Downfiring a 300,000 btu/hr American Standard Steam boiler?

Koan

Gentlemen. I appreciate all the input. There have been great ideas presented here. Everyone has been incredibly helpful and I am grateful.

I find myself in a bit of a dilemma - I have re-pied the near boiler wet return, installed flush valves, new trap cages and two new BJ 2CR big mouth cross overs. Radiators were flushed and refinished, carted up strairs and reinstalled. Cleaned out the boiler really well and put in a new boiler drain valve. Replaced the pigtails on the vapor stat and 36 OZ gauge. Vacuumed underneath and the burners. Threw in 2 Steamaster tablets, and filled it up.

Fired the system up tonight. Was difficult to get the standing pilot to stay lit but it finally stayed. For an hour I was the proudest man in the world. System worked flawlessly. All radiators hot, finally cycled on 10 OZ pressure. No leaks no drips all was right. I felt like Tom Hanks in Cast Away..." I have made steam heat!"

After about an hour the system stopped working. The standing pilot was out. I tried to relight and hold the red button but no matter how long I held it the was no joy. When I released the button the pilot would no stay lit. The sensor tip was glowing red but I assume the gas valve did not sense the pilot was lit. I tried tightening connections, no luck. Please help.

1) how can I tell if it is the sensor or the gas valve.
2) can someone guide me to the correct sensor part please, or are they universal???
3) if is the sensor , how do I remove the burner rail to get to it.

Please help -- it's getting cold and I'm so close to getting heat.

Pics attached

Thank you all!!

Kelly

Koan

Is this what I need??

Fred

@Koan You need to replace the thermo coupler (the small rod in front of the pilot) There are universal thermal couplers that you can get almost anywhere. Home Depot carries both Honeywell and Rheem. The only difference is the length of the copper tube that runs back to your Gas Valve (24" or 30"). I doubt that you will need to take the burner tube out but if you do, there is probably a clip on the front of the tube and it just drops into a slot in the back. Make sure that only 1/8 to no more than 3/8's of the rod is actually in the pilot flame or the thermo coupler will only last a few months. This is a common replacement part, usually every few years.

Koan

Sorry. URL did not post

supplyhouse.com/Honeywell-Q390A1046-24-Thermocouple-1721000-p

Steamhead

Koan, we have thermocouples on our trucks. You know where to find us

BTW, thanks for referring your neighbors to us!

Koan

@Fred Thank you so very much. I am sure you could sense the panic in my post. You have been an enormous help to my project to refurbish the radiators and piping, and you have made it so I might even sleep tonight. You are a good soul. I hope to be reporting good news soon!

Koan

@ Steamhead

Thank you sir. If my efforts tonight fail you will promptly hear from me. This part failed on the HWH and I was able to get that back. Trying not to panic. I was hoping to wait to get you over to look at the combustion analysis when your schedule lightens up. It was running so well, every radiator hot all the way across! At least I ran it enough to boil off the excess oxygen.

Thanks for helping out the neighbors - they were very complimentary of you!

Koan

@Tim McElwain
Tim McElwain Member Posts: 3,625
November 19
Keep in mind much of the efficiency on Mod/Cons has to do with smaller chambers and very direct heat transfer. I am not sure if present combustion analyzers really get it correct. I for one do not always follow the manufacturers recommendations to only touch the throttling screw. Sometimes a pressure adjustment is in order (I do not however recommend the run of the mill service tech touch the pressure screw unless you have been properly trained).

The concern here is that Koan has an oversized piece of equipment and should really be looking at replacing it.


Tim - yes sir , I think you hit this right on the head.
I have a circa 1970 boiler, well built, and now cleaner inside than it has been in a long time. It is coming up on 46 years old, but may (probably) still have a good 10 years left.
A new boiler will probably have a 20 year lifespan.

I have to see if the fuel savings make it worth removing a functional oversized old beast. But either way - not this heating season - maybe next?

Tim McElwain

You need to take millivolt readings with a multi-meter on the thermocouple and at the same time monitor the combustion with an analyzer. Pilots can go out due to mechanical failure (the thermocouple) or the magnet assembly in the gas valve (that requires a new valve) or it can be a poor combustion condition smothering the pilot or robbing the pilot of sufficient air to operate. The pilot flame should envelope the upper 1/2 to 3/8 of the thermocouple and the tip should be a dull red.

A pilot safety turn down test should also be done to insure that in all cases the pilot application is going to work with this equipment.

With a system this old and perhaps neglected for too long it may be difficult top get this system to work correctly.

Koan

@Tim McElwain
It has already been a challenge. I think it makes sense to try the part that is most probably the source of failure and not expensive first to see. I can do that, but I do not have the expertise to dial in a new gas valve.

I cannot see how the main burners were running for an hour with good looking flame if there were an air deprivation or smothering problem. The pilot flame also looked good, not yellow or lifting.

