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 04-24-2009, 01:18 PM   #1
C44
Just trying to be frugal
 
Join Date: Mar 2009
Posts: 16
Share |
Question

Brainstorming help on controls


Please help me make a list of all the ways to do this: I want to control a damper on my system based on pressure in ductwork. Simple "on" and "off" is fine if the trigger pressure is adjustable.

Background: A 2-stage AC system, where I want to consider a fresh air vent to the return plenum which can only open in 1st stage. When the system is in 2nd stage it is working harder to meet temperature setpoint and I see no sense in feeding it outside air and making its job harder.

Ideas for non-electric ways to control a damper would be particularly welcome. I know there are electrical signals that could get the job done, am looking for all the possible ways. Perhaps someone makes a pneumatic bellows that can move a damper control arm?

Thanks for any ideas -- C44

C44 is offline   Reply With Quote
Old 04-24-2009, 02:18 PM   #2
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Default

Brainstorming help on controls


Quote:
Originally Posted by C44 View Post
Ideas for non-electric ways to control a damper would be particularly welcome.
What are your pressures, forces and stroke lengths? How fast does it have to respond?
It may not be possible to do this unless you can use an air pump.

Yoyizit is offline   Reply With Quote
Old 04-24-2009, 02:34 PM   #3
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 24,371
Default

Brainstorming help on controls


One way.

Use a barometric damper(like the kind used for zone systems), and install it backwards.

Set the weight that it takes more pressure then first stage air flow to close it.

Drawback. It will also be open when the system is not running.
beenthere is offline   Reply With Quote
Old 04-24-2009, 02:53 PM   #4
C44
Just trying to be frugal
 
Join Date: Mar 2009
Posts: 16
Default

Brainstorming help on controls


Quote:
Originally Posted by Yoyizit View Post
What are your pressures, forces and stroke lengths? How fast does it have to respond?
It may not be possible to do this unless you can use an air pump.
I will answer what I can. Vacuum in the return plenum is expected to be about 0.15 inch w.c. in low stage, and about 0.30 in high. If it responds in less than 1 minute that is fast enough.

Could you clarify what you said about an air pump?

-- C44
C44 is offline   Reply With Quote
Old 04-24-2009, 03:45 PM   #5
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Default

Brainstorming help on controls


Quote:
Originally Posted by C44 View Post
Could you clarify what you said about an air pump?
The system would not be elec., only pneumatic, but it might need an air pump that does run elec.

You maybe can have the damper powered by pressure differences as long as you don't try to get more energy/power out than goes in, or you have the ductwork pressure control an air pump that drives the damper.
Yoyizit is offline   Reply With Quote
Old 04-24-2009, 03:51 PM   #6
Member
 
newtech's Avatar
 
Join Date: Mar 2009
Posts: 245
Default

Brainstorming help on controls


Quote:
Originally Posted by C44 View Post
I will answer what I can. Vacuum in the return plenum is expected to be about 0.15 inch w.c. in low stage, and about 0.30 in high. If it responds in less than 1 minute that is fast enough.

Could you clarify what you said about an air pump?
I think he ment air compressor. To move a pneumatic control you need air pressure. You can have a n/o, n/c, d/a, or r/a control. The air pressure will either open or close it.
-- C44
Just my 2c
newtech is offline   Reply With Quote
Old 04-24-2009, 10:20 PM   #7
C44
Just trying to be frugal
 
Join Date: Mar 2009
Posts: 16
Exclamation

Brainstorming help on controls


Quote:
Originally Posted by C44 View Post
I will answer what I can. Vacuum in the return plenum is expected to be about 0.15 inch w.c. in low stage, and about 0.30 in high. If it responds in less than 1 minute that is fast enough.

Could you clarify what you said about an air pump?

-- C44
FWIW I have far less return vacuum than I had thought, in low stage. Just measured it as 0.06 inch w.c.
High stage is the same 0.30 as stated before.

Probably does not change the thread much, but wanted it to be correct.

Regards -- C44
C44 is offline   Reply With Quote
Old 04-25-2009, 08:38 AM   #8
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Default

Brainstorming help on controls


Quote:
Originally Posted by C44 View Post
FWIW I have far less return vacuum than I had thought, in low stage. Just measured it as 0.06 inch w.c.
High stage is the same 0.30 as stated before.

Probably does not change the thread much, but wanted it to be correct.

Regards -- C44
1" WC = .04 PSI, so 0.3" gives you .01 PSI. If your damper takes 1 pound to operate you'd need a diaphragm or piston with a surface area of 100 sq. in.
http://www.onlineconversion.com/pressure.htm
I'm not sure anyone makes this bulky gadget for this purpose.
Yoyizit is offline   Reply With Quote
Old 04-27-2009, 07:31 AM   #9
C44
Just trying to be frugal
 
Join Date: Mar 2009
Posts: 16
Lightbulb

Brainstorming help on controls


Quote:
Originally Posted by beenthere View Post
One way.

Use a barometric damper(like the kind used for zone systems), and install it backwards.

Set the weight that it takes more pressure then first stage air flow to close it.

Drawback. It will also be open when the system is not running.

This sounds simple and elegant. However I am only vaguely familiar with the device. Would it be possible for you to post a link to a good example of this kind of barometric damper?

I did try to search the web and what I found were for wood stoves and those seem to me for a different application.

Thanks very much -- C44
C44 is offline   Reply With Quote
Old 04-27-2009, 08:12 AM   #10
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 24,371
Default

Brainstorming help on controls


Look at the PRD-RD

Here
beenthere is offline   Reply With Quote
Old 04-27-2009, 08:55 AM   #11
C44
Just trying to be frugal
 
Join Date: Mar 2009
Posts: 16
Default

Brainstorming help on controls


Thank you, that is a big help. The wood stove barometric dampers are entirely different!
C44 is offline   Reply With Quote
Old 04-28-2009, 05:38 PM   #12
C44
Just trying to be frugal
 
Join Date: Mar 2009
Posts: 16
Default

Brainstorming help on controls


I appreciate all the ideas. Now I have thought a little more about the application, which is a fresh air (FA) intake on a 2-stage air conditioner. There might not be a *mechanical* way to shut off the FA intake during heating hours, and I don't think FA will be necessary or desirable when heating. So an electric damper may turn out the best way after all.

All you guys in places with 4 actual seasons, could simply make a change at the beginning and end of winter and that would be OK. In Texas we don't have 4 seasons, more like 2 or 2-1/2. Our winter comes and goes, often with air conditioning needs in the same months.

Thanks for all the help! -- C44

C44 is offline   Reply With Quote
Reply

Tags
air, condition, control, damper, fresh air


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
Humdifiers and Controls Rookietinner HVAC 1 03-12-2009 05:53 PM
Shower controls ctsmiths Plumbing 7 02-16-2009 04:12 PM
SP-30 Goldline controls cszimmer HVAC 1 03-15-2005 08:52 PM




Top of Page | View New Posts

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