UPS heat output

[ad77]

I am looking at a computer room with a 50 kVA UPS located within the room together with the aasociated batteries.

The UPS spec indicates a 40 kW maximum output (i assume the product of 50kVA and PF 0.8).

The computer room client is unable to provide a detailed listing of all of the equipment located within the room together with the associated heat output.

If the UPS is supplying power to various server based equipment what is the maximum heat load that could be expected???? (answering my own question assuming power in = heat out the maximum is 40 kW - does anyone have access to diversity figures?????????)

The UPS equipment will provide a heat output to the room (the tech spec does not indicate the amount) can a factor of say 10 - 20% be added to the UPS eletcrical output to estimate the approximate heat contributed to the space?

Will appreciate any comments.

 

[IRstuff]

Most power conditioning equipment are on the order of 66% to 85% efficient.

TTFN

 

[MintJulep]

UPS is basically a battery. Possibly some filtering on the input, and a rectifier in the charging circuit.

Under normal conditions, I would expect it to consume very little power, and hence produce very little heat.

Adding a factor over the rated maximum output will be way too conservative.

 

[rbulsara]

All UPS manufactures show this data on their data sheet. Ask them or your electrical counterpart.

One of the manufacture data I have indicate heat output for a 50kW unit ranging from 11,500 btu/hr to 14,000 btu/hr depending upon the voltage ratings.

This should be close enough for other mfrs too.

 

[MintJulep]

Over a ton? No way.

APC 45 kVA unit lists 430 BTU/hr heat dissipation when fully charged. 1150 BTU/hr when charging.

This link may be too long to work:

http://nam-en.apc.com/cgi-bin/nam_e...X4mcF9wcm9kX2x2bDI9fmFueX4mcF9wYWdlPTE*&p_li=

 

[rbulsara]

mintjulep:

I am not sure what you are lookig at here the link to APC. see heat dissipation of 40kW unit..11,500btu/hr.

http://www.apc.com/resource/include/techspec_index.cfm?base_sku=SY10K40F

My earlier post was different mfr.

 

[MintJulep]

Rbulsara,

Hum. I agree, your link says what you say it says. My link actually seems to work, and also says what I said it said. It is a page from APC listing several models. The values I cited earlier were the highest in that list.

11,500 BTU/hr is better than 3 kW. Just doesn't make an sense to me. The thing is just a trickle battery charger.

 

[rbulsara]

mint:

It appears that you have not seen a room with a UPS in it. You can trust me on this that the data I posted is more accurate and we have years of experience designing and installing UPS systems (ranging from 40 kVA to 2250kVAs).

UPS is not merely a battery charger. Even idling rectifier and inverter put out a lot of heat.

3 kW is less than 10% of 40 kW and it is very much what our experience is. Remeber 3kW loss is at full load, but the relationship is not linear. There not much difference in heat loss say at 40% load and 100% load.

Just like your computer puts out similiar amount of heat weather or not you are using it or its idling.

 

[rbulsara]

mint:

even in your own link....what you are reading is minuscule UPS for computer I believe.

In the product selection go to Symmetra PX type UPSs and locate a 40kW unit..and see what you get..

 

[IRstuff]

There seems to be a bit of confusion.

The 430 BTU/hr is listed for a SmartUps 5kVA system rated for 3750kW, while the 11,600 BTU/hr is for a 40kW system.

That puts quiescent dissipation of the 3.75kW system at 3.4% of peak power, while the 40kW system is at 8.5% of peak power. And, they are from different product families, so such a difference might not be unexpected.


TTFN

 

[MintJulep]

Ah, I see the error of my ways. I was looking at 4.5 kVA unit, not 45 kVA one.

 

[DRWeig]

Hi Guys,

If you don't mind an EE pitching in, the reason that the heat load is so high for a UPS is that it's more than just a battery charger.

Even with utility power present, all the power flows thru it, first being converted to DC (rectified) and then back to AC (inverted). On loss of the utility power, the DC bus in the middle gets its power from the batteries.

The inefficiencies are in the 5 to 10 percent range at full load, so a 40 KW machine would be expected to dissipate between 2 and 4 KW of heat.

While it's true that the batteries are just trickle-charged during normal operation, you still will have all the power going thru the inverter at all times.

You can consider the 40 KW limit to be the heat put into the rest of the room (plus lights and people and stuff not on the UPS), although a good engineering practice is to not load the UPS past about 80 percent (32 KW). You might even find that the load is actually very small if they're planning for lots of future growth. You'd be best to size for the growth though -- it's a lot easier to add electrical capacity than it is to make a cooling system bigger.

Have a good 'un! U guys rock...

Old Dave

 

[ad77]

Thanks Old Dave,

You have provided some backup to the anecdotal information that has been provided from several sources.

Not loading the UPS beyond 80 %, you state this is good practice - recommended by whom?

You hit the nail on the head – in their current room we measured the electrical output as ~10kW.

What is typical electrical density (W/m2)that you have experienced? We are looking at ~1000 W/m2 for server based equipment.

Thanks again.