Still need Help

JUGHNE

This bad boy has 18 burners for 10 sections, the plug idea has occurred to me but as you say... Once upon a time there were boilers from the factory with 1 or 2 orifices plugged. Isn't the real issue with non heated sections within the boiler, uneven heating etc?

Fred

One of the issues is uneven heat distribution across those 10 sections. I'm wondering what Burnham might say about using a smaller gas valve and plugging every other orifice?

KC_Jones

I can NOT advocate it for anyone else and my boiler is a good bit smaller, but I had 2 burners plugged off on my old Weil for about 12 years with no ill effects. I know it is frowned upon big time, but it helped with my oversize condition and only cost me 2 pipe plugs. It was my equipment my personal risk. If it went bad it was my issue. Honestly in this situation it might not be a bad idea to at least explore a full boiler change out for the smaller one. At least look at it from a standpoint of cost, excess fuel usage versus labor and materials for the proper size boiler. In my mind the biggest difficulty would be getting money out of the existing boiler. Not sure what kind of market there is for used steam boilers? Perhaps a local non profit that needs a new boiler cheap? That is probably a LONG shot though.

JStar

Fred said:

One of the issues is uneven heat distribution across those 10 sections. I'm wondering what Burnham might say about using a smaller gas valve and plugging every other orifice?

The flame might not travel quickly enough across the burners on light-off and cause a minor explosion.

JUGHNE

Thanks for all the input, I have considered everything you 3 have said today. Still working on plan of correction for basement piping. This includes a drop header which would ease a boiler change out it the future. It will have a 4" header which would really be a plus for a smaller unit.
All the piping needs corrected anyway and perhaps the 2 stage gas valve would make the situation more presentable.
The biggest problem for HO is spitting vents with water loss and boiler refilling. Some noise also which they are used to having.
In any case it will be the HO's call on boiler.

And as JStar mentioned delayed ignition, it really gets your attention and if you are close to burners it gets your beard.

Fred

Do get that Pressuretrol up above the water line also. I think that will go a long way towards getting the pressure down and may well stop the spitting valves/water loss. As it is today, that pressuretrol isn't seeing any pressure. You probably need to set the right expectation with the HO, as well. Make sure they understand that the work you are doing is necessary for any boiler they install, in the future, but that it may well not give them a problem free steam system until the boiler is properly sized or at least more closely sized to the radiator EDR.
I know it is a bitter pill to swallow, but if it were mine, I'd go ahead and change the boiler out and be done with it. Let it be a distant, bad memory and a real learning experience.

JUGHNE

I will suggest that the piping mentioned be corrected, The pressuretrol and better gauge install. Try it for one more season and then decide. I now can really see the advantage of the double swing fittings that the drop header will provide with the possibility of boiler change out in the future.

Yes, I believe they realize that any improvements would stay with the house and enhance the next potential boiler.

Steamhead

Given our experience with Burnham, it's safe to assume they'll tell you to buy a whole new boiler.

JUGHNE

Plugging orifices is pretty well off the table for me.
What is your guess on their comment for an after market 2 stage gas valve?
Would this be a hi-lo-hi fire? The 2 stage furnaces I'm familiar with start on high fire to establish flame and draft then cut to low fire. I'm assuming this would want to light off on high for the same reasons, especially since we are relying on gravity venting only. And always restart on high fire for every cycle regardless of pressure in boiler.

Fred

They typically do light on "Hi" and then step down to "Lo", which is OK. It can start on Hi to get the water boiling and the pressure up to maybe 6 to 8 ounces and then step down to low and run at low to about 12 to 14 ounces before shutting down on pressure. To be perfectly honest, even at "Lo" it will still be so over-sized that there will probably be minimal benefit from a two stage valve. You can try a smaller, single stage gas valve but I don't know how small you can go before you start having burner/combustion issues. I'd say if you can down-fire the boiler by 15% to 20% (using a combustion analyze, of course) you'll get about the same result as using the "Lo" side of a 2 stage valve.

JUGHNE

Fred, by smaller valve do you mean simply lowering manifold gas pressure? I believe that lowering the gas pressure to much could cause lighting problems with delayed ignition.

I believe the physical size of the valve doesn't matter unless it is to small to pass the maximum gas flow for the connected load which is determined by the size and number of orifices.

However the gas pressure at the manifold is typically 3.5" WC. The gas valve mentioned above, 700-064 is set at 3.5 hi fire and 1.3 low fire. I believe that would produce about a 30% drop in firing rate giving a 70% firing.

The NG furnaces I use have 2 stage burners starting on 3.5" and dropping to 1.7" for low fire. Their manual indicates that their low fire produces 65% of high fire.

I thinking that it is not a direct ratio, that is cutting the pressure in half does not cut the firing rate in half.

Comments from all are appreciated......Thanks.

