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Posted By: renosteinke Oil Burner Primer - 01/31/09 01:58 AM
Last month I encounterd an oil-burner furnace, one that was itself a conversion of an older coal burner. It occurred to me that I am of the last generation to actually remember coal-fired furnaces, so I thought a little 'primer' was in order for those who do service work.

First, an overview:

[Linked Image from i143.photobucket.com]

If you look closely, just above the blower you can see doors for loading coal, as well as clearing out the 'clinkers.'

The blower has another component attached to it. That rectangular part, under the blower and to the left, is the ingnition transformer. Carefull - these generate 10,000 volts! The black coupling on the wiring actually IS an electrical coupling; electrical hardware once had a glossy black finish.

[Linked Image from i143.photobucket.com]

Now, if you followed those wires, one place they would lead is to this gizmo, mounted on one of the ducts:

[Linked Image from i143.photobucket.com]

Called a 'stack controller,' this is what tells the furnace to fire. The loose wires you see are the thermostat leads.

The proper wiring method is: dedicated circuit -> disconnect -> stack controller -> blower assembly -> neutral.

What I actually found in this basement was 'does it all circuit' -> blower assembly -> stack controller -> disconnect -> neutral. This lead to two undesireable things:
1) The basement light was out when I turned off the furnace power; and,
2) The HVAC guy got shocked even though the disconnect was opened; everything was still 'hot,' the result of having the disco LAST, rather than first.

How did this happen? Well, the original sparky wired the knob & tube up that way (white wire as 'hot'), and the various homeowner additions only made it worse. Here's the splice:

[Linked Image from i143.photobucket.com]

Finally, here's the basement lighting I was deprived of with the furnace power off:

[Linked Image from i143.photobucket.com]
Posted By: leland Re: Oil Burner Primer - 01/31/09 05:23 PM
Wish I knew this would show up.
My Dad had an old coal fired boiler,converted to oil in the 60' and just upgraded about 5 yrs ago. Boy was that a beast!

Those older systems seem to be the ones I know best,as that is what my early yrs consisted of,working with my uncle and Dad as a child.
Posted By: Alan Belson Re: Oil Burner Primer - 02/01/09 12:38 AM
You can glean much information from a picture. The make 'RAY' is unknown to me, a european, but the principle of the pressure-jet burner is universal. A gear pump draws oil from a tank. This passes to a pressure relief valve, usually set at about 100psi. Some oil is directed to a nozzle jet, where it is broken up into a spray-mist and ignited by a spark of 5-10,000v between ignition tips. The flame is formed in a 'retention head' to keep it attached to the burner and not get blown out by the high flame velocity. Excess oil [ up to 90% of the total drawn ] travels back to tank - the jet size and the pump pressure control the amount of oil burned. This is usually marked on the nozzle in US gallons/hr at the [standard] 100psi. The two line-fuel arrangement shown here is recommended if the tank is lower than the burner, to prevent oil cavitation. The motor, usually only about 100W, drives the gearpump and also an axial-blower which provides air via a variable flap, all combustion air being under pressure and adjusted to a get clean efficient burn. These burners can handle a variety of oils and kerosenes, but usually burn diesel of some sort, as it's cheaper.

Around here they were commonly added to the loading door of old woodfired boilers, hot-air furnaces being a rarity, and seemed to work quite well, if a bit noisy.

Underslung from this setup in the black box is probably the 'controller'. This usually employs a flame monitoring photo-cell device to provide 'flame out' safety before during and after burn, locking out the burner if 'unsheduled' burns occur! This is handy, as it precludes spraying oil into a flue fire! It also switches out the ignition arcs after a delay of about 15-30 seconds to conserve the igniter tips, and sometimes a pre-purge start delay to get the pump line up to pressure before firing- this saves fuel by ensuring a good spray at start. Recently electronic versions have appeared, displacing the mechanical-switched versions of yore, designed specifically to stop Alan building specials from junked units displaced by woodpellet burners!

I notice the RAY is standing on a Cast Iron tripod adjustable for height - marketed as an add on for solid fuel conversions perhaps?

