Chiller Problems

[brian john]

Yesterday one week after the problem started, the utility admitted it was a utility issue and they would get a crew on it ASAP. ASAP=7 days later?

I assume tap changers are typically operate all three phases simultaneously?

 

[hillbilly1]

Yesterday one week after the problem started, the utility admitted it was a utility issue and they would get a crew on it ASAP. ASAP=7 days later?

I assume tap changers are typically operate all three phases simultaneously?

It was amazing they admitted it, I had a power issue at a church where the power would drop in the middle of services every Sunday leaving the sanctuary in total darkness for about 15 minutes. (HID's'The engineer that designed it kinda neglected to spec emergency lights with a minimum on time, fixed that with an on delay relay and contactor), but anyhow, the poco put a voltage recorder on their transformer, and said it was not on their end, so the church hired us to put one on their main. The customer said that all of the sudden once the poco found out we put one one, they had trucks running up and down the road working on the lines feveriously. Mysteriously we never recorded any problems, and the lights never went out again.:roll:

 

[Hv&Lv]

Yesterday one week after the problem started, the utility admitted it was a utility issue and they would get a crew on it ASAP. ASAP=7 days later?

I assume tap changers are typically operate all three phases simultaneously?

Not unless they are on PMT's or station transformers

 

[brian john]

Not unless they are on PMT's or station transformers

I was discussing automatic tap changers are you saying they are or are not per phase or switch as a 3-phase unit?

 

[Open Neutral]

The customer said that all of the sudden once the poco found out we put one one, they had trucks running up and down the road working on the lines feveriously. Mysteriously we never recorded any problems, and the lights never went out again.:roll:

I did not know that ComCast had gone in the PoCo business, but this sure sounds like their SOP.

If it's not them, I bet they'll sue your PoCo..... for stealing their patented business model.

 

[Hv&Lv]

I was discussing automatic tap changers are you saying they are or are not per phase or switch as a 3-phase unit?

Sorry, when I hear tap changers, I think of transformer tap changers to switch from one primary voltage to another.

Regulators will change the primary voltage down the line by 5/8 percent each step. They have to be single phase units because each phase isn't balanced with the others.

Did they ever say exactly what the problem was?

 

[mivey]

I was discussing automatic tap changers are you saying they are or are not per phase or switch as a 3-phase unit?

They do have load tap changers that are part of the three-phase transformers (or added on). Normally these would shift all three phases together. Some of these are made of single-phase units and have individual selector switches so I guess you could build them to step separately if you had a control panel that allowed that. Even for the normal case of stepping together, individual units can fail and cause an unbalance. The problem with these type units is that you have to take the whole thing out of service for repair.

What we normally have is three separate single-phase units that operate independently. This gives more operational flexibility and makes repairs easier. These do not step together but I suppose you could force them to step together by having the separate control panels talk to each other. However, I think this would remove some of the benefit of having separate units.

I do see value in having the units talk to each other to control unbalance but that has not been the way they have historically operated as you normally use the same set points for each control panel and they stay in balance. When one control panel goes haywire, the cross-communication might fail as well but there may be a possibility that the other two units could react. But what if the bad unit runs away to the max: do you really want the other two to follow along?

 

[mivey]

Sorry, when I hear tap changers, I think of transformer tap changers to switch from one primary voltage to another.

The ones we have on the primary side are made for changing with the transformer unloaded and one switch on the side of the tank moves the taps for all three phases.

 

[Hv&Lv]

The ones we have on the primary side are made for changing with the transformer unloaded and one switch on the side of the tank moves the taps for all three phases.

Yea, we are on the same page with the tap changer for a three phase PMT. I was under thre assumption that these were single phase pots banked together. At first I thought the OP was talking about transformers, then I realized he may have been talking about regulators.

I am sure our regulators work just like yours do, stepping individually in response to load. Ours are set at 123V with about a 2 volt bandwidth.

 

[LeeB]

Same Utility Issue

Same Utility Issue

I experienced the same problem with a 4160v chiller. Although I can't remember the exact voltage difference (I remember thinking it did not seem like much), one of the phases was
was lower than the others and it turned out to be the utility. They were able to adjust the phase voltage and cleared the current imbalance on the chiller.