Gen Set Additional Load

You would need to upgrade the existing gen set to a larger one or add a second gen set.

If this is for an emergency backup system you could consider connecting only the critical loads to the existing 750KVA generator (up to around the generators maximum current capacity).

we dont want to opt to purchase a secondary genset or upgrade to a larger genset considering our existing genset has a rating of 750 KVA and our present load is just roughly 304KVA which is 40.53% of our max capacity, is there any way that we can add another similar load like the previous that we have ..

thanks for the help

If you calculated that your current load is 304KVA and you have 750 available why do you have a question to add another 304 ?

Yes, something doesn't sound right. What's the problem with running your gen set at roughly 2 x 40.53% = 81.06%?

If you are concerned about inrush current or peak load operation of your equipment potentially overloading the gen set then you will need to perform an assessment of all your inductive and capacitive loads and check against the gen set specifications. We cannot tell from here if some special loads of yours will overload the gen set in your particular case during start-up or normal operation.

If you do have inrush current concerns you could consider a staged start-up of your equipment to limit peak starting currents.

then so are we going to connect the additional load in parallel and a ups so as to stabilize the current provided to the load?

thank you

Why do you need a UPS to stabilize the current for a 304kVA load?

Can you please explain in detail what loads you have connected up to your gen set at the moment and what you want to add.

800 A at 380 V 3-phase ~527 KVA.

That's what I get too.

Not sure how OP figures only 40% present loading.

Bigger genset may be required but then we don't know if the OP's load figures are measured or calculated off the labels on the loads.

Depending on how much load is on at any one time and their duty cycles and their sequence of operation then that one generator might work but one would need to look at things that only OP can see right now.

Then there's mention of a UPS....a bit of a cluster.

He just answered that, Mildred.

Are you simply adding another similar load after the first 304 KVA load is up and running? Although it is close to its maximum, as long as you avoid sudden inrush currents (slamming the whole second load cluster on at the same moment for instance) you should be okay... your resultant combined load would be less than the rated capacity of the generator.

Why is this a problem? Or why do you perceive this as a problem?

Ah well, in light of post number 16, this post is meaningless. Please dis-regard.

Has it been established:

1. The load is single phase (hence 304kW from the OP) or as we suspect three phase (527kW).

2. The nature of the load, and the application to which the load is put, have not been given. (If the genset load is predominantly motors then the generator headroom may well be required to get the motor away.)

The OP said 3-phase.

After reading the post and comments I am a bit confused as to what is the exact nature of the problem.

However having a little experience with generators Id say this simple thing: U can run a gen set to a near max load. BUT do not switch on everything at the same time. And provide leeway for machinery with intermittent loads (for example like cutting wood which is intermittent). The smoothest are pumps which run constantly and take a constant load.

Good luck

if your existing load is 800 amps on a 750 Kva DG set you need to add another set to impose load of same rating as Maximum current you can draw from 750 kva would be 1050 amps check the spec sheet of your DG set if its standby or prime rating then talk to engine manafacturer

I suppose it should go without saying that if you double the load, you have to double the circular mils on the outlet cables. "should" being the operative word here.

Hi all

sorry for the mistake, the present computed load was 526.54 KVA, our present DG was rated at 750 KVA, 380 V, 3 phase, is it possible to add an additional 526.54KVA load without adding another genset unit and how?

P.S.

the genset is used as a back up to support a load consisting of lighting fixtures computers and kitchen equipment during blackouts

thanks for the usual support I' am quite new to gen sets

See Post #1 for the answer.

If the present and proposed loadings stated are correct then the answer is no.

That's a lot of lighting, computers and blenders you have there.

I'm guessing this is a hotel.....any elevators?

How come the loading now needs to double anyway? This all seems a little strange. Smells a bit of brow beating by bean counters who want an answer that they like as the truth blows out their poorly guessed budgets.

What's happening there mate?..omit names to protect the guilty.

Dexter531,

Gensets usually have a modest reserve capacity, to allow for brief overloads. However, you are looking at a continuous load, not an intermittent or short-time load. You are talking about a 33%+ overload, which is NOT possible on a genset. Note the word "continuous" above. That sort of load is not to go beyond 80% of the rating of your over-current protective device (only a few are rated for 100%). If you have two loads, each with its own over-current protection, the sum of these shold not exceed the capacity of the genset; your hopes are shipwrecked on this one.

Options:

1. Have a means to automatically shed loads when they are transferred to the genset (such as only transferring a portion of the lighting, etc.) Be careful, but firm when needed. You may succeed in cutting each of the loads to keep within the 750kVA capacity of the genset.

2. Have a means to automatically shed some of the loads when the actual load being drawn on the genset nears its capacity (such as 90%). I suspect that some of the connected loads are intermittent or only occasionally used.

3.Look back at how you came up with the 800A stated in the post. If this is the rating of the breaker feeding your present loads, this may be sized noticeably higher than the actual connected load. I suggest here the use of a power analyzer or recorder to tell you the number of amps on each phase for a week or a month. Typically such a device will measure the minimum, peak, and average for each subdivided time period (such as 1-hour). This will give you a very good profile of when loads peak and what they actually are. Many of them will also give you the power factor and kVA, kW, and numerous other calculated values.

4. Look at some of the loads, such as water heating. They could be kept off the genset or be connected only when capacity exists. Some other loads can be handled similarly.

5. Don't overlook motors, particularly large ones. You MUST allow sufficient capacity for the substantial starting inrush current of the motors (can be anywhere from 2x to 10x the full-load current, depending on the motor and its starting method).

--JMM

thanks for the help i owe much to you all