02 rises to 10-11 with door open.

icy78

Draft after dilution was -0.025. Door 50 feet away opened 4" and draft went to -0.06. O2 went from 8.6 to 10.8. Natural draft Raypak H3-0724. (I'm rather new at this and want to get good at it. Reccomend me a good manual. Something from Tim McElvain?) Anyhow numbers yesterday were 4000 ppm CO. Cleaned it up and have 4 COAF, 8.6 02, CO2 was 6.9%,flue gas is 362. EWT 156, LWT 178 at reading. So my question is: flue gas temp at 362 before dilution. and 268 after dilution, will I condensate in the brick chimney? (I thought I'd read I would need 325 minimum in the stack to keep from condensation.) Also: the draft increased with the door open and the 02 went up too high?

Jamie Hall

Suggests to me that the space the unit is in doesn't have adequate ventilation.

icy78

> @Jamie Hall said:
> Suggests to me that the space the unit is in doesn't have adequate ventilation.

Yes I agree. What I don't know what to do with is the higher 02. Should I be concerned about that? Also the stack temp has me wondering.

Jamie Hall

Honestly, I have not idea! I do steam and hydronics and some solar -- and I have carefully avoided learning about burners and testing!

ch4man

your underfired, flue temp is too low, CO2 a bit low. O2 too high.
need to get the draft under control first;

summon Jim Davis captain CO here and the other sites you visit for guidance. rundawg is another good refference. you know where to find him

Zman

How is the space ventilated?

Bill_Kitsch69

Look for a well sealed room with lack of, or inadequate combustion make up air. Have you checked this effect without the burner running at room static, door open & door closed?

Look for negative pressures from exhaust ventilators or other posing negative pressure in the space.

Anytime mechanically ventilating a boiler/heater room,
a POSITIVE PRESSURE FAN is to be used, with relief provided.
NEVER EXHAUST FANS.

Tim McElwain

I am not in the office but will get back to you tomorrow. In the meantime Jim may come on and assist you. I do have a series of three manuals on Combustion Testing Design Gas Equipment.

hot_rod

Is this that same Raypak 726,000 BTU project? That beast will need some serious combustion air. What does it have now?

icy78

It sits in a 60 x 60 x9 storage area. 3600 sqft. No dedicated combustion air. Stack draft was -.025 with a mandoor closed. -0.06with door 8" open and wind blowing in. At that draft, the 02 rose to 10-11. Factory Fixed manifold pressure of 4".

GW

Curious what the co is when the door is closed

icy78

> @GW said:
> Curious what the co is when the door is closed

Post #1. 4 COAF with door closed.
Here's the issue. 4 with door closed, 4 with door open. 02 was 8.6 with door closed. 10.5-11 with door open. Draft after dilution at -0.025 door closed, -0.06 door open.

Draft before dilution with door closed -0.001 to 0.000
Draft after dilution with door open, -0.06.
Also note: wind aided air thru door, and no relief air.

I think bill_kitsch69 said something about relief air. Been mulling that and I can see how that may be an issue here.

Zman

The results you are getting are no surprise. What goes out must come in. When the door is closed, the boiler is struggling to pull that air through cracks and crevices. When you open the door the boiler is getting the air it needs to run properly.You need properly sized combustion air.

icy78

> @Zman said:
> The results you are getting are no surprise. What goes out must come in. When the door is closed, the boiler is struggling to pull that air through cracks and crevices. When you open the door the boiler is getting the air it needs to run properly.You need properly sized

Yes, I do. As CH4man said earlier, "it looks like I'm underfired when the door is open" or, as I am thinking, TOO MUCH air being forced in by the wind causes an appearance, of underfired. I agree that it's starving, although, can that be shown by 4ppm CO, and decent numbers?
( Except that draft numbers are not good with door closed) anther thing is I don't have the manufacture numbers for combustion and it could be that with the door open and the O2 at 10.5, that that is want they want.

I don't just want the correct results, I want to know WHY and HOW.☺

Tim McElwain

What is the total BTU requirement of the space? The area you have should be able to provide sufficient air for up to 648,000 BTU's.

The boiler 726,000 and if I am not mistaken is a 2 stage system low fire/hi fire. That is also a copper tube heat exchanger which must be very clean or you can have problems. Also make sure the tubes are not distorted or damaged.

It looks like you need provision for dedicated air in order to meet the requirements of this equipment.

It may also be advantageous to install a barometric and eliminate the draft hood. That will allow you to adjust draft.

GW

I'm unfamiliar with that boiler, basic sectional unit with several burner tubes? You get 4ppm co over the hx ? Did you move the probe around? Doesn't 4 seem a bit low for over the hx?

ch4man

dont forget the flue flue gas temperature.......
should be 270' to 370' above supply temps on a cat1 nat appliance; your only 184 deg above

that also played into the reason i said underfired. sure, the excess O2 will bring the fire temp down thus reducing the flue temps. but not that much.

i still say your underfired

icy78

> @Tim McElwain said:
> What is the total BTU requirement of the space? The area you have should be able to provide sufficient air for up to 648,000 BTU's.
>
> The boiler 726,000 and if I am not mistaken is a 2 stage system low fire/hi fire. That is also a copper tube heat exchanger which must be very clean or you can have problems. Also make sure the tubes are not distorted or damaged.
>
> It looks like you need provision for dedicated air in order to meet the requirements of this equipment.
>
> It may also be advantageous to install a barometric and eliminate the draft hood. That will allow you to adjust draft.

I had the burner assembly out and cleaned up. I did not ream all (900?), holes on the burners but did brush them. The htexs ex section was slightly sorted and a layer of rust on top from the draft diverted. All cleaned up but just with water and brushed the top and vacuumed. "Looks" clean. Delta thru boiler at high fire was 10f. I set it to 23 per Raypak.
All in all the whole system is SO much better than before, flows, tank and fill match now, clean boiler, operating control set correctly (not short cycling any more). New Guage.
I doubt they'll let me do more but on a slow day I may be able to get in there.
I like the barometric idea tho.

icy78

> @ch4man said:
> dont forget the flue flue gas temperature.......
> should be 270' to 370' above supply temps on a cat1 nat appliance; your only 184 deg above
>
> that also played into the reason i said underfired. sure, the excess O2 will bring the fire temp down thus reducing the flue temps. but not that much.
>
> i still say your underfired

Can you elaborate on the stack temp. X above supply temp?
Pm me if you like. Thanks

ch4man

the stack temp over supply temps are some of the things taught at NCI's combustion analysis class.

the higher burner efficiency the lower the delta, as there is more heat transfered into the medium (water or air) thus less going up the chimney.

an induced draft FA furnace will need 170 - 270 deg above supply temps. these are more efficient machines than a CAT 1 nat appliance that requires 270 - 370 deg above supply medium temps.