter and more efficient (not particularly less fuel cost) heating. The idea is to not run the furnace at full capacity unless that is necessary.

The variable speed motor (GE ECM motor) is for the blower in the furnace. There are lots of reasons this is a GREAT feature, with lots of benefits to the HO.

Do a search on the forum for VS furnaces, you will get lots of reading material!

[rChris]

Alright looks like I should back up and start from the beginning (and learn the equip I sell a bit better )

So is a furnace with a ECM motor considered to be variable speed???

Yes, talking about the RGPR

[amickracing]

So is a furnace with a ECM motor considered to be variable speed???

For the sake of arguement... no, just because it has an ECM motor doesn't make it variable speed unless it has the board to control it and make it variable speed.

FWIW, American Standard (and Trane) use ECM motors on their heat pump and A/Cs (well, some models), but they indeed aren't variable speed. They do how ever use less energy (usually), so this help them gain that illusive extra SEER.

[drsmith012]

For the sake of arguement... no, just because it has an ECM motor doesn't make it variable speed unless it has the board to control it and make it variable speed.

FWIW, American Standard (and Trane) use ECM motors on their heat pump and A/Cs (well, some models), but they indeed aren't variable speed. They do how ever use less energy (usually), so this help them gain that illusive extra SEER.

I thought the motor microprocessor was calibrated to determine the air flow and maintain it on ALL ECM motors. Ex. set the dip switches for 1200cfm and the motor will automatically adjust RPM for 1200cfm until it reaches its max RPM. Block the filter or the discharge and you will hear it rev up. I do know that the GE ECM2 has a pwm input that the main cpu uses to tell the motor what the target airflow is.

So Trane and AS do not use the technology they sell to the consumer to dynamicaly maintain the desired air flow. Glad I went with Waterfurnace.

[mark beiser]

I thought the motor microprocessor was calibrated to determine the air flow and maintain it on ALL ECM motors. Ex. set the dip switches for 1200cfm and the motor will automatically adjust RPM for 1200cfm until it reaches its max RPM. Block the filter or the discharge and you will hear it rev up. I do know that the GE ECM2 has a pwm input that the main cpu uses to tell the motor what the target airflow is.

So Trane and AS do not use the technology they sell to the consumer to dynamicaly maintain the desired air flow. Glad I went with Waterfurnace.

You are misinterpreting what he said. AS/Trane use variable speed ECM blowers in their indoor units that ramp up/down to maintain the airflow.

He was talking about the ECM outdoor fan motors that AS/Trane uses in some outdoor units. They are ECM, but run at fixed speeds.

AS/Trane, and most other equipment manufacturers, also have indoor units with the X13 blower motor. It is an ECM motor, but it has speed taps and has similar airflow performance to a standard blower, but uses less energy.

Just because a motor is an ECM type doesn't mean it is "variable speed".

Oh, and most manufacturers systems don't use the PWM input on the variable speed motors. AS/Trane have a non programable thermostat that uses it, and their zone control uses it and modulating dampers to manage airflow.
I don't know if any other manufacturers use the PWM input on the ECM2.3 motors.
The Carrier Infinity uses the ECM2.5 serial communicating motor, so no need for PWM signals.

[jrbenny]

I think Lennox uses the PWM for their Harmony. I seem to recall a post discussing this in the past.

[drsmith012]

You are misinterpreting what he said. AS/Trane use variable speed ECM blowers in their indoor units that ramp up/down to maintain the airflow.

He was talking about the ECM outdoor fan motors that AS/Trane uses in some outdoor units. They are ECM, but run at fixed speeds.

AS/Trane, and most other equipment manufacturers, also have indoor units with the X13 blower motor. It is an ECM motor, but it has speed taps and has similar airflow performance to a standard blower, but uses less energy.

Just because a motor is an ECM type doesn't mean it is "variable speed".

Oh, and most manufacturers systems don't use the PWM input on the variable speed motors. AS/Trane have a non programable thermostat that uses it, and their zone control uses it and modulating dampers to manage airflow.
I don't know if any other manufacturers use the PWM input on the ECM2.3 motors.
The Carrier Infinity uses the ECM2.5 serial communicating motor, so no need for PWM signals.

Ok, misinterpreted. I can understand an outside unit having fixed speeds.

I guess on traditional split type air source heatpump air handlers the taps perform the function of the dip switches on Waterfurnaces. Since traditional splits are well split it make sense to put settings directly on the motor since the majority of the controls resides in the compressor section.

PWM, dip switches and serial connection are all ways of telling the ECM motor how fast to run. I guess it all depends on what the manufacture wants. I suspose manufactuers could order ECM motors that maintain fixed speed based on input. While others order motors with a PID function to set air flow and let the motor's processor figure out what speed it needs, like Waterfrunace.

[mark beiser]

Ok, misinterpreted. I can understand an outside unit having fixed speeds.

I guess on traditional split type air source heatpump air handlers the taps perform the function of the dip switches on Waterfurnaces. Since traditional splits are well split it make sense to put settings directly on the motor since the majority of the controls resides in the compressor section.

PWM, dip switches and serial connection are all ways of telling the ECM motor how fast to run. I guess it all depends on what the manufacture wants. I suspose manufactuers could order ECM motors that maintain fixed speed based on input. While others order motors with a PID function to set air flow and let the motor's processor figure out what speed it needs, like Waterfrunace.