Fred

I guess my thinking is that if a 2 stage gas valve will drop to 1.7" WC at lo fire that installing a singe stage rated at around 1.5" to 1.7" (or adjusting the current gas valve, if it has that much adjustment) will probably still be sufficient for the number of orifices on this boiler but you may be right about delayed ignition. I'm wondering about changing out the orifices to more closely match the reduced WC of the gas valve??? There is no "best solution" for this boiler other than a complete change out. Whatever is done as a "band-aid" will have to be safe over the long haul as I doubt the HO will replace that boiler as long as it seems to work reasonable well.
Is there any chance of putting in the 2 stage valve and re-installing the 5 radiators that were removed?

Charlie from wmass

Two stage gas valves do nothing to adjust combustion air. If you plug the four outside orifices you will have a cleaner burn than dropping the gas pressure.

Abracadabra

Charlie from wmass said:

Two stage gas valves do nothing to adjust combustion air. If you plug the four outside orifices you will have a cleaner burn than dropping the gas pressure.

I'd plug a couple orifices on the far side of the pilot too, but this is an atmospheric boiler no? Combustion air shouldn't be an issue unless his boiler has some kind of shutters for the air.

JUGHNE

There was a posting on the wall sometime back about lower gas pressure in a burner did somewhat adjust/lower the air mix simply by less venturi flow caused by lower gas flow, which would pull in less air to mix with fuel.

The example the OP used was a stove top burner. adjust the gas pressure up & down the air/fuel mixture stayed somewhat the same. Maybe to oversimplified, but the theory is there.

Does anyone recall that posting?

Abracadabra

JUGHNE said:

There was a posting on the wall sometime back about lower gas pressure in a burner did somewhat adjust/lower the air mix simply by less venturi flow caused by lower gas flow, which would pull in less air to mix with fuel.

The example the OP used was a stove top burner. adjust the gas pressure up & down the air/fuel mixture stayed somewhat the same. Maybe to oversimplified, but the theory is there.

Does anyone recall that posting?

The only one I can think of is this one:

http://forum.heatinghelp.com/discussion/152939/modulating-atmospheric-gas-boiler

ChrisJ

JStar said:

Fred said:

One of the issues is uneven heat distribution across those 10 sections. I'm wondering what Burnham might say about using a smaller gas valve and plugging every other orifice?

The flame might not travel quickly enough across the burners on light-off and cause a minor explosion.

Interesting how "minor" doesn't seem to make that any more appealing.

ChrisJ

Hatterasguy said:

ChrisJ said:

JStar said:

Fred said:

One of the issues is uneven heat distribution across those 10 sections. I'm wondering what Burnham might say about using a smaller gas valve and plugging every other orifice?

The flame might not travel quickly enough across the burners on light-off and cause a minor explosion.

Interesting how "minor" doesn't seem to make that any more appealing.

You'd have to conclude that all gas boilers with multiple burners suffer from a "minor explosion" each time they start. There is a single point of ignition on a single burner. That flame must then jump 3-4 burners both sides of the original to light all of them off.

It all depends on your definition of "minor".

Nothing in that definition fits what my boiler does when it ignites.

My boiler burner had "minor explosions" which slammed the barometric damper shut every time it lit after a certain contractor "serviced" it. After I put the proper nozzle back in it and readjusted the air bands it stopped though. Of course, it didn't fix the plugged chimney issue that he ignored.

JUGHNE

Thanks to Abracabra, that was the posting I had in mind. The concept sounds good. 2 stage furnaces have a 2 speed induction fan motor which handles the change in air flow.

ChrisJ..... If your ignition failed on your oil burner and you kept hitting your reset/restart several times until you flooded the chamber with enough oil and then the ignition decided to work on the next reset.....you might experience the sensation of delayed ignition with "minor" explosions.

Most Atmospheric Gas burners such as we are discussing here, have a carry over tube/trough to carry the flame from pilot left and right to the front of the ribbon burners. You will just about always hear a little "woof" of ignition of burners, (very minor explosion).

If this action is slow or especially if the carry over and front of ribbon burners are partially plugged with crud, and the back part of the burners are flowing gas which has to "find" the pilot flame and then that "delayed ignition" that would remind you of an explosion. That is then a big "WOOF" (depends how close you are to it).

I saw a long neglected LP furnace blow the front cover about 6' across the room. That was when HO finally decided it needed attention.
Or at least the flame rolls out and cooks all the wires in the burner compartment, sometimes melting the plastic knob on the gas valve. LP is heavy and sluggish to move to find the pilot, thus the explosion is more than "minor".

ChrisJ

No carry over tube on my EG series.
It does light with a bit of a manly sound...but nothing I'd call a minor explosion.

BobC

When the ignition transformer was getting weak on my old V75 steam boiler I occasionally heard a delayed ignition whump. While waiting for a new transformer I once had the draft diverter thrown against the cellar wall that was 8ft away.

Bob

hot_rod

combustive ignition

Abracadabra

A WM LGB-23 ~2800MBH has something like 40-45 burner tubes. It'll sometimes ignite with what I like to call a "minor explosion"

JStar

I don't like putting in a smaller single-stage GCV because your start-up heating period will be very long and you may never establish enough steam production. With a 2-stage GCV, you'll always start in High Fire to make steam, then drop to Low Fire to maintain steam.