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Space Heater Connection Size

11/29/2013 11:40 PM

Can anyone tell me what size orfice I need for an LP propane space heater? I have a small shop (12X16) and I am converting the space heater to LP from NG. I have changed the regulator to LP and now I need to reduce the orfice size by 2/3. I plan to sodder them shut and then drill the correct size for the five burner orfices and the pilot. Where can I get a small enough drill to accomplish this. Heater will get very limited use. Maybe an hour or two in a week. Gas will be completly off when not in use.

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#1

Re: fhuwe123

11/29/2013 11:58 PM

What size is the orifice now? It's not orfice. Select a drill that is 1/3 the size of the opening now.

It's solder, not sodder.There are many places to buy small drills. They do not need to be anything special, since sodder is really soft.

Harbor Freight sells cheap inexpensive drills. (Not an endorsement)

There are websites the can guide you. Do a search.

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#9
In reply to #1

Re: fhuwe123

11/30/2013 11:12 PM

Buy the correct size fittings. They are really cheap... and you don't risk anything.

They just screw onto the ends....

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#2

Re: fhuwe123

11/30/2013 12:08 AM

Perhaps it is distributed differently in your place, but normally the line pressure of NG (natural gas) is much lower than LP propane. Normally you will need a bigger opening in your orifice.

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#3

Re: fhuwe123

11/30/2013 12:14 AM

Sorry, I have read it wrong, you convert from NG to LP. In principle, to calculate your orifice hole diameter, you need to know the line pressure and capacity of your burner.

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#4

Re: Space Heater Connection Size

11/30/2013 10:55 AM

Yes. The manufacturers of the heater can relay this information. If the work is done by a registered gas fitter, such as one registered under the CORGI scheme in the UK, then the documented report on the work carried out will not invalidate the buildings insurance should an incident occur.

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#5
In reply to #4

Re: Space Heater Connection Size

11/30/2013 11:00 AM

Dogs are that well trained in Austraila?? What happens if their fur catches fire?

Well, come on CORGI.............., Corgi. I couldn't let that one go by.

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#8
In reply to #5

Re: Space Heater Connection Size

11/30/2013 10:30 PM

Now when he switches to Propane, the dog is more in danger, unless he extends the paws (legs) with some feet. With NG boss man, standing upright, dies first.

Sorry, only when it goes wrong.

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#17
In reply to #5

Re: Space Heater Connection Size

12/02/2013 4:57 AM

Confederation Of Registered Gas Installers [CORGI], silly.

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#6

Re: Space Heater Connection Size

11/30/2013 7:57 PM

I don't know your location, but in the U.S.A., these "burner drills" are often carried in NAPA (National Auto Parts Association) stores. Numbered drills in the range of about 40 to 80 are also suitable, and can be obtained from most hardware stores.

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#7

Re: Space Heater Connection Size

11/30/2013 10:22 PM

What you are attempting to do is more risk than gain. You are dealing flammable gas. It doesn't cost that much for the correct nozzle. It all depends on how much you think your life is worth.

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#10

Re: Space Heater Connection Size

11/30/2013 11:28 PM

Re: Space Heater Connection Size

Hypothetically, if I were doing it, I would ask myself these questions:

What is the BTU rating of the heater?For instance 30000 BTU.

Then I would consult a LP orifice chart for that number of BTU's and use a numbered drill bit of the indicated size to drill the orifice.

Does the heater have only one orifice?If not, I would divide the total BTU's by the number of orifices and size the orifice accordingly.In the example above, if I had 5 orifices, the BTU per orifice would be 6000,and would require a smaller orifice.

A regulator,such as goes on a BBQ grill has an output pressure of from 10 to 11 inches of water column pressure.(usually 11)They are not normally adjustable.

I know I must use the numbered drill bits to drill the orifice.This is the number referenced to in the chart.

And, I would go here to consult the chart:http://www.joppaglass.com/burner/lowp_chrt.html Now all of this is saying what I would do in certain circumstances,but I cannot advise you to do it unless you have experience in this field of knowledge.

