Morso 4560, Instructions For Installation And Use Manual

DK ENG

1.8 Draft conditions

If  smoke  spillage  occurs  when  the  fire  door  is  opened,  it  is  probably  due  to  poor  chimney 
draft. This type of stove requires at least  pa of chimney draft to achieve satisfactory com-
bustion  and  smoke  spillage  prevention.  However,  in  cases  where  the  stove  door  is  opened 
too vigorously you could expect that slight smoke spillage may occur. 

4560: the flue gas temperature at the rated output is 291˚ C relative to 20˚ C.
          the flue gas flow is 4.9 gr/sec.

5060: the flue gas temperature at the rated output is 333˚ C relative to 20˚ C.
          the flue gas flow is 6.6 gr/sec.

If you have any doubts, you may want to have your installer measure the draft in the chimney.

Draft conditions

the chimney’s draft is the resulting effect within the flue caused by the dif-
ference  in  temperature  within  the  flue  and  the  cooler  temperature  outside. 
Other  factors  that  can  influence  the  level  of  draft  include  the  length  of  the 
flue, insulation of the chimney, adverse weather conditions or tall buildings or 
trees nearby the flue terminal.

Poor draft occurs when:

•  the atmospheric temperature difference is too low, e.g. a poorly insulated  

chimney. If the chimney is excessively cool, it may help to ‘prime’ the flue        
before the fire is lit. Just place a screwed-up sheet of newspaper in the              
flue-ways of the stove and ignite. 

•  the outside temperature is too high, e.g. during the summer months.
•  there is no air movement (wind) outside.
•  the chimney is not tall enough, with the result that the terminal sits in the     

lee  of the roof surface or in the vicinity of tall trees or neighbouring                       
buildings. these conditions are also associated with downdraft where the      
flue gases are pushed back down the chimney. 

•  Flue draft is diluted by residual air entering the chimney, e.g. due to                         

inadequate flue-pipe joints or leaks at the cleaning door or flue collar.

•  Unsealed, unused fireplaces are connected to the chimney.
•  the flue is blocked, e.g. by soot, due to inadequate cleaning, loose debris or 

even a birds nest.

•   the house is too tightly sealed (see section on Fresh air supply).

A good draft is achieved when:

•  the temperature difference between the chimney and outside is high. this al 

so applies during firing, when the need is greatest.

•  the weather is clear and there is a good wind.
•  the chimney is of the proper height, i.e. minimum 4 meters over the stove      

and the termination adequately clear of the roof line.