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High Efficiency Furnace
on an ICP Comfort Maker Model NTVM forcd warm air furnace. Set up for LP gas.
This is using a SV9540Q Honeywell Smart Valve. When this unit is set up for Natural Gas the Low pressure setting is 1.7" WC and 3.2" WC.
What would you set them for on LP gas? There is nothing listed anywhere on the unit for LP.
Here is what I found on high fire the unit is making 300 ppm CO on low fire it goes up to 800 ppm. This unit firing at the same pressures on LP as it would on natural?
The unit uses a two speed draft inducer. Low speed for low fire high speed for high fire. It has a variable speed ECM system blower.
What would you do to get CO down to a safe and efficient level?
This is using a SV9540Q Honeywell Smart Valve. When this unit is set up for Natural Gas the Low pressure setting is 1.7" WC and 3.2" WC.
What would you set them for on LP gas? There is nothing listed anywhere on the unit for LP.
Here is what I found on high fire the unit is making 300 ppm CO on low fire it goes up to 800 ppm. This unit firing at the same pressures on LP as it would on natural?
The unit uses a two speed draft inducer. Low speed for low fire high speed for high fire. It has a variable speed ECM system blower.
What would you do to get CO down to a safe and efficient level?
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Comments
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Timmie,
My Honeywell Smartvalve book says 10.0" High fire and 4.9" low fire. This is in Honeywell book number 69-1227-1 page 13. Also, the propane conversion kit number is 396021. if you need to know since it sounds like the wrong regulator spring is in there.
OOPS. Found a link for you Timmie. This is a pdf file.
ICP Installation manual for NTVM
Go to page 16. It shows just what I said above - 10.0" High/4.9" Low. There is also a listing for propane orifaces on page 17. I think it said # 54 for 0 - 2000 ft. altitude.
Glenn Harrison, Residential Service Tech
Althoff Industries Inc. Mechanical and Electrical Services
Crystal Lake, Illinois
Althoff Industries website0 -
Natural - LP
Normally you would think that LP would be 10-11" but I have heard of some manufacturers that use the same pressure on both. This is where I use O2 and Flue temperature to find the proper pressure. O2 should be 6-9%. If O2 is above 14-15% the CO readings you got would be normal, but as you increase gas pressure they should fall. It only take the slightest adjustment to see if this will happen. If the furnace is an 80% flue temp should be at least 300 degrees. If a 90% it should be 120-130 degrees, both reading in high fire.0 -
CO level
Forgot--Co levels must be less than 100 ppm as measured. This is less than the 400ppm "Air Free" it is certified to run less than. "Air Free" means no O2 in your sample. We will normally have 6-9% in most flue gas samples So 100ppm is equal to about 150-200ppm "Air Free"0 -
Thanks Jim and Glenn
this was a case of the installer not being informed or trained and installing this furnace on LP he changed the orifices but did not set up for LP gas. My notes on this system were for Natural only. Of course as is often the case we can not get hold of the original installer. This is just the beginning of problems on this system. I will be back today with a local contractor who knows his stuff and we will get this thing squared away.
By the way the homeowner is a lawyer.
Jim you are right some systems have a set up that they run at same pressures on Nat and LP. ICP got in touch with me this AM as also Glenn's post and gave me the info. This sytem runs at 4.8" WC on low and 10" on high. They are also going to send me the info they recommend for analysis readings on this sytem.
Once again thanks.0 -
Same pressure Nat & LP?
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Any time, Timmie
Glad to be of assistance to you.
Glenn Harrison, Residential Service Tech
Althoff Industries Inc. Mechanical and Electrical Services
Crystal Lake, Illinois
Althoff Industries website0 -
Here's a good one for ya
If you convert a Lennox G26 High efficency furnace to propane, they want the gas pressure set at 7.5", but Natural gas is run at the standard 3.5". Go figure.
Jim, do you have any suggestions for lowering the O2 levels on an indused draft 80% or 90% furnace with inshot burners with no shutters, when the gas pressure is normal and the meter clocks at the proper BTU input. I come accross a lot of these units where the O2 is 9.5 to 10% and I was taught by Rudy Leatherman that it should be 7 to 9% on natural.
By the way, Jim, are you by chance having a road trip to or anywhere near Chicago this year with your classes? Let me know, please.
Thank you.
Glenn Harrison, Residential Service Tech
Althoff Industries Inc. Mechanical and Electrical Services
Crystal Lake, Illinois
Althoff Industries website0 -
Results
Relocated air intake.
Shoveled snow away from vents outdoors.
Set High fire to 10" WC
Flue Temp 142 degrees
CO2 8.7%
O2 6%
CO 75 PPM air free
Efficency 86%
Set Low Fire to 4.5" WC
Flue temp 120 degrees
CO2 9.5%
O2 5%
CO 95 PPM air free
Efficiency 87%0 -
Glenn
I have had a Carlin G3A conversion burner 120,000 BTU's with a barometric damper. Chimney and over fire draft -.03 this into a 30 foot inside masonary chimney.
CO2 10.5 %
O2 3.5 %
Net Stack Temp 300 degrees
83% efficiency
15% excess air
CO 75 PPM air free
Point there are times in my experience that you can have high CO2.
It is important that equipment has been cleaned and prepared very carefully. Control of excess air through the burner only.0 -
Timmie, please reread post
The problem I am seeing is high oxygen (O2) levels and low carbon dioxide (CO2) levels. I would love to see an 80% or 90% Induced draft natural gas residential furnace run at the numbers you listed and yet still have fired at the right BTU's.
