Code Quest.: Chillers and Boiler in Same Room? 2

[stellabella]

Is there a code that prevents chillers and boilers from being located in the same mechanical room? if so, does anyone know when this went into effect? Is there any boiler or chiller size that triggers the code? And, why is there such a code, if it exists. Thanks!

 

[krb]

I don't think so, we have a couple of mechanical rooms here (in the US) with both in the same room. Some of them are new, so they comply with the latest codes. I was not the design engineer, so I don't know what codes reveiw they went through.

KRB

 

[Whoops]

I think there is, or was, a mention in a British Standard in the UK. I can't recall the details, something to do with toxic fumes if refrigerant was drawn into a boiler & burnt.

 

[DRWeig]

Can't come up with a code, but it's a good practice to consider what happens in the event of a catastrophic refrigerant leak. Snuffs out the boiler flame due to lack of combustion oxygen. In some older machines, might cause a resultant furnace puff (or worse) when re-ignition occurs since flame might be snuffed at full throttle, thus dumping a bit of gas into the furnace before the safeties shut it down.

Modern flame safeties should prevent this, and also your chiller's rupture disk should be piped outdoors, so it's more of a thoughtful thing than a real need...

Best to all,

Old Dave

 

[friartuck]

If I remember right, certain refrigerants when exposed to a flame produce phosgene gas which is toxic. A refrigerant leak theefore could be dangerous.

I know of a number of jobs where the fridge pipes have been enclosed when passing through a boiler house.

Alternatively, if you really have to put refrigerants in a boiler house, then perhaps some form of emergency ventilation might be appropriate.

My initial feeling however would be to keep 'em separate and avoid the risk in the first place.

Friar Tuck of Sherwood

 

[spector]

DRWeig and friartuck are both correct,

As to any code requirements, you should check with your local jurisdiction. ASHRAE 15-2001 does not prohibit it, local/state code might.

Most federal agency instructions do prohibit it when designing themself a new chiller/boiler plant....Same for some industrial owners....It all depends on their own written instructions and in many cases, that of their insurance carrier.

A large hospital here in my town just commissioned a new combined plant and had no problem passing state/city code.

Keep in mind that if the boiler(s) and chiller(s) are located together, the plant must meet ASHRAE 15-2001 concerning proper leak detect and emergency ventilation requirements....and the ventilation provided must be in addition to that required for boiler combustion air.

 

[walkes]

There is a CSA (Canadian Standards Association) code B52-99 that will not allow flame producing equipment in a refrigeration machine room. The requirement is based on the amount of refrigeration in the system and the type of refrigerant. The reasoning is that if the refrigerant goes through the combustion process it may become more toxic and carcinogenic.

Small modular chillers can be installed in the same room as boilers, but I believe you must still have a refrigerant detection system that will shut down the flame producing equipment when a leak is detected.

Some of the requirements of separation may also be avoided by having the appropriate Power Engineers on site during occupancy. (Power Engineers Act up here)

 

[lilliput1]

ASHRAE 15-1992 Safety Code for Mechanical Refrigeration Paragraph 11.13.5 says "No open flames that use combustion air from the machinery room shall be installed where any refrigerant other than carbon dioxide is used."

In installations where it is not possible to partition off the boilers from the chillers consider providing an interlock w/ the refrigerant leak monitor system, to shut off the boilers when refrigerant is detected. Hopefully the refrigerant leak can be purged out before the facility have any problems from lack of heat. This procedure may not be allowed in hospitals where a redundant boiler is required and also where steam sterilization processes or other process heating are in used.

 

[krb]

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 combustionprocess in the event of refrigerant leakage.

KRB

 

[Whoops]

One relevant British Standard is;
BS 4434:- Safety aspects in the design, construction and installation of refrigerating appliances and systems (No longer current but cited in the Building Regulations)

The pertinent clauses are;

3.2 Machinery Rooms serve for accommodating refrigeration machinery but need not serve exclusively for this machinery. It is however recommended that boilers and other naked flame devices should be excluded.

H.3.2
The installer or manufacturer is required by the Health and Safety at Work Act to draw the attention of the user to........the extra danger to health from decomposition products caused by smoking or naked flames in the presence of certain refrigerants.

This document is 15 years old and refrigerants have changed a lot in that time. There's probably other BSs with similar safety clauses.

 

[jherbert]

hi,

steelabella asked for the reason for the code(s) and although newer refrigerants are somewhat safer, phosgene (mustard gas) formation is a real concern when traditional refrigerants (say R11, R- 12, R-113, R- 114) decompose.

Refrigerants and flame don't mix.

cheers,
John

 

[MintJulep]

Let us not forget that direct-fired adsorbtion chillers exist.

ASHRAE 15 appears to be attempting to prevent the formation of decomposition products by reducing the likelihood that refrigerants and flame will share the same space at the same time.

 

[cme]

A chiller room is held at negative pressure, the cfm depends upon the lbs of refrigerant per ASHRAE 15, a value for min cfm and another for max cfm. Boiler rooms on the other hand are at neutral to positive pressure.

 

[triton99]

I think that Section 1104.3.4 (including the exceptions)of the 2000 International Mechanical Code outlines all items necessary to prevent the decomposition of refrigerant (i.e. boiler in the same room). They can be in the same room, but if it is a natural draft boiler you have to have a refrigerant monitor interlocked with the boiler. If you have a force draft boiler there is nothing that you have to do. ASHRAE 15 wants a refrigerant monitor regardless, but that is more for safety.