Oil burners and bi-fuel ballon

[mike.m]

On an earlier thread we were discussing the question of the cost of using an oil based boiler to source summer hot water and concluded that the most cost effective system was overnight electric heating . In case others are unaware if you have a ballon (preparateur) heated by the serpent from the boiler  you can bypass this system by installing a relatively cheap (300 euros ) element which fits into an existing ballon . A bit like plugging in an element into a kettle . Thus if you dont want the boiler sourcing summer water you just switch it off and it reverts to a standard overnight heating system using cheap edf rates .None of the plumbers volunteered this solution it was suggested by an adviser at the wholesalers. You can also buy bi-energie ballons if its a new installation.

                                                                                       My specific question - and I hope Gluestick is tuned in -is about oil burners . I'm replacing my defunct boiler with a 35 kw system and the best quote came from a chap who wanted to replace the whole unit - boiler and burner . Another chauffagist has suggested that the existing burner is up to the mark . I dont have the technical documentation but on taking the casing off the burner it looks brand new . Its a Cernod N 4 and I've checked their website ; am I correct in reading that this model can deal with  18 to 40 kws .? Is there something else I need to ask/know .

 

                                                                                                   Much appreciated

                                                                                     

[Gluestick]

Many French oil boilers come sans the Brûleur, which is the pump, injectors and etc all in one unit.

For example, a nominal 35KW central heating only boiler (Chauffage Seul) was only  € 499, sans Brûleur, whereas the whole shooting match was more than € 1500.

I have no idea unfortunately, what your specific Brûleur can deliver in terms of maximum heat output: that will be a manufacturer query.

I would most definitely consider replacing the boiler body and using the existing Brûleur, provided it delivers sufficient output.

Western society throws away far too much kit which is perfectly servicable.

If it aint broke, why fix it?

Friends last year had a quite old boiler overhauled and serviced by our local top plombiere, chauffagist and his firm simply fitted a new Brûleur since when it has all been working splendidly.

 

[mike.m]

Hello Gluestick,

                         Sound advice as ever .On re-checking the manufacturers website I'm pretty sure that the output  is in the range 20~40 Kws.  Is it better or worse, more or less efficient to have a bruleur working at the top end of its capacity ?

[Gluestick]

All boilers these days tend to be made with a wide heat output range.

Actual heat output is set by installing the correct jets on installation and adjusting either the pump pressure and flow (oil) or gas valve (gas) on commissioning.

Thus with your Brûleur, for example, the installer would (should!) set it up for anywhere between the 20 to 40 Kw capacity, depending on system demand.

There is no point in setting a Brûleur above the level of heat output which can be conveniently managed by the boiler: the excess heat would just go straight up the chimney!

Expensive!

Personally, I'm a great believer in "Grunt"!

If the rest of the central heating system is correctly designed and installed and the appropriate controls are in place (diverter valves, motorised valves, room stats, TRVs etc) are correct, then the system will only demand what it needs to meet the design parameters.

In other words if the system is calling for 35 Kws, once the room spaces are to temperature, the system will shut down until the room temps drop significantly, (Allowing for the built in designed and natural hysteresis of the stats etc: in other words the inevitable "lag" of demand waiting for the system to respond).

All that said, modern systems (particular combi type and condensing boilers) and the associated rads tend to be designed optimally, as it is believed this is more energy-efficient.

I am not too happy with this philosophy: my own belief is that if a house requires x BTUs/KWs to reach and maintain the desired temperatures, then designing in "Overkill" doesn't make any difference! The system will demand x BTU/KW and no more.

I also like to have some over-capacity, in terms of rad sizes and gross boiler output; otherwise a sudden dramatic drop in temperature causes the boiler to be on all the time as it tries to reach the desired rooms temps and maintain them. (Due to the faster rate of heat loss to the outside air).

 Sudden temp drops are very common in France: in the North during Paques, the temperature nose dived in hours and we had a severe blizzard! Two days later the temperature went up almost ten degrees and the sun was shining!

So, when specifying your new core boiler unit, opt for the top end, in terms of heat output, rather than a lower size.

It should mean it actually cycles for shorter periods as it is able to deliver more heat per time period than a smaller unit.

Hope it all goes well.

 

[mike.m]

Hello Gluestick,

                           I've called the manufacturers and the bruleur is indeed  good for the job so recycling will prevail . The chauffagist is coming back tomorrow and I will incorporate your comments into our meeting .Many thanks .