A challenge...

Jamie Hall

and an offer.



We often talk here about "pickup factor" (in steam) or "mod/con" (in hydronics) etc.  And in large power boilers, variable firing rates are common -- they have to be.  But I have yet to see or hear of really good variable firing for residential or small commercial use.



Now with at least some types of gas burners it doesn't seem to be that hard to achieve variable firing; there seem to be options out there.



But not all of us have reasonable access to gas.



And back in the bad old days, there were devices -- beautiful devices -- for coal fired boilers which varied the draught according to the pressure in the system (look at some of Dan's wonderful historical documents).



So.  Here is the challenge.  Would some oil burner manufacturer be interested in working on an oil burner design which had at least a 3 to 1 turn down from full fire to low fire (more would be better -- gas turbines achieve at least 10 to 1 turn down) but which maintained a proper flame pattern in the fire chamber over the entire range and which maintained a proper fuel/air ratio for maximum efficiency (and minimum air pollution) over the entire turn down range?  I envision something with a controllled oil flow (could this be done with variable pressure?  Or would it need a variable nozzle pattern as well?) and a controlled air flow (perhaps working on a feedback from an oxygen sensor or two?)(probably requiring both control of forced draught as well as over fire and stack draughts) all responding -- very sensitively -- to a steam pressure sensor.



Here is the offer: if some manufacturer is interested in developing such a contraption, and would provide the installation and tech. support, I would be interested in letting them play with my system...

Jean-David Beyer

I would think they could do it.

Remember in the old days when automobile engines used carburettors to mix the gasoline and air for combustion? It turns out that the mixture must be pretty much of a constant (I forget the ratio) over the entire speed-power needs of the engine from idle to maximum acceleration up a hill or anything in between. And they could do it. Now oil is more viscous than gasoline, so you would not use an automobile carburatter to run a modulating heating boiler..



The best ever automobile carburettors were made by an Italian named Eduardo Weber. And he started designing these thing to enable heating type oil to be burned in automobile engines. I do not know how well that worked, but they worked great on gasoline.



The main control of the fuel available to the engine was the disk in the throat (venturi) of the carburettor. For a heating boiler, I assume a variable speed fan would be used instead, since there are no pistons going up and down to power the air flow. Now in a venturi, the air flow mixture ratio is not right to maintain a constant mixture, so what is done is to bleed air into the gasoline mixture as it passes through the unit. This is done with a secondary jet in the gasoline stream with holes in it at various levels.l But in any case it can be done. So perhaps a similar technique could be used in the "carburettor" of a heating boiler.

Jamie Hall

Do I ever remember...

Webers, SUs, Rochester, Carters... some set ups were easier to handle than others!  Multiple carb. setups with SUs were a bear.  Triple Webers weren't too bad (some Corvettes).  The big Rochester Quadrajets weren't a whole lot easier.  Carters with mechanical secondaries and manual chokes (think Stage II muscle cars of various flavours) were the easiest.



Those were the days...

Jean-David Beyer

Webers...

I had two Weber 40 DCOE's on both my Lotus 26's from the early to mid 1960s. They had a reputation for being difficult to adjust, but they were actually very easy to adjust, if you understood them and had a synchronizing tool. The only thing I did not like is if the butterfly valves (the ones hooked up to the gas pedal) in a single carburettor were out of synch. You had to put a wrench at each end of the shaft and twist it. Scary. They really needed very little adjustment.



But running an oil-fired heating boiler would be simpler than running a car engine. It would need no butterfly valve, no acceleration pump, no choke (well, Webers did have a choke, though you could not see it because it worked very differently from the others.



Those SU carburettors could, in theory, provide exactly correct mixture at all times, but they did not because the least amount of dust or dirt could impede the movement of the piston in there. and it was right in the air stream, so dust was always available. And if a mechanic was dumb enough to put oil on it, ... .

JStar

OIL

Apparently CARLIN has a H2L two-stage oil burner that is only being shipped on certain furnaces. I THINK the main controller changes the motor frequency to deliver less gas/air on low fire.



http://carlincombustion.com/literature/datasheet/burners/residential/oil/mnezh2lc-041508.pdf



One would almost want to find this control and adapt it for use on ALL burners. Hmmmmm...maybe "somebody" is working on this, and may have some test data to offer in the near future.

pecmsg

Thermo Pride

Thermo pride has a 2 stage system

pecmsg

challenge

Jamie

I don’t think it’s a question of can it be done; I think it’s more of a question of will the consumer be willing to pay for it.

vaporvac

for Gas?

I know this question was for oil, but it seems the pickings are slim for gas as well. The modulating burners were very expensive and I only found one or two multi-stage burners compatible with the SF Tr50s, but could never get info or price. What do the modcons use?



Riello is currently working on a nozzle that would allow hlh burn on its g400 gas conversion burner. Hopefully next year. They indicated, it would be possible to swap out my current nozzle for the new one, which is one of the reasons I went for the Riello. Plus, the price they ballparked didn't seem that much for the gain. ( This was tech support that I was talking with.)



I don't understand the huge price differential between single-stage and multi-staged firing. as it's only the nozzle.

I'd be happy to be a guinea pig for a small multistage gas nozzle.

SWEI

Most mod/con burners

are based on a zero pressure or negative pressure gas valve paired with a variable speed induction fan.  As the incoming airflow changes, the valve maintains consistent gas stoichiometry.  The Midco LNB looks for all the world like a mod/con burner mounted to an adapter plate.



The change from single-stage to two-stage on a power burner would require (at a minimum) some method of reducing (and calibrating) a lower fan speed and a more complex gas valve.

Charlie from wmass

Riello all ready has the burner

http://www.riello.ca/products/commercial-burners/com-oil/rl28-38-50

The thing is it is not yet approved for the 80 series boilers around your size.

Jamie Hall

Not that I really need it...

We have Cedric so closely dialed in that it really would be superfluous...

Charlie from wmass

The fact you named the boiler

really makes me smile. The use of the modulating burner would be best if you were to have TRV's and reduced the heat in certain areas on a room by room bases.

Weezbo

i like this thought

it reminds me to ask again about the Herrmann burner experiment.