Converting from oil to gas

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  #1  
Old 07-27-12, 08:10 AM
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Converting from oil to gas

Hi,

I'm new to the forum, but am an avid do it yourself person. I live in CT, my home is a colonial style house (1400 square feet). I've lived in the house since I was 2, and we've always had the same furnace. Its an american standard arcoliner, model 4b j4. I've cleaned and maintained it each year. Until now, it had a beckett oil burner with a .85gph tip. The furnace has a quickie chamber that is surrounded by granular vermiculite. I just changed the quickie chamber last year, the old one was probably 20 years old. the heating surfaces are large cast iron radiators, and there is only 1 zone. Due to the high price of oil, and the issues I've had with my burner over the last few seasons, I decided I was going to put in a gas conversion burner. I have natural gas at my house already, we have always used it for hot water and cooking. I have the burner, and am now preparing to run a new gas line for it. I've already spoken the the gas company, and they say I'm already on the heating rate (I'll check my next bill) and that my meter is of sufficient size for heating load. The real question I have is that do I need to keep the quickie chamber in the furnace, or can I run this burner (Carlin EZ-gas that will be firing at 125,000 btu/hr) without this chamber. I'd like to clean out the furnace if I can fire it unlined. It seems to me that I'd get a lot better heat absorbtion in the furnace waterwalls if the vermiculite and the quickie chamber were not there.

I know there is the question of efficiency, and that I should just put in a new boiler, but that is extremely expensive. This boiler has lasted many years and will probably last many more if properly maintained. I'll probably get this project done for under $1000.00.

So the real question in all of this is about the funace liner. Any info would be appricieated.

Thanks
 
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  #2  
Old 07-27-12, 11:45 AM
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Your old boiler could potentially be less than 60% efficient with a conversion burner.

It's time to let it go. Even the cheapest gas boiler out (natural draft with a damper) there now will burn far less gas than what you have.

Since the goal is to save money on fuel, a conversion burner is not the way to go. Lifecycle cost has to be taken into consideration, not only capital cost.

-------------------------
125k is a ridiculous amount of heat for a 1400 sq ft house unless it has no insulation and single pane windows, but then again, half of it may go up the chimney.
 
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Old 07-27-12, 02:31 PM
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Usually the combustion area is separated from the heat exchanger where heat is transferred to the water. A ceramic liner of the kind you have is probably what you should have with a gas burner as well.

You really need someone who can determine the correct rate of fire based on measurements of CO2 , O2 and CO in the combustion gasses based on instrument readings and it takes judgment and experience to set up a conversion burner properly and safely. Not a DIY project in my view.

You wont increase the efficiency of the boiler, but you will benefit from a much lower fuel cost.
 
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Old 07-27-12, 03:40 PM
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"You really need someone who can determine the correct rate of fire based on measurements of CO2 , O2 and CO in the combustion gasses based on instrument readings and it takes judgment and experience to set up a conversion burner properly and safely. Not a DIY project in my view."

A very good point.

I don't think anything gas or refrigeration related should ever be done by someone who isn't licensed. The risk is unacceptable.

I'm not and would never attempt to install a conversion burner -> electrical repairs are okay though.
 
  #5  
Old 07-28-12, 05:54 PM
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Thanks for the input, I realize this wouldn't normally be undertaken, but I own the burner, so the project will proceed. I will say that I have a mech. engineering degree, and I worked in the boiler industry (not residential, but power plants) so I sort of get how they work, The only reason I was going to size the BTU output like I mentioned is that thats approximately what the current oil unit puts out. (.85 gph tip X 140,000 btu/g for #2 oil). Perhaps I'll start with a lower output and see how the stack temp looks. These units' output is mostly controlled by an orifice in the gas inlet line after the inlet regulator. I do have access to a combustion analyzer from my old company, and I will borrow it once I get the unit fired.

