Air Intake for Boilers
Air Intake for Boilers
(OP)
There is a boiler room with three new forced draft oil burning boilers (2 ea. 300 HP and 1 ea. 100 HP). I was asked to provide the air intake fan. These boilers will be sequenced according to laod. Any experience with modulating vs. single speed fans and sizing of the air intake system will be appreciated.





RE: Air Intake for Boilers
I have a spreadsheet based on BS6644 for boilers over 60kW. Its very simple and works out mechanical and or natural ventilation but I dont know how to append the excel file.
Anyone got any ideas?
Friar Tuck of Sherwood
RE: Air Intake for Boilers
RE: Air Intake for Boilers
I'd recommend a small handbook titled Fan Engineering published by the Buffalo Forge Company. It contains excellent Chemical Engineering information. Its Chapter 15 deals with the various forms of fan control: variable pitch, variable inlet vanes, dampers (inlet and outlet), variable speed and even number of fans, that may interest you.
RE: Air Intake for Boilers
What is your idea? Do you want to have single variable flow fan for all the three boilers? With single fan, the excess air control may become difficult.
RE: Air Intake for Boilers
RE: Air Intake for Boilers
RE: Air Intake for Boilers
determine air requirements at 100% boiler load.
size air intake based on X velocity or Y ΔP across air intake. recommend not placing boiler room static pressure < atmospheric pressure as this can impact boiler combustion.
if installing louvers, i'd also consider placing interlock on louvers such that boilers do not operate with louvers in closed position.
if in US, contact your local boiler inspector for further direction.
good luck!
-pmover
RE: Air Intake for Boilers
I cant send you the relevent British Standard Excel spreadsheet I have, but I can summarise the basics for you.
The BS6644 relates to boilers over 60kW.
For natural ventilation only you will need ventilation for combustion and to control boiler house temperatures. Natural openings should be at high and low level. The high level vent also allows the escapes of natural gas in the inadverdent event of a leak.
So:
HL Vent=270cm2 + 2.25cm2 per kW input (over and above 60kW)
LL Vent=540cm2 + 4.5cm2 per kW in excess of 60kW
These are free areas. Typical louvre areas are 50% free so the above results should be doubled to give overall louvre sizes.
Where you wish to use mechanical input to the plant room, you need to :
supply 1100 litres/sec per kW
extract 450l/sec per kW (input for natural draft blrs)
or for forced draft you:
supply 900l/sec per kW
extract 600l/sec per kW input
you really need the local codes but these will give you a good start.
PS it is also permissible in the UK to supply only and exhaust naturally, provided the exhaust is at high level and doesn't create a high plant room pressure.
ciao
Friar Tuck of Sherwood
RE: Air Intake for Boilers
RE: Air Intake for Boilers
If however you decided to use per kW, I know a really good fan manufacturer who can supply 'woppers'. Well spotted that man.
Friar Tuck of Sherwood
RE: Air Intake for Boilers
RE: Air Intake for Boilers
Friar Tuck of Sherwood
RE: Air Intake for Boilers
This is a good application for an H&V unit with a steam coil, preferably with face & bypass dampers. You could use the unit also to heat the space in the winter.
Best of luck,
CB
RE: Air Intake for Boilers
RE: Air Intake for Boilers
RE: Air Intake for Boilers
Check out http://us.exhausto.com/