The right relay

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lanceh5
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The right relay

Post by lanceh5 » Sun Dec 12, 2004 7:07 pm

I want to use a thermostat ( using 12 to 16 volts) as a switch to turn on a relay to operate a 110 volt 0.6 amp fan. Which of the following relays would be most reliable and trouble free?<p>
12 VDC, 3PST N.O. RELAY, 30 AMP
http://www.allelectronics.com/cgi-bin/c ... type=store<p>
9VDC 10 AMP RELAY, SPST N.O.
http://www.allelectronics.com/cgi-bin/c ... type=store<p>15 AMP SOLID STATE RELAY
http://www.allelectronics.com/cgi-bin/c ... type=store<p>RELAY,ENCL,SPDT (953-1C-12DM)
http://www.jameco.com/webapp/wcs/stores ... tId=121273

gerty
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Re: The right relay

Post by gerty » Sun Dec 12, 2004 11:03 pm

Except for the 9v (you stated 12 to 16v) they all look ok. Never tried a solid state relay on a motor before, I've used them on resistave loads mostly with a lot of success...

paulrevelcet
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Re: The right relay

Post by paulrevelcet » Mon Dec 13, 2004 3:47 am

I would think the solid state relay would last the longest with the proper diode protection, because it has no moving parts.

k7elp60
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Re: The right relay

Post by k7elp60 » Mon Dec 13, 2004 3:50 am

You didn't say what the voltage is that you are swithing with the thermostate. If it is AC then you need to use a AC relay. The other consideration is the contact rating of the thermostat. Generally the contact rating(amps) is adequate for most relays.
AC relays will work on DC, but DC relays will not work on AC. Relays like other componets have a dissipation rating in addition to the votage rating on the coil. This means that if the applied voltage is to great the relay may be damaged.
The DC coils are rated in max watts, while the AC coils are rated in max VA. Another factor is if the relay is enclosed or open frame.
I just checked the typical specs of both AC and DC relays @ 12 Volts. Both should be okey at up to 16 volts.
If the thermostat is switching DC any of the relays except the 9V should be okey.

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Externet
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Re: The right relay

Post by Externet » Mon Dec 13, 2004 8:07 am

Hi.
If you use an airconditioner/heater wall thermostat, you may not need the relay nor the 12 - 16 V. supply. Its contacts handle that current at 115V with no need for anything else.
Miguel
- Abolish the deciBel ! -

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philba
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Re: The right relay

Post by philba » Mon Dec 13, 2004 8:22 am

Check the thermostat to see if it is spec'd to handle AC. If so, bag the relay.<p>AC vs DC relays: this refers to the coil, not the contacts. A DC relay can switch AC - it doesn't care. Just make sure that the contacts are rated for the load you want. I would overspec the contacts by 2X for safety. Your load is pretty small.<p>You dont say what the duty cycle/usage is but if its 10 to 20 per day, a relay spec'd for 1 Million cycles will last, on average, for 50K days (136 years). If the relay you are looking at doesn't have this spec available, reject it. There are relays that are only spec'd for 100K operations which would be only 13.6 years, on average. I'm not sure what the distribution curve of failure is but it could fail as early as 1/2 the average.<p>Solid state relays are great but cost 3-4 times a mechanical equivalent. Benefits are not only life span but also no noise which is a great for equipment in a residential environment.

lanceh5
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Re: The right relay

Post by lanceh5 » Mon Dec 13, 2004 8:27 pm

I think this line voltage thermostat will work.<p>http://www.grainger.com/Grainger/produc ... 24&ccitem=<p>I have two fans to control which are on separate circuits so will need two thermostats. I don't think one of these thermostats could control two fans because of the two different circuits.

gerty
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Re: The right relay

Post by gerty » Mon Dec 13, 2004 8:39 pm

Maybe I missed it , but I didn't see the current rating. Since it's line voltage it should be ok.
With a line voltage thermostat you'll need suitable wire, did you run romex or low voltage thermostat wire? It is the easiest way to go..

