Generator Problem

[trinaldi88]

Hello all I'm new to this site and I have a problem. I have an existing building with two generators supplying emergency power. Both generator's accessories (radiator fan, etc) are circuited to the same panel powered by only of the generators. So if one generator is out the other one will not be able to work properly due to none of its accessories having power. I have been trying to find a code that prohibits this in both the NEC and NFPA 110. Does anyone know of such a code that says the generator's accessories can only be powered by that specific generator. Thank you all!

 

[ceb58]

Hello all I'm new to this site and I have a problem. I have an existing building with two generators supplying emergency power. Both generator's accessories (radiator fan, etc) are circuited to the same panel powered by only of the generators. So if one generator is out the other one will not be able to work properly due to none of its accessories having power. I have been trying to find a code that prohibits this in both the NEC and NFPA 110. Does anyone know of such a code that says the generator's accessories can only be powered by that specific generator. Thank you all!

Take a look at 700.12 B 4. There is another code section that states that the wireing for such equipment such as batt. chargers originate from the gen. supplied panel. But for the life of me I cannot think which one it is

 

[zbang]

Code or not, it sounds like a pretty stupid way of doing things.

 

[Cold Fusion]

...There is another code section that states that the wireing for such equipment such as batt. chargers originate from the gen. supplied panel. But for the life of me I cannot think which one it is ...

I work with a lot of backup, blackstart, generation, sometime leagally required, rarely "emergency". I never wire a generator's battery chargers off of that generator's supplied panels. I really want the gen starting batteries to be supplied from a normally on source.

However, it would not supprise me that a code section is written as you say - but I hope not.

cf

 

[Cold Fusion]

Code or not, it sounds like a pretty stupid way of doing things.

I'd agree with that. A station service transformer, switchboard, and panel for the local auxiliaries is a real good idea - but can be seen as expensive, non-essential add-on, detailed in the engineered plans.

This installation sounds like it got "value engineered"

cf

 

[ceb58]

I work with a lot of backup, blackstart, generation, sometime leagally required, rarely "emergency". I never wire a generator's battery chargers off of that generator's supplied panels. I really want the gen starting batteries to be supplied from a normally on source.

However, it would not supprise me that a code section is written as you say - but I hope not.

cf

????? Why wouldn't the panel be normally on.
Where, in a case of having only one panel, being backed up by a generator would you feed the charger and/or block heater and such?

Both generator's accessories (radiator fan, etc) are circuited to the same panel powered by only of the generators.

Although it possible, I have never seen one that did not power its radiator fan from the engine. Ether way what the OP has is a PP design.

 

[Cold Fusion]

????? Why wouldn't the panel be normally on.
Where, in a case of having only one panel, being backed up by a generator would you feed the charger and/or block heater and such? ...

I didn't word my response very well. For the case you list, I agree with you.

... Although it possible, I have never seen one that did not power its radiator fan from the engine. ...

They are out there. I've seen several in the +1MW range and two in the 300kW range, that have electric drives for the cooling fans. I'm not in the desgn business, so I can not comment on the exact thinking, however there are two issues that come to mind:
In the case of the 1 and 2MW units, 50hp is a lot of power to transmitt and control with a mechanical drive off the front end of a gen.

In cold climates (-30F and colder) it may be better to have a separate space for the radiator and fan and not pull the outside air through the generator compartment. I've seen this done on as small as 300kW. An electric drive makes this easier.

... Ether way what the OP has is a PP design.

I'd agree with that.

cf

 

[dbuckley]

[Talking about elecrically operated fans] They are out there. I've seen several in the +1MW range and two in the 300kW range, that have electric drives for the cooling fans.

Having the fan and water pumps driven electrically is common on gensets that are installed in buildings and the radiators are a pipe run away. In these cases the fans and pumps are (when well designed) driven using the power the genset produces, so typically three phase pumps and fans.

One spectacularly terrible design I've seen had five paralled gensets (3 ng cogens on the root, two big standby diesels in the basement) with all the pumps and fans driven off "normal" building power, the idea being that with utility failure the gensets would all start up, syncronise and take the full building load, and the engines would be OK for 30 seconds without coolant flow until the whole thing came on line.

Trouble is, the day the sets didn't want to sync quickly the lack of cooling for some minutes caused all the gensets overtemp protection to operate, causing engine shutdown. So all these gensets were reduced to useless piles of hot metal, and the water-cooled IBM mainframe powered itself off through overtemperature well before the 20 minute UPS battery window expired. No power - no cooling water pumps...

I seem to recall that the problem was that if any of the three cogen sets were running when the utility went out then the syncronisers didn't work. From a cold start with everything stationary (as it always was during commissioning testing) it worked every time...

 

[ceb58]

They are out there. I've seen several in the +1MW range and two in the 300kW range, that have electric drives for the cooling fans. I'm not in the desgn business, so I can not comment on the exact thinking, however there are two issues that come to mind:
In the case of the 1 and 2MW units, 50hp is a lot of power to transmitt and control with a mechanical drive off the front end of a gen.

In cold climates (-30F and colder) it may be better to have a separate space for the radiator and fan and not pull the outside air through the generator compartment. I've seen this done on as small as 300kW. An electric drive makes this easier.



cf

And I can see there being a need for that. Just glad I dont live in the -30deg area. But I think, as for the reason you listed, we are all in agreement that it is a bad design.

However, the OP did not state what type building or loads he is supplying. Some times the words "emergency power" are used to describe loads that are really not by definition "emergency". But if it is an emergency system I think the wording and intent of 700.12 B 4 is that those circuits be supplied from the source that the generator serves. And, for arguments sake, if the system is truly an emergency system then it could also fall into art. 708. And an argument that would back up what the OP is trying to accomplish would be 708.8 B.

 

[Cold Fusion]

...One spectacularly terrible design I've seen had five paralled gensets (3 ng cogens on the root, two big standby diesels in the basement) with all the pumps and fans driven off "normal" building power, ...
Trouble is, the day the sets didn't want to sync quickly the lack of cooling for some minutes caused all the gensets overtemp protection to operate, causing engine shutdown. So all these gensets were reduced to useless piles of hot metal, and the water-cooled IBM mainframe powered itself off through overtemperature well before the 20 minute UPS battery window expired. No power - no cooling water pumps...

I love it. These are my kind of designers. I'm not being facetious. If not for them, I'd be sitting in an office bored to tears.

cf

 

[dbuckley]

This ickle foopah was at a then brand new office, which had been built in an almost no expense spared manner, and the power system was designed by a top flight engineering consultancy. Something like 8MW of generation in that collection of equipment.

It does illustrate that sometimes you really dont get what you pay for.

There was also a secondary data centre on the same site that had its own dedicated diesel genset and when the lights went out it harumphed up and delivered the juice on cue. Problem was, the secondary data centre (8000 sq ft) was empty, everything was in the primary...