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PSWired

join:2006-03-26
Annapolis, MD

Variable speed drive

Is anyone aware of a small, inexpensive 120v single phase variable speed drive with a slow-start function?

I have a single speed air handler for my central air system. It just has a single relay triggered by the thermostat that turns the blower on. The blower is pretty noisy when it starts, so I'd like to have a slow-start function that ramps it up to speed over a few second period. Also, when the house is running on generator, it'd be nice to limit the inrush current to reduce light flicker when the AC kicks in.

Anyone know of something that'll fit the bill that's not expensive?

laserfan

join:2005-01-14
Texas
said by PSWired:

...it'd be nice to limit the inrush current to reduce light flicker when the AC kicks in.

I'll be interested too if a VSD motor can help with this. I'd thought light flicker was strictly owing to the compressor kick-on.

Zach1
Premium
join:2006-11-26
NW Minnesota

1 edit
reply to PSWired
Any VFD I know of would be a quite expensive but an upgrade to an ECM blower motor may meet your requirements while not blowing your budget....

quote:
RESCUE EcoTech® - The High Efficiency ECM upgrade for PSC blower motors

The RESCUE EcoTech motor is an ECM replacement for a PSC blower. Exclusive speed-control technology provides the efficiency of an ECM. Installation is a snap. RESCUE EcoTech drops into existing permanent split capacitor (PSC) direct drive blower applications, without complex wiring modifications or time-consuming changes to system controls.

Electronically Controlled Motor (ECM) technology gives RESCUE EcoTech motors up to 82% efficiency, saving 25% or more of the watts in A/C or heating mode and 75% of the watts in circulation mode. Updated designs are now dual voltage (115/230V) and multi-horsepower, so one size, or at most two, fits all your needs.


»www.usmotors.com/Our-Products/HV···cue.aspx

These motors offer soft starting as well as other speed options. The local HVAC supply house has the dual voltage, multi-HP 5552ET direct-drive blower motor priced at $180 so you can probably do better on the 'net somewhere.
--
Zach


shdesigns
Powered By Infinite Improbabilty Drive
Premium
join:2000-12-01
Stone Mountain, GA
Reviews:
·EarthLink
·Comcast
·Atlantic Nexus
reply to PSWired
I have not seen many VFD's for single-phase motors. Most use 3-phase motors.

I have one set up on my metal lathe. Lots of settings for startup speed and spindown. It is a Toshiba 1/2HP VFD and a 1/2HP 3-phase motor. Both bough used under $100.

One plus with a 3P motor is there is less torque vibration (hum.) My motor just makes a hiss.

A new VFD and 3P motor will cost you about $300.
--
Scott Henion

Embedded Systems Consultant,
SHDesigns home - DIY Welder


PSWired

join:2006-03-26
Annapolis, MD
Thanks for the ideas so far. Replacement blower motor looks interesting... wonder if it's just a regular induction motor with a built-in drive?

Laserfan, the blower doesn't contribute too much to the inrush current of the whole system, but it's something. I added a hard start kit to the compressor and that made things much easier on the generator. Last summer when the power was out for 7 days, I ran the air handler blower constantly to avoid the synchronized start with the compressor.

laserfan

join:2005-01-14
Texas
said by PSWired:

I added a hard start kit to the compressor and that made things much easier on the generator.

I added hard start kits to my compressors and two out of three blew-up! I took the third out before IT blew up too! Dunno why/how this happened as they were properly sized & wired, or so we thought (me & the HVAC tech).

Anyway those RESCUE motors look interesting to me as apart from the energy usage and "lights dimming" issues, I also find our blowers to be inordinately loud (not the motors per se, but the airflow) and maybe those would help with that too. As it is, on one of my blower motors I re-wired to the lower RPM windings...

tberg

join:2001-08-23
Greenville, SC
reply to PSWired
Check out the A. O. Smith retrofit motors. »www.centuryelectricmotor.com/Mot···3&id=296
Theirs have the intelligence so that one motor will replace multiple HP sizes. It also learns which direction it is supposed to turn and the speed at which to turn. Great for those that need to carry spares on their trucks. It is made to plug right in where the PSC motor came out.


ECM motor

@mycingular.net
reply to PSWired
Whether you choose the motor in the first link or the one in the second, they are the same. In fact, all commonly available ECM motors used in HVAC equipment are made by Regal-Beloit. GE pioneered the technology and Regal acquired it in the early 2000s.

garys_2k
Premium
join:2004-05-07
Farmington, MI
Reviews:
·Callcentric
reply to PSWired
I wonder if a relay board could be cooked up to:
- Receive a call from the thermostat for cooling
- Immediately start the air handler fan
- Wait five seconds, then start the condenser fan
- Wait five seconds more, then start the compressor.

This would allow all the motors' inrush currents to subside before the next one comes on. Starting all three at once is the real b*tch.


whizkid3
Premium,MVM
join:2002-02-21
Queens, NY
kudos:9
said by shdesigns:

A new VFD and 3P motor will cost you about $300.

