11. Setting up the Burner
Setting up the Burner
The Gas Supply: (Also read Guide # 10 - Gas Basics)
The gas used in the burner is supplied as a compressed liquid that follows the immutable laws of physics. Simplified for this note, these mean that when liquid gas in the master reservoir is transferred to a storage container, the storage container will get colder, as will the master reservoir. When the gas is drawn off in gaseous form during use, the storage container will again get colder. These facts require particular attention
“Miniature Steam” steam plants have the refillable gas tank attached to the gas delivery line with a knurled nut fitting and the tank is not physically secured to the mounting tray. This is to enable easy detachment for refilling in open air.
Depending on the ambient temperature at the time and the rate of filling, the tank will cool and may even frost up. If this happens, the tank should be brought back to room temperature by dunking it in warm water before refitting it to the plant.
In normal circumstances the above step should be sufficient to get optimum gas release in starting the operation of the plant but there is still the possibility of chilling from rapid gas expansion during early use. This will reduce the amount of gas available for heating and affect the performance of the plant. “Miniature Steam” plants locate the gas tank as close as practical to the boiler (preferably unlagged) so that there is progressive warming of the gas tank as operation proceeds. In extreme ambient conditions it may be necessary to divert the steam exhaust line through a coil wrapped around the gas tank, to provide the additional warming to offset the cooling process.
The Burner Operation:
The burner converts gas into heat by burning a gas and air mixture in the burner assembly to create heat. “Miniature Steam” burners use individually designed cast ceramic burner inserts to provide maximum burner efficiency for each boiler. There are two components that enable the adjustment to the burner flame.
The first is the gas pipe which delivers gas from the gas tank to the burner. It is attached to the gas tank by a knurled nut for easy removal. At the burner end the pipe is soldered into a brass tube that has a gas jet in the end. The jet limits the amount of gas allowed into the burner, is specific to each burner and not a commercially available jet size.
The second component is the gas mixer tube fixed to the bottom section of the burner that allows the tube carrying the jet to slide in and out. It has a locking screw for securing a setting. The calibration of the burner flame is carried out by sliding the jet holder tube in/out of the gas mixer tube variously exposing an air hole to vary the amount of air admitted to the burner to mix with the gas.
Calibrating “Miniature Steam” Cast Ceramic Burner:
“Miniature Steam” cast ceramic burners are specifically designed to provide optimum burning characteristics in enclosed spaces such as the centre flue or firebox of a boiler. They differ from other ceramic burners made from heating tiles designed for radiant room heaters.
The gas/air mixture of a “Miniature Steam” cast ceramic burner,burns outside the ceramic insert. This results in a more efficient transfer of heat to the boiler’s heating surface. The burner also remains relatively cool thus improving the thermal efficiency of the burner and minimizing the chance of back burning.
Please note that when the burner “roars” it is probably operating efficiently. 2” and 3” boilers have a steady sound where the 4” boiler has a “stuttering” sound imposed over the top of the roar. These sounds are normal for “Miniature Steam” burners.
As the gas supply may vary by location and from batch to batch, it is advisable to undertake a calibration process before starting up a boiler for the first time and when changing gas batches.
To achieve the correct burning characteristics of the unit with any gas batch, the jet holder is moved in the air/gas mixing tube to establish a correct air/gas ratio in the fire tube.
We recommend the following procedure:
- connect the gas source to the burner gas pipe and insert the jet holder into the gas mixer tube
- remove the burner assembly from the boiler and place it on a firm surface with the burner facing up. (Note: keep your fingers away from the burner shroud – it may heat uncomfortably during the calibration process!)
- start by sliding the jet holder in the gas mixer tube to leave the air holes about 2/3 closed.
- turn on the gas at the gas tank and light the burner. You should see a lazy flame flecked with yellow. If not, adjust the jet holder to achieve this. This position indicates that insufficient air is being added to the gas/air mix.
-slide the jet holder to expose more of the air holes until the flame is blue but is ”dancing” on the surface of the burner. This indicates that there is too much air in the gas/air mix.
- move the jet holder back to reduce the air hole exposure until a stable blue flame is evident. This is the optimum setting for the air/gas mixture.
- secure the jet holder in the gas mixer tube in this position with the Allen key supplied by tightening the stainless steel 3 mm grub screw or slotted head screw provided.
- turn the gas off and allow the burner to cool a little before reinserting it in the boiler fire tube. The following image is what you should see when the burner is correctly calibrated.