power gas versus oil gun

Unknown

Can you give an example of a 90% or higher steam boiler?

Tim's answer: None that I know about.

The Burnham Independence series is just barely more efficient with a power vent. What boilers are gaining 3-4% just because of the power vent?

Tim's answer:When I am talking a power vented system I am talking about a system that develops positive pressure in the vent by design not a retrofit.

Would adding a draft inducer make a power gas boiler run more efficiently? If I could gain efficiency and solve my chimney sizing issues in one shot it might pay. Is there any risk of sucking out the flame or pilot on the hot water heater with a draft inducer?

Tim's answer: lets be clear about something here a gas power conversion burner is not the same thing as a design gas boiler using an assisted or power vented design characteristic. You will never get a design oil boiler made today with a gas power burner above 83% combustion eff. and even that is with a real pro doing the ORSAT.
If the water heater is flued into the same vent connector with a fan assisted system there can be problems with that type hook up. If you are however converting an oil boiler and want to flue the water heater with it there should be no problem as long as they are sized correctly and the chimney or vent are sized adequately. The only time you would need a draft inducer with a conversion burner would be if you are having venting problems otherwise not a good idea.

steve_173

How does one compare the efficiency of a power gas versus oil gun for the identical boiler. Clearly power gas is better than atmospheric gas but isn't that due to the wet base boiler and the inherent air fuel advantage of the power gun? Some say gas flame temp is lower than oil and so power gas is less efficient then oil on the same boiler. Is there anyway to calculate this? What about the electric consumption of the fan for the power gas burner?

lownox

If the boiler is listed in the GAMA directory (IBR/Hydronics Institute) you should be able to get an efficiency number for the boiler with a gas burner vs. an oil burner.

In a cast iron boiler, for instance, using the oil burner will be 1%-3% higher efficiency due to the radiant heat of the oil flame. The heat transfer is simply better with oil.

Atmospeheric gas vs. power gas... power gas can run higher combustion efficiency since it has better air/fuel mixing over atmospheric burners. This means you can operate with lower excess air levels thus operating at higher efficiency.

You would have to do the math to decide whether the 2-3% efficiency hit is worth the change to gas. I would, however, stay away from atmospheric burners. It is to easy for them to "crap the bed" and start making CO... in my opinion.

Steve

Unknown

Steve as one who has

installed over 3,500 atmospheric and power gas burners I can attest to the fact that you will not be sorry converting.

As for atmospheric they are not made anymore so forget that. All gas conversion burners made today are power burners. Good companies are Midco, Carlin, Riello are the best.

As for comparison of efficiency all the burners I have ever installed all had combustion efficiencies over 75%. In the last 15 years I can up that to over 80%. In many cases it is not unusual to get over 83%. Typical readings are 4% O2, 10% CO2 400 degree net stack with CO air free at 50% or less depending on the oil boiler. That charts out to around 82% eff. Remember this is combustion eff not AFUE.

By proper adjustment and good excess air control you can get the gas flame above 3200 degrees in many cases this will give a very good comparison to oil. There are many other factors which make conversion a good idea not the least of which is cost of fuel. I do however recommend keeping the oil burner just in case gas prices go above oil.

Last but certainly not least proper preperation for the oil boiler is critical. That means the individual installing must have been properly trained to do this type of install and testing.

One more thing many boiler manufacturers do not encourage converting their boilers from oil to gas, so I would check with them first. That has never stopped me from converting them but it is good to let the customer know that warranty may be voided in some cases.

steve_173

The GAMA directory has the boilers but only in the oil configuration. So you are saying that the 85.6% efficiency will drop to as low as 82.6% (3% drop) or is the difference 1-3% of the efficiency making the worst case a 2.57% drop (3% of 85.6) and 83% efficiency?

steve_173

This is why I am using the Smith G8 boiler. Smith supports the Carlin power gas gun from the factory.

What is the typical oil flame temperature?

Can a plumber installing this properly tune the gas gun for optimal performance? Does the gun need retuning periodically?

Aren't most gas boilers still atmospheric in design?

Unknown

Steve

This is why I am using the Smith G8 boiler. Smith supports the Carlin power gas gun from the factory.

Tim's answer: That is a good choice, properly set up with the EZ burner you should get equal eff to oil

What is the typical oil flame temperature?

Tim's answer: It depends on the amount of excess air at 25% excess air #2 fuel oil will be around 3400 degrees. It is possible with some high end mod/con gas systems to get flame temps in and around 3350 degrees.

Can a plumber installing this properly tune the gas gun for optimal performance? Does the gun need retuning periodically?

Tim's answer: It depends on that plumbers knowledge of combustion. My experince is that most plumbers because it is not their area of expertise are not very good at combustion issues. They must understand these concerns because it can affect the installtion itself.Installing the burner is pretty straight forward, it is other things that must be addressed that they come short in. Send them to me for at least a one day training session along with my manual given out with the course on Conversion Burner Installation and set up and they should do okay. Preferable my three day combustion course would serve them better.

Aren't most gas boilers still atmospheric in design?

Tim's answer: Yes there are still some standing pilot atmospheric boilers made with vent dampers 78%. There are also some that use a combustion air blower which allows for higher efficiency 80%. Then still others that are power vented 84%. Then finally we have those that use a draft inducer with a negative pressure gas valve which allows for the higher flame temperatures spoken of in my previous posting 90% or higher.

lownox

Everything Tim said.

Flame temperature shouldn't be your concern though. Air/Fuel ratio with the proper amount of excess air should be the only concern. Trust me, if a boiler could be designed to operate over 14% CO2 on oil as installed... it would be.
You need to hire someone competent to make the conversion. If they don't have a combustion analyzer with them... send them away.

There are still a bunch of atmospheric gas boilers available, but many (if not all) of the oil fired models can also fire gas (power burner).

steve_173

Can you give an example of a 90% or higher steam boiler?

The Burnham Independence series is just barely more efficient with a power vent. What boilers are gaining 3-4% just because of the power vent?

Would adding a draft inducer make a power gas boiler run more efficiently? If I could gain efficiency and solve my chimney sizing issues in one shot it might pay. Is there any risk of sucking out the flame or pilot on the hot water heater with a draft inducer?

lownox

Adding power vent won't help your efficiency on that G8. The series 8 you have can be fired on gas with the carlin burner you mentioned. I think they have a midco and a heatwise setup on that one too... can't remember.

Your rated thermal efficiency will be about 2% lower with the gas burner. That's that. Smith can tell you what CO2 level to set the gas burner you choose. I recommend calling them and finding out which burners they have tested. It should be 3 or 4 different ones. I just can't remember off the top of my head.

Steve S.