Conference 7.286::digital

    System and Options catalog typically has these numbers
    
                                                        David

    For AlphaServers the Heat Dissipation in terms of BTU/hour can be
    found in the Systems and Options Catalog. Its there for some other
    systems but not all.You can find it on the Specifications page at the end 
    of the section for each product.

    
    There are partially available on the Web::
    
    http://sawhorse.cxo.dec.com
    
    Select SYSTEM select the model, and then select Environmental.
    
    Sandra

    re: The SOC...you should be very careful using the numbers in the SOC. 
    And definately don't show a customer that has an IQ higher that a rock
    has without checking the SOC information over beforehand.  I was
    sitting in a customer meeting when one of them asked about the normal
    operating temperature of a printer we were proposing to fix a problem
    with a printer type that we had sold them.  "Sure",says I, "It should be
    right here in the SOC."  Look it up and it says normal operating temp
    is 900 degrees F., with the equivalent C. notation.  Didn't even try to
    explain it.  
    
    Just a word of caution...
    Bryan

    
    	BTU rating on a system?  How amusing.
    
    	Maybe all those VAX9000's have a legitimate use after all.  Does
    	anybody need a replacement for their old wood stove?  0-80 degrees
    	in 50 nanoseconds!!
    

BTU's ? British Thermal Units ? What ever happened to the wonderful metric 
system we were all supposed to used - Newton-Flopsies per Dynamyte (or 
whatever it is).

I'm getting too old for this job !!!

    If all else fails, I guess you could measure the current draw
    with an ammeter, figure out the watts, and converts the watts
    to BTUs.

Not all the power sucked in is converted to heat.

/john

    In computers very little of the input power is converted to anything
    but heat- when was the last time you saw one of them move very fast?

    I thought he was talking about the flashing lights.

	1W = 3.41 BTU/hr

	Just so you know, those numbers listed in the specs
	are "worst case" with a substantial safety margin
	added in for the purposes of the safety agencies. 
	Actual power dissipation is somewhere in the 50-75% range
	depending on what options are installed.

	Customers who are asking usually need that info for the
	HVAC needs of their building. In the U.S. the HVAC
	industry still operates in the BTU realm. Ironically
	the British abandoned the British Thermal Unit when
	they entered the Common Market, aka the EU. But that's
	another rat hole.

> In computers very little of the input power is converted to anything
> but heat- when was the last time you saw one of them move very fast?

  You and John Covert are both correct. But when you say "power",
  that can't be computed simply by multiplying Volts x Amps because
  some of the Amps that the computer sucks in on one half-cycle of
  the line voltage waveform are (conceptually) simply returned
  unused to the power line on the next half cycle.

  That is, the computer isn't just a resistive load. Instead,
  low-end computers are usually massively capacitive. Some of
  the energy dumped into this capacitive load simply returns to
  the power line.�

  So you need to multiply the VA (Volt-Amp) rating of the system
  by a number knowns as the "Power Factor" to get the Watts
  actually consumed. Then you can turn Watts into BTUs.

  Power companies don't like massively capacitive loads so higher-
  end computers nowadays usually use sophisticated power supplies
  that employ active circuits to provide "power factor correction"
  and make the loads look a lot more resistive than they used to
  back in the days of big VAXen.

                                   Atlant


� Also, the waveform of the curent drawn from the line is
  nowhere enar sinusoidal. Instead, it tends to be two extreme
  pulses of current drawn at the crests of the voltage sinewave.

    The overrating of supplies is a major expense for our customers. SW800
    cabs have 30 amp 3 phase power lines. Customers buy HUGE power cords,
    pay lots of money to hook them up, then when you get a fully loaded cab
    and MEASURE the current its only 2 or 3 amps. The customer looks at the
    specs, and the actual measurements and concludes we are nuts.
    
    We have 26 HSZ40/SW800's at this site. They have paid huge ammounts to
    supply things like UPS connections and power distribution pannels, all
    huge overkill, because we took a 'conservative' rating.

    Are you measuring the start-up current or the steady-state current. 
    For some devices these can be drasticly different.
    
    Jc
    
    (who in a previous existance had to power on devices one at a time to
    avoid taking out the big breaker on the wall :-)
    

    re .13
    
    There's a whole list of thing that have to be assumed in order to meet
    various standards, including safety.
    
    We have to assume that the customer will eventually fill up every
    possible option with the highest power consuming parts possible. 
    Assume the line voltage will be at it's minimum, which means amperage
    is at it's maxiumum.  Assume the system is operating at high
    temperature, and so the fans are drawing more.   Etc, etc...
    
    When you look at it this way you'll see why the line ratings are 
    usually quite conservative.   "Fully loaded" might not really be fully
    loaded from an electrical perspective.
    
    -Steve