room sealed flue

[piperdave]

im currently doing my gas courses at the moment but im struggling to find this in my viper book/notes

i know for open flued boilers it has to be 600mm before a bend but is this the same for room sealed ? or can it be elbowed straight away

all help appreciated
piperdave

 

[Puddle]

Well you have to check manufactories instructions

presume you are talking about fan assisted room sealed appliances
On most new appliances elbows can be fitted straight away you just have over all length reduction per elbow to take into account as each elbow increases resistance on fan
Some or the older f/f-r/f appliances did not allow elbows to be fitted
even some today only recommend one elbow to be fitted,this is usually the one on top of boiler and usually the cheaper models


The 600mm rule for c/f-o/f comes from the fact that when they were are designed and tested, there is a 600mm straight length of flue put on top during testing therefore you should not bend before this height,they do work and many are fitted below this straight length although sub standard installations

 

[piperdave]

yes sorry puddle thats what i mean the room sealed fan assisted

so am i right in thinking on that type of flue it can have a bend straight away say if you are doing a vertical flue, you just have to allow for the bends fitted and what they compensate for ? when calcualting full length of flue

 

[Puddle]

Well yes
Most manufacturers will take the first elbow into account on a standard horizontal flue,so you will be allowed have elbow on top of boiler and say 3m to 4 m of standard intake and outlet flue,then remove say .5m for each extra elbow fitted

Again you are governed by manufacturers instructions,however if elbows are allowed,they can normally be fitted straight to boiler
As said there is no reason for a straight length on f/f-r/s appliance and as no natural pull is required,as fan in doing the work,therefore position of elbows is not a factor,just amount

 

[piperdave]

ok i understand thanks alot for your help puddle really appreciate it ! thanks again