Reno, I think the wiring may also be incorrect, [apart from the shock hazard!!] if shutdown also turns off the light! The duct stat should shut down the burn as 'furnace hot enough' by signalling the controller. The hot air should continue to flow to the dwelling by the ducting blower. A stat or programmer in the house should initiate 'call for heat' and 'call satisfied' signals to the controller and simultaneously control the ducted air blower to turn on/off the burn and the flow of hot air. Burns should be as a long duration as possible to use less fuel, as start ups are less efficient.
Posted By: Alan Belson Re: Oil Burner Primer - 02/01/09 01:04 AM

I might add my atavar shows an early model of my 'waste vegetable oil' burner, running on test at night to get a good flame pic [ and deemed unsuitable due to unburned oil in the flame lacquering the boiler innards!] The 'flame retention head' is just visible, glowing dull red hot. This is about 100,000 BTU / 30kW power, based on Danfoss parts.

I'm currently able to get a blue 40kw flame from WVO by thermally cracking the oil at 700F before the burner head, unit mothballed till the spring as other projects have taken priority, like 'her indoors' insisting on a kitchen! I'll post more then.

Alan
Posted By: Trumpy Re: Oil Burner Primer - 02/01/09 02:28 AM
John,
Great thread, mate!

We need more like it too, you can't buy info like this.

Thanks also to Alan for your input. cool
Posted By: frenchelectrican Re: Oil Burner Primer - 02/01/09 03:53 AM
That is good details there John and yes I do remember early coal fired boiler / warm air furance those unit were huge and I did work on one steam boiler { 15 PSIG system } it took a while to get the steam up but once you got there it stay there for very long time and it last pretty long time before have to refired again.

Those common resdentail / light commercal- industrail burners you can able change the firing rate { size } by changing the nozzle size and adjust the air door a little.

Yeah they can burn almost any fuel it go thru but not gasoline { too fast for combustion chamber } they can burn #1, #2 Diesel fuel / Heating fuel , Keronse , Jet fuel , some case old engine lube oil { if preheated yeah it will burn pretty good }.

Merci,Marc
Posted By: renosteinke Re: Oil Burner Primer - 02/01/09 07:24 PM
Alan, you are correct ... our codes have required furnaces to have their own dedicated circuit for decades. That is, the circuit needs to supply nothing but the furnace and associated equipment (for example, a hunidifier or air cleaner). Or, with proper switching, an air conditioner can use the same source of power.

This house, though ....
The panel was on the outside of the house, and the circuit ran up the wall to the attic. Where else it went on it's journey through the house, back to the basement, is anyone's guess. All I can say for certain is that the light, and several other things, went out when the heating guy shorted the wires to ground.

A reminder ... he didn't do that deliberately ... rather, he opened the disconnect, adn shorted the wires while attempting to remove the stack controller. They were still hot, as the disconnect was on the "neutral" side of the circuit.

You often find the neutral and hot reversed in knob and tube installations, as the insulation is often all the same color: black. This house was the exception; there were cloth-covered wires in black, red, green, and white.

Lest one become confused ... remember, Knob & tube wiring pre-dates then use of green wire for grounding. In such a house, the green is very likely to be hot! When I had sorted out the wiring, everthing was hot ... EXCEPT the black, which was the neutral!

I 'solved' this one by running a new, dedicated, circuit to the disconnect, and re-wiring the furnace. Now, the furnace just may be the only code compliant circuit in the house.
Posted By: aussie240 Re: Oil Burner Primer - 02/04/09 01:11 AM
If I may ask a dumb question, coming from a country where residential central heating is not common, (certainly not this oil fired kind), what stops the flames and/or carbon monoxide going into the ducts? Is there some kind of heat exchanger? If so, what if it leaks?
In Australia, oil heaters were popular from the 1960's up until the mid 70's, but they were installed in the living room, like a gas heater or enclosed fire place. The oil seemed to be more like kerosene, and I discovered it burnt just as well in hurricane lamps. There was a tank mounted on the side of the house that would need filling about once a year. Used to be a common sight around suburbia to see an oil truck parked outside someone's house with its black hose trailing down the driveway.
We had a late 60's model in the first house I lived in, which burst into flames in the middle of the night. It had a burner much like a gas ring, and you opened the door to light it with a match. It was replaced by a more modern version that looked more like a gas heater, with ceramic panels to radiate the heat from the burner underneath. Ignition was from a heating element; after a few minutes it would suddenly burst into flame.
Posted By: renosteinke Re: Oil Burner Primer - 02/04/09 03:58 AM
Aussie, that entire monster unit is a heat exchanger. Exhaust fumes are vented outside through their own duct. House air is circuilated over the exchanger inside that unit.
Posted By: frenchelectrican Re: Oil Burner Primer - 02/04/09 04:28 AM
The other thing I forgot to mention here that some of the old furance some are gravity curicationed { sans force air blower } as warm air rise the cool air sink that how it work on old furnce but one major gotcha what many oldtimers know do not overfire {overfueled} them.

