Relay for boost pump

[gear1]

What relay(s) are in use for the fuel boost pump and smoke pumps? Where have you been sourcing them?
Thanks!

[cfiidon]

Check the specs for current rating on your switches and then for the pumps. I believe you will find that relays are not necessary.

Don

[vlittle]

Originally Posted by cfiidon

Check the specs for current rating on your switches and then for the pumps. I believe you will find that relays are not necessary.

Don

An AFP fuel pump is rated for 5A, with a 10A breaker (for surge). A regular toggle switch rated for 15A should be fine, if it is well made.

I have experience many switch failures (Carling Switch) due to poor construction of the riveted terminals. I would suggest using a higher quality supplier.

In my HR-II I eliminated most switches that carried more than a couple of amps of current and used relays to switch the loads. The one switch failure I had in the Rocket was (the only) Carling switch I used for a master switch (progressive transfer). It's being replaced with a $35 Honeywell switch.

Switches carrying moderate to high currents that are subject to vibration may develop loose terminals and subsequent corrosion. These terminals are riveted in place with the Carlings using hollow rivets. Honeywell uses solid rivets which are more secure.

The worst loads are Landing lights, gas-discharge Strobe power supplies and motors (pumps). All three of these loads increase their current as voltage drops, which stresses the switches and contacts.

Look at automobiles.. there are almost no switches carrying load current anymore. They directly control relays (electronic or electromechanical) using relatively low currents. Saves weight in switches and wiring and increases reliability. Of course, many loads are now controlled by a computer... like the Vertical Power systems have done.

So, I like using relays to control most loads. Adds a bit of complexity, but pays off in reliability.

[gear1]

Thanks, Don and Vern.
I did check out the ratings for my Infinity stick switches. They are rated at 6 amps, just enough to power the fuel boost and smoke pumps. However, it would appear that switch life may be shortened a bit because of utilizing the switches to their maximum.

[WingsOnWheels]

Originally Posted by gear1

Thanks, Don and Vern.
I did check out the ratings for my Infinity stick switches. They are rated at 6 amps, just enough to power the fuel boost and smoke pumps. However, it would appear that switch life may be shortened a bit because of utilizing the switches to their maximum.

I would double check that rating. Just because it says 6 amps does not mean A) 6amps at 14v, B) 6 amps inductive load. higher-end switches usually have a data sheet available with all those separate load limits identified. I don't know what switches infinity uses, but most likely that rating is not at 14v DC. If you are putting the boost pump switch on the stick, I would use a relay for sure.

[N427EF]

I would not use the switch on your stick to run the boost pump or anything rated for more than an amp or two.
What has been said is correct in that panel installed switches are generally used for boost pump,landing lights and such.
If you plan on using the functions on your stick grip I would definitely use a relay. One of these will do nicely.

http://www.radioshack.com/product/in...ductId=3020762

You can find one of these relays in any automotive store with many different configurations to suit your need and most of these are rated at 20amps for thousands of cycles. Van even sells these for use in the RV10 door safety switch.

[WingsOnWheels]

Some more information:

Unless otherwise noted, most switch ratings are for resistive loads. Inductive loads (like a motor) require that the switch be derated from it resistive load capacity.

AC43-13 provides derating factors in table 11-4

NOTES:
1. To find the nominal rating of a switch required to operate
a given device, multiply the continuous current rating
of the device by the derating factor corresponding
to the voltage and type of load.

2. To find the continuous rating that a switch of a
given nominal rating will handle efficiently,
divide the switch nominal rating by the derating
factor corresponding to the voltage and type of load.

12 VDC Motor derating factor - 2

[vlittle]

I prefer the relays with an integrated snubbing resistor or diode, for example:

http://www.digikey.com/product-detai...B681-ND/807758



For me, the resistor is better because you can wire the coil up in either polarity. The internal diode ones are polarity sensitive.

This saves wiring in an external component. Relay sockets are also available.



Cheers,

[gear1]

Don, Vern, Ernst and Colin,

Thank you all for your input. I now know far more than I did a couple of days ago! Relays for pumps it is!

[GalinHdz]

Originally Posted by vlittle

I prefer the relays with an integrated snubbing resistor or diode, for example:

http://www.digikey.com/product-detai...B681-ND/807758



For me, the resistor is better because you can wire the coil up in either polarity. The internal diode ones are polarity sensitive.

This saves wiring in an external component. Relay sockets are also available.

Cheers,

I use a similar relay from the local Auto Suppy (Pep Boys, Advance Auto, Autozone) for anything above 5A. The relay socket, if you decide to use one, is about twice the cost of the relay.