A story comes to mind about a skydiver, on his first jump is in a panic,and cannot find his rip cord.

As he is falling, he meets a guy on the way up.

He yells "Hey!You know anything about parachutes?"

"No! Do you know anything about gas heaters?"

Your first mistake may be your last.

So,basically, proceed at your own risk.

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#18
In reply to #10

Re: Space Heater Connection Size

12/02/2013 9:47 AM

Thank you, very helpful and good information.

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#11

Re: Space Heater Connection Size

12/01/2013 3:21 AM

Would solder not melt at the temperatures achieved near the flame? Possibly brazing would work, but I agree with the other comments: buy the correct nozzles!

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#13
In reply to #11

Re: Space Heater Connection Size

12/01/2013 5:35 AM

Solder will not melt when used in the nozzle.

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#16
In reply to #11

Re: Space Heater Connection Size

12/01/2013 8:22 AM

Actually, no, it does not. The gas upon escaping will cool the solder. The propane...even more so.

I know... I have done that. I was a little surprised as well.

The annoying part is drilling through the solder with those tiny drill bits. You have to sort of spot the drill down...let it load up and pull it out to clean it. Don't let it load up too much or you break the bit.

Though now that I see, HTRN has already responded to this.

What he said....

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#12

Re: Space Heater Connection Size

12/01/2013 3:49 AM

"Soldering," would not work as the heat from the burner would melt the solder! ===ignition===short period of normal operation===!!boom!! Silver soldering also would not work, the orifice must not only be the right size, it must also be shaped properly! An improper or "rough" shape would cause turbulence in the gas stream, causing improper combustion or worse. The gas must achieve laminar flow in order to insure even delivery to all the jets, and complete combustion. In other words, use your homemade orifice and you'll suffer from CO poisoning IF your lucky! If your heaters are commercially made, the manufacturer will probably send you the proper orifices for free! (They don't like anyone blowing themselves up with their product for some reason ;-)

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#14
In reply to #12

Re: Space Heater Connection Size

12/01/2013 5:55 AM

Solder will not melt in the nozzle.The nozzle itself hardly gets hot.The gas ignites a slight distance from the nozzle,and the expansion of the gas keeps the nozzle from getting hot.

I have built many custom, trailer mounted cookers,the type used for cooking whole hogs,deer,or goats,and I always have to make custom orifices for the cookers.The minor roughness inside is not a problem.It is not as critical as a carburetor jet.

I also make my own burners and mixer valves.The burners are made from pipe with slots cut across about 1/2 way thru at the far end from the nozzle, tapering back to a 1/4 cut at the nozzle end.This gives an even flame the whole length of the burner,which is around 4 feet long, depending on the customer needs. A piece of 3" angle iron is used as a "tent" over the burner to shield it from grease and reduce flare-ups.

The proper air/fuel mixture is important.A noisy flame has too much air, and a lazy yellow flame has too much fuel.The proper mix is reduce air on the noisy flame until it is silent, but not so much as to become yellow.Or, alternatively,increase air on the lazy flame till just below noise.

The information I give is based on years of experience, not on an unfounded assumption.

The above is not meant to be instructional, or to encourage anyone to try it, it is simply the method I have used successfully for many years.And I will admit,I got a few singed eyebrows in the learning process.I was lucky it was not worse.

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#15

Re: Space Heater Connection Size

12/01/2013 6:28 AM

A picture showing the nozzle and any adjustable air control would help immensely. What was the supply pressure with NG and what is the supply pressure of the LP?

If you start off drilling a hole that is too small, as already posted here by someone else, you will have a noisy flame that will be unstable = too much air.

Then drill it a little bit larger and try again till its right.

Use the air mixing control, if fitted, to assist you in getting a good stable flame.

Do the following outside, preferably a day with some wind. Away from possible sources of flmes or sparks....

If you need to dismantle to work on the jet, make sure that any seals are eventually replaced. Test for leaks with a length of flexible plastic tube stuck in your ear and run the other end over and around the whole thing. That is not a 100% method, a tiny leak might still not be heard.....leak detectors usually use a sensitive high frequency microphone to "hear" all leaks.

