Because even the parts in the conditioned space probably vary in temperature.  
A simple 70-80 deg. temperature change in a 500 gallon 50/50 mix of pg will 
change the volume 1.4 gallons by the formula in the annex.  Do they up the 
thermostat on the weekends?  Keep it cooler in the winter?  My office ranges 
from 65-77 year round.  These are just what I've noticed at 5:30 am in January 
and 5:30 pm in July.  Yes, I only work half days, I'm a slacker.  I have no 
idea what happens on the weekends.  

As suggested get the details on the system and call one of the manufactures to 
get a size of the tank they would sell you based on your temperature range.  I 
usually called them because their charts are based on 100 deg and many times I 
need usually 130 ish.  Then you can think long and hard about how much air is 
in the system that is not accounted for in tank sizing.  If it's a small system 
and the temps are really well controlled you are probably fine.  A really big 
system and well controlled temps and you might be fine with the trapped air.  A 
really big system and 20 deg temperature changes and you are probably SOL.  The 
fact it's been there OK gives you some level of comfort. 

And is it a Listed tank for fire vs. we see a lot of plumbing tanks?

Curious, why are you asking?  Was this an inspection?  Don't think you are 
responsible to redesign.  Yes, applaud noting odd things to investigate when 
beyond scope of work.  Just don't get yourself in a knot over an issue beyond 
something that sounds like an approved existing condition.  There has been many 
a conversation on this forum about that.     

Chris Cahill, PE*
Senior Fire Protection Engineer, Aviation & Facilities Group
Burns & McDonnell
8201 Norman Center Drive
Bloomington, MN 55437
Phone:  952.656.3652
Fax:  952.229.2923
[email protected]
www.burnsmcd.com

Proud to be one of FORTUNE's 100 Best Companies to Work For
*Registered in: MN




-----Original Message-----
From: [email protected] 
[mailto:[email protected]] On Behalf Of Vince Sabolik
Sent: Tuesday, July 31, 2012 8:29 AM
To: [email protected]
Subject: RE: E x p a n s i o n T a n k s

Thanks guys, but my point is this:

The entire system is filled with glycerine.

Only a very small part of the piping is exposed to temperature extremes.

If anti freeze expands only when temperature extremes are encountered, why size 
a tank for the whole system that sits in in conditioned or heated air?

Just curious!

At 09:03 AM 7/31/2012, you wrote:
>Vince,
>
>My gut tells me to use numbers. If you post the system capacity, mix 
>percentage, temperature extremes, and chamber max working pressure, I 
>can tell you what the max static pressure at the chamber can be.
>
>-----Original Message-----
>From: Vince Sabolik [mailto:[email protected]]
>Sent: Monday, July 30, 2012 5:58 PM
>To: SprinklerFORUM
>Subject: E x p a n s i o n T a n k s
>
>I need a genuis quick!
>
>A small amount of piping on an existing antifreeze system runs through 
>an area where temperature "extremes" can occur. The rest of the system 
>is located in conditioned air. I'd estimate the split at maybe 95-5% .
>
>Although the entire system is antifreeze, has a one gallon tank, and 
>the pressure has never "spiked".  The expansion will all be in the 
>conditioned area.
>
>So, my question is, should I have the owner consider a new tank on this 
>basis? My gut tells me it's needless... what's yours tell you?
>
>
>thanks,
>Vince
>
>
>
>Vince Sabolik, West Tech Fire Protection, Inc.
>11351 Pearl Road / Strongsville, Ohio 44136       440
>238-4800     Fax 440 238-4876
>____________________________________________________________________
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