Boiler and burner sizing

[GWardrope]

I have a small 110kW boiler. Gratful if anyone can advise if I can fit a larger rated burner to the boiler i.e. 160kW. It is a small cast iron sectional boiler. the system has been designed with a variable flow from 100% to zero. This seems incorrect?

 

[rmw]

You can mount the bigger burner if you don't have any physical limitations. Having a bigger burner only means that the burner will cycle to low fire and/or off more often than a burner sized more closely to the boiler capacity.

rmw

 

[pmover]

no!, the larger burner does not seem correct to me.

i'd highly recommend contacting the boiler mfg BEFORE recommending &/or conducting the work.

why are you wanting to install the larger capacity burner than what boiler is rated for?

-pmover

 

[GWardrope]

Hi,

basically the boiler is a small cast iron sectional boiler. it is used to heat a building with main/standby. There is not data on teh boiler and the manufacturer is no longer in business (in went to the wall following the argentine currency crash). The with a full rated burner the boiler does not get up to temperature. The quality of the gas is supect (they boost the supply with air during high winter demand period)

 

[kbs]

You should find a rating plate attached to the cast iron sections under the cabinet somewhere. Usually attached to the tie-rods holding the sections together. On it should be the heating surface area. You should be able to size a burner from that. There is no sense putting more heat into the boiler than it can transfer to the water. You would only be heating your chimney.

 

[pmover]

ok, short of any mfg data . . . and not getting "up to temperature" . . .

it seems to me that if combustion is taking place and boiler water is not getting up to temperature, then there may be other matters to look into. hence, the following list of questions or suggestions.

has the cast iron boiler been examined or inspected for scale/mineral deposits? scale will inhibit heat transfer, thus waste energy or increase the amount of fuel consumption.

has temperature probe for controlling temperature been inspected/examined for cleanliness and proper operation? a faulty or fouled probe will impact boiler temperature control; thus fuel consumption.

have other boiler safety & operational equipment been examined and inspected for proper operation? low-water shutdown device (if water boiler), boiler relief/safety valve, water supply/return/make-up system, etc.

is the burner an atmospheric burner (no blower) or a power burner (has a blower)?

when combustion takes place, is it possible to observe the amount of flame inside boiler relative to available volume in combustion box?

something to ponder or examine, if not already accomplished.

good luck!
-pmover

 

[olmedo]

No, you should not fit a larger burner. The furnace volume is fixed and was designed to accomodate the heat release rate of the existing burner. Simply to say, If you fit in a larger burner the furnace volume will not be correct anymore.

 

[TBP]

Aside from any operational issues, folks should be very careful regarding the capacity of the existing safety or relief valves when considering a larger burner.

 

[GWardrope]

Guys,

Thanks very much for your views.

We have opened up the boilers and cleaned the water and fire tube sides. The problem may well be the practice of the gas supplier pumping compressed air into the system to boost the gas pressure during peroids of high demand. This is lowering teh calorific value of the fuel.

In argentina they work on a design temperature rise of 5 Deg C rather than 10 Deg C that we use in the UK. In the UK we are also used to the practice of keeping the return boiler water temperature up to avoid back end corrosion, but in Argentina they are not.