X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 29 Mar 2013 10:00:20 -0400 Message-ID: X-Original-Return-Path: Received: from imr-mb02.mx.aol.com ([64.12.207.163] verified) by logan.com (CommuniGate Pro SMTP 6.0.4) with ESMTP id 6170157 for lml@lancaironline.net; Thu, 28 Mar 2013 21:51:48 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.207.163; envelope-from=cavittp@aol.com Received: from mtaout-da01.r1000.mx.aol.com (mtaout-da01.r1000.mx.aol.com [172.29.51.129]) by imr-mb02.mx.aol.com (Outbound Mail Relay) with ESMTP id 590B138000098 for ; Thu, 28 Mar 2013 21:51:14 -0400 (EDT) Received: from [172.20.3.143] (rrcs-24-43-220-66.west.biz.rr.com [24.43.220.66]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by mtaout-da01.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPSA id A5F6FE0000CC; Thu, 28 Mar 2013 21:51:13 -0400 (EDT) References: Mime-Version: 1.0 (1.0) In-Reply-To: Content-Type: multipart/alternative; boundary=Apple-Mail-052A5FDC-B3FB-47C8-9F14-4AB8A81675B1 Content-Transfer-Encoding: 7bit X-Original-Message-Id: <85A6D99D-A801-40D8-8A72-03DAC8072C03@aol.com> X-Original-Cc: "lml@lancaironline.net" X-Mailer: iPhone Mail (10B329) From: CavittP Subject: Re: [LML] Re: Hydraulic gear pump failure - Relays X-Original-Date: Thu, 28 Mar 2013 15:51:13 -1000 X-Original-To: Lancair Mailing List x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:353518368:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d33815154f39137dc X-AOL-IP: 24.43.220.66 --Apple-Mail-052A5FDC-B3FB-47C8-9F14-4AB8A81675B1 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable I used continuous duty relays (metal not plastic) that are of the same type a= s used on battery master switch applications. No problems after 15-years a= nd over 1700 hours. Pete Cavitt - N320PL +1-619-701-0784 Cell www.petecavitt.com On Mar 28, 2013, at 8:12, Sky2high@aol.com wrote: > Bill, et al, > =20 > Relays should have a diode reverse connected across the coil to stop the v= oltage surge generated by the field collapse when power is removed from the c= oil. This will help protect the pressure switch contacts. > =20 > Grayhawk > =20 > In a message dated 3/28/2013 12:58:55 P.M. Central Daylight Time, super_ch= ipmunk@roadrunner.com writes: > Would there be any drawback to using a higher- rated contactor? I found t= he Lancair part to be a P.O.S.- it was marked continuous duty but when put o= n a power supply it rapidly overheated and shorted to the case. > =20 > Instead I=E2=80=99m using an antique 50A Leach B-5B aircraft style that ea= sily operated for hours. The pump supplied with my IV-P draws a maximum of 5= 0A, so the Leach might be marginal but I think I=E2=80=99ll try it initially= . > =20 > On Colin=E2=80=99s recommendation I also purchased a TYCO LEV100A5ANH , ra= ted 100A that I could use instead, or elsewhere. The Leach draws 0.16A, the T= YCO draws 0.25A at 28V. The Lancair- supplied Suco pressure switch is rated f= or 4A as best I can determine so either unit should be compatible. > =20 > I don=E2=80=99t know what other models might use but consider the contac= ts inside the pressure switches. If they should get overloaded and weld clos= ed the effect would be the same as welding the relay points. -Bill Wade > =20 > From: Gary Casey > Sent: Thursday, March 28, 2013 9:36 AM > To: lml@lancaironline.net > Subject: [Norton AntiSpam][LML] Re: Hydraulic gear pump failure - Relays > =20 > Pardon me if I'm jumping into a discussion a little late (and a dollar sho= rt), but there might be some confusion on how and why relays are designed fo= r intermittent duty. As an example, take a standard master relay. It is ra= ted for continuous duty and something like 80 amps. That means the coil won= 't overheat if left on forever and that the contacts also won't overheat whe= n passing 80 amps and that the contacts won't weld when interrupting 80 amps= . It is often the limitations when opening the circuit that determines the r= ating. Current will try to keep flowing and if the contacts don't separate r= apidly and with enough force the inevitable arc could create enough heat to w= eld the contacts and prevent opening. If it is desired to design a relay in= the same package (for cost, size and weight reasons) that can be used inter= mittently to pass a much higher current the design parameters are different.= More force is required to increase the rate at which the contacts are open= ed so a higher force spring is installed. Then more force is required to cl= ose the contacts, so fewer turns of heavier wire are used in the coil (that'= s right, FEWER turns, but that's another discussion). The result is that th= e relay can now successfully switch maybe 300 amps, but the coil will overhe= at after a few minutes of operation. That's the difference between a master= and a starter relay. And I have never, ever heard of using a relay as the "= weak link" in the system. > Gary > ps: My Lancair list emails now come all messed up (see below). Why is th= at? Am I doing something wrong? > =20 > The only caveat with that fix, Fred, is that intermittent relays are ther=3D= > e > for a purpose. They are supposed to be the weak link in a circuit where =3D= > a > continuous stuck relay could result in greater problems than a failure.=3D= 20 > Does that protective function matter in this circuit?=3D0D > Should be considered.=3D0D > John=3D0D --Apple-Mail-052A5FDC-B3FB-47C8-9F14-4AB8A81675B1 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
I used continuous duty relays (metal n= ot plastic) that are of the same type as used on battery master switch appli= cations.   No problems after 15-years and over 1700 hours.

