chiller + boilers in same equip. room

[dpoppeli]

Anybody know what code issues I might run into by locating a 50 ton chiller in same room as two one-million btuh boilers? Someone seems to think there may be issues and one person has eluded to ASHRAE standard 15. This is in Indiana, USA. I am looking at a split type chiller system so actually only the evaporator barrel would be in the equipment room.

 

[friartuck]

I seem to recall that if refrigerants come into contact with a flame, then Phosgene gas is produced which is deadly.


Friar Tuck of Sherwood

 

[CarolinaPE]

I have seen chillers and boilers in the same mech room many times, very common. It sounds like you have cooling towers & condenser water? I am aware (at least for our state) that gas fired appliances over a certain BTU cause a room to be fire rated.

 

[TXiceman]

ANSI/ASHRAE 15-2004, para 8.12(a) states that no flame producing device or continious operating hot surface over 800 dF shall not be in a refrigeration machinery room. This is for refrigerant meeting para 7.4.

The problem with phosgene gas was from chlorine based refrigerant, primarily R-11.

Ken

TXiceman

http://www.rae-corp.com

 

[dpoppeli]

Hmmm... boiler rep doesn't see an issue. He is saying that flue temp shouldn't get over 400deg-F (assuming conventional venting) and that the combustion chamber is surrounded by the water jacket. Wondering if sealed combustion is required? Chiller rep doesn't see any issues either. Gonna check the Mechanical code...

 

[DUMechEng]

as long as you have refrigerant detection interlocked to kill the burners in the event a leak is detected you should be fine.

 

[krb]

From a previous post on this subject:

After checking the ASHRAE 15 code a little more in depth, I found the following:

8.11.6 No open flames that use combustion air from the
machinery room shall be installed where any refrigerant is
used. Combustion equipment shall not be installed in the
same machinery room with refrigerant-containing equipment
except under one of the following conditions:
(a) combustion air is ducted from outside the machinery
room and sealed in such a manner as to prevent any
refrigerant leakage from entering the combustion
chamber, or
(b) a refrigerant detector, conforming to 8.11.2.1, is
employed to automatically shut down the combustion process in the event of refrigerant leakage.

KRB

I would suggest that you get a current copy of ASHRAE 15 and review it for your application, and consult your local codes on the issue. Sections 8.11 and 8.12 are both applicable.

KRB

 

[dpoppeli]

Thanks krb & TXIceman for diving into ASHRAE 15. We are under the International mechanical code and I notice that it contains most of the ASHRAE items that you have been mentioning in one form or another....

 

[cme]

My view is that it id poor design practice to locate both systems in the same room ..... I'd avoid the situation like the plague

Chiller rooms are under negative pressure

Boiler rooms ar under neutral to positive pressure

 

[CarolinaPE]

I'd avoid it in particular if it compromises service access to the equipment (or getting new boilers & chillers in the room). Piping and pumps also take up a lot of room. I've been in rooms where pumps cannot be serviced/removed and walls have to be torn out to remove equipment. Doggone architects!

 

[lilliput1]

Refer also to ASHRAE 15 for reqirements on refrigerant leak monitor, exhaust requirement and refrigerant venting requirements.

 

[ITSTOAST]

We have all of our boiler rooms integrated with the chiller plants and most have been designed within the last 7 years by some of the top engineering firms in the country. All applicabble codes were strictly adhered to since we have building occupancies anywhere from 3000 to 9000+ depending on location. Refrigerant leak monitors and combustion air are two key factors along with automatic exhaust fans operated upon detection of leak. We had of course, removed all R-11 and R12 plants prior 1992.

 

[tombmech]

The absence of R-11 and R-12, while admittedly more dependable in creating phosgene gas, does not remove the potential.

Here are the three refrigerants most used today -

DuPont's MSDS on R-123:
"Decomposition products are hazardous. This material can be decomposed by high temperatures (open flames, glowing metal surfaces, etc.) forming hydrochloric and hydrofluoric acids, and possibly carbonyl halides."

DuPont's MSDS on R-134a:
"Decomposition products are hazardous. This material can be decomposed by high temperatures (open flames, glowing metal surfaces, etc.) forming hydrofluoric acid and possibly carbonyl fluoride."

DuPont's MSDS onn R-22:
"Decomposition products are hazardous. "FREON" 22 can be
decomposed by high temperatures (open flames, glowing metal
surfaces, etc.) forming hydrochloric and hydrofluoric acids,
and possibly carbonyl halides."

Note that some carbonyl halides form phosgene gas.