Then go over all joints and flexible lines with a mixture of water and washing up liquid on an old paintbrush and check for bubbles.....do this regularly to make sure it is leak free.

On connections that leak, I use gas sealing tape or paste sealant for gas for a final job.

I had to redo my caravan gas system from the UK standard to the German standard. Basically replacing copper pipe with steel. I worked with 1 bar air pressure and got it all sealed up. You are allowed (test pressure air at twice the gas pressure of 50 mB) to lose 10% in 10 minutes or so. Mine lost nothing......the testing person was overwhelmed....

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#19

Re: Space Heater Connection Size

12/02/2013 1:07 PM

Assuming that you know the heat release rate required (h), the calorific value (CV) of the fuel gas, the set point of the regulator (P) you have just purchased then the calculation goes like this:

gas flow rate (q) = h/CV

and q also = 1300 x Cd x D2√(P/SG) where D is the required jet diameter and Cd is the coefficient of discharge of the jet. The Cd takes care of the neck in the stream of gas leaving the jet. For a well engineered jet this will be 0.95 and for a hole drilled in a thin flat disk it will be 0.55. Given the proposed method of "soldering" the jet up and then re-drilling it I would suggest using 0.75. This should give you a little leeway and allow you to increase the jet size if necessary.

UK sourced commercial propane fulfills the following criteria:-

Commercial ButaneCommercial Propane
Density of liquid (kg/m

3)

2.3942.4362.1002.142
Litres/tonne @ 15.6°C1723176019652019
SG against air1.92.11.41.55
Volume of gas/kg of liquid (m

3)

0.4060.4310.5370.543
Ratio gas/liquid233274
Boiling point-2-45
Latent heat of vapourisation (kJ/kg)160154
Specific heat of liquid (kJ/kg K)2.3862.512
Sulphur content (% by weight)Negligible0.02Negligible0.02
Limits of flamability (% by Volume)1.809.002.2010.00
Calorific Values
Gross (MJ/m

3 dry)

121.893.1
Nett (MJ/m3 dry)112.986.1
Gross (MJ/kg)49.350
Nett (MJ/kg)45.846.3
Stoich air/gas ratio3024
Standard conditions15.6°C
1015.9mbar

The Butane figures were in the table and I could not be bothered to delete them. I will leave the units conversions to you.

That takes care of the engineering but does not address the competence issue. If you have to ask the question you are not competent to carry out any work on a gas installation, at least in the UK.

By the way the arbiter of competence in the UK is the Gas Safe Register not CORGI which was replaced some years ago.

As you may have guessed from my user name this is what I do for a living.

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#20

Re: Space Heater Connection Size

12/02/2013 4:19 PM

Lots of good information here, but one thing I see missing that I've used over the years for reducing orifice jet size, is 'peening' not directly with a hammer, but by placing a small steel ball over the orifice and tapping. This reduces the size and the proper drill held in a pin vise can be used to re-size.

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#21
In reply to #20

Re: Space Heater Connection Size

12/02/2013 4:55 PM

Fair point. I have done the same myself

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#22

Re: Space Heater Connection Size

12/05/2013 3:31 PM

Most commercial appliance parts suppliers have an orifice drill kit with a drill size to BTU conversion chart in it. Drop a drill through the present orifice to see what size it is, get the BTU for the pressure your natural gas was operating, go up the LP column to that BTU, go over to the drill size. Biggest concern is if the heater has ANY automatic controls, there could be problems. LP can pop when it turns off and blow the pilot out so the next time it tries to come on, if the safety does not work, it will fill the room with gas. -- JHF

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#23
In reply to #22

Re: Space Heater Connection Size

12/05/2013 4:26 PM

With all due respect for the original question, gas is not a game. Do the right thing and encourage him to just go buy the right one. Some things you can alter or remake, some just should be left alone and go buy the right component for the job. Gas components fit into the category of leave it alone. His life hangs in the balance of his actions. Error on the side of safety.

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