How to Pick the Right Transformers and Fuses for Them

hey guys as you may see I'm in my pickup 
today because my van is in the shop so I'm   very limited in what it can do and I thought I 
would do a video I've been planning for some time   about Transformers and 
fuses the VA ratings on them and it's been a while since I've done a tech 
tips video so here we go with one okay guys let's   assume you're shopping for a Transformer you may 
have found one that's blown you'll notice on these   Transformers they all have a VA rating so what 
does the VA rating mean that is basically volts   times amps which is the same thing as wattage 
that's how many watts a Transformer can handle   and I'm gonna try to show a screen here that was 
a 40 that's a 40 VA Transformer so that means   40 watts is what it can handle so you take 
that 40 and you divide it by 24 we're assuming   24 is going to be your secondary 
voltage and that tells you how many   watts that Transformer can handle all right 
so here it is is 40 VA divided by 24 volts   that tells you that Transformer 
can only handle 1.67 amps so it's not meant for high amperage of any kind 
and in fact we often put a three amp fuse on these   that means between 1.67 amps and three there 
is space where that Transformer can burn up   but not blow the fuse in those instances you 
need a bigger Transformer like a 50 VA or a 75 VA   I have run across this where people have tried to 
run a zone system off the same Transformer that's   in the air handler and it don't work out it burns 
up the Transformer now a 50 VA divided by 24.


Can   handle 2.08 amps and I'm going to show a picture 
here of a 50 VA that has a 2.5 amp breaker on it once again there's a little bit of room right 
there where it could burn up the Transformer   and not trip that little bit that little breaker 
so the lower the fuse the better I have actually   seen some of them fused on the high voltage 
side which is something you should never do   you can fuse on the high voltage side but the 
fuse would have to be up to 10 times smaller   than the one that you need on a low voltage 
so always fuse on low voltage inside   now in more commercial equipment you might see a 
Transformer that reduces down to what's control   voltage it might be 120 volts you have 120 volt 
contactors and stuff like that on the equipment   it's the same thing they come in VA ratings 
in the actually the wattage rating on those   is for both the high side and the low side 
either side no matter how you hook it up the   VA rating is the same all right guys so 
I hope that was a little bit helpful and   helping you decide what size Transformer 
to get explaining what the VA rating means   and um maybe selecting the right size fuse 
for example if you're using 40 or 50 VA   you need to use the smallest one possible even 
a 2.5 is just a little bit too big for 50 VA   so if you up the fuse size from three to 
five that gives it more room to burn up   that Transformer before it blows the fuse 
alright guys I hope you enjoyed that little   video and I hope it was informative to some of 
the new guys if you like these kinds of videos   how about like And subscribe it really 
does help out I'll catch you on the next

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