ECM or PSC blower for zoned WaterFurnace Legend?

[seandarcy]

I've got an open-loop 6 ton WaterFurnace Legend at a summer house in Northeast Pa.

I'll use cooling maybe a week a year. I keep the heat at 55-60 during the winter, except for 4-6 vacation weekends.

There are two zones. My contractor has told me that we should use a PSC blower. He says an ECM blower won't work with the WaterFurnace zone system. As the zone system balances the supply air the ECM blower will try to rebalance it, creating a feedback loop. In addition, he says the ECM blower would not be cost effective ($0.14/kwh).

This doesn't sound right to me. I'd appreciate any help.

sean

[Kevin Weaver]

In order to receive your 30% tax credit, I am pretty sure you will have to chose the ECM motor. Even not, I would still chose it.

He has the 2 motors reversed. The psc motor uses the most energy for sure. The ecm motor hardly uses any power at all.

This must be 1 big house, 6 tons is large!, especially zoned.

[beenthere]

I'd want the ECM blower. The X13 is the standard motor for that unit. the PSC is an optional motor.

[tipsrfine]

If the contractor has a proven track record with zoned systems and with the equipment he is installing, I would listen to someone who has expertise in that area. An ECM motor is more energy efficient when it is running in "circulate only" mode, so the cost effectiveness of the motor is not as great when compared to a PSC motor operating only during calls for heat or cool. Have the contractor back his words up in a good warranty and you should be good to go.

[seandarcy]

It's not really a warranty issue. I assume both will work, though interestingly the WF site says that an ECM motor has an expected life of 15-18 years, compared to PSC of 10 -12. But, as I said, this is not the issue.

Has anybody used ECM with a zoned system? Does the zone controller "chase" the ECM motor?

I'd expect to leave the motor on all the time. Cathedral ceilings, so I'd like to keep air circulating.

What sort of price difference between ECM and PCS? Is there any? Can one motor be switched for the other once installed?

sean

[tipsrfine]

Here is something I found regarding this matter. Hopefully some zoning experts will chime in.
http://www.ewccontrols.com/zoning_an...able_speed.htm

[SkyHeating]

I'd want the ECM blower. The X13 is the standard motor for that unit. the PSC is an optional motor.

PSC motor is standard on legend units with an upgrade option to high static PSC or to a 5 speed ECM a.k.a X13.
WaterFurnace has the intellizone system which can modulate the ECM blower based on the percentage size of the zone calling for heat. I have never installed a legend unit so I am not positive the intellizone system works with the 5 speed ECM, but i know it does work with the ECM 2.3 motor(variable speed motor on 5 series).
Personally I would upgrade to a dual capacity series 5 with an AXB and install the intellizone two system. The intellizone 2 is a communicating zoning system that will control blower motor(about 12 stages of blower capacity) and compressor based on how much heat/cooling is needed in each zone. It also has energy management features and can be remotely controlled via the Aurora Web Link(a future release)

[beenthere]

From WF' web site on the legend.

BLOWER MOTOR: A 5 speed X13 ECM blower motor allows the unit to provide precisely controlled comfort, quiet operation and energy savings. (PSC motor available).

I never seen one, so i don't know.

[George2]

I've got an open-loop 6 ton WaterFurnace Legend at a summer house in Northeast Pa.

I'll use cooling maybe a week a year. I keep the heat at 55-60 during the winter, except for 4-6 vacation weekends.

There are two zones. My contractor has told me that we should use a PSC blower. He says an ECM blower won't work with the WaterFurnace zone system. As the zone system balances the supply air the ECM blower will try to rebalance it, creating a feedback loop. In addition, he says the ECM blower would not be cost effective ($0.14/kwh).

This doesn't sound right to me. I'd appreciate any help.

sean

The ECM motor is the only way to go. It will only "ramp" (chase) up or down with a barometric by-pass.

If you use a modulating by-pass you'll be fine.

Your contractor doesn't know what he's talking about, which scares me regarding his knowledge on ductwork. That's a whole different issue.

It's a good thing you asked (here) to fine out the real story before you regret it for a very long time. ECM motors are more reliable, energy efficient and quieter.

[seandarcy]

This is it. He's installing a barometric bypass. I had no clue that made any difference. And, he installed the barometric bypass yesterday!

Is it difficult/costly to change a barometric by-pass to a modulating by-pass? What is the difference, and why would one want one over the other?

[George2]

This is it. He's installing a barometric bypass. I had no clue that made any difference. And, he installed the barometric bypass yesterday!

Is it difficult/costly to change a barometric by-pass to a modulating by-pass? What is the difference, and why would one want one over the other?

A baromatric by-pass will work okay with a PSC or X13 motor. If your system has a ECM motor (blower), then a modulating by-pass is needed so it won't "hunt" for the right airflow.

To change it is only possible if the zone control board will allow it.