There is no excuse for not segragating boilers from chillers with fire-rated walls. As can be seen, even hot metal is enough to cause a problem. I cannot imagine "some of the top engineering firms in the country" allowing this to take place in high occupancy environments. Any Fire Department with which I'm familiar would dismiss the construction out-of-hand.

Refrigerant detectors do not stop leaks or exposure to combustion, neither do exhaust fans. The detector only warns of the event after it's occurred, and exhaust fans can only limit the breach once a leak has started. A proper design does not allow the potential for exposure in the first place.

 

[ITSTOAST]

There is the most important excuse-money. The second most important excuse-space. Customers don't like to part with either and unless there is a code issue. They will not accept the additional cost and space loss just because you like the idea. All of our plans and buildings are inspected by local and State Fire Marshals. We are also inspected by Factory Mutual and Hartford Insurance semi annually. You know not of what you speak. I did not say the new refrigerants were safe around flames, I just indicated that we didn't have the older types that were being discussed.

 

[ITSTOAST]

I was hoping someone would give the specifics of the code that we are dealing with. Our chillers are litium bromide, I apologize for not stating that, but I wanted to hear the answer to the original question, not a critique of our facilities. I agree with the safety issue entirely, but it has to be backed up with code specifics.

 

[tombmech]

1. The code requirements for segregating boilers are due to combustion and combustible fuel sources.
2. Lithium Bromide "refrigerant" is a dry powder in an aqueous solution used for heat-driven, absorption chillers. It is not a CFC, HCFC, HFC, or even ammonia, all of which are refrigerant gases that use compression to input refrigeration cycle work. It is apples and oranges on a grand scale with respect to the conversation.
3. Absorption chillers are heat-input devices, and are very similar to boilers. In fact, a direct, gas-fired absorption chiller has virtually the same NFPA code requirements, and may actually double as a hot-water boiler.
4. The applicable codes regarding facility design and segregating combustion fuel sources and combustion equipment can be found in NFPA 85, NFPA 101, ASHRAE Std 15, and many various national, international, regional, and local codes.

You will find that your direct-fired, combustion heat equipment is separated from the rest of your building(s) with significant fire ratings. Also, the lithium-bromide absorption refrigerant solution and cycle is much older than many of the refrigerant gases mentioned.

I would state some pointed things at your opinions of codes vs. safety, but that's too much of a digression at this point. Suffice to say that code adherence is a minimum threshold, and does not completely warrant the Engineer (or owner) from liability.

Apology accepted at your not mentioning that you used heat-driven chillers the first time (and other stuff). Not to put too fine a point on it, though, but that's what "integrated" your heat and chiller plants - by definition.

 

[tombmech]

Back to the original question, most codes prohibit any introduction of chlorine or chlorine-containing chemicals anywhere in the proximity of combustion equipment (boilers). This is because of the Phosgene gas potential (and ignition).

The question posed in the first post should not be allowed. Even the evaporator barrel has the potential for leaks or rupture. Further, depending on the refrigerant, there may be a chance of a vacuum potential with a leak. It is also prohibited in that case - since it may draw in combustible or explosive mixtures from the boiler room.

Many boiler installations use fuel oil as a backup. The segragation of fuel oil spaces is a familiar requirement. There are many other codes that cover these issues. NFPA 54 and 31 deal with combustion fuels, and BOCA and SBCCI also deal with combustion and ventilation air. There are others, as well.

Smaller packaged steam or hot water boilers may have greater flexibility, but I would note that even residential hot water boilers have minimum requirements for fire-rated enclosures.

It is correct to suggest that cost and space are the issue: because fuel and combustion devices require a greater investment in facility costs. Economically, the choice is reducing that area and that cost, not increasing it by co-locating other items that require additional protection from the pre-existing equipment.

Ultimately, it is up to the Engineer to recognize these dangers. No code can instruct on the knowledge of the equipment design, its operating materials, or which codes apply.

 

[cme]

So say in a hospital where steam is used for laundry, sterilizers, etc year round and you have a leak from a chiller, the whole plant goes down

That doesn't make good engineering practice in my book!

 

[haneyrm]

cme makes a valid point about specific applications. Our firm trys to follow ASHRAE 15 to the highest degree feasible. Sometimes it is just not reasonable to separate refrigerant from combustion. Many engineers would make the counter-argument that putting the integrity of the equipment operation ahead of life safety is bad engineering practice. I fall into that category. Your mileage may vary but for us, life safety is #1. If there ever was an issue, we could at least demonstrate that we followed the standards or codes available at the time of design and exercised due diligence in attampting to protect the health and welfare of the facilities occupants. If it ever got to court, without the ability to prove that you exercised reasonable caution (such as following the available standards at the time of design), you are had.