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Dwyer Magnehelic Gauge to measure draft

MikeAmann
MikeAmann Member Posts: 426
edited April 29 in THE MAIN WALL
Is there a model suited to measure draft of an oil boiler?
Ideally the scale should read Zero to -.05 inches of water.

Comments

  • Steamhead
    Steamhead Member Posts: 15,425
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • MikeAmann
    MikeAmann Member Posts: 426
    The gauges I see on ebay - none of the needles are on zero.

    Shouldn't they be or would the gauge have to zeroed depending where it is located (relative to sea level)?

    I can get either of these straight from Dwyer:
  • HVACNUT
    HVACNUT Member Posts: 4,622
    I use this for over fire draft. The analyzer records draft in the flue. It also does velocity for airflow tests in ductwork. 
  • ethicalpaul
    ethicalpaul Member Posts: 3,751
    edited April 29
    MikeAmann said:

    The gauges I see on ebay - none of the needles are on zero.

    Shouldn't they be or would the gauge have to zeroed depending where it is located (relative to sea level)?

    The magnahelics have a zeroing screw so set them to zero after installation. In eBay photos who knows what way they are oriented and that can have a large effect on a low pressure gauge.
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,139
    Yes, you turn the zeroing screw. It's not uncommon to have to do that especially on the low-pressure gauges. The #460 however will never lie to you. Not as convenient because you have to use fluid, but nothing ever goes wrong with them. Most of the Dwyer's you have to use Dwyer's colored fluid which does have a different specific gravity than water and the manometer is calibrated for that fluid, so you have to use it. That being said the Magnehelics are pretty rugged.
    mattmia2
  • MikeAmann
    MikeAmann Member Posts: 426
    I'm kinda blown away by this - on Amazon:
  • mattmia2
    mattmia2 Member Posts: 5,733
    I'd go with the inclined manometer.
  • MikeAmann
    MikeAmann Member Posts: 426
    You mean this?

    I was thinking about this - no batteries, no calibrations, basically unbreakable, but then I saw the digital units. Using this I can see myself getting it all set up and leveled, and then it gets bumped and I have to do it over and over again. Decisions.... decisions....
  • mattmia2
    mattmia2 Member Posts: 5,733
    I don't think that has the precision you need for draft. I'm curious how that other kit works, is it also inclined or does it use something much less dense than water or some combination of the 2?
  • mattmia2
    mattmia2 Member Posts: 5,733
    Oh, i see, the 460 is a flow meter, i thought it was a manometer. the 460 is what you want I think.
  • MikeAmann
    MikeAmann Member Posts: 426
    I will check it out.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,139
    edited April 30
    @MikeAmann

    This is what I used to use. We used to have a ton of those at the shop. Weil McLain used to ship them out with commercial boilers so the service tech could measure overfire and breeching pressure. In fact, Weil McLain had their name put on them. We got them for free because the pipefitters installing the boilers didn't know what they were for so they would give them to us. You could use them as a straight manometer for gas pressure up to 16"wc or as an inclined manometer to read draft and breeching.

    I used them on the Trane roof top units that had a negative pressure gas burner

    https://tab.dwyer-inst.com/products/test-equipment/manometer/portable/series1227.html
  • rick in Alaska
    rick in Alaska Member Posts: 1,378
    It still amazes me on the price on that u-tube manometer. It's just a piece of plastic bent in a u shape, and a sliding gauge on it. I'm thinking $40 for it....
    Rick
    MikeAmannmattmia2
  • MikeAmann
    MikeAmann Member Posts: 426
    I don't doubt that the manometers using fluids are really accurate.
    But that's more than old-school.... that's ancient school. ;)

    For me, I would prefer to just shove a tube in a hole and read a number.
    I am looking at a used UEi EM201B (latest model) for nearly the same price that I can get one of the cheap China copies for.
    Does it really matter though? The UEi is made in Taiwan. :(
  • MikeAmann
    MikeAmann Member Posts: 426
    edited May 1
    I agree Ed.
    I made an offer on a UEi EM201B digital manometer and it was accepted, so that will arrive soon.
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,724
    You’re not going to stick that into a flue pipe, are you?
    steve
  • MikeAmann
    MikeAmann Member Posts: 426
    edited May 1
    Ha-ha, no, I have to add a length of metal pipe to do that, correct?
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,724
    I don't think it's the right tool for the job. If I had to use that, I'd only use that one for measuring gas pressures, and air flow.
    steve
  • mattmia2
    mattmia2 Member Posts: 5,733
    You could make your own with a piece of tubing. Laying out an inclined scale could be a bit tricky and I think you need the inclined scale for the precision you need for draft if your fluid is water. That was what I did when I wanted to measure the gas main pressure. Problem was I wanted it worst case so I did it when it was around 0 f and the water froze by the time I got it torn down.
  • ChrisJ
    ChrisJ Member Posts: 13,066
    I own a 460 and I also own a slacktube.


    You can call them old school but they're always accurate, no matter how long they sit.

    I'll take a Dwyer slacktube over anything digital any day.  Same goes for the simple 460.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    mattmia2MaxMercyEBEBRATT-Ed
  • MaxMercy
    MaxMercy Member Posts: 291
    edited May 3
    This one is my favorite, but they are discontinued. They are big, sturdy, and accurate. You can find these Bacharach MZF gauges on ebay with some careful shopping, sometimes as part of the Bacharach combustion wet kit. Bacharach also makes a pocket draft gauge but that of course can't be permanently installed like the MZF can.




    This one isn't marked, but the negative side is to the right of zero if you were wondering. The needle swings around zero depending on how the gauge is leveled, but just place it on top of any flat surface and move the adjustment lever on the right side.

    As far as electronic gauges, I don't trust them as far as I can throw them. I've spent a career in electronics including design and just don't trust the long term accuracy of transducers.

  • MikeAmann
    MikeAmann Member Posts: 426
    @MaxMercy
    That is the idea I had in mind when I made the post about the Magnehelic.
    Nice gauge you have there.
    MaxMercy
  • MikeAmann
    MikeAmann Member Posts: 426
    The UEi digital manometer arrived and works great. I am happy with the purchase.
  • reggi
    reggi Member Posts: 188
    MikeAmann said:
    The UEi digital manometer arrived and works great. I am happy with the purchase.
    Good.. did you get a Dwyer to check the UEI 'S accuracy ?
    One way to get familiar something you know nothing about is to ask a really smart person a really stupid question
  • MikeAmann
    MikeAmann Member Posts: 426
    edited May 5
    NO, I just need to see that there is a difference between draft over the fire and at the breach.
    But I did make sure that the numbers returned to zero after I removed the tube to fresh air.

    Now that you have mentioned it, this unit is capable of doing the differential because it has two inputs.
    I think that I will do that test tonight. Thanks.
  • reggi
    reggi Member Posts: 188
    No you got me wrong.. you got a heck of a deal on pre-owned and I didn't realize that 0 was 0 and that means all is accurate.. Look at $$$ less than new and that easy to verify it's a steal.. Good luck and enjoy..Btw how did your test go tonight ?  AOK ?
    One way to get familiar something you know nothing about is to ask a really smart person a really stupid question
  • MikeAmann
    MikeAmann Member Posts: 426
    edited May 6
    The short answer is that I got .007 in the differential mode between over fire and breach.
    Tested individually -.034 over fire and -.045 in the breach for a difference of .011.
    Of course the numbers do fluctuate a bit.