HVAC 24 volt transformer

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GG

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Why do some manufacturers of HVAC equipment ground one wire of the secondary on the 24 volt transformer while some leave both wires ungrounded?
 
I've not noticed. Are the ones you mention 240 volt primary ? If so, ans this is simply a "stab in the dark", but, since there are RARE situations listed in 250.20(A) where they would be required to have a grounded secondary and there is little if any reason not to, by grounding them all the required ones are avaialble.
 
GG said:
Why do some manufacturers of HVAC equipment ground one wire of the secondary on the 24 volt transformer while some leave both wires ungrounded?
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It was a design choice made by the engineers that designed the equipment.

On some machine tools the secondary was left ungrounded because the designers were afraid of stray currents.

If I need to troubleshoot equipment with an ungrounded secondary on the control transformer I carry jumpers with aligator clips and ground it for trouble-shooting purposes.

If you want you can call the manufacturer and check to see if they have a good reason for not gounding the secondary.
 
augie47 said:
I've not noticed. Are the ones you mention 240 volt primary ? If so, ans this is simply a "stab in the dark", but, since there are RARE situations listed in 250.20(A) where they would be required to have a grounded secondary and there is little if any reason not to, by grounding them all the required ones are avaialble.
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The one I saw with a grounded secondary was a 240 volt Trane air handler.
 
I agree that it's a manufacturers design choice. If one side of the secondary is grounded, only the other side needs fused. If both sides of the secondary are ungrounded, I believe both sides of the secondary need fused.

Therefore, I believe most manufacturers probably ground one side to eliminate one fuseholder and fuse.
 
steve66 said:
I agree that it's a manufacturers design choice. If one side of the secondary is grounded, only the other side needs fused. If both sides of the secondary are ungrounded, I believe both sides of the secondary need fused.

Therefore, I believe most manufacturers probably ground one side to eliminate one fuseholder and fuse.
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Actually very few ever fuse the seconday or primary. It is very smart to put an inline fuse on the secondary
 
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