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Edd
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Re: The right relay

Post by Edd » Mon Dec 13, 2004 9:41 pm

That units current spec is a hefty 22 amps ….as per:
http://www.grainger.com/Grainger/wwg/vi ... F.shtml?br owserCompatable=true&adobeCompatable=true&CatPage=3361 <p>Also they are touting their utilization for:
Electric Heat Line Voltage Thermostats<p>And do go further on in specifying:<p>Uses: Non-inductive electric heating loads;
electric infrared, heat cable, electric
baseboard, or radiant panels.<p>If you were contemplating using that thermo unit solely for full AC power switching:
In your case, the load on that unit is to be inductive, that reasoning would be uncertain, without further info on its internal switching components construction. My personal thought being that the switch mechanism is a very gradual
make/break movement with contact arc over being a distinct problem on induced back EMF in the case of an inductive load. A distinct quick snap action is needed to create a well spaced out contact gap when switching that type of load.<p>73's de Edd
[email protected] .........(Interstellar~~~~Warp~~~Speed)
[email protected].........(Firewalled-Spam*Cookies*Crumbs)
;) ;)<p>[ December 13, 2004: Message edited by: Edd Whatley ]</p>

lanceh5
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Re: The right relay

Post by lanceh5 » Wed Dec 15, 2004 8:57 pm

The relay spec is
******************
Thermostat,Linevoltage<p>Snap Action Thermostat, Type Heat/Cool, Control Range 50-90 Degrees Fahrenheit, Anticipation Range Heat (0.15 to 1.2 Amps Adjustable), Cool (Fixed), Switch Action SPDT, Switching Fan Auto/On, Height 3 3/4 Inches, Depth 1 5/8 Inches, Width 3 1/8 Inches, Color White, Application Gas, Oil, Electric,<p>Grainger Item: 4E036<p>Manufacturer: WHITE RODGERS<p>Mfg. Model#: 1A65-641
********************************<p>from this web site<p>http://www.grainger.com/Grainger/produc ... 24&ccitem=<p>So it is a snap action switch. It does not give an amp rating for cooling which it will be used for. <p>I will use 14 gage romex wire.

redrocker
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Re: The right relay

Post by redrocker » Thu Dec 16, 2004 3:14 am

lh, I think the "snap-action" description is incorrect. It directly contradicts the description on the catalog page referenced in the link by Edd. I went to White-Rogers website and looked at the installation instructions. The instructions have a prominent warning explicitly stating that this thermostat is not to be used for motors. Perhaps you could combine various suggestions made thus far, though it will not be inexpensive. Combine the Model# 1A65-641 White-Rogers thermostat you want with an AC activated relay such as the Jameco P/N 282247CR. It costs around $7 and has quick-disconnect terminals. Therefore your system will consist of two components and associated wiring.

Deal
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Re: The right relay

Post by Deal » Thu Dec 16, 2004 4:26 pm

I get the secret prize basket of cheze and apples. This guy wrote searching for a relay to carry a half amp fan load at 115 v. Forget all the grainger motor talk (actually you can learn alot from grainger catalog) this is a muffin fan. Yes EDD posted a good write, and we could all profit from some relay basics (most of it comes down to the size of the contacts that clack together to make the circuit -same as any switch)but at a half amp (yes 115v) there is probably not a relay made that won't work. Send my Frozen turkey soon, I'm starting to chatter

lanceh5
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Re: The right relay

Post by lanceh5 » Thu Dec 30, 2004 5:58 pm

This is just a status report. The dry wallers are not done yet and appears that this electronic part of the house will not be installed by me for a couple of months. The solution will be a cheap thermostat mounted near the ceiling operating two relays. <p>The relays I think will be used are listed in "All Electronics" catalog as Cat# SRLY-15. This is a solid state relay made by Continental Industries #RLDA-240/15-000. Input 3-32 Vdc output 15 amps @ 24--280 VAC. <p>My considerations for this are safety, longevity and maintenance free. Lots to do before I install these components. <p>Thanks for all the input and suggestions. <p>Happy new year from the Calif. high desert.

Hello
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Re: The right relay

Post by Hello » Fri Dec 31, 2004 4:26 am

I'd like to get us off on another tangent. This applies especially to mechanical relays switching 120 VAC loads. What about approaches to reducing the electrical noise (interference) generated when the relay is swithched on and off? I'm talking about the type of trash you see and hear on TV's and radios.

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Chris Smith
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Re: The right relay

Post by Chris Smith » Fri Dec 31, 2004 7:15 am

Caps and chokes usually filter out hash. <p>Apply them to the AC line, right at the points.

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