Antifreeze vs Dry Pipe

[gfire]

What are the advantages/disadvantages of a dry pipe system vs an antifreeze system? The existing building I'm working with has 2 seperate unheated combustible concealed spaces on each end of the building one 1300 sf and the other 950 sf. It also has an exterior overhang that will require an additional 4 sprinklers. Is there a size limitation for antifreeze systems? Are there situations where a dry pipe should be used over antifreeze, or vice versa?

 

[MGXFP]

Not so much a size limitations to antifreeze systems, but be aware that if the system volume exceeds 40 gallons then it is required to calculate it with the antifreeze (using Darcy Weisbach) and depending on antifreeze mixture can greatly increase friction losses.

In this instance I say layout a dry system and an antifreeze system (antifreeze loop on the existing system if not over system area limitation) to see if which or both works. Then figure the costs required for either scenario.

 

[skdesigner]

Once your pipe capacity exceeds 40 USGal in a glycol system, you have to do a darcy-weisbach calc along with the H-W calc. Depending where you are, and what kind of ambient temperature you will use to calculate the viscosity of the fluid, it can be extremely limiting. Also, what I see alot of guys miss is the 13 requirement for a listed expansion tank - runs me about $800.00 vs. $50 for an unlisted model. Advantage of glycol over dry pipe is that it is essentially a wet pipe system, and you can use a c-factor of 120 in your calcs, and you don't get hit with the 30% area increase.

Definetly not black and white, but I would say >40USGal, go with glycol, <40USgal, dry pipe. Be sure to use the proper C factor for dry, unless you go with galv. pipe.

 

[LCREP]

Take a look at this link

http://www.nfpa.org/newsReleaseDetails.asp?categoryid=488&itemId=48583

Perhaps this may also apply to commercial systems??? If so look out, go with a dry system, you will look good if they do.

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Fire Sprinklers Save Firefighters’ Lives Too!

 

[NJ1]

The only time that a dry valve will be required vs antifreeze is when an antifreeze calculations exceeds the limitation of Darcy-Weisbach.
In your case I see (2) remote unheated combustible rooms as you stated (2 seperate unheated combustible concealed spaces on each end of the building)which could cause an issue with dry valve water delivery.
In my opinion i would go with separate glycol loops to minimize gallon capacity and also long runs of pipe. It also allows for more cost effective installation and maintenance since dry pipe valve are more expensive and requires more maintenance thru the year.

 

[LCREP]

Do not know where you are located BUT, take a look at these limitations on antifreeze listed below. This is from the NFPA link I gave you. IF you are in a cold climate can you meet the freeze points with the % of the products listed below. Also how much more $$ will FACTORY premixed solutions be? Also many jurisdictions will require a RPZ backflow device, not cheap to be added once you add the antifreeze system.

?Use only propylene glycol or glycerin antifreeze solution.

?The antifreeze solution should be the lowest possible concentration required for the needed freeze potential but under no circumstance should the antifreeze solution exceed a maximum concentration of 40% of propylene glycol or a maximum concentration of 50% of glycerin. Consideration should be given to reducing these concentrations by an additional safety factor.

?The antifreeze solution should only be a factory pre-mixed; use of factory pre-mixed solutions is essential to ensure the proper concentration level and solution integrity

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Fire Sprinklers Save Firefighters’ Lives Too!