I have found from other forums that my particular unit was not meant to have a refractory lining, as the furnace floor and walls are filled with water and are thus heat transfer surfaces. I will probably put some firebrick against the back wall where the flame will impinge. I'll also improve the firebrick in the upper convection area to minimize the area and keep flue gas velocities up.

We'll see how we do compared to a normal oil season, I would typically go through about 700 gallons in a season, That's about $2,500 at the current prices. I have to assume that I'll do a lot better with the gas (because its cheaper, not because of eff.)
 
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Old 07-29-12, 12:29 PM
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You obviously know more about this than I do, but if you put a smaller input burner in (lower volume of exhaust won't "scrub" the heat exchanger walls as well), won't it run even less efficiently?
 
  #7  
Old 07-29-12, 06:26 PM
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You're right,

Less fuel burned and less air mixed in means less flue gas volume, which will lead to lower flue gas velocities over the heat exchange surfaces. I will say that with the old burner, flue gas temps at the exit of the unit were about 500 degrees F. that's pretty high. it needs to be high (not that high) for oil fuels so the sulfuric acid in the combustion products doesn't begin to condense out and form liquid acid. This is not such and issue with Natural gas. I will say that the boiler plate says the unit is rated for 1.35 gph of oil, thats about 190,000 btu/hr, which is a lot. We have been running the unit at .85 gph (around 120,000 btu/hr). I may start at a lower output , say 85,000, and check the efficiency. Luckily its easy to change the orifice, so if the low setting is not too effective, I can move up. We'll see, but I know I'll save a lot compared to the crazy oil prices.
 
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Old 07-29-12, 07:33 PM
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Frankly, it's pretty clear that you don't have enough expertise to set up a conversion burner properly.

The gas utility I used to work for leased out and installed thousands of conversion burners ---- and all too often paid damages when someone was killed by a poorly maintained maintained conversion burner.

Most gas furnaces these days have a lot of safety devices on them and its' pretty hard to kill a house full of people with them.

Conversion burners however, depend on proper installation and maintenance to protect people from being killed. You are putting your family at risk, in my opinion.

Secondarily, efficiency is heavily dependent on correct installation and maintenance.
 
  #9  
Old 07-30-12, 08:52 AM
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I truly appreciate everone's concern's. I don't intend to take this project lightly. What was it that killed the people? Was it CO from improper combustion due to not enough combustion air or a blocked flue? Was it gas leaks leading to explosions? I truly want to address anything that may be an issue. I maintained and cleaned the oil burner and the furnace each year before firing it, and I intend to do the same here. If it doesn't perform to my liking, I'll have someone come in to tune it.
 
  #10  
Old 12-14-12, 11:36 AM
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My conversion burner experience

Older post, hopefully everything worked out prior to the heating season. I figured I'd post my experience with a split scope DIY conversion burner install since it took me quite a while to piece together what is typically done and then read through the NYS codes to make sure I didn't miss anything. For those who are curious, I started life as a mechanical engineer sizing and troubleshooting industrial boilers, AHU’s, pumps, heat xchangers, etc in the semiconductor industry. Went back to school for an MS in mech eng with a focus on controls. I’ve spent the last 8 years as a controls development engineer in the power gen industry. With that out of the way, I wanted to provide my experience for those who have a similar skillset and are planning a conversion and save them some time.

My original setup
I dialed in the old oiler burner about as efficient as this model would allow. The baseboard in my house is oversized and I am able to run the supply temp setpoint at 165 with about 158 degrees returns even when its -10 out. No outdoor reset needed here
Dunkirk Empire II Boiler
.5 GPH nozzle at ~170psi
92000 BTU @87% eff (last years tune)


Scope of work for conversion
Contractor Scope
Run gas supply line from meter to boiler gas valve
Clean, set gas pressure and tune boiler

My Scope
Install SS chimney liner
Install New single wall chimney pipe from boiler to liner
Install Double acting baro damper
Install Spill switch
Install Aquastat to burner controls wiring
Carlin G3b burner setup