Glenn Harrison, Residential Service Tech
Althoff Industries Inc. Mechanical and Electrical Services
Crystal Lake, Illinois
Althoff Industries website0 -
Looks like pretty good numbers to me
Glad to see you got it working well.
Glenn Harrison, Residential Service Tech
Althoff Industries Inc. Mechanical and Electrical Services
Crystal Lake, Illinois
Althoff Industries website0 -
Forgot to mention
I tried something with this unit I have not done before. I have worked on a couple of these units with natural gas but never with propane. I have temporarily increased the air intake pipe to 3". When I was with the gas company we did this on some Amana units and it worked pretty good. We could do this because they are using an old window opening for venting. We removed existing piping and increased to 3" and reinstalled. If it is okay in a week or so we will make it permanent.
I agree with you my experince with these two stage 90 + units has not been good. If this works I am going to try it with a job on natural gas. High 02 and low CO2 has been more the case than not. AFUE ratings really do not impress me as there is too much built into those figures. I do the best I can to get everything as close as I can and safe. After that we do a yearly degree day analysis and see if usage decresed without a loss of comfort. I actually think some of these 80+ and 90+ units may be less efficient than some of the old equipment. One of the other things I have found is to change the cycles per hour at 50% of heating load from 6 cycles per hour to 3 cycles per hour. By multiplying the amperage draw of the primary control by 1.4 and setting the anticipator to a higher setting less resistance-less heat on bimetal-longer cycles- less cycles. Did this on a couple of new installs with high bills, worked pretty well.
Furnaces were a lot less problems when we could have a temperature on temperature off fan control. These EFT and Integrated controls are a real problem (time on time off).
I wish I could hook up a gas meter directly to every boiler and furnace and measure exactly what they use.
I am still trying to sort out all the discussions about Thermal Efficiency. I bookmarked all of them when I have time I will sit down with all my old books and figure it out. I need to get alone in a room with Jim Davis for about a week. I have a strange feeling we are doing some of the same things and need to sort through the words we use. It is called COMMUNICATION.
I just try to keep it as simple as possible for all the new folks here on the Wall.
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That's interesting Timmie,
I'vee had the opposite experience in that I have had a couple of 90% Carrier units that had high CO levels, after doing everything else, I have installed a 3x2 reducer on the exhaust termination to sloow the flow in the venting and would get a substantial drop in CO output. Unfortunatly, the last time I did this I only had a CO meter to test with so I don't know what the other readings were.
Glenn Harrison, Residential Service Tech
Althoff Industries Inc. Mechanical and Electrical Services
Crystal Lake, Illinois
Althoff Industries website0 -
Fine Tuning
Timmie,Its alway's pleasure to hear how you take it one step further. That be, and this case the anticipator setting.
Even know we set the anticipator to microamps,sometime its
not enough. High mass boiler verse a furnace with same gas control.Better not forget the fan timer and those high mass
rads. This is when experience wins over text book.
Thanks for sharing...0 -
that fan is made
> I'vee had the opposite experience in that I have
> had a couple of 90% Carrier units that had high
> CO levels, after doing everything else, I have
> installed a 3x2 reducer on the exhaust
> termination to sloow the flow in the venting and
> would get a substantial drop in CO output.
> Unfortunatly, the last time I did this I only had
> a CO meter to test with so I don't know what the
> other readings were.
>
> Glenn Harrison,
> Residential Service Tech
>
> Althoff Industries
> Inc. Mechanical and Electrical
> Services
>
> Crystal Lake, Illinois
>
> _a
> href="http://www.althoffind.com"
> target="_blank"_Althoff Industries website_/a_
0 -
that fan is made....
to perform at 5 feet to 50 feet, you may be onto some things here!! Party at your place before the "wetstock II" ,send me the directions so i can get out these two hunert invitations!! thanks glenn ,we'll see you there !!
Murph' (SOS)0 -
NOOOOOOOOOOOOOOOOOOOOO! :-)
My poor little hole in the wall can barely hold the six people and one dog in it now (Wife, four daughters, dog, and myself). Besides, I have a crazy lady who has called the PD on me for my dog barking outside for thirty seconds. Ican only immagine what she would do with two hundred people in the neighbor hood :-). All you wetheads wouldn't be able to handle my schorched air house anyways, the burned air would make you all sick.
As far a the venting goes, I am convinced that there is more to venting these 90% units than just looking on a sizing chart and going with manufacturers recomendations, although this is a great place to start. Ever since I got my testo, I have noticed a lot of induced draft furnaces that have high Oxygen levels, and I am thinking it is due to overpowered inducers and somewhat oversized pipes allowing too much air to the burners. I just wish I had more time to look into it, but my employer does an excellent job of keeping me busy.
Looing forward to meeting you and all the Wallies at Wetstock II! See ya there.
Glenn Harrison, Residential Service Tech
Althoff Industries Inc. Mechanical and Electrical Services
Crystal Lake, Illinois
Althoff Industries website0 -
I think a lot of this has to do with furnace
heat exchanger design and the resistance through the secondary heat exchanger. I tried increasing intake on a few other furnaces and it did not make a bit of difference. It also depends on how the combustion air blower is set into the furnace. Too many variables you have to take them one at a time and work them until they work right. Every job is a new experience. You would think that after 42 years I would figure this stuff out.0 -
Hey Murph!!!
I am not attending this Wetstock, but I would be more than happy to help you plan the party at Glenn's place.
I think that the porta-potty guy we used last time covers that area. I'll check and get back to you!!
Mark H
To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"0
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