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garys_2k
Premium
join:2004-05-07
Farmington, MI
Reviews:
·Callcentric
·callwithus
reply to PSWired

Re: Variable speed drive

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
·callwithus

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.


Zach1
Premium
join:2006-11-26
NW Minnesota

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:
·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

garys_2k
Premium
join:2004-05-07
Farmington, MI
Reviews:
·Callcentric
·callwithus
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