# How To Measure The Stack Draft In Water Column (inches?)



## SmokeEater (Sep 4, 2011)

Am installing new PB 105 and the instructions say not to install the venting in a chimney over a certain length according to a table in the manual.  It looks like that if I vent the boiler and connect its 4" vent to my 8" masonry chimney (lined with a 6" liner), the vent will exceed the recommended overall length.  My masonry flue is constructed as a 28' vertical connected to an 8" diameter horizontal 18" tile.  My install manual says that's too long.  Anyone know why?  Is it because the boiler has a positive exhaust pressure?  Also, the manual suggests that the draft in a tall chimney may be too high.  It should not be over 0.85" on the water column.  What is the device that this is measured with and how can it be done?


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## laynes69 (Sep 4, 2011)

An inclined manometer is used to measure draft. Dwyer makes one that will cost around 50 dollars. Manufacturers test their units with a set draft. If draft exceeds a set level, efficiency and operation are compromised. Draft can be checked with a small hole in the flue of the unit where a tube is inserted from the manometer. There are other tools to measure but I have no experience with them. Does the manual suggest any type of draft regulator like a barometric damper?


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## SmokeEater (Sep 4, 2011)

The manual instructs not to use any manual or barometric damper in the vent system.  The recommended method to reduce the draft is to put a restrictor plate at the vent's outlet.  Seems like that $50 inclined manometer is a one-time-use expenditure.  Is there any other way?


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## laynes69 (Sep 4, 2011)

There are directions somewhere on here to make a inclined manometer. I didn't have any luck, but maybe others have. I bought ours because our furnace recommends a barometric damper if draft exceeds .06". The problem with a restrictor plate is draft will vary based on exhaust and outside temperatures. A manometer is nice to have to diagnose draft problems. Calling someone out to check the draft may be more than a 50.00 service call. I dont recall seeing anyone here that have used restrictor plates. Hopefully someone comes along and has a better option. Good luck!


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## Duetech (Sep 4, 2011)

A search for manometer on ebay revealed a wide variety of pricing $15 to $275 and a host of others. You could gather some needed info perusing their listing before you actually decide to buy one.


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## SmokeEater (Sep 5, 2011)

Thanks for the great advice.  Sounds like a tool that will be handy for a good long time.


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## Singed Eyebrows (Sep 5, 2011)

I have a Magnehelic gauge permanently hooked up to my boiler & it works well. These are about $100.00 list & I bought it off Ebay for around $10.00 new. You want one that is sensitive enough to measure the slight draft & I believe the one I have has a range of 0 to 2 1/2" WC. If you need the model number just ask, Randy


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## pybyr (Sep 5, 2011)

How to DIY an inclined manometer:

https://www.hearth.com/econtent/index.php/forums/viewreply/379845/


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## maple1 (Nov 11, 2011)

Randy, could you give that number please.

Or could someone post up an Ebay link to decent gauge.

I've been searching manometers & magnehelics, and am just confusing myself.

Also, pybyr (or anyone), if pics could be posted of DIY manometers, that would help immensely - I am having a hard time deciphering the instructions. I suspect it is pretty simple, once seen.

Thanks!


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## Singed Eyebrows (Nov 11, 2011)

maple1 said:
			
		

> Randy, could you give that number please.
> 
> Or could someone post up an Ebay link to decent gauge.
> 
> ...


Maple, That is a Magnehelic cat. no. 2000-00   This reads 0 to .25 WC   Randy


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## maple1 (Nov 11, 2011)

Thanks - I'll do some more checking. 

I did a bit more after posting last night, that cleared a bit of stuff up on these things. I'm spending too many late hours roaming the nets, I think...


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## taxidermist (Nov 11, 2011)

watch my youtube video and you will see the one i use.

Rob


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## maple1 (Nov 11, 2011)

That vid is great - pretty well answers all the questions I had. Guess I should have looked earlier - time to find one now.

BTW, I think that's the first time I've seen a baro on the bottom of the pipe. Mine and I think everyone elses around here is in the smoke stream. Makes more sense having it there, where things are cleaner. Mine is continually accumulating creosote. How high is your chimney?


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## taxidermist (Nov 11, 2011)

maple1 said:
			
		

> That vid is great - pretty well answers all the questions I had. Guess I should have looked earlier - time to find one now.
> 
> BTW, I think that's the first time I've seen a baro on the bottom of the pipe. Mine and I think everyone elses around here is in the smoke stream. Makes more sense having it there, where things are cleaner. Mine is continually accumulating creosote. How high is your chimney?



Yeah it works great where i have it. Kinda had to do it that way because it was a after thought and the adapters were $$$$ to put it in the smoke stream. I think its like 18 or 20' tall I dont really remember. It really helps to keep my boiler in the sweet spot while the temps and conditions change outside. They want you to tune your boiler to the a certain draft. Thats great one day but then the weather changes and now your sucking the hot air out of the boiler with higher stack temps. Also that is on a eko 60 not 80 like I said.


Rob

http://www.grainger.com/Grainger/DWYER-INSTRUMENTS-Molded-Plastic-U-Inclined-2T650?Pid=search


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