It could be a good idea, except that not too many people have 3-phase power to their residence.

said by garys_2k:

I wonder if a relay board could be cooked up to:
- Receive a call from the thermostat for cooling
- Immediately start the air handler fan
- Wait five seconds, then start the condenser fan
- Wait five seconds more, then start the compressor.

This would allow all the motors' inrush currents to subside before the next one comes on. Starting all three at once is the real b*tch.

Doesn't have to be 'cooked up'. Delay timers are used all the time with HVAC equipment for this very function. Generally, individual timers at each piece of equipment, with different delay settings.

garys_2k
Premium
join:2004-05-07
Farmington, MI
Reviews:
·Callcentric
My furnace/AC is dumb, once the 'stat calls for cooling all three motors start at once (air handler, condenser fan and compressor). If a stepped time delay could be added I'd bet that not only would the lights not dim so much but (if I wanted to add one) a smaller standby generator would be needed to power it, too.

tberg

join:2001-08-23
Greenville, SC
reply to tberg
By the way, the biggest beauty of the ECM's is that they draw a lot less power. My PSC motor pulled 900 watts. The ECM draws 75 watts. Since I run my fan 24x7, it paid for itself in about 12 months with the power savings.

Zach1
Premium
join:2006-11-26
NW Minnesota
reply to garys_2k
said by garys_2k:

My furnace/AC is dumb, once the 'stat calls for cooling all three motors start at once (air handler, condenser fan and compressor). If a stepped time delay could be added I'd bet that not only would the lights not dim so much but (if I wanted to add one) a smaller standby generator would be needed to power it, too.

ICM has the timer you need to stage your equipment start-up. ICM is a common product line at most HVAC supply houses.

»www.icmcontrols.com/TIME-DELAY-R···ist.html
--
Zach


shdesigns
Powered By Infinite Improbabilty Drive
Premium
join:2000-12-01
Stone Mountain, GA
Reviews:
·EarthLink
·Comcast
·Atlantic Nexus
reply to whizkid3
said by whizkid3:

said by shdesigns:

A new VFD and 3P motor will cost you about $300.

It could be a good idea, except that not too many people have 3-phase power to their residence.

You missed the point, the VFD converts single-phase power to 3-phase. Actually it is a 3-phase PWM signal. Since it is generating the phases, frequency and PWM, it had a lot of control over the motor.

My VFD, has ramp up/down, PWM frequency, current limits, braking and failsafe options.
--
Scott Henion

Embedded Systems Consultant,
SHDesigns home - DIY Welder


pike
Premium,MVM
join:2001-02-01
Washington, DC
kudos:3
reply to Zach1
said by Zach1:

RESCUE EcoTech® - The High Efficiency ECM upgrade for PSC blower motors

I can definitely vouch for the Rescue Ecotech replacement blower motor. I installed one myself in my air handler and was pleasantly surprised by the soft start and extremely quiet operation. A huge difference in my electric bill also when running the blower 24/7.

garys_2k
Premium
join:2004-05-07
Farmington, MI
Reviews:
·Callcentric
reply to Zach1
said by Zach1:

said by garys_2k:

My furnace/AC is dumb, once the 'stat calls for cooling all three motors start at once (air handler, condenser fan and compressor). If a stepped time delay could be added I'd bet that not only would the lights not dim so much but (if I wanted to add one) a smaller standby generator would be needed to power it, too.

ICM has the timer you need to stage your equipment start-up. ICM is a common product line at most HVAC supply houses.

»www.icmcontrols.com/TIME-DELAY-R···ist.html

Thanks, yes, those are exactly what I'm talking about!

laserfan

join:2005-01-14
Texas
reply to garys_2k
said by garys_2k:

I wonder if a relay board could be cooked up to:
- Receive a call from the thermostat for cooling
- Immediately start the air handler fan
- Wait five seconds, then start the condenser fan
- Wait five seconds more, then start the compressor.

This would allow all the motors' inrush currents to subside before the next one comes on. Starting all three at once is the real b*tch.

Great idea--I even have an ICM TD relay or two around here somewhere. Can't remember why I bought them--probably to avoid contact bounce on my well pump control yrs ago.


whizkid3
Premium,MVM
join:2002-02-21
Queens, NY
kudos:9
reply to shdesigns
said by shdesigns:

You missed the point, the VFD converts single-phase power to 3-phase.

Cool. How about a link?

Zach1
Premium
join:2006-11-26
NW Minnesota
The Eaton/Cutler-Hammer NFX9000 series VFD offer single-phase input up to 2HP and the M-Max series offer single-phase input up to 3HP. Allen-Bradley, Square-D also offer small VFDs with single-phase input.

Link to relevant Eaton/CH catalog pdf:

»www.eaton.com/ecm/idcplg?IdcServ···06_TAB02
--
Zach