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-   -   what VA TRANSFORMER DO I NEED (http://www.diychatroom.com/f18/what-va-transformer-do-i-need-91923/)

markadams 01-10-2011 06:43 PM

what VA TRANSFORMER DO I NEED
 
I have a boiler and dont want it to freeze up on me so i want to put an alarm system.when the tempp gets too low an alarm should go on. I have a Ranco ETC-111000-000 Digital Temperature Controller. So when the temp drops it will relay a signal to an alarm. However the Ranco is 120 volt and the alarm is 24v. So what kind of transformer do i need HOW many VA?

Here are the spec of the ranco controller:
pecifications:
Temperature Setpoint Range: -30 to 220F
Differential range: 1 to 30F
Input Voltage: 120VAC, 208, 240VAC
Pilot duty: 125VA at 120/208/240VAC
Sensor: Thermistor, 2" long x 1/4"dia with 8' cable (included)
Control Ambient Temperatures
Operating: -20 to 140
Storage: -40 to 176
Ambient humidity: 0 to 95% RH, non-condensing
Enclosure: NEMA 1
Dimensions: 6.52" high x 2.7" wide x 2.48" deep
Agency Approvals: UL listed, file E94419, Guide XAPX, CSA certified, file LR68340, class 4813 02

Relay Output Ratings - NO (NC)

120V
Full load amp 16 (5.8) A
Locked rotor amps 96 (34.8) A
Resistive amps 15 (5.8) A
Horsepower 1 (1/4) HP

http://www.etcsupply.com/ranco-etc11...ller-p-86.html

brric 01-10-2011 06:48 PM

What is the power requirement of the alarm?

As a side note why would a boiler be subject to freezing?

markadams 01-10-2011 06:53 PM

Specifications
Operating voltage: 6 - 14 VDC
Sound output: 105 dB @ 12 VDC
Current draw: 180 mA @ 12 VDC
Dimensions: 2.9 x 4.8 x 1.7
Color: Ivory body with red strobe
Material: UV-resistant, high impact polycarbonate plastic
Wiring: Red-positive, Black-common

markadams 01-10-2011 06:56 PM

Only reason it might freeze is if something fails like thermo coupler pump etc during the night. BOiler is outisde in greenhouse. get to -4 F down here. So if tsomething messes up it will freeze up quick


Specifications
Operating voltage: 6 - 14 VDC
Sound output: 105 dB @ 12 VDC
Current draw: 180 mA @ 12 VDC
Dimensions: 2.9” x 4.8” x 1.7”
Color: Ivory body with red strobe
Material: UV-resistant, high impact polycarbonate plastic
Wiring: Red-positive, Black-common

brric 01-10-2011 07:24 PM

You need a device cable of a minimum 180mA @ 12 VDC. A transformer alone will only provide AC.

3 legged dog 01-10-2011 07:50 PM

How about one of these

http://www.radioshack.com/product/in...uctId=3875403#

a7ecorsair 01-10-2011 10:27 PM

That AC adpt will work but how will you connect it to the controller? I read through the spec sheet and I only see an analog output of 0 to 10 vdc.

3 legged dog 01-10-2011 10:39 PM

The Ranco Tstat is line voltage. The relay output could be wired to a receptical or something like that.

a7ecorsair 01-11-2011 07:53 AM

This unit isn't part of the boiler system? Keep in mind the relay has no output but can be used to control voltage up to its rating. I guess I don't quite understand your project...

rjniles 01-11-2011 09:01 AM

It sounds like the temperature controller has a dry contact output. Most alarm systems will accept a contact closure. You should be able to interface them directly.


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