I had to make a few calls to get a reasonable estimate to do the gas piping and clean/tune but eventually I found a company that did great work at a great price. I ordered the majority of materials online, and got a great deal on my liner off of ebay. Most of the work is very straight forward. First thing is to get the real manual for your boiler and conversion burner. I had to email Carlin to get one. This is one of my pet peeves, I can download a 1,000,000+BTU burner manual but residential manuals are not readily available. Had similar issues with AC/heat pumps. Anywho…

Consult your boiler and conversion burner manuals for chimney liner sizing, double check your local codes. The liner install is easy depending on the type of chimney you have. Mine was clay lined and straight so it was a breeze to shove 27ft of liner down it. There are plenty of YouTube videos show you how (and how not) to do it.

The exhaust connection from the boiler to the liner should be similar to what you have now. In my case I swapped out the single acting barometric damper for a double acting and added a spill switch. I also keep a CO monitor in my mechanical room for added safety.

The Honeywell aquastat used line level voltage to turn the burner on. So when there was a call for heat and the boiler temp was under the setpoint+db the aquastat would energize the burner 120V contacts. The oil burner was installed with the main power connected to the switched burner output of the aquastat and the T-stat jumpered to always on. This was all right for oil operation but not gas. To ensure proper purge cycles in the case of loss of flame, I needed to provide full time supply power to the burner and trigger operation via the T-stat(24v) input on the burner. I used an interposing relay (NO) that was driven by the 120V burner output to energize the relay and close the contact which was wired to the Carlin burner's 24v t-stat contacts. I also tied the spill switch into this circuit so that I could keep it a low voltage circuit. This work is the only work I did ahead of time.

I bought the Carlin G3B off of craigslist for about 1/3 the retail cost. The homeowner had only used it for ½ a season and said it never provided enough heat so they upgraded to an entirely new furnace. The unit looked great. I wired it up and dry fired it to make sure it operated properly and went to the safety purge mode. After all was good I looked to see what size orifice was in it. I found that it was the original orifice that was never drilled. Now I know why it didn’t heat well for the previous owner. Some contractor took them for a ride…. How lame. So I drilled it out with a #15 (~95000btu), set the air in accordance with the manual and we were ready to go.

Install Day
On the day of installation the contractor came at 8am and we both had our work done by 1pm when the gas company showed up. The gas guy was a nice experienced guy who installed the meter and then did a pressure test and set the supply pressure. Once that was done I flipped the power and the burner lit right up. Talk about quiet, the only reason I know its on is from the sound of the blower fan. We then did a combustion test and got 80%, which I felt was a bit low. We redid it after a good cleaning and it improved to 83.5%, right at the 3% eff loss I expected.

Savings

In terms of savings, I just received my first bill and my cost of energy has been reduced by over half. I went through about 600 gals of oil last year and this conversion will pay for itself in the first year. I did consider upgrading to a high efficiency unit, but my boiler was pretty new and the yearly savings would have been less than $130 per year vs the conversion burner. In my case this was the right choice. Gotta love heating 2600 ft^2 on the cheap
Most mid efficiency boilers (80-86%) like these that I’ve seen are often oversized and not tuned.(I had to call 3 different contractors before I found one that did a tune and have had to show 1 guy how to use the equipment). When I bought this house, the nozzle was sized for 140,000 btu’s and I reduced it to 95,000btu. In addition to significantly reducing the amount of short cycling, it also yielded a 3% efficiency increase. Let me stress, don’t tune any burner by eye… Its worth spending the cash to measure the O2 (or C02) and exhaust temp to validate the system.

Hopefully that helps anyone who is considering the conversion. I’m loving my cheap gas heat and I’m always ready to switch my burner back to oil if it becomes inexpensive again by some miracle.
 
