Weil Mclain CG Boiler flames to big

junior_money

I've got an old Weil Mcain CG boiler that has worked well for many years. A few weeks ago I got a slight smell of gas, checked on the boiler, flames were erratic and yellow. Pulled the burners, kinda rusty and the pilot burner bracket was on its last leg so I replaced all the burners. I also found the boiler sooted up from the bad flames so I cleaned it well. Put it back together and the flames are still big and yellow. Checked the gas valve pressure, 3.5 inches water column as specified on the valve so that is ok. When the vent valve opens it drafts strong, shares a vent with the hot water heater and that is working fine. Plenty of combustion air available as well. Letting it run will pop the flame rollout TFE switch and shut it down. I feel like I've covered all the bases here but what could I be missing. Seems like the gas is just WAY to high but the measurement checks out.

Thanks for your help

junior_money

Here is a video of it running https://www.youtube.com/watch?v=aSjAkEFfm2s

unclejohn

To much air. You need some body with combustion equipment to do it right. If it trips the roll out switch that's just to save your life.

Tim McElwain

Unclejohn is correct too much air. You say you replaced the burners are they the correct burners? Do they have air shutters? If so slowly close them until the flame settles on the burners. Then recycle the burners to make sure you have safe lightoff. What you have now is called lifting flames caused by too much primary air at the burners. Then you need to have a combustion analysis done by a professional. I would also clock the burners using the meter test dial.

junior_money

I totally agree that it's not right. Where is there another adjustment on this boiler. There are no air adjusters on the burners . New ones are exactly like the old ones, cleaned the old ones and tried them as well. Same results but lazy flames. Where can I adjust the boiler to fix it?

nicholas bonham-carter

If there is no adjustment for the air, then there is too much gas getting through the valve, even though the inlet pressure is right.
Can you clock the meter to verify what amount of gas is being burnt?--NBC

Tim McElwain

You can make air shutters from some soft metal and add them to the burners so they can be moved back and forth. What is the input required by the rating plate. You stated the outlet pressure was 3.5" w.c. so the orifices may be sized incorrectly. Clocking the burners with the test dials on the meter will help you to determine this. If you do not know how to do that I will walk you through it.

4Johnpipe

May be worth a call to your gas utility provider to have your meter and regulator checked. They should do this at no charge. If you smell gas and have this new condition it points to a fuel delivery issue. This could originate at the gas meter or even a defective gas valve at the boiler. One question is the water heater natural draft or power vented into the same chimney? Is the water heater new?

junior_money

So I clock the gas meter. It came out to about 50,000 BTU the unit is rated at 52,000. When I put the inspection plate on it seems like it's a little bit better but I can still see a lot of yellow flame in there which I don't think I should see. That video looks like its wrong correct? Way too much yellow flame?

Both the boiler and the hot water heater have not changed in many years. The hot water heater is naturally vented. The flames on that are nice and blue when it fires. No soot at all in the vent from the hot water heater.

I tried using a piece of steel to cover up the entrances to the burners where the air comes in and it seemed to get a little better but that can't be the answer because it's not designed to have shutters. So even though that might fix it it doesn't solve what originally went wrong.

When I get back there I'll let it run for a while with the gauge on it and see if I get any variance from that 3.5 inches water column.

Tinman

Over-sized orifices and high manifold pressure are the only things that would cause it to over fire.
Flame impingement may be causing the sooting?
It's been rare, but twice I have seen burner orifices not drilled straight. Caused severe sooting both times.

junior_money

I don't see how I could be orifices the boiler has been there for over 15 years and No trouble until now. I don't see how the orifices could have changed or worn out. I'll check to make sure they're not plugged up or dirty

JUGHNE

Was anything recently changed to change the draft over the fire?
Draft diverter closed off.....baffles of some sort on the top of the boiler maybe between sections removed....pan under burners changed?

Tinman

Taking long shots - any newly installed fireplace or large exhaust fan in the building?