Merci,Marc
Posted By: noderaser Re: Oil Burner Primer - 02/04/09 04:38 AM
I'm assuming that the heat exchange takes place over the cast iron surface of the old stove, and that the air is circulated through the galvanized sheet enclosure built over the old shell.
Posted By: maintenanceguy Re: Oil Burner Primer - 02/04/09 02:49 PM
Aussie:

Two common types of combustion central heating in the US:

The first is just like you mentioned, an oil or natural gas fired burner with a heat exchanger to separate flue gasses from heated air. The heat exchanger is several layers of thin steel, every other space between layers has either combustion gasses or heated air.

The second type is hydronic heating where a oil or natural gas fired burner heats water which is pumped through radiant heating units throughout the house, Several styles of radiators are available.

Most heaters are now natural gas since every urban and suburban neighborhood has gas delivered by the local utility. I live in a rural area and I have an oil fired heater with a 275 gallon oil tank that we fill about once a month.

And the oil is very similar to kerosene. Fuel oil is given grade numbers here based on how thoroughly it's refined. No. 1 oil is kerosene. No. 2 oil is diesel fuel or home heating oil. I've never seen anything heavier than No.2 in anything other than a large commercial or industrial application. The heaver grade oils need to be heated in the tank or they won't flow in cold weather.
Posted By: Alan Belson Re: Oil Burner Primer - 02/05/09 12:05 AM
Here's a more or less 'modern' version of a pressure jet burner, cover off. Exactly the same functions as the 'Ray', except all the parts are crammed into the smallest possible space to make maintenance a nightmare. [Just like under the hood of your car!]. This one happens to be running on vegetable oil, hence the fryer at rear heating the oil to get the viscosity and flash point closer to diesel oil's.

https://www.electrical-contractor.net/PC/AB_CIMG0741.JPG

The main safety feature in pressure jet burners is a photoresistance coupled with the controller. At 'call for heat', the photoresist circuit will not allow the oil solenoid to open if it 'sees' light or IR, for that indicates that the boiler/furnace is already on fire! Assuming it's not, the controller instigates ignition, and the photoresistance must now see light/IR within about 15 seconds, or it shuts down the burn. It monitors that burn throughout ensuring flame outs dont cause a hazard. This is to prevent the firebox filling with diesel, all primed to burn your house down next time ignition succeeds! Finally at 'call end' the controller resets, awaiting next call.
Older controllers are just a series of relays and timers arranged to a safe sequence, modern ones may be solid state.
If a burn sequence fails, it's usual for the controller to 'lock-out' and await a manual reset. [I should add that there are other sequences in the controller, such as pre-heat nozzle, spark on/off, motor on/off etc.]

Aussie, what you saw was probably a wick type burner. These only ran on kerosene [paraffin to us limeys!], a lighter fraction which is re-processed to remove low flash-point fractions [petrols]. This fuel was first used earlier last century as lamp oil. The wick burners are very efficient, hence the blue flame, but obviously need more care to keep the wicks in good trim. When I was a kid smaller units ran in folks houses exhausting fumes into the rooms. Deodorised kero was often used, [Pink Dont Stink, Esso Blee-Dooler, ]
I have lately noticed these in-room blue flame heaters on sale here in France. And they do stink!

As to bursting into flame, that is thankfully a rare event, but it does happen. A guy up the road from here lost his home in an oil boiler fire. The burner malfunctioned and pumped diesel into the fire. The granite walls melted!





