# Louver control for dryers using multiple circuits



## mpcxl (Dec 9, 2015)

My question is how would you all wire 8 different dryers to control one louver /damper for air flow?

I will be coming off fan relay in dryer @120V to control another relay to turn damper motor on

Will I have to use 8 different relays to prevent crossing phases or is there simplified way to do this? 

Thanks in advance


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## Wirenuting (Sep 12, 2010)

Are the contacts dry?
If so then they are wired in parallel with a separate power source that operates the louver’s.

We have done many units were the exhaust from the dryer bank dump into a common duct with a heat sensor that opens the louvers and starts an exhaust fan.
It keeps from having an extra pair of control wires entering the dryer. Easier dryer swap out.


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## mpcxl (Dec 9, 2015)

Wirenuting said:


> Are the contacts dry?
> If so then they are wired in parallel with a separate power source that operates the louverâ€™️s.
> 
> We have done many units were the exhaust from the dryer bank dump into a common duct with a heat sensor that opens the louvers and starts an exhaust fan.


Yes. I need to know how to do this. 

Will I need a 24VDC relay wired in parallel with all contacts to trigger louver motor?

Sorry. Just trying understand when you say “dry contacts “


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## CoolWill (Jan 5, 2019)

If each dryer has a relay, parallel the dryer relays to the louver control onba single control Circuit.


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## Wirenuting (Sep 12, 2010)

mpcxl said:


> Yes. I need to know how to do this.
> 
> Will I need a 24VDC relay wired in parallel with all contacts to trigger louver motor?
> 
> Sorry. Just trying understand when you say “dry contacts “


A dry set of contacts has no internal power. The relay coil only moves the contacts open or closed. Ie: a cube relay.

What kind of dryers are these? Industrial, commercial, crappy cheap HO ones?

I thought you wrote that you were coming off a relay inside the dryer. I assumed it was one already provided by the mfg.


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## joe-nwt (Mar 28, 2019)

Check the fan relay. There may be an unused set of N.O. AUX contacts you could use. Wire in parallel to operate the damper.


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## mpcxl (Dec 9, 2015)

joe-nwt said:


> Check the fan relay. There may be an unused set of N.O. AUX contacts you could use. Wire in parallel to operate the damper.


This

My plan is to come off motor or fan contactor to an external cube relay to trigger damper motor

I’ll just use motor power for control circuit and coil circuit. 

I received this email from service:

“Factory recommendation: The blower motor contactor has a spare NC contact that can be used inverse to provide a signal for the louver. This can only be used as a signal, all power for louver control must be external and dedicated.”

Why they recommend NC is unclear.


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## JRaef (Mar 23, 2009)

mpcxl said:


> This
> 
> My plan is to come off motor or fan contactor to an external cube relay to trigger damper motor
> 
> ...


I don't read that as they RECOMMEND using the NC contact, just that there IS a spare NC contact. There is likely also an NO contact, but they are already using that.


If it were me, I would look at the make and model of the starter and just buy another NO aux contact for it.


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## mpcxl (Dec 9, 2015)

JRaef said:


> mpcxl said:
> 
> 
> > This
> ...


Yes

I’m going to need NO contacts having multiple dryers hooked up. NC will not work correctly.


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## micromind (Aug 11, 2007)

If NC is all that's available, you can invert the contact with a relay with an NC contact. The NC contact in the machine will energize the relay coil which will make its NC contact NO.


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## mpcxl (Dec 9, 2015)

micromind said:


> If NC is all that's available, you can invert the contact with a relay with an NC contact. The NC contact in the machine will energize the relay coil which will make its NC contact NO.


Yes

But with multiple dryers, all dryers would have to be running before the relay will “open up” or reverse

I’m looking to see if there are available NO contacts or possible add one to the existing module. 

I won’t know until tomorrow when I get pictures. Unfortunately , the drive is too far to take a look. I need all the right materials before I go down.


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## gpop (May 14, 2018)

N/C is fail safe

8 dryers all wired in series N/C any one of them starts you have a open circuit. 

One relay and your done. (if the dampener is set up to open when the the switch is open you will not require the relay)


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## mpcxl (Dec 9, 2015)

gpop said:


> N/C is fail safe
> 
> 8 dryers all wired in series N/C any one of them starts you have a open circuit.
> 
> One relay and your done. (if the dampener is set up to open when the the switch is open you will not require the relay)


If possible, can you draw this out for me right quick?

Sorry for ignorance. I’m still learning new tricks


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## dronai (Apr 11, 2011)

JReaf said it, buy an Aux for the existing starter


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## mpcxl (Dec 9, 2015)

dronai said:


> JReaf said it, buy an Aux for the existing starter


I’m really diggin this idea by gpop. But first I need to wrap my head around it.


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## dronai (Apr 11, 2011)

The dryers I've worked with, were for Large Air compressors to lose the moisture, what are these used on ?


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## CoolWill (Jan 5, 2019)

mpcxl said:


> If possible, can you draw this out for me right quick?
> 
> Sorry for ignorance. I’m still learning new tricks


Just think. A relay is added and held energized by voltage that goes through each of the dryer N/C contacts. One after the other. If any dryer starts, the contact opens breaking the entire circuit and de-energizing the added relay. The dampers are controlled by the added relay.


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## mpcxl (Dec 9, 2015)

CoolWill said:


> mpcxl said:
> 
> 
> > If possible, can you draw this out for me right quick?
> ...


