ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

Page 1 of 2 1 2 >
Topic Options
Rate This Topic
#69221 - 09/02/06 09:44 AM Very low duty cycle timer?
NJwirenut Offline
Member
Registered: 09/15/01
Posts: 806
Loc: Bergen County, NJ
Does anyone know of an inexpensive method of automatically turning on a small 120VAC load for a couple minutes once a week or so?

The application is an automatic water drain for an air compressor. I want to install a solenoid valve at the bottom of the tank, and turn it on once a week or so to drain out the accumulated water. The exact time of day that it actuates isn't important, and neither is the exact frequency of operation. A standard intermatic type time switch gives a minimum "ON" cycle time of 15 minutes, which is much longer than needed to blow out the water, and would waste a lot of air. I have seen digital programmable devices, but they seem like overkill for this application, with mulitple outputs and setpoints which I would never need. Time switches would also need to be reset after a power interruption, which is annoying. I am thinking of something like a time delay relay with a repeat cycle mode, but I don't know of any with such a long cycle time.

Yes, I know that there are automatic float type valves that are made just for this purpose, but we have tried several models, and they all failed shortly after installation. A solenoid valve/timer should be a lot more robust, since it isn't relying on floats which tend to bind up over time.

[This message has been edited by NJwirenut (edited 09-02-2006).]
Top
Work Gear for Electricians and the Trades
#69222 - 09/02/06 09:58 AM Re: Very low duty cycle timer?
Tiger Offline
Member
Registered: 05/04/05
Posts: 706
Loc: Crystal Lake, IL USA
Isn't there a small tank & pump used in HVAC to pump whatever drips out of furnace/a.c. units?

Dave
Top
#69223 - 09/02/06 10:17 AM Re: Very low duty cycle timer?
JCooper Offline
Member
Registered: 12/30/02
Posts: 228
Loc: Kendall Park, NJ USA
I think I know what you are looking for NJWirenut, my firehouse has the same thing on our compressor but it fires once every half hour or so for about a second. I will take a look at what is running it later today and post back.
Top
#69224 - 09/02/06 10:34 AM Re: Very low duty cycle timer?
circuit man Offline
Member
Registered: 11/05/01
Posts: 273
Loc: saluda,s.c.
harbor freight sells an automatic tank drainer that is hooked up through the unloader line on the pressure switch.it empties when it comes on & when it shuts down. works pretty good. has every thing ya need in the box.some of the supply houses should have these.
Top
#69225 - 09/02/06 11:45 AM Re: Very low duty cycle timer?
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
I have used these electric auto drains with good success.



They did not clog up in a very damp and dirty environment.

If you must build your own I know timers that will work but they are not inexpensive. $100 - $200.



[This message has been edited by iwire (edited 09-02-2006).]
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts
Top
#69226 - 09/02/06 01:57 PM Re: Very low duty cycle timer?
CharlieK Offline
Member
Registered: 03/10/03
Posts: 21
Loc: Baltimore. Md. U.S.A.
NJ. try a Intermatic C8855. It has an on renge of 21/2 seconds to 5 minutes every 24 hours and sells for about 100.00

Charlie
Top
#69227 - 09/02/06 03:46 PM Re: Very low duty cycle timer?
JoeTestingEngr Offline
Member
Registered: 11/04/05
Posts: 781
Loc: Chicago, Il.
NJ, If you follow your 24 Hr />=15 min timer with any of a number of "interval on" timers, your final result would be a shorter purge every day. You could fine tune the combination any way you wanted.
Joe
Top
#69228 - 09/03/06 07:26 AM Re: Very low duty cycle timer?
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
Joe brings up a good point about the timing.

A few seconds a day is IMO a better idea than once a week.

The electric one I posted above we might even set for 1 or 2 seconds per hour.

A quick PSSHHHHT every hour and the tank stays dry.
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts
Top
#69229 - 09/03/06 09:11 AM Re: Very low duty cycle timer?
Helectric Offline
Member
Registered: 01/07/05
Posts: 90
Loc: Brandon, SD
They make automatic drain valves for just this pupose. If you contact an air compressor supplier or visit their web site you should find one. Here's a link to one that is similar to those that I've used in the past. They're available in all voltages. The ones that I've used typically come equiped with a 110v cord.
http://www.generalairproducts.com/pages2/drainvlvs.html
Top
#69230 - 09/03/06 09:28 AM Re: Very low duty cycle timer?
NJwirenut Offline
Member
Registered: 09/15/01
Posts: 806
Loc: Bergen County, NJ
Looks like McMaster-Carr carries the one Iwire posted. Will probably order one of those.

Hopefully the electric setup will hold up better than the float type.

Thanks, all!
Top
Page 1 of 2 1 2 >

Member Spotlight
Member Since: 12/24/00
Posts: 4259
New in the Gallery:
SE cable question
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box


Who's Online
0 registered (), 46 Guests and 11 Spiders online.
Key: Admin, Global Mod, Mod
 
New in the Gallery:
SE cable question
 
Top Posters (30 Days)
Admin 47
HotLine1 43
gfretwell 19
Ruben Rocha 12
Trumpy 9
 
Newest Members
Scotto, Freecrowder, clee512, Jdscott2005, FAIZAN

ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals