transformer?

Status
Not open for further replies.
jute

jute

Senior Member
Location
SO CAL
View attachment 2169
I was called on a troubleshooting call for a storage complex, This complex has (8) buildings and each building is fed from it's own subpanel located at the end of the building. I took voltage readings on all buildings and all checked within the range of 118v to 119.6v except for one which read 150v coming into the the panel. There is a Acme transformer in line with this panel also. the catalog # is T-1-13075, primary 120/240, secondary 16x32. could this have anything to do with the 150v I'm reading?? Thanks, JB

sorry so vauge... any suggestions??
 
jute said:
View attachment 2169 could this have anything to do with the 150v I'm reading?? Thanks, JB
Click to expand...


Yes it could, Did you get a line to line voltage reading ?
If it is a line to line reading it could be a loose neutral or connection.
If it is a line to neutral phase , then that's a different story.
 
Last edited:
View attachment 2170

Yes it could, Did you get a line to line voltage reading ?
If it is a line to line reading it could be a loose neutral or connection.
If it is a line to neutral phase , then that's a different story

Thanks for the quick response... This is the panel in question, from the line to nuetral coming into the panel there is 150v. I also took readings from line ot neutral from the load side of the breakers and all are 150v. I then checked breakers and all are on the same phase. Thanks, JB
 
That is a buck/boost transformer.
Is this for the farthest building? to help with voltage drop?
What was the load on the panel when you took your measurements?
 
wasasparky said:
That is a buck/boost transformer.
Is this for the farthest building? to help with voltage drop?
What was the load on the panel when you took your measurements?
Click to expand...

That is what I was thinking too...nameplate says it is for fire alarms or something...
 
I had the same problem with that transformer. I believe the problem was the xo connection. I think it needs to be connected to x2 or x4. I cant remeber. I do remember the wiring diagram was very unclear and had to call acme for tech. support.
 
wasasparky said:
That is a buck/boost transformer.
Is this for the farthest building? to help with voltage drop?
What was the load on the panel when you took your measurements?
Click to expand...

This sounds like what it's there for but I know 150V is coming out of the transformer, so next step in order to verify if it's the transfomer would be to see what's feeding it... Right?? Thanks, JB
 
jute said:
...so next step in order to verify if it's the transfomer would be to see what's feeding it... Right?? Thanks, JB
Click to expand...

I believe we know it is the transformer. The transformer appears to be set up for 120V primary and 32v secondary to get the 150V. Potentially fine if you have a high constant load, which I would doubt they do.

What are the loads? If they are light why even bother with the buck/boost? Possibly the panel could be rewired for 120/240V instead of straight 120V, which would in itself cut the voltage drop problem in half...

...back to - What are the loads?
 
080904-1219 EST

jute:

Based on the label on the transformer there is no way its output is 150 V. Its maximum secondary output is 32 V. But this secondary (that is the transformer output) added to the 120 V input will produce about 150 V, or 90 V depending on phasing.

The transformer labeling is not really confusing. When you have two identical primary windings these can be connected in series to work from 240 or in parallel to use 120 input. The layout of the screw terminals is to make wiring either way easy and to avoid getting the phasing incorrect. This is a standard layout. If there are no screw terminals, then just follow the drawing and labeling.

For 120 input remove the jumper from H3 to H2. This separates the series connection of the two primaries. Then jumper H1 to H3 (these are adjacent screws) and separately jumper H2 to H4. Now H1-H3 is one side of the 120 V source, and H2-H4 is the other side of 120.

Based on the results you have I would believe the H1-H3 and H2-H4 connection is the way the transformer is wired. And probably the secondaries are in series.

If the primary wires on one coil are reversed relative to the other primary coil, then you could have a fairly good short circuit across the line. This would burnout a transformer. Depending upon how low the impedance was would determine whether the breaker would trip or not.

What is the voltage from H1 to H4?

.
 
gar said:
080904-1219 EST

Based on the label on the transformer there is no way its output is 150 V.

.
Click to expand...


:-? Splitting hairs aren't we? :cool:

I would consider the output of this autotransformer to be 150V.:smile:
 
SEO said:
What is the voltage at the buildings suposed to be?( 120V , 120/240 or 120/208)
Click to expand...
If voltage is 120/208 they may be trying to obtain 240V by adding a buck-boost transformer.
 
gar said:
080904-1219 EST

jute:

Based on the label on the transformer there is no way its output is 150 V. Its maximum secondary output is 32 V. But this secondary (that is the transformer output) added to the 120 V input will produce about 150 V, or 90 V depending on phasing.

I was told yesterday that there was a troubleshootimg call put in for the gate because it opens on it's own every now and then?? When I talked to the gate guy he said that he was only getting 90v and that is causing the gate to reset and open at will??

The transformer labeling is not really confusing. When you have two identical primary windings these can be connected in series to work from 240 or in parallel to use 120 input. The layout of the screw terminals is to make wiring either way easy and to avoid getting the phasing incorrect. This is a standard layout. If there are no screw terminals, then just follow the drawing and labeling.

For 120 input remove the jumper from H3 to H2. This separates the series connection of the two primaries. Then jumper H1 to H3 (these are adjacent screws) and separately jumper H2 to H4. Now H1-H3 is one side of the 120 V source, and H2-H4 is the other side of 120.

Based on the results you have I would believe the H1-H3 and H2-H4 connection is the way the transformer is wired. And probably the secondaries are in series.

If the primary wires on one coil are reversed relative to the other primary coil, then you could have a fairly good short circuit across the line. This would burnout a transformer. Depending upon how low the impedance was would determine whether the breaker would trip or not.

What is the voltage from H1 to H4? unknown

I'll be going back out there on monday to get these readings...

.
Click to expand...

Thanks to all for the help on this and for the explanation given above..JB
 
wasasparky said:
I believe we know it is the transformer. The transformer appears to be set up for 120V primary and 32v secondary to get the 150V. Potentially fine if you have a high constant load, which I would doubt they do.

Is "120V primary and 32v secondary to get the 150V" telling me that the tranformer is the problem?
Is is the transformer for sure?? How would I verify it is the transformer before putting out the $500 to replace it?

What are the loads? If they are light why even bother with the buck/boost? Possibly the panel could be rewired for 120/240V instead of straight 120V, which would in itself cut the voltage drop problem in half...

...back to - What are the loads?
Click to expand...

When I go back I will find out all loads on this panel... Thanks, JB
 
Last edited:
SEO said:
What is the voltage at the buildings suposed to be?(120V , 120/240 or 120/208)
Click to expand...

I'm assuming 120v shoud be at the building as in the other 7 buildings? Thanks, JB
 
jute said:
View attachment 2170

Yes it could, Did you get a line to line voltage reading ?
If it is a line to line reading it could be a loose neutral or connection.
If it is a line to neutral phase , then that's a different story

Thanks for the quick response... This is the panel in question, from the line to nuetral coming into the panel there is 150v. I also took readings from line ot neutral from the load side of the breakers and all are 150v. I then checked breakers and all are on the same phase. Thanks, JB
Click to expand...

Also,
This 120/240V panel has been jumpered to make a 120V panel.
I count 6 hots and 3 neutrals...3 overloaded neutrals...
 
Status
Not open for further replies.
Top