Love it. Thank you


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## mpcxl (Dec 9, 2015)

dronai said:


> The dryers I've worked with, were for Large Air compressors to lose the moisture, what are these used on ?


Literally , commercial gas dryers for clothing/ fabrics/ bed sheets


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## micromind (Aug 11, 2007)

mpcxl said:


> Yes
> 
> But with multiple dryers, all dryers would have to be running before the relay will “open up” or reverse
> 
> ...


Connect the relay NC contacts in parallel. If one or more of them changes state, you'll have a closed circuit.


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## micromind (Aug 11, 2007)

dronai said:


> JReaf said it, buy an Aux for the existing starter


This would be the easiest by far but might not be possible.


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## paulengr (Oct 8, 2017)

micromind said:


> Connect the relay NC contacts in parallel. If one or more of them changes state, you'll have a closed circuit.



Missed it on this one. For shame you’re very good with controls.

With NO contacts when a contact closes it closes the circuit. So if you want to trigger off multiples, just wire them in parallel. This is the preferred way to do it because losing power also means everything stops. Think about how you wire multiple start buttons in parallel...same concept. But it sounds like the NO contacts are used up.

With N.C. contacts it triggers to open (break the circuit). This is exactly like most Stop buttons or E-Stops. So just like stop buttons, interlocks, etc., wire them in series if you want them all to work together where any one triggers an action.

However with the NO contacts we get power (complete the circuit) when any input triggers. With N.C. contacts we lose power if any input triggers. See it’s backwards if we want to energize to open louvers.

No problem. Just wire the input to a relay and use the correct set of contacts. If we use NO contacts it just follows what the input does. This is useful if we need to use more current or different voltages. If we use the N.C. contacts the output does the opposite. So if the input is on the output is off and vice versa.

In terms of relay logic, contacts in parallel is a wired “OR”. Contacts in series is a wired “AND”. NO contacts on a relay is a buffer. The N.C. contacts is an inverter or “NOT”. That’s why it’s called relay logic. This is how we did everything before PLCs and computers came along


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## micromind (Aug 11, 2007)

The NC relay contacts are held open by the NC contacts on the motor starters. 

I guess stating that the relay NC contacts are now NO would have been better.......


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## gpop (May 14, 2018)

mpcxl said:


> If possible, can you draw this out for me right quick?
> 
> Sorry for ignorance. I’m still learning new tricks


If you have a 24vac transformer and a 8 pin tube based relay (24vac) with standard base.

Transformer x2 to fuse holder to dryer 1 n/c contact
dryer 1 n/c contact to dryer 2 n/c contact
dryer 2 n/c to ..........

dryer 8 n/c to relay base pin 7 
relay base pin 2 to transformer x1

If the louver has built in power supply connect open switch to pins 4 and common to pin 1

If louver requires 24vac power connect common to transformer x1 then connect other side of the transformer x2 to relay pin 1 then pin 4 to the louver motor.

most of us will ground one side of the transformer secondary as it makes troubleshooting easier. (ground x1 in this example)


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## Wirenuting (Sep 12, 2010)

Don’t use power from any of the dryers for control power to your louvers.
Use a separate power source to control and operate the louvers. 

If you don’t the louvers won’t open “WHEN” that dryer fails.


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## dronai (Apr 11, 2011)

....


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## dronai (Apr 11, 2011)

Out of the *NC* contacts from the fan starter with your own power source, 24V signal circuit to another relay that would be energized, until the dryer starts, use the *NO* contacts for the louvers. These contacts close when the new relay is de-energized, or use a latching relay. Parallel the rest


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## dronai (Apr 11, 2011)

Wirenuting said:


> Are the contacts dry?
> If so then they are wired in parallel with a separate power source that operates the louver’s.
> 
> We have done many units were the exhaust from the dryer bank dump into a *common duct with a heat sensor that opens the louvers and starts an exhaust fan.*
> It keeps from having an extra pair of control wires entering the dryer. Easier dryer swap out.


This


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## dronai (Apr 11, 2011)

EditUse the normally closed contacts on the last relay, that way when the circuit D energizes , It turns on your motor


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## mpcxl (Dec 9, 2015)

Thanks y’all. Def learned a lot on this one. Makes sense now


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## joe-nwt (Mar 28, 2019)

gpop said:


> If you have a 24vac transformer and a 8 pin tube based relay (24vac) with standard base.
> 
> Transformer x2 to fuse holder to dryer 1 n/c contact
> dryer 1 n/c contact to dryer 2 n/c contact
> ...


Why use a 24V transformer? So you have more parts to fail/replace in the future? Use 120V.


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## gpop (May 14, 2018)

joe-nwt said:


> Why use a 24V transformer? So you have more parts to fail/replace in the future? Use 120V.


safety

When the dryer is unplugged for service work the louver power supply will still be live from a different source. Im to lazy to make warning labels when a 24v door bell transformer is less than 20 bucks


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## paulengr (Oct 8, 2017)

gpop said:


> safety
> 
> 
> 
> When the dryer is unplugged for service work the louver power supply will still be live from a different source. Im to lazy to make warning labels when a 24v door bell transformer is less than 20 bucks



You ALWAYS assume external connections to dry contacts are energized until proven otherwise. Especially on old 1960s or earlier stuff that used 480 V control power!


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