Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 03-29-2012, 12:56 PM   #1
Member
 
Join Date: Oct 2011
Location: Alabama
Posts: 231
Share |
Default

Fan Relay Wiring, Purpose of #5 terminal???


Hello All,

I had to troubleshoot some issues with my air handler (defective sequencer) but have a general question in regards to the Relay. This is just FYI in trying to undertand what purpose the #5 terminal on a spdt fan relay serves, as I cannot figure it?


#1 (green) goes to the tstat and is used to energize the relay.
#3 (brown) goes to the Sequencer 24v terminal and supposed to serve as the common for the 24volt, as I understand.


#2 (black) is 120v direct from the breaker.
#4 (brown) is 120v and comes from the fan. It gets it's power from the other leg of the breaker, via capacitor. These two terminals are normally "open" to each other (no continuity). However, when the relay is energized they "close" (continuity) and thus supply 240v to the fan which starts it.


#5 (black) is designated as low speed fan heat. A wire runs from it to the top of the Sequencer on left side.

* When the system is idle it is normally closed (continuity) with the #4 terminal. You thus get a useless flow, nothing is being asked to occur, of 120volts from the fan up-to the left side of the Sequencer.

* When the system is energized (heat or cold) the #4 and #5 are then open (no continuity) between each other, because the #4 is then switched to the #2(which starts fan, as noted). The #5 then becomes a dead-end and again apparent useless terminal? If you turn on the heat, the sequencer will close, and you will get a reverse flow of 120v down-to the #5 terminal but again useless, as it is a dead end when the relay is energized?



Am I missing something or does the #5 terminal indeed serve a purpose?


Thanks
Attached Thumbnails
Fan Relay Wiring, Purpose of #5 terminal???-zzzzzzzzzzzz.jpg  


Last edited by Ralph III; 03-29-2012 at 01:05 PM.
Ralph III is offline   Reply With Quote
Old 03-29-2012, 04:26 PM   #2
AKA HVACTECHFW
 
Join Date: Nov 2010
Location: NE Indiana
Posts: 2,318
Blog Entries: 1
Default

Fan Relay Wiring, Purpose of #5 terminal???


it changes the blower speed.

__________________
IT IS WHAT IT IS
hvactech126 is offline   Reply With Quote
Old 03-29-2012, 07:13 PM   #3
Member
 
Houston204's Avatar
 
Join Date: Oct 2009
Location: Texas
Posts: 586
Default

Fan Relay Wiring, Purpose of #5 terminal???


It insures that the fan will become energized with a heating demand, even if you replace the stat and forget to configure the new stat to energize G (fan) on demand for W (heat).
Houston204 is offline   Reply With Quote
Old 03-29-2012, 08:34 PM   #4
Member
 
Join Date: Oct 2011
Location: Alabama
Posts: 231
Default

Fan Relay Wiring, Purpose of #5 terminal???


Quote:
Originally Posted by Houston204 View Post
It insures that the fan will become energized with a heating demand, even if you replace the stat and forget to configure the new stat to energize G (fan) on demand for W (heat).
Ok, that makes sense. So as long as everything is hooked up or working properly with the thermostat (g wire energizes fan) then it really only serves as a redundant feature.

That would be useful if the Relay ever froze in it's normally idle/closed position (#5, #4). With that type failure, the #2 and #4 couldn't close together in order to engage the fan as normal. Therefore, you could have an air handler heating up with no moving air. With the redundant feature it will be reversed energized from the Sequencer, through the #5, with a call for Heat. This helps insure you always have air flow with a call for Heat, which could avoid a possible fire hazard.

People think of everything....

God Bless

Last edited by Ralph III; 03-29-2012 at 08:57 PM.
Ralph III is offline   Reply With Quote
Old 03-30-2012, 09:53 PM   #5
Member
 
Houston204's Avatar
 
Join Date: Oct 2009
Location: Texas
Posts: 586
Default

Fan Relay Wiring, Purpose of #5 terminal???


Your G (fan) signal will open as soon as the call for heat ends but the heating elements will have a delay on break because of the sequencer. Wiring the fan to the sequencer will add this delay on break for the fan in heating mode, increasing efficiency and possibly extending the life of your heating elements.

Last edited by Houston204; 03-30-2012 at 09:59 PM.
Houston204 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Compressor terminal post wiring connector came apart - remnant still sticking to post justplumducky HVAC 11 07-06-2011 08:04 PM
electric wiring in house remodel wis_remod Electrical 6 04-02-2009 02:40 PM
Electric wiring AMPIN88 Electrical 1 02-21-2009 10:31 PM
New Home Wiring - Seeking Expert Advice Dirtrnr Electrical 3 02-10-2009 10:33 AM
Knob & Tube wiring - How concerned should we be? hotdiggitydog Electrical 6 04-11-2006 07:52 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.