Help with Magnehelic reading - please - Enviro M-55C-FS

Hey guys - based on postings/recommendations here, I've picked up a Dwyer magnehelic 2000-00 (0 to .25" WC) and attempted to check the draft on my Enviro M55-C-FS (using the port on the side of the ash pan.)

The issue I'm running into is no matter how wide open or fully closed the damper is, I'm still pinning the magnehelic at .25 whenever the "probe" (1/8" hose barb, filed down) mates with the test hole. I've tested at high heat (5) and low (1) and it makes no difference.

The magnehelic is dead level and is zeroed out when not taking a reading (it's in a stationary stand).

I'm using 5" of tubing (not sure if length could be a factor) and the Magnehelic (used from eBay) is missing the elbow barb on the back of the gauge. I also have a 2" OAK in use.

Any thoughts on what I may be doing wrong?

Thanks for any feedback and for the info I've found here in a few months of lurking!

MF

bob bare said:

Sounds like you have your combustion air trim turned up too far?

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corkman said:

did you follow the instructions in the manual.feed 3,combustion air 3 and let her burn on heat setting 5 for an hour before taking the reading

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Thanks guys. I did set the feed and air trims to 3 and heat on max for an hour before taking the reading. When it was still reading .25+ after adjusting the damper to both extremes, I did try setting the air trim to 1 and adjusted the damper again to both extremes - it still showed as .25+ on the magnehelic - so I'm kind of at a loss.

hyfire said:

The gauge has 4 ports 2 high and 2 low, you need to plug 1 low and connect to the other low and leave at least 1 high port open...to atmosphere

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Great, thanks for confirming. Mine matches that configuration.

Any other thoughts you guys have on this.

Thanks again.

ohbix said:

Can you test your gage on another device? That way you can rule out a faulty gage.

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I may have to find someone local with one - not a bad idea.

batchman said:

Tubing length should not be a factor, mine is about 24" long although I'm using copper tube. What happens if you close your draft all the way down, as in remove the collar (assuming it's like my Maxx)?

Curious,
- Jeff

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Thanks - I tried cutting down a length of tubing to 6" and it didn't seem to change anything. When I completely close the draft slider I still see the mag pegged at +.25 wc (even if I turn the trim down to 1 (from the 3 I had been testing it at.))

I have a feeling there's user error here.

My "probe" here is a 1/8" hose barb that I've filed the end down so it fits snugly into, but not through the test hole in the ashpan - I placed a tiny rubber bushing on the barb, so when I press it to the test hole, the hole is totally sealed and the tip of the filed down barb is flush with the opening. Do I need something that fully penetrates the hole to get a reading (like the turkey baster needle another user posted?) I'm grabbing at straws thinking I'm creating some sort of a venturi effect or something.

Thanks again guys.

batchman said:

If you are near Nashua/Lowell I may be able to help - maybe try your gauge on my stove. PM me if that would help.

For reference my stove end just pokes an 1/8" copper tube into a 3/16ths hole in the firepot. I thought I'd have to JB Weld it in place but appear to have no problems with it just poking in there, after all on most installs that hole is just open.

Cheers,
- Jeff

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Thanks for the offer Jeff. I have a couple folks nearby that I can hit up, but I do appreciate the offer.

I came across an old thermowell that I don't need and can grind down the tip so it has an orifice and fits neatly with the tubing. Still getting wacky readings, but it looks more professional at least.

Thanks guys.
MF

corkman said:

an inflating needle for a ball will work also

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Thanks. I just rigged one up that way too. I have plenty of options here. I may take it to the stove shop where they have my model up and running and see what it's pulling and compare it to their magnehelic.

Eureka!

I went to the stove shop and took a measurement on one of their stoves and asked them to do the same with their mag - the numbers matched, so the mag was ruled out as an issue.

The service techs were at a loss why I was getting readings of .25+. When I mentioned that I had an OAK they told me to get rid of it, so I detached the hose from the end of the stove and took a reading and voila, it was in the high teens. Tonight I'll take a hack at tuning it again now that I'm seeing sensible numbers.

Thanks guys for the help.

Hey guys,

I went to two different stores within the same company when buying the stove. A rep at one store said that an OAK was an absolute must have for my 20 year old house. A rep at the other store said that they were not at all needed and that ambient air from the house was enough and that the cold air from outside was harder on the ignition mechanism, and that warm air was much better, easier on the stove and provided a much quicker flame (I kind of scratched my head at that one.)

To his credit, he did think my wooden magnehelic "cradle" was sexy.

Anyways, I didn't end up completely remove the OAK from the loop - I ended up just un-mating the OAK from the flange on/in the stove but left the OAK hose about 1/4" away from the flange - basically I just broke the OAK seal, but the outside air is still available to the stove. That disconnect resulted in my draft going from somewhere in the +.25 wc range to +.15.

Thanks again
MF