Posted By: frenchelectrican Re: Oil Burner Primer - 02/05/09 01:27 AM
Alan.,

There one thing it did remind my old days I used have old oil stove that is not a wick type more like pot burner type dang., set it low to med setting you will keep the house more than just a toasty warm but only one glitch is once a week to twice a month clean up the burner { more often if burn on #2 diesel fuel unless you snagged 400 liter worth of JP-8 now that is very clean fuel }

And that burner you show to us it simuair what we have in the states not much differnce on design.

Merci,Marc
Posted By: noderaser Re: Oil Burner Primer - 02/05/09 06:47 AM
I remember one of the "pot" type oil furnaces at my grandma's place. It was a brown glazed metal, about the size of one of the old woodstoves, obviously made to replace such a stove. If I remember correctly, the oil was siphon fed and you had to light it manually. It had a fairly large compartment that you could remove the burning bowl from for cleaning; I vaguely remember that it was also used to burn papers and things in, although I'm not sure if that was a valid use or not.
Posted By: Alan Belson Re: Oil Burner Primer - 02/05/09 02:45 PM
Those wick-less bowl burners were probably the infamous 'drip-feed' heaters. They were cheap to make and were often used as additional heating appliances, being portable and almost always used unvented in the UK, mainly by poorer folks. In 1956 in Britain, over 2000 house fires were attributed to these beasts. By 1958, the number of fires had doubled to over 4000, and they represented over a third of all domestic fires. In 1960 a Private Members Bill was placed before Parliament, forcing makers to introduce safety features so onerous that it effectively killed them off, thank goodness. The problem was that in quite mild drafts, less than 4mph, the bloody things went off like a bomb, with flames emitted in all directions. That sometimes meant just opening a door! Folks burned to death refuelling them while they were running. Many of the fatalities were young children and babies, and it became illegal to leave kids unattended in a room with one. Even so, the fires spread so rapidly that, in at least one instance, adults in a room were powerless to stop children getting badly burned. The legislation also covered wick-type burners, the main effect being that they were fitted with a tilt device, so that in the event of the stove getting knocked over, it triggered a snuffer to put out the flame. A friend of mine burned his ass by sitting on one in the fifties! Ouch!



Posted By: Alan Belson Re: Oil Burner Primer - 02/05/09 03:00 PM
Here's an old style British-made 'Aladdin' blue-flame wick burner of the period. Makes a handy stool, don't you think?

http://www.hattersley.co.uk/images/products/b1.gif

Alan

Posted By: Rewired Re: Oil Burner Primer - 02/06/09 07:12 AM
Pressure jet burners used to be common on garbage incinerators in older apartment buildings and schools. I still see complete units in the boiler rooms of these places but never operational.

A.D
Posted By: frenchelectrican Re: Oil Burner Primer - 02/06/09 07:29 AM
beside that alot of larger furance or boiler have dual fuel set up so they can run either natural gaz or fuel oil { diesel fuel } majorty of them used on gaz but keep the oil on stand by or where the gas supply drop a bit.

there are serveral way to get the oil system on but two most common is either high pressure pump or use the steam {more often used with HFO ( Hevey Fuel Oil )]

Merci,Marc
Posted By: Alan Belson Re: Oil Burner Primer - 02/06/09 07:04 PM
Marc, you mentioned burning waste lube-oils. These short US videos give an excellent description of the pressure jet burner adapted for that purpose, show a burner set up, running and what oils it will burn, [ These are adverts, so this is not a personal endorsement of the product.]

The parts are described in American English.
You will note that there is no gear-pump, the oil being delivered by air-powered venturi nozzles, so an air compressor is required. The nozzles look similar to Danfoss-Hago stainless-steel types which I've used. The machine is fed from a day-tank, scales to about 20-30 US gallons. The oil is heated to about 212F/100C for viscosity and ignition purposes - veg oil has to be a lot hotter. The air is heated too, with a cartridge-heater; this is an essential part of the machine.
This is a powerful burner, twin top-end Hagos could put out well in excess of a million BTU/hr = 290kW.

You can rate oil consumption at roughly :
1 liter waste lube or veg oil = 10kW hours
1 US gallon " ditto " = 129,000 BTU

http://www.youtube.com/watch?v=q4ZriEMN0FQ&feature=related

http://www.youtube.com/watch?v=4SX1lNvUjZg&feature=related

http://www.youtube.com/watch?v=BrTXJDcTzn4&feature=channel

Alan





Posted By: Alan Belson Re: Oil Burner Primer - 02/09/09 12:12 AM
Back on topic. Conversions of solid-fuel apparatus to oil, gas or other automatic-supply fuels will be a very rare event, given that many of these will have been obsolete for decades.