  #11  
Old 12-14-12, 01:41 PM
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Hello BigBlock,


You appear to be the rare person with the competence to do this kind of conversion. Of course you have huge advantages with your experience as an engineer in understanding and solving the problems that converting a boiler presents.

But for just these reasons, I would use your experience as more of an example why DIY conversions are more to be recommended against that recommended.

Also, I don't see in the results you post a test for the PPM carbon monoxide in the flue gasses, which is something that should be done in my opinion.
 
  #12  
Old 12-14-12, 02:06 PM
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I agree whole heartedly. I've had some bad luck with Pro's work in the past, so I definately don't want the average DIY'er attempting this. I've been lurking in the forums and wanted to give back and provide some experience so that DIY'ers who are having the work done have a better feel for the scope.

As for the CO in the flue gasses, I have been unable to find a contractor in the area who has the equipment. Each year I try someone new and they always show up with a Fyrite. Unfortunatly most seem suprised that I even want a true combustion test. Thats the main reason that I set up the burner myself to ensure its exact to the manufacturers specs and that the exhaust temps, CO2, and draft are as expected. But I can't be positive I'm on the correct side of the CO2 curve.
 
  #13  
Old 07-09-14, 07:17 PM
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Question Oil to Gas conversion costs

@bigblock - I would appreciate you advise/inputs on oil to gas conversion which I am thinking of getting done this summer.

I have the below equipment installed in 2008:

Dunkirk Empire II oil burner furnace
Model# 3EW1.00Z


The current efficiency is 86%. The furnace is used for both heat (base board) and hot water currently.

Due to high oil price, I wish to get it converted to gas. I would like to know the approx. cost for getting it done via a licensed contractor.

Can this furnace be converted to gas by simply changing the burner? What other things needs to be done for the conversion and what would be the costs involved.

The gas company will bring the line upto my house for no cost. Can you also tell me the approx cosr for doing the internal piping for gas line.

I understand that I can get quotes from various contractors but you being an engineer and expert, I would like to get your inputs.

Thanks
Raj
 
  #14  
Old 07-10-14, 12:35 PM
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first thing you need to do is download the full Dunkirk boiler manual and verify that it is okay to do a gas conversion.if it's not recommended for your unit then ur taking a risk by doing the conversion. In terms of costs I never even bothered to call a licensed contractor because just purchasing the parts new would cost over $1000 for my installation.I was able to do it myself for about 1400 total but I was able to get some parts at cost through friends as well as the burner off of Craigslist...so my costs is it really representative of what most people would pay. in general I've seen quotes for gas piping very quite a bit. The company I used and was very happy with charged the same amount for my installation as my friends installation that was a much shorter and easier Run. Same company just different guys doing the quote. finally, there is a lot more to think about and just replacing the burner me to make sure that the proper controls are in place as well as the key safety equipment items. This is where as I explained in my above post I researched the local state and federal codes to make sure the installation was up to spec. every installation is unique, I would recommend that you call a licensed contractor to get a quote and scope of work for your specific project.

just as a follow up from my other post the burner is still working great and did pay for itself in the first year. This past year I got to enjoy the full savingswith my heating bill being less than half of the equivalent it cost for oil
 
  #15  
Old 07-12-14, 10:55 AM
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@bigblock.. Thank you for the prompt response. I downloaded the manual but could not find anywhere talking about gas conversion. Please see link below. I did spoke to a Contractor yesterday and he said that for this model he has checked and it can be converted using Carlin Gas burner and Total approx cost would be $3000. If chimney liner is required it will add another $1400.

He said it is safe to convert and that many people using this model have converted but the remaining 12 years warranty from Dunkirk will be void as Dunkirk is very strict about their warranty and do no allow conversions.

He will come and take a look next week.

From a Safety standpoint, are there any points I need to keep in mind or check whether done/included by the Contractor?

Appreciate all your help/advise on this.

http://www.ecrinternational.com/secu...ument/2895.pdf
 
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