Service size upgrade?

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WA_Sparky

WA_Sparky

Electrical Engineer
Location
Vancouver, WA, Clark
Occupation
Electrical Engineer
Typically on every project i always start with giving the utility a call to see what their max peak demand is over 12/mo. This will tell me the max demand a specific facility has drawn over a given interval; winter heating, summer cooling and busy seasons..
We have a federal government project that has its entire building backed up by a 400 KW gen. Existing HVAC is Electric cooling and gas heating. They want to go to electric heating. If I used the peak demand given from the utility (metered in June = summer month) and summed up the estimated heating load its over their service capacity.

I've been told another option would be to take the max peak during winter months instead since heating is intended to be removed. Not sure if this is standard practice or if there's a better way to do it. Just seems like its doing a bit of hand waving and making assumptions. Bottom line, if winter months peak cannot be used new service, generator, ATS's.... all need to be replaced which would be $100,000's. I dont want to raise any red flags unless its certain.

Thanks,
 
xformer said:
Couldn't you just compare the new heating load to the existing AC load?
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This place specifically gets down to -20F in the winter and highs of 80's in the summer. Similar to Alaska I imagine the heating load is much higher than the cooling load. I guess it may be worth looking into the existing BTU's of cooling capacity subtract that from peak demand then use that as a starting point for estimating remaining load for new heating load..
 
Are there any nearby similar structures, using electric heat, whose usages you can compare?

Maybe not actual usage amounts, but at least compare their heating-to-cooling cost ratios.
 
Just like the Government, go from an efficient way to heat, to costing the taxpayers $$$$! Might ought to figure in all those portable electric heaters under the desks after they do the swap, because it will not be as warm!
 
You are always making assumptions. The question is 'can you support those assumptions'?

You could simply do an article 220 calc and be done with it, except that doing so will almost certainly give an even higher number than the utility demand. But this calculation technique is a known conservative set of assumptions.

You are adding heat. This will only be used certain parts of the year. Right? (Well it is an assumption, can you support it? Maybe the electric heat system that they want to install also provides hot water, and is actually used all year round. )

Article 220 describes ways of using utility demand numbers, and you want to deviate from this in what seems to me a very reasonable fashion. But it certainly requires assumptions.

Jon
 
Most likely your heat will be the greater of the 2 loads so you don't have to use the a/c in the calculation. I assume you know that but I will put it out there.

220.60 Noncoincident Loads. Where it is unlikely that two or
more noncoincident loads will be in use simultaneously, it shall
be permissible to use only the largest load(s) that will be used
at one time for calculating the total load of a feeder or service.
Click to expand...
 
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