More likely is that the electrician may see an oil fired unit converted to burn....solid fuel! crazy

Step forward..dah! dah! The wood pellet central heating burner!
These are popular in Nothern Europe, where they gotta lotta trees. The pellets are made from waste wood, highly compressed into cylinders about 5/16" diameter x 1" long. The 'glue' is lignin, which is part of the wood's structure. It 'melts' at about 200F in the pressing operation and is a natural binder. Pellets are force dried after pressing.

Here's a few samples of the genre from Denmark:

http://wood-pellet-ireland.blogspot.com/2006/06/danish-pellet-burner-units.html

Ignore the political drift. The information is basic, but the pics are good.
Costs? Not good, given that a quality p.j. oiler can be had locally for well under $500. They will get cheaper in time.

These are obviously second cousins to the pressure jet oil burner. Ignition on the 80,000 btu model I examined locally was by an electrical hot-plate, set in a tiny firebed, which was raised to about 500-700F prior to a burn. There may be an issue here on the electrical costs of starting up? It took about 15 seconds to get to 'ready to fire'. The next [automatic] sequence was the start of a screw-auger to pull up pellets from a store bin. A small quantity of pellets [about 3 oz?] tinkled into the firebox, the fan started and she was away! Much quieter than a pressure jet. This cycle of three ounces of pellets was repeated every 60 seconds or so. As this was a friend's brand new machine, [ I noted the yellow duster on the bench, we are all the same us techno geeks, aren't we! blush], I felt it to be slightly discourteous to rip it apart to find out how the fuel is metered- it may be just a timer. Pellets are very dry, between 6-10% moisture, [as compared to c.18% for airdry cordwood], and must be stored & kept dry. Their net calorific value will be c. 6000 btu/lb @ 10% m.c. This value takes account of the wood's hydrocarbon contribution, [one pound of hydrogen burns to about nine pounds of water!]. With any biomass fuel, a low liquid water content is vital. All water in the fuel [or formed in combustion] must normally leave the stack as steam, as water has a tendency to fall downwards! One pound of water needs c. 1000 btu of latent and sensible heat to convert to steam. This is why wood has a much lower net heat content than coal.
Ash is removed weekly. Wood has surprisingly little ash content, compared to that of coal at any rate.
Controls are exactly the same as for a diesel burner, a roomstat/programmer giving 'calls' to start/stop the burner.

Store bin was 4 cubic metres, 140 cubic foot, the pellets being 'blown' in pneumatically by a bulk tanker. The auger draws pellets up to about 6 feet before they drop toward the burner inlet port.

Pellets are supposed to be 'eco friendly' as they reduce the use of fossil fuels, plus the CO2 is continuously cycled to the atmosphere. My criterion would be cost. Pellets at 10% moisture content need to be priced at under US$200 a ton to compete with oil today and give one a payback to justify the capital outlay if converting from destroying fossils. In my area the price is too high IMHO, at c.= US$320 per ton. I may add that many of these machines will also burn corn [maize] kernels. I costed shelled maize locally at c.=US$180/ton in bulk. It also contains a small % of oil, so its calorific value is c. 8% better than wood at the same m.c.

I'll post a pic of my mate's set up, if I can break in to his boiler room un-noticed next week....

Alan





Posted By: frenchelectrican Re: Oil Burner Primer - 02/09/09 02:53 AM
Alan.,

Sorry to get off topic but you mention pellet burning stove yeah we have in few diffrent size in North America side.,

Let me get the link up for outdoor burning wood/ pellet boiler { yeah they have dual fuel option so you can burn wood or oil/gas set up }

Central Boiler unit

That something from time to time I have to hook up the power to the outdoor units they don't draw much current mostaly for coolant cirulation pump { useally less than 5 amp @ 120 V }

Merci,Marc
Posted By: noderaser Re: Oil Burner Primer - 02/09/09 04:26 AM
The pellet stoves are gaining popularity around here for replacing old woodstoves. They are really toasty for their size! Fuel usually comes in 50lb. or similar bags, though; haven't seen truck delivery yet.
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