ECM Variable Speed

[newgage]

Can any one tell me how a variable speed furnace/ecm blower motor operates while running in conjunction with a heat pump.

My guess is it runs on high speed only while in cooling.

Does the speed vary while in heating mode on the heat
pump?

Is the major advantage 1. Cheaper than a PSC Motor and 2. comfort while running on the gas furnace?

Please enlighten me on ECM!

Thanks!

[beenthere]

You set the CFM for each mode independent of the other.

You can set them for the same speed for cooling as for heating, or have either higher then the other.

The provide better comfort, and operate cheper then a PSC motor, if the duct system isn't undersized too much.

[mark beiser]

Typically the motor will run at the same maximum speed for heating as it does for cooling on a heat pump system. If the blower uses an enhanced ramping profile in the cooling mode, like Trane's "Comfort-R", the blower won't use the enhanced profile in the heating mode.

Typically equipment with ECM motors is marketed based on energy savings and better humidity control in the cooling mode.
The marketing is true, but I think the #1 best thing about them is that we can set the airflow the equipment needs and the bolower will maintain that airflow as conditions change in the system. Filter gets dirty, filter gets changed, coil gets extra wet when its humid, etc.

[amickracing]

Originally posted by mark beiser
Typically the motor will run at the same maximum speed for heating as it does for cooling on a heat pump system. If the blower uses an enhanced ramping profile in the cooling mode, like Trane's "Comfort-R", the blower won't use the enhanced profile in the heating mode.


Actually it will use that ramping profile for heating aswell... some call it the jalepeno mode because it'll help make a heat pump make warmer air than a standard heat pump.

[mark beiser]

Originally posted by amickracing

Originally posted by mark beiser
Typically the motor will run at the same maximum speed for heating as it does for cooling on a heat pump system. If the blower uses an enhanced ramping profile in the cooling mode, like Trane's "Comfort-R", the blower won't use the enhanced profile in the heating mode.


Actually it will use that ramping profile for heating aswell... some call it the jalepeno mode because it'll help make a heat pump make warmer air than a standard heat pump.

Nope, with Comfort-R enabled and no power going to the O terminal in the air handler, the blower will run at 50% for 1 minute then ramp up to 100%. It won't do the 7.5 minutes at 80% in the heat mode unless you wire it so O in the air handler is getting power in the heat mode.

[jrbenny]

They've reprogrammed things. I've seen '02 and '03 airhandlers that would complete the ramp regardless of the O signal. My XV80 from '96 would not do it. It had to have the O. Otherwise, it would skip the 80% portion.

[behappy]

[/QUOTE]

Actually it will use that ramping profile for heating aswell... some call it the jalepeno mode because it'll help make a heat pump make warmer air than a standard heat pump. [/QUOTE]

I like this!

Some Mgf's call it the "Hot Heat Pump Mode" on the 2 speed heat pumps.

The fan runs slower in the low speed mode to keep the discharge temp. up (just like a two stage gas furnance), then a little slower if this setting is pinned out.

On the cooling side the fan will run slower if you have a humidistat connected for a colder coil and more dehumidity control (per the manuf. ).

[beenthere]

York Affinity will run the blower slower in hot heat pump mode in second stage until the line temp reaches x degrees.

[behappy]

Originally posted by beenthere
York Affinity will run the blower slower in hot heat pump mode in second stage until the line temp reaches x degrees.

You know I have heard this before but...
The old TS had a discharge sensor to read this, the new Affinity does not have a discharge sensor...
How can they do this???

[behappy]

Sorry.. I just reread the post...
line sensor... :(

[docholiday]

Originally posted by mark beiser
Typically the motor will run at the same maximum speed for heating as it does for cooling on a heat pump system.

To continue where Mark left off, in a dual fuel set up it will run the same speed in heat or cool when the HP is running, however, when it switches to the fossil fuel, it will use the furnace heating speed slected and programmed.

[newgage]

Thanks for the info.
It clears things up. If the furnace ran for only two weeks out of the year and the rest of the year it ran on the heat pump I can't seem to justify spending the extra money for variable speed.

[stafford]

Originally posted by newgage
Thanks for the info.
It clears things up. If the furnace ran for only two weeks out of the year and the rest of the year it ran on the heat pump I can't seem to justify spending the extra money for variable speed.


Not sure how you got there man. You are thinking like variable speed is just a regular PSC motor with speed taps. It's so much more.

And currently Trane's on-board Comfort-R needs to see 24v on O or else the VS motor just ramps up easy to 100% cfm.

[mark beiser]

Originally posted by newgage
Thanks for the info.
It clears things up. If the furnace ran for only two weeks out of the year and the rest of the year it ran on the heat pump I can't seem to justify spending the extra money for variable speed.

You get the benefit of reduced energy use and correct airflow any time the system is running, regardless of what cycle it is.
The biggest benefit of the variable speed blower is in the cooling mode anyway.

[mark beiser]

Originally posted by jrbenny
They've reprogrammed things. I've seen '02 and '03 airhandlers that would complete the ramp regardless of the O signal. My XV80 from '96 would not do it. It had to have the O. Otherwise, it would skip the 80% portion.

The control board in the gas furnaces requires O to be powered for Comfort-R to work. I have verified that myself several times, hehe.

[newgage]

Originally posted by mark beiser

The biggest benefit of the variable speed blower is in the cooling mode anyway. [/B]


Its running on high speed pretty much continually while in cooling - correct? The biggest benefit then is what?

[mark beiser]

Originally posted by newgage

Originally posted by mark beiser

The biggest benefit of the variable speed blower is in the cooling mode anyway.


Its running on high speed pretty much continually while in cooling - correct? The biggest benefit then is what? [/B]

It is different timing for each equipment manufacturer, but the blower can be set so that it will run at lower speeds at the beginning of the cooling cycle. This allows the coil to get cold faster and more humidity to be removed than you would get with a standard blower.

The motor uses a fraction of the power that a standard motor uses.

When the unit is installed, the installer sets the desired airflow for the system. The blower will maintain that set airflow by speeding up or slowing down as required to compensate for the the filters getting dirty, wet coil, etc. In a system with a standard blower, the airflow goes down as the filters get dirty, wet coil, etc.

I think you are misunderstanding what "variable speed" means. Most blower motors are multispeed, and can be run at different speeds for different operating modes.
Only an ECM motor can vary its speed to maintain a set airflow as conditions change in the system.

[docholiday]

in a heat pump it's pretty much a constant CFM fan. The variable comes into play when the duct static changes. Assuming you have a decent duct system, you can count on a pretty significant electrical savings with a heat pump because the winter run times are very long and the watts used will be less. That said if you have a marginal or poor duct system, you could actually use more power.

An ecm will deliver the proper air flow. At higher statics it will too, but can be costly. A PSC motor in the same duct system will simply not deliver the correct air. Bottom line there is if your duct system is weak, fix that and enjoy a significant electrical savings. In adition you will better protect your systems compressor by keeping proper load on the coil. A PSC deilivering low airflow will reduce your compressor's life significantly.

Next thing is what value you put on sound? A PSC generally has a whine or wind up sound as it's coming up to speed in the first few seconds. The ECM will slowly ramp up and down eliminating this. How about humidity control? It was mentioned earlier that in the mild times of cooling season your system run times may not offer enough dehumidification. An ECM can be configured in many systems to lower your sensible capacity and increase that latent removal. Hard to put a dollar figure to that.