Venting Question....Boilerpro

Unknown

does not give a min for the NAT. The HE is not classified a FAN equipment. It is a category I venting boiler.

However if it was then with a 30' chimney it would be 452 min to 946 Max for 9" and for 10" 626 min and 1193 max. In that case we could have gone with a 9".

Boilerpro

Venting size for power vent boilers with barometric dampers

Just got called in on a installation that hasn't worked right since it was installed over 10 years ago. 3- propane fired W-M HE series 167,000 input each boilers vented into old 35 to 40 foot chimney with a common vent manifold about 12 feet long and about 16 inches diameter. The two boilers closest to the chimney have trouble lighting off regularly and the one farthest occasionally. Problem appears to be greatest when there is a strong northeast wind....building is located out in the cornfields with a few trees around. Often only the first two burners in each boiler will light unless you bend down and blow into the combustion chamber. Already found that the gas pressure drops too much when the boilers fire, the air intake is too small and I also suspect that there is way too much draft, but still need to check that to be sure. Twas wondering in this application where the barometrics should be installed (the factory boiler instructions don't even mention thier use) and if using barometrics on this application, the vent should be sized to the natural draft tables or the power vent tables? I suspect the natural draft, but would like some input. Thanks all!


Boilerpro

Unknown

Weil-McLain HE

Dave I just got off the phone with Weil-McLain rep here locally. He advised that the HE boiler series can be vented into a chimney with out power venter and defintely no barometeric. This system needs to be completely re vented. I would tear it all out and start from scratch on the vent. I am trying to get info on a local rep from Weil-McLain in your area for you. Exactly what is the location of this job.

As for the drop in pressure when boilers come on I would get the propane provider out to refigure the line to system and pressure. There should not be any drop in pressure.

Off the top of my head, I did not get the book out and actually size the vent but it seems a little large to me.

Give me a little more info as to chimney etc. Is it lined or unlined, how far from farthest boiler to chimney etc. I am on the way out of the office, will be back in this evening and will recheck then with you. Glad to be of help.

Unknown

Still in the office

got a phone call and have to stick around. Did a few calculations:

From National Fuel Gas Code Book Table 10.9 Masonary chimney with single wall connectors serving two or more category I appliances.

30 foot chimney with a 3' rise will handle 524,000 btus (yours is 501,000 total) with a 10" connector to the chimney.

The chimney inside dimensions need to be between 78 to 113 square inches a 10" to 12" round or roughly 10" x 10" would do it or larger.

If you go double wall all the way on the connectors it does not change much.

The vent connector is definitely over sized and no need for power venter or barometric in my estimation.

If the chimney is unlined that may be a problem. Then you could use the old chimney as a chase and run double wall up through the inside to the roof.

Hope this helps.

Unknown

What is the MINIMUM

What is the minimum firing rate for that size, Timmie?

Noel

Boilerpro

Thanks Timmie...

The power vents I was referring to are the ones built into the boilers. Connector rise is probably only one foot, if that. I was thinking of using barometrics to get the chimney draft under control, since ther are no draft hoods and I bet it is pulling through the power vent fans and creating excessive draft in the boilers. The evening I was there,I could here the chimney howl with little wind and an outdoor temp of 45F.... So there is alot of draft pulling on the boilers. I'l get in contact with my local Weil Rep, I'me still looking for his card though. I was figuring a ten inch also. Need to investigate further on site now that you and others have confirmed my suspicions. Thanks, and I'l keep you informed.

Boilerpro

Unknown

I remember the HE as a boiler with a fan

If the minimum is more than 1 boiler's firing rate, do you interlock the boilers so that only one can never run alone?

By definition of Fan Assisted Combustion System, NFPA 54:

An appliance equipped with an integral mechanical means to either draw or force products of combustion through the combustion chamber or heat exchanger.

It falls under FAN Max and FAN Min collumns in Category I, FAN+FAN.

These new tables sure can be confusing.

Noel

Unknown

The techs at Weil Mclain

advised me that it was not categoried as a FAn Appliance. I do not have my books handy they are at the center on HE. You may be right. I will check when I go down there today.

Unknown

Weil McLain HE correct info

Noel was correct.

Weil McLain HE(Series 3) Gas Fired, Induced Draft

INSIDE CHIMNEY

Must be lined - vitreous tile lining recommended

1. Two Inch clearance from combustible

2. Do not use chimney with open fireplace

3. Inspect and clean chimney

4. Make horizontal runs as short as possible, Long runs cause condensation

5. Proper support with hangers on long runs

6. Do not vent into bottom of chimney

7. Do not go beyond inside wall of chimney

Minimum breeching sizes even though the pipe out of the HE is 3"

HE 3 4" Diam

HE 4, 5, 6 5" Diam

Outside chimney has to be lined with corrosion resistant metal liner

Sizing from NFGC Table 10.9

30 foot chimney with 1 foot rise will handles

Fan MAX 864,000

Fan MIN 430,000

9" connector

can be galvanized

must seal all joints with 400 degree silicone sealant

Minimum 10" x 10" inside chimney

Boilerpro

Looks like definitely too big of chimney....