Pete C= avitt - N320PL
+1-619-701-0784 Cell

On Mar 28, 2013, at 8= :12, Sky2high@aol.com wrote:

=
Bill, et al,
 
Relays should have a diode reverse connected across the coil to stop th= e=20 voltage surge generated by the field collapse when power is removed fro= m=20 the coil.  This will help protect the pressure switch contacts.
 
Grayhawk
 
In a message dated 3/28/2013 12:58:55 P.M. Central Daylight Time,=20 super_chipmunk@roadrunner.c= om writes:
  Would there be any drawback to using a higher- rated contactor= ? I=20 found the Lancair part to be a P.O.S.- it was marked continuous duty but w= hen=20 put on a power supply it rapidly overheated and shorted to the case.
=
 
Instead I=E2=80=99m using an antique 50A Leach B-5B aircraft style th= at easily=20 operated for hours. The pump supplied with my IV-P draws a maximum of 50A,= so=20 the Leach might be marginal but I think I=E2=80=99ll try it initially.
 
On Colin=E2=80=99s recommendation I also purchased a TYCO LEV100A5ANH= , rated=20 100A that I could use instead, or elsewhere. The Leach draws 0.16A, the TY= CO=20 draws 0.25A at 28V. The Lancair- supplied Suco pressure switch is rated fo= r 4A=20 as best I can determine so either unit should be compatible.
 
  I don=E2=80=99t know what other models might use but consider t= he contacts=20 inside the pressure switches. If they should get overloaded and weld close= d=20 the effect would be the same as welding the relay points.  -Bill=20 Wade
 
Sent: Thursday, March 28, 2013 9:36 AM
Subject: [Norton AntiSpam][LML] Re: Hydraulic gear pump failur= e -=20 Relays
 
Pardon me if I'm jumping into a discussion a little late (and a dolla= r=20 short), but there might be some confusion on how and why relays are design= ed=20 for intermittent duty.  As an example, take a standard master=20 relay.  It is rated for continuous duty and something like 80 amps.&n= bsp;=20 That means the coil won't overheat if left on forever and that the contact= s=20 also won't overheat when passing 80 amps and that the contacts won't weld w= hen=20 interrupting 80 amps.  It is often the limitations when opening the=20= circuit that determines the rating.  Current will try to keep flowing= and=20 if the contacts don't separate rapidly and with enough force the inevitabl= e=20 arc could create enough heat to weld the contacts and prevent opening.&nbs= p;=20 If it is desired to design a relay in the same package (for cost, size and= =20 weight reasons) that can be used intermittently to pass a much higher curr= ent=20 the design parameters are different.  More force is required to incre= ase=20 the rate at which the contacts are opened so a higher force spring is=20 installed.  Then more force is required to close the contacts, so few= er=20 turns of heavier wire are used in the coil (that's right, FEWER turns, but= =20 that's another discussion).  The result is that the relay can now=20 successfully switch maybe 300 amps, but the coil will overheat after a few= =20 minutes of operation.  That's the difference between a master and a=20= starter relay.  And I have never, ever heard of using a relay as the=20= "weak link" in the system.
Gary
ps:  My Lancair list emails now come all messed up (see=20 below).  Why is that?  Am I doing something wrong?
 
The=20 only caveat with that fix, Fred, is that intermittent relays are=20 ther=3D
e
for=20 a purpose.  They are supposed to be the weak link in a circuit where=20= =3D
a
continuous=20 stuck relay could result in greater problems than a failure.=3D20Does=20 that protective function matter in this circuit?=3D0D
Should=20 be  considered.=3D0D
Jo= hn=3D0D
<= /div>
= --Apple-Mail-052A5FDC-B3FB-47C8-9F14-4AB8A81675B1--