[tipsrfine]

Hey George2, can you clear that up a bit. Sounds like you are saying a modulating by-pass is needed with an ecm motor but not with a x13 motor; but the x13 is an ecm motor.

[George2]

Hey George2, can you clear that up a bit. Sounds like you are saying a modulating by-pass is needed with an ecm motor but not with a x13 motor; but the x13 is an ecm motor.

I'll try to make it understandable.

A X13 motor is a constant torque motor. When the ESP increases, the airflow will decrease (like a PSC motor), but the torque is not effected as much as with a PSC motor.

When the ESP increases (as with zoning or a dirty filter), the ECM motor will automatically increase the airflow.

Thus, with a barometric (weighted) damper, the airflow will go up and down ("hunting" for the right airflow) with a ECM motor.

I hope that helps a little. There is probably more on this if you visit the Arzel zoning website.
That's how I learned some of this. Another source for me was www.achrnews.com

Enjoy!

[tipsrfine]

You missed my point George2. Your previous statement seems to imply that a x13 is not an ecm motor;at least that is how I read it. Thanks.

[skippedover]

Following up on what George2 was saying, you need to first understand that when any blower/fan comes on, there is a certain amount of resistance to airflow. In a ducted system, we refer to all of the resistance outside of the equipment jacket as External Static Pressure (ESP). In a single zone system, the ESP is what it is based on the design and installation. Ideally it would be, in a residential application, about .5 IWC (inches water column).Anything above 1.0 IWC is huge and a definite no-no. The ways to reduce ESP are to keep all filter and coils clean, as well as a properly designed and installed duct system. If the duct system is too small, the ESP goes up quickly.

Now to the zoned system. Clearly if the system has an ESP of .5 IWC with all zones open, then closing one or more zone will serve to decrease the overall size of the duct system and the ESP goes up. Recognizing this issue, the designer of the zone control system must design in some sort of 'relief strategy' to eliminate the excess static pressure. A common solution for basic zoned systems is to install a barometric by-pass damper that responds to high static by opening and therefore limiting the ESP to some tolerable value. However, a modulating zone system can accomplish the same thing but without the damper. This is done by some sort of 'intelligent' controller that controls ESP by opening zone dampers as needed to keep ESP below a specific value. In the case of modulating zone systems, a by-pass damper is not used. Likewise, with the modulating system, the variable speed blower motor is directly regulated by the system controller and also aids in keeping ESP under control.

Now come the complication of a by-pass damper. Since a variable speed blower is regulated primarily based on ESP (the resistance to airflow is reflected in motor RPM and amps) a by-pass damper will first open, reducing ESP, causing the ECM motor to increase in speed to keep ESP within set parameters but some of the increased airflow will travel through the by-pass and into the return air, thus reducing the return static, causing the ECM motor to slow down, which causes the by-pass to close, increases the ESP, increases the return air static, which causes the ECM to increase. This is a never ending 'hunt' for the variable speed (ECM) motor. This is also the reason that ECM motors are NOT allowed on 'twinned' systems, where more than one blower motor operates in the same static environment as another. Hope this helps. SO

[George2]

Skipper..............I don't know if Arzel came out with it first, but about 10 years ago they introduced a modulating by-pass damper. All of their other dampers did not (modulate) change. The duct dampers either opened or closed. The mod. by-pass sensed the ESP and opened as needed. It is a very slick item.

I know that Carrier, and others, now have the systems that your explaining.

[George2]

You missed my point George2. Your previous statement seems to imply that a x13 is not an ecm motor;at least that is how I read it. Thanks.

Sorry..........the X13 is based on a ECM platform but doesn't have the "brains" to be variable-speed.

Thus the reason the a barometric by-pass will work with a PSC or X13 but not recommended with a "true" ECM motor.

Skippedover explained it (maybe) better than I in post #15.

[tipsrfine]

Sorry..........the X13 is based on a ECM platform but doesn't have the "brains" to be variable-speed.

Thus the reason the a barometric by-pass will work with a PSC or X13 but not recommended with a "true" ECM motor.

Skippedover explained it (maybe) better than I in post #15.

Hate to harp on the subject, but there are several ECM motors out there that are not variable speed ECM motors. The X13 is a ECM motor. The evergreen motor is a ECM motor. Your previous postings seem to indicate that all ECM motors are variable speed ECM motors, and anything that is not variable speed is not an ECM motor. There are ECM motors that are not variable speed.

[seandarcy]

I'm learning a huge amount, and I do appreciate all the comments.

But I'm still confused: can I use the X13 (ECM?) motor from WF if I have a barometric bypass installed? I think I understand that you shouldn't use a standard ECM with a baromteric bypass. Is the WF X13 different enough from a "standard" ECM to allow it to be used?

Is X13 a WF brand, or a specific type of ECM motor?

Or would I need to install a modulating bypass? Is changing from a barometric to a modulating bypass a major undertaking?

[beenthere]

Yes, you can use the X13 with a barometric bypass.