Some Information on the Connections the DG Set currently has as on March 2021

(updated 14 April 2021) 

In order to get a better picture of the load on the DG Set, I walked into our Association office to get the information. The team there seemed to have a fair idea of the load and provided the following details:

Generator Capacity
	250	KW	x	2	500	KW	Max Capacity

Typically, 70-80% of the Rated capacity is considered safe to handle for short periods and 60-70% is considered OK for continuous use, something like our long 10am to 6 pm power cuts.

The following are the Load Areas to which the DG connects to: 

 High-level Overview:

 The below is an estimate from a trusted source. 

Sl.No	Description	KW	A broad Classification
1	WTP	66.5	Always
2	STP	88.2	Always
3	OWC	5.59	Always
4	Swimming Pool and Fountain	3.2	Always
5	Lifts	84	Always
6	Fire Booster Pumps	178	Emergency
7	Lift Lobby Area lights	145	Night
8	Stair Case lights	48	Night
9	Street Lights	2.2	Night
10	Ballard Lamp	2.8	Night
11	Badminton Court	1	Night
12	Main Gate	1	Night
13	Club House	2	Always
14	Terrace Lights	4.5	Night
	Total Load in KW	631.99

 * "Always" in the above table means "Should be always available" as the load varies and has a good probability of full utilization during certain periods of the day. For example, a large proportion of lifts will be operational during 4:00 PM to 7:00 PM when children come down to play and people come out to enjoy the evening.

 ** The above breakup is based on the 630 KW total estimated connected load

 Data Table:

Time of Day	Active Standby	Emergency (only pumps included - lighting to be estimated)	Additional Night Load
Estimated Load (Full utilization)	249.49	178	201.7
Percentage	39.48%	28.17%	31.92%

Details for some of the Areas covered above

	Numbers	Rated Power	Units	Power in Watts		Consumed Power
Usage
Street Lights Big	42			50	W	2100	W
Street Lights Small	53			9	W	477	W
Club House
LED Bulbs	10			9	W	90	W
AC in Gym	1			2000	W	2000	W
Swimming Pool	2	2	HP	1492	W	2984	W
Water Fall (opp Main Gate)
Ad Displays	15			30	W	450	W
Motors
Lifts	15	7.5	HP	5595	W	83925	W
OWC (Organic Waste Convertor)	1	5	HP	3730	W	3730	W
Fire Booster Pumps	16	7.5	HP	5595	W	89520	W
WTP (Water Treatment Plant)	2	5	HP	3730	W	7460	W
Water to Tank	10	7.5	HP	5595	W	55950	W
Shifting Motor	1	3	HP	2238	W	2238	W
Borewell Pumps
B1	1	2	HP	1492	W	1492	W
B2	1	3	HP	2238	W	2238	W
B3	1	5	HP	3730	W	3730	W
B4	1	10	HP	7460	W	7460	W
B5	1	7.5	HP	5595	W	5595	W
STP
Raw Water Motor	2	3	HP	2238	W	4476	W
Small Air Blower	2	5	HP	3730	W	7460	W
Air Blower	3	7.5	HP	5595	W	16785	W
Filter Feed Pump	3	5	HP	3730	W	11190	W
Sludge Holding	2	2	HP	1492	W	2984	W
Automatic Cistern	3	7.5	HP	5595	W	16785	W
Garden Motor	2	5	HP	3730	W	7460	W
Back Wash Motor	2	7.5	HP	5595	W	11190	W
Exhaust Fan	1	7.5	HP	5595	W	5595	W
Fresh Air Fan	1	3	HP	2238	W	2238	W
Rain Water (Pump?)	4	5	HP	3730	W	14920	W
Flats
Parking Area Lights
Lobby Lights
Floor Common Area	135			9	W	1215	W
Inside House (1 Fan 64W)	548			64	W	35072	W
Inside House (1 Light 20W))	548			20	W	10960	W
Total (expected)						408809	W

This is the difference that we get: 

Difference

91191

If you observe, I have not included items which I do not know - for example, parking area lights and lobby lights (anything which falls outside of what I calculated)

I was trying to get to the 400w spare capacity we are talking of that can be redistributed to the houses. If I were to look only at the difference, I would see only 91,191W available, this would leave us with 166 W per house. This is good enough to kill the DG Set at peak loads. 