The variable speed ECM blower in your Water Furnace is the exact same motor and module that is in Trane, and most other manufacturers, variable speed equipment that uses the ECM2.3 motor.
The blower control boards that send the control signals to the motor module vary somewhat, but they have the exact same outputs to the motor module, regardless of manufacturer. The blower control board with the dip switches, or jumpers in some cases, does no processing, it just switches control voltage to pins in the 16 pin harness to the module on the end of the motor, it isn't even sending signals, its just power/no power to a given conductor/conductors in the harness.
The modules use the same control inputs, the only difference is the programing of the module on the end of the motor.

The PWM input that is available on the ECM2.3 motor is a completely different form of communication with the motor module than the serial communication of the ECM2.5 motor.

[drsmith012]

The variable speed ECM blower in your Water Furnace is the exact same motor and module that is in Trane, and most other manufacturers, variable speed equipment that uses the ECM2.3 motor.
The blower control boards that send the control signals to the motor module vary somewhat, but they have the exact same outputs to the motor module, regardless of manufacturer. The blower control board with the dip switches, or jumpers in some cases, does no processing, it just switches control voltage to pins in the 16 pin harness to the module on the end of the motor, it isn't even sending signals, its just power/no power to a given conductor/conductors in the harness.
The modules use the same control inputs, the only difference is the programing of the module on the end of the motor.

The PWM input that is available on the ECM2.3 motor is a completely different form of communication with the motor module than the serial communication of the ECM2.5 motor.

I respectfully disagree. I have a ECM2 motor that I have sucessfully run and controlled by only applying 240VAC and a PWM signal from an intergrated circuit chip designed for the purpose of generating a pwm signal. I am poositive that the PIC (brand name) processor on my contorl board sends the motor a pwm signal based on dip switch settings. there is also a Dehumidify setting which reduces what ever the air flow setting is to 85% of the set value. I have the ECM because it came with a 4 ton E series Waterfurnace heatpump my contractor gave me. I am converting the ECM blower into a whole house fan. And using the coax and my old heat pump to build a heatpump water heater.

[mark beiser]

I respectfully disagree. I have a ECM2 motor that I have sucessfully run and controlled by only applying 240VAC and a PWM signal from an intergrated circuit chip designed for the purpose of generating a pwm signal. I am poositive that the PIC (brand name) processor on my contorl board sends the motor a pwm signal based on dip switch settings. there is also a Dehumidify setting which reduces what ever the air flow setting is to 85% of the set value. I have the ECM because it came with a 4 ton E series Waterfurnace heatpump my contractor gave me. I am converting the ECM blower into a whole house fan. And using the coax and my old heat pump to build a heatpump water heater.

All ECM2 and 2.3 motors can be controlled by a PWM input, most manufacturers do not use it though, at least not with the standard controls the unit comes with.
Trane, and possibly Lennox, zone controls both use a PWM signal to control the airflow, but most manufacturers never make use of it.
There really isn't much to gain using PWM control in a single or 2 stage system that always runs the same CFM in each mode, other than a reduction in the amount of wiring.
The function of reducing airflow for dehumidification in the cooling mode can be accomplished without PWM input by simply not sending 24v through one of the conductors in the 16 pin harness. I could have just missed it, but it didn't look like the dehumidification mode on the Water furnace was something that could be set up as an "on demand" type function with a dehumidistat or thermostat with a dehumidification terminal. It looks like it is either in normal mode, or locked full time into dehumidification mode, based on the dip switch setting...

I looked over the installation literature for the single and multistage Water Furnace units, and for their zone control. They don't use PWM inputs at all. The zone control system does have direct control over the ECM blower, but only because it has a 16 pin harness running from the zone control directly to the motor module.
In a zoned system, Trane actually makes much better use of the variable speed blower than Water Furnace...

[jrbenny]

Hmmm....now which wire would that be?

Carrier has used PWM on some of their furnaces before they switched to ECM 2.5. They only have five wires in the 16-pin connectors.

[mark beiser]

Hmmm....now which wire would that be?

Carrier has used PWM on some of their furnaces before they switched to ECM 2.5. They only have five wires in the 16-pin connectors.

Wire #10 in the harness for PWM, but it is also used for non PWM applications, usually for dehumidification on demand, and is usually jumpered to R by default.

The bottom line is, there are 16 CFM settings available, 25% to 100% of the max CFM the module is programed for, in 5% incraments.
All 16 of them can be accessed by either PWM input or 24v inputs to combinations of wires in the 16 pin harness.
Its up to each manufacturer to decide how they want to do it, but you get the same results either way.

[drsmith012]

Wire #10 in the harness for PWM, but it is also used for non PWM applications, usually for dehumidification on demand, and is usually jumpered to R by default.

The bottom line is, there are 16 CFM settings available, 25% to 100% of the max CFM the module is programed for, in 5% incraments.
All 16 of them can be accessed by either PWM input or 24v inputs to combinations of wires in the 16 pin harness.
Its up to each manufacturer to decide how they want to do it, but you get the same results either way.

Now I'm absolutly clear. You wouldn't happen to have, or be able to point me in the direction of, a pinout for the motor control connector? I think I would rather control the motor using the selection pins.

You are right about the dehumidification mode on the Waterfurnace. It is not on demand. But is easily "field modified" to be controlled by a humidistat

[klyons20]

[QUOTE=rChris;1511988]Not looking like Rheem makes a VS furney, just a 2 stage that has a ECM motor.

So if that's the case, could someone esplain what's so great about these motors. Looked at the lit' not really seeing i

Chris these motor use 1/2 or less power than the psc motor..

regards,
K

[cliebold]

Its my understanding the blowers we are talking about are both high efficiency dc drive motors but the true v-spd has ramping profiles and the std ecm does not. More comfort specific with the true v-spd.