As an expert whose advice I value once said,"It should also be mentioned that many times it is the policy of some to replace the thermocouple on a call and clean the pilot. It is not a bad thing to do. However, about 85% of the time, it is the thermocouple giving the problem."

1. IS THE PILOT LIT?
it was , but then stopped. I could relight it but could not remove my thumb from the red plunger
2. IS THE PILOT CLEAN? (NOT YELLOW)
Yes - good looking flame
3. IS THE PILOT HITTING THE UPPER 1/2 TO 3/8 OF THE THERMOCOUPLE?
Yes - it was
4. ARE CONNECTIONS TIGHT?
Yes - they were
5. IS TIP DAMAGED?
Did not appear so
6. IS THE COLD JUNCTION BEING HEATED BY THE PILOT OR MAIN BURNER FLAME?
Definitely the pilot

When taking OC readings of DC Mv of the thermocopuple, I know one lead goes to the thermocouple tip, does the other go to the theromcouple body or the lead that goes to the thermocouple?

Thanks Tim!

captainco

hatterasguy; This could be a long post but lets try to explain this another way. Combustion efficiency in reality is usually 99.99%
Now of this 99.99% some is sensible and some is latent. Dealing with just the sensible how much of this is actually available for transfer. That is totally dependent on how much excess air there is, but not so much the O2 but the N. If a flame burns at 3600 degrees then 100% of the potential energy is converted to thermal energy. How ever if the flame is only 2800 degrees then there are btus stolen by the Nitrogen. So how many btus is 2800 degrees? 100,000 btus equals 90,000 btus sensible and then at 2800 degrees for simplicity is now only 81,000 btus. How many of those btus would have to be transferred to be 80% efficient? 100%? Not likely!

I had this weird thought the other day which almost makes sense. (not the weird thought)
What the combustion efficiency chart may be telling us is how much of the btus actually available are transferred. The problem is we don't really know the exact amount made but we did transfer 80% of them. 80% of what, who knows. That's why we measure airflow and Delta T and calculated btus an it isn't even close to what a combustion analyzer is calculating.

Mod-con are the first equipment I have ever seen that runs with a low O2 in all firing rates. 3% to 4%. That just has never been done on any other type of modulating equipment. Again they are transferring 98% of something, just don't know what that something is.

captainco

My conclusions regarding flame temperature are absolutely correct. Mod-cons are the first burner to run O2 near 3% in low fire which gives a flame temperature of around 3200 degree out of 3600 degrees. No other type equipment has accomplished this.

The discussion is whether combustion efficiency calculations represent the actual efficiency (btus delivered). The answer is no and moist of the time not even close.

One more example: 90% furnace - O2 = 14%
Flue T = 90 degrees
Analyzer efficiency = 99.9%
I don't think so!

captainco

By the way, the picture above looks like the pilot is aimed at more than just the top of the t-cpl

captainco

100% of what I have posted is based on factual field results and intended to help answer questions and educate. Some prefer to stick to old falsified mis-information and opinion. I never intended on disagreeing with what everyone believed, it was field results that accomplished that. If all was perfect would this website even be necessary?

ChrisJ

captainco said:

100% of what I have posted is based on factual field results and intended to help answer questions and educate. Some prefer to stick to old falsified mis-information and opinion. I never intended on disagreeing with what everyone believed, it was field results that accomplished that. If all was perfect would this website even be necessary?

Jim,
How did you measure the actual efficiency of a boiler out in the field?

I've been trying to figure out a way to measure the amount of condensate my boiler produces in X amount of time to see the actual efficiency (Fuel input vs energy output) for over a year now and I've still yet to come up with an easy way. The problem being 104,000 BTU/H produces very little condensate in 10-20 minutes to be able to measure it accurately.

If the charts are all wrong, what else is there to go by?

captainco

So if I have a steam boiler making 175# steam and the O2 is 5% and the net Flue T is 300 degrees it is 82.1% efficient. right?

captainco

Hatterasguy said:

Notice how the combustion efficiency climbs with a drop in the net stack temperature.

This chart further confirms the 1% drop in efficiency with a 2% increase in oxygen.

Still a bogus fabricated chart that may calculate the flue loss of the btus we are making, but we don't have a clue on how many btus we are making only a volume of fuel.

ChrisJ

captainco said:

So if I have a steam boiler making 175# steam and the O2 is 5% and the net Flue T is 300 degrees it is 82.1% efficient. right?

My thoughts were 125+- cubic feet of natural gas per hour input to boiler and 12.7 gallons of condensate being returned per hour equals 82% efficiency.

captainco

Chris, check your steam temperature chart.

ChrisJ

captainco said:

Chris, check your steam temperature chart.

That was for 212F steam I believe.

captainco

175# steam is 377 degrees.

ChrisJ

captainco said:

175# steam is 377 degrees.