So, what some experts opined on the telegram group was right - there is no slack if you consider that your output (for continued periods) is only 80%. In fact, it is in deficit. 

A Second View: 

I am taking a guess on where the 400W slack (mentioned in various meetings) is coming from. 

There is Some slack available in the following areas: 

Slack
Fire Booster Pumps (will be used only in case of fire or Tests or Drill)	16	7.5	HP	5595	W	89520
Inside House (1 Light 20W)) (assumption: will be used only during the night)	548	0	0	20	W	10960
Back Wash Motor (might not be used continuously)	2	7.5	HP	5595	W	11190
B4 **	1	10	HP	7460	W	7460
B5 ** (of the 5 Borewell pumps, two are used on rotation).	1	7.5	HP	5595	W	5595
Street Lights Big (used in the night)	42	0	0	50	W	2100
Street Lights Small (used in night)	53	0	0	9	W	477

This and the difference of 91,191 W comes to 2,18,493 W and could come to 399 units of slack. (With a lot of assumptions)

Another Way to Calculate Slack Capacity

One way (as suggested on Telegram group) of calculating Slack Capacity is to look at at the actual usage of the DG and calculate the slack. In most Manufacturing Units, once production starts, this is the established way to look at productivity and Slack. Also, all the time the BESCOM power is available can be considered as Slack time for our DG Set. However, for our discussion, let us take slack as "Prime Power Rating" provided by the manufacturer. 

 The prime power rating is the maximum power accessible at the variable load for an unlimited number of hours per year in a variable load setting. It is not advisable that the variable load exceed 70% average of the prime power rating during any operational period of 250 hours. (Source: Google and https://www.generatorsource.com/Standby_vs-_Prime_vs-_Continuous_Generator_Power.aspx and https://support.wellandpower.net/hc/en-us/articles/360001827297-What-is-Prime-Power-How-do-you-know-if-you-need-a-Generator-for-Prime-Power-What-is-PRP-)

 In most cases, a 250 KW DG Set could have a 200 KW prime power rating. Get 70% of that and we have 140 KW (for situations like 10 am to 6 pm power-cuts). Multiply that by 2 and we have 280 KW as the peak we can hit for a sufficiently long DG life. So any time we are exceeding 140 KW per DG set for extended periods (an hour or more), we might have to be concerned. Yes. let us dig into some data for this.

The photos of the Register where the load data is recorded are in the following folder: https://drive.google.com/drive/folders/17MqadpPb5mwRExnTkT7TaHn1-qxzkYdV?usp=sharing. Yet to digitize and make a graph of the usage.

Ommissions: 

1. I did not get the rating for the Fire PA system, the Cameras System and the power used by the common Airtel DTH connection. These still not included. And a few more are blank.
2. Play Area and Main Gate lighting / facilities not included in the details.
   
3. Does not include the temporary lighting for our night cricket infra on CA land. There are approximately 10 lights each with a capacity of 50W. That would make it 500W of load.
   
4. This is just a rough estimate. Feel free to let me know what I missed.
   

My Own View:

1. I do not see any slack left by the builder for further expansion of the DG set. Possibly, that was the minimum required for them to get an approval, especially for the fire systems.
2. The slack is just at the safely margin and anything we add to the load (like our advertisement display systems and our extended lights on the CA land) only gets us out of the safety net.
3. I agree with one of the opinions on the group - Common amenities are for common areas. 
4. Please realize - the above are also "Assets" in PH books and for our common usage. While we need to optimally utilize them, we also need to ensure their long life. 
   

Open Questions:

1. I do not see a plan on how Fuel used would be apportioned between those who opt in for the extension and those who opt out. I am not even sure of the legality of extending a common resource for those who are ready to pay an upfront cost and piggy back on a common asset.
2. Who bears the cost if a DG set fails? Would those who opted for extension elect to pay ~4.5 times more (400W) for the asset than those who use the default (84W)
   

 

You can download the calculation file here: DG Load Calculation Sheet

Related Links

1. Additional Information on DG Set and its monitoring
2. DG Set Power vs Your own UPS for your flat - IMHO
3. DG Set Extension - Need vs. Stated Goals
   
4. Overview of PH and its Facilities 
5. Services Available within PH 
6. Electrical Outlets in your 3BHK Flat