I was just checking my Metalbestos book and it looks like we could drop down to 8 inch round B-vent for the common vent 720,000 x .9 (reduction for mannifold)= 648,000. What is a "corrosion resistant metal liner"? Also I would like to stage fire thse boilers, since in a church on the typical winter day only about 25% to 35% of the peak capacity is needed. Haven't run a heat load yet, but I suspect the building will easily heat with only 2 of the 3 boilers. If I stage fire, I suspect that only one boiler firing may go under the minimum values. Then, I imagine it may be necessary to introduce dilution air with barometrics to keep the vent from condensing and design the vent using Nat + Nat values....or am I just all wet here? FYI I did talk to my local WM rep and he did say there was problems with flame carry over from burner to burner on these boilers and that new burners should of been installed in the last few years to rectify the problem.

Boilerpro

Unknown

Special venting for HE

You can not use a barometric damper with an HE boiler. In fact you should not use barometric dampers with any designed gas boiler or furnace unless specified by the manufacturer.

Corrosion resistant metal liner is stainless steel.

There are several factory change outs on these boilers that you should look into. There were some problems with the draft inducer motors also.

I have all the literature on the three phases of HE. If you are going to be at the "Gathering" I will bring you a copy of each one.

There are several ways to vent HE boilers too complex to post here. I suggest you look them over before you do anything. I would also see if Weil McLain has a boiler plan for tandem hookups or staging for these boilers. I am sure they have something.

Steamhead

BP, is that church old enough

that the original boiler was coal-fired? If so, that explains the chimney's raw power- it had to pull air thru a bed of coal. Power-venting seems a waste of time with such a draft.

I'll be interested to hear how you solve this one!

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Boilerpro

Many and much thanks , Timmie...

I think I may just drag the reps out here to look things over. Its obvious the venting system is a mess and so is the piping (the zone circs are in series with the boiler circs). Already told the owners that the propane guys need to check thier equipment. After that, will see if the lines betwen the second stage reg and the boilers are properly reamed(and sized). Will keep you posted.

Boilerpro

Boilerpro

Pretty likely

> that the original boiler was coal-fired? If so,

> that explains the chimney's raw power- it had to

> pull air thru a bed of coal. Power-venting seems

> a waste of time with such a draft.

>

> I'll be

> interested to hear how you solve this one!

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 157&Step=30"_To Learn More About This Contractor,

> Click Here to Visit Their Ad in "Find A

> Contractor"_/A_

Boilerpro

Pretty likely...

Building is old enough, but not the system isn't. I 'm interested too...could you give me some hints?

Boilerpro

Boilerpro

Oh, and on barometrics and power vent boilers into chimenys

Putting the two together occurred to me from the Hydrotherm HI-B and ID-A series boiler. They also have draft inducers and the installation instructions state that if the chimney draft is too strong it will cause erratic boiler operation and barometric dampers should be installed to control chimney draft. Thought you might find that of interest.

Boilerpro

Steamhead

The Dead Men made a really big deal of this

in their books. I believe it is mentioned in every one I have- that an inadequate chimney would render a coal-burning boiler almost useless. Around here, I find very strong chimneys in all the older houses- which is one reason I like stack dampers, since an overachieving chimney can suck the heat out of a boiler quickly during the off cycle.

What I really need to do is to make some draft measurements on the chimney in my house at different outdoor temperatures. Hopefully I'll have the time to do that this winter.

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Unknown

That is okay as long as

boiler or furnace manufacturer gives the okay. I will usually ask them to give me a factory authorized bulletin when they make such a solution to a venting or any other problem. You just can not apply that to every situation.

I think when you look at the HE book there are some venting options that may solve this problem for you. One of those is using the existing chimney as a chase and running a dedicated vent all the way to the top of the existing chimney.

Boilerpro

Looking at dedicated wall vent option

Got to get back out there and start measuring. Closest outside wall faces due north...not good... so I am going to see how far it is to the east wall. I agree with Steamhead, it seems to make no sense to use a power vented boiler when you've got a strong chimney to use. I think it must go back to the fact that most of the market here is forced air, and with hot air the only energy efficient furnaces are those that use power venters (and that's the only kind I ever see around here), so that must also apply to boilers in local contractors' minds. Oh well, I'll just keep cleaning up the messes and keep whistling on my way to the bank.

Boilerpro

Unknown

The price we pay for

efficiency. Steamhead is correct. That is why so many instructions for mid and hi efficiency do not allow venting into chimneys. The other porblem I have found that even when using the charts and tables and doing it exactly the way they tell us the venting system still does not work correctly. The only option then is side wall venting. With that then staying away from prevailing high winds. We get a lot of that here in New England along the ocean.

Many times when we converted old coal fired boilers to gas conversion burners we would cut in a neutral pressure point adjuster into the flue. The code books showed it in front of the diverter. My experience was to put it as close to the chimney as possible after the draft hood that way I controlled draft overfire and at the chimney, worked like a charm. Just can not do that stuff with all this new stuff.

Simple truth as efficency goes up excess air has to go down, CO2 has to go up and stack temp down. Then we have the problem of not being able to create sufficient Delta "T" with chimney height to get the chimney to work. Add to that tight construction, polluted combustion air and attic fans OH my how I do go on sometimes. Good Luck. I should say God Speed.

Dale

Thoughts on this job

Getting the propane line sizing right should be done first, lightoff is certainly affected by gas pressure. Next I wonder what the chimney cap looks like, is there one, looks like there's too much draft. How about the supply opening air? There can be too much, can you reduce the opening and still be legal? Barometric dampers are the last resort and work nicely, always better to get the manufacturers OK but the reason they're not used more is cost.