Searching for a 30Volt Transformer

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Old 09-22-18, 06:53 PM
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Searching for a 30Volt Transformer

So I have a low voltage wiring system for most of my switches in "this old house." (A bit of a nightmare.) The OLD transformer blew I have been doing a bit of searching online I would like to buy the correct one.
All that is written on the old one is R or BT-1 Class 2 - 30 V.O.C. GE. It has a lead and a return plus two wing nut screws for the low voltage
Any help or advise would be grateful Thanks.
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Old 09-22-18, 07:31 PM
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I think this transformer would be a suitable replacement for yours. It states that it replaces RT-1 transformers:
https://www.kyleswitchplates.com/ge-...mer-115v-277v/

There are additional parts on this website for GE Low Voltage Lighting Systems as well.
https://www.kyleswitchplates.com/ge-...tage-lighting/
 
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Old 09-22-18, 08:39 PM
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The VA rating of a replacement transformer should be the same or higher than the combined VA of the connected load. If the VA rating isn't listed on the old transformer. a starting point is to measure the resistance of the total load being in the ON state at the same time . The amps (I) is calculated as volts/resistance for resistive loads (incandescent lights) . If the load is/are relays or a mix, the calculated value is less than the actual due to a phase shift between the voltage and current in a coil. Get a replacement transformer with double the calculated VA value should be OK. I would install a fuse holder and a fuse in the load line as a good insurance policy. Make sure the fuse and fuse holder are rated for 30 volts AC and the fuse amp rating the same as the amp rating of the replacement transformer. Good luck.
 
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Old 09-23-18, 06:46 AM
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I have not seen a transformer that states voltage as "V.O.C." Normally it would be VDC or VAC. I suspect the one that Austin posted would work fine.
 
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Old 09-23-18, 12:36 PM
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VOC is abbreviation for volts @ open circuit. My guess is in the early days of transformers, the secondary voltage reduced from the open circuit voltage as load increased due to losses in the magnetic core of the transformer. The manufacturer couldn't be charged with false advertising. Manufacturing methods available today allow minimizing magnetic losses so a VA rating is used.
 
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Old 09-23-18, 02:48 PM
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I've used Honeywell 24vAC 50va or 75va transformers to operate the GE switching system.
Most 24vAC transformers measure around 27-28voc.
 
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Old 09-25-18, 07:53 AM
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Powerstat Var Autotrans substitute for a transformer

Could I use a Powerstat Variable Auto-transformer ( temporarily) for a transformer till the replacement comes in . 120V 0-140 10 amp 1.4kva are the marking.
The one it would replace is a GE 120 to 30 v Rt-1 class 2 link from previous post below. not sure what the amps are. I am just trying to figure out if something else maybe shorted on the low voltage lines .

https://www.doityourself.com/forum/e...ansformer.html
 
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Old 09-25-18, 09:00 PM
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Like topic - threads combined.

NO....... you cannot use a Variac there as it is not isolated from the AC line.
 
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Old 10-01-18, 08:58 PM
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Originally Posted by PJmax View Post
I've used Honeywell 24vAC 50va or 75va transformers to operate the GE switching system.
Most 24vAC transformers measure around 27-28voc.
I found a Hampton Bay at HD that works fine thanks again PJ and everyone else !
You were right mine is reading 29 voc
 
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