I'm a bit confused as to why you're mentioning 175 PSIG steam?

captainco

Just wanted to see if anyone noticed the flue temperature is lower than the steam temperature. Combustion analyzer chart doesn't know what we are making. Flue temperatures cannot be lower than the water or steam temperature.

ChrisJ

captainco said:

Just wanted to see if anyone noticed the flue temperature is lower than the steam temperature. Combustion analyzer chart doesn't know what we are making. Flue temperatures cannot be lower than the water or steam temperature.

I assumed you meant 175 pounds of steam.

Koan

Well - It appears the gas valve is not working. The system ran great for a couple hours but now the pilot won't stay lit. I replaced the thermocouple but no joy.
I think we may have a combustion analysis soon!

captainco

Hatterasguy said:

captainco said:

100% of what I have posted is based on factual field results and intended to help answer questions and educate. Some prefer to stick to old falsified mis-information and opinion. I never intended on disagreeing with what everyone believed, it was field results that accomplished that. If all was perfect would this website even be necessary?

You have not controlled any of your variables in your results in the field and rely on anecdotal evidence from building owners who wouldn't know a degree day from a hole in the wall.

Therefore, I conclude they have led you down the wrong path, and, sadly you continue down that road.

I guess every engineer and energy auditor and utility I know is stupid. It is a shame you have nothing positive to add to a conversation but your lack of reality.

Koan

Ok - last night @Steamhead helped me out with a new valve and combustion test. The thermocouple was good on his tester and the new evolve fixed the pilot safety lockout issue. New valve kept the pilot lit. 30 seconds for the 2 cu ft meter to revolve once, so clocking at 252.0 Mbtu/h is where it ended up using 1,050 btu/cu ft

Here are the combustion results. I really like the 0ppm CO, I really am not jazzed about 26.1% Stack Loss.

Still 74% efficiency from a 47 year-old massively oversized boiler can't be all bad.



Finally - I have heat!

Need to tinker with the traps a bit, (I think one crossover trap is failed open) but we are on the road.

My thanks to @Fred, @Steamhead ,@Sailah, @Tim McElwain , @MilanD, @Jamie Hall,@Dave0176, @KC_Jones, @Hap_Hazzard, @ChrisJ, @SWEI, @Paul S, @delta T, @hot rod, @RomanGK_26986764589, @EBEBRATT-Ed, @JUGHNE and everyone else here who has shared their knowledge. Sorry if I missed anyone.

You have all helped me learn so much so fast, and your tips and insights have been invaluable.

A special thanks to @Dan Holohan, @DanHolohan for creating this virtual repository of helpful and collaborative thought, and to @Erin Holohan Haskell for continuing to carry the torch.
BTW Dan -I have read 'We got Steam Heat" and "The Lost Art of Steam Heating" and would encourage everyone who owns a house with steam heat to read both books.

I think @captainco and @Hatterasguy have a spirited discussion going and I am grateful for your insights. You are both very talented. I sincerely hope for continued kindness and dignity in your possible differences of opinion.

All my best
Kelly (Koan)

DanHolohan

Thanks, Kelly!

captainco

Thanks for using Steamhead. I never meant for my comments to be augmentative.
Any gas company that delivers 1050 btus per cu.ft is losing big bucks, but that's another story.

If I were to calculate the actual efficiency of your boiler it would look like this:

Latent heat loss - 14%
O2 loss - 8.6%
Flue Loss - 17% 520 Net Stack divided by 30 degrees
Total loss - 39.6 %
Actual eff - 60.4% (approx.)

This is fairly typical and not bad for a steam boiler. Sounds like the boiler could use a bit of descaling though.

Erin Holohan Haskell

Thanks, Kelly!

Koan

@captianco

Thank you. Yup Frank and Gordo are tops.
Forgot to thank @Gordo

I used this data for heat content - I'm in Maryland:

https://eia.gov/dnav/ng/hist/nga_epg0_vgth_smd_btucfm.htm

I washed that darn thing out for hours with a wand until it was clear. Nothing but a little surface rust left inside. Must have removed 5-10 lbs of crud. That reminds me to thank @gerry gill for wand idea. It was really helpful.

Steamhead

In my experience, the numbers on that printout are pretty typical for that American-Standard model series. Energy was pretty cheap back then and people weren't really concerned about efficiency that much.

Koan and I talked about maybe replacing that boiler next year. If we do, we'll post the results.

Fred

Glad to hear your problem has been fixed, Koan!

Erin Holohan Haskell

Thats enough, @Hatterasguy and @captainco.

captainco

Happy Thanksgiving

Koan

@captainco and everyone. Happy Thanksgiving to you.
@Fred . Thank you! Nice to not have to worry about things getting too cold outside. You are a good man and a kind soul.
I assume many others here are as well . I would be stuck without this forum, or worse risk injury.

Today, I am thankful for all the help, and that there are still good, kind, and considerate people in the world ( many of them here). It is refreshing to be the recipient of genuine consideration.