Dwyer Mark II Manometer Questions

guysnydr · Post by **guysnydr** » Tue. Feb. 21, 2017 4:22 pm

Ok, please don't shoot - I know this subject has been beaten to death and I have read enough posts that my head is now spinning. If you guys could kindly answer a few questions for me (that I hope are simple), I would appreciate it. Weeding through these threads to find what you are looking for can be, well, a little tedious so your patience is appreciated!

#1 - I see most of you are using a brass fitting with steel or copper tubing. Does the metal tubing go through the fitting and on into the chimney pipe, or is the fitting just through the wall of the pipe and no additional length inside the pipe is necessary? If the fitting is flush to the side of the pipe with no tube extending into the flue, doesn't it get cruddy with ash buildup eventually? Seems like this would hinder operation. If the tubing does go on into the chimney pipe, how many inches of metal tubing should protrude past the fitting and into the flue pipe?

#2 - Is there a specific diameter of steel or copper tubing that I should look for or is any size acceptable as long as the tubing that comes with the manometer will slide over it securely?

#3 - I assume the metal tubing should be straight into the flue pipe and not on any kind of angle, right?

#4 - I am guessing that I need to bring the stove up to a fairly normal burn temp in order to test draft, correct? Right now it is fairly warm here in north central PA (near 50 day) and the stove is probably running just above idle. I should wait for a colder day to check the draft, right?

Might have a few more questions, but this will get me going for now.

Sorry again, I am sure these questions have already been answered elsewhere, I found so many posts, didn't even know where to start...

Thanks,

Guy

lsayre · Post by **lsayre** » Tue. Feb. 21, 2017 6:01 pm

1) Mine does not extend into the flue, but others have done the extension. Doesn't seem to matter.

2) Any diameter should work. Wider means less pressure drop though. Likely not enough to lead you astray though...

3) Again, it doesn't seem to matter. But technically longer lines, and/or lines with bends will mean more pressure drop, and thereby somewhat less of the actual draft being indicated by the manometer.

4) A hotter stove will generally generate more draft, but if you are setting the baro damper to open at 0.05 (for instance), and you are hitting that in warm weather, it will still be the same 0.05 as when its colder outside.

WNY · Post by **WNY** » Tue. Feb. 21, 2017 6:15 pm

the small compression brass or steel fittings, it just snug fit around the metal tubing. doesnt' have to be real tight, the only reason we use the metal tube to keep the heat away from the rubber tubing, a foot or two is fine if that. I just used a piece of metal or copper tubing that the rubber would fit snug over it.

Usually just drill a small hole and make it a little smaller than the fitting , then you can just ream it out a little at time so the fitting can thread in relatively tight.
Some fittings you can put a nut on the inside if you can get to it, otherwise, just gently thread it in snug so it doesn't fall out.

Draft is normally set at normal burning temps, to maximize draft.

Sunny Boy · Post by **Sunny Boy** » Tue. Feb. 21, 2017 6:26 pm

guysnydr wrote:Ok, please don't shoot - I know this subject has been beaten to death and I have read enough posts that my head is now spinning. If you guys could kindly answer a few questions for me (that I hope are simple), I would appreciate it. Weeding through these threads to find what you are looking for can be, well, a little tedious so your patience is appreciated!

#1 - I see most of you are using a brass fitting with steel or copper tubing. Does the metal tubing go through the fitting and on into the chimney pipe, or is the fitting just through the wall of the pipe and no additional length inside the pipe is necessary? If the fitting is flush to the side of the pipe with no tube extending into the flue, doesn't it get cruddy with ash buildup eventually? Seems like this would hinder operation. If the tubing does go on into the chimney pipe, how many inches of metal tubing should protrude past the fitting and into the flue pipe?

I drilled a hole just big enough so as to allow the tubing to slip into the pipe. It doesn't need to be air tight a slip fit works fine. The pipe fittings that come in the kit are plastic bacuse the kit is designed to measure pressure differences in air handling systems. It works just as fine for stove pipe but the plastic pipe fitting shouldn't be used with a stove.

#2 - Is there a specific diameter of steel or copper tubing that I should look for or is any size acceptable as long as the tubing that comes with the manometer will slide over it securely?

At your auto parts store,, you can get a short length of 1/8 brake pipe - pipe is measured by it's outside diameter, If you then also get 1/8 inch vacuum tubing - tubing is measured by it's inside diameter. Automotive vacuum tubing can take higher temps than most other types of rubber or plastic tubing. With the factory flared ends of the brake tubing cut off the 1/8 inch vacuum tubing fits over it nicely.

For the mano end of the vacuum line. Put a short length of the gray rubber tubing that comes in the kit, onto the right-hand port (low pressure) that is on the top left end of the mano gauge. Then slide the 1/8 inch vacuum line over that tubing.

#3 - I assume the metal tubing should be straight into the flue pipe and not on any kind of angle, right?

No, we just did tests in another thread and it showed that facing into, or 90 degrees to the flue gas flow will give false high readings.

Facing into the flow causes velocity induced higher pressure in the pipe. With the pipe end at 90 degrees to flow, that causes a Bernoulli affect which also increases the reading. Even more so as the flu gases speed up at higher mano readings.

Bend the brake tubing so that it faces slightly down stream inside the pipe. Then it also is less likely to have soot settle on the tube opening.

#4 - I am guessing that I need to bring the stove up to a fairly normal burn temp in order to test draft, correct? Right now it is fairly warm here in north central PA (near 50 day) and the stove is probably running just above idle. I should wait for a colder day to check the draft, right?

As long as the mano housing is mounted level and the fluid level is set to exactly zero (zeroed with the hose off), the mano will read any amount of draft from a hair above zero on up to, suck the cat right off the floor.

Might have a few more questions, but this will get me going for now.

Sorry again, I am sure these questions have already been answered elsewhere, I found so many posts, didn't even know where to start...

No problem. We'll be here.

Paul

Thanks,

Guy

Post by **coaledsweat** » Tue. Feb. 21, 2017 6:57 pm

I'm not a fan of a permanent install. The device needs to be calibrated before each use and you can't do that while connected.

Post by **Lightning** » Tue. Feb. 21, 2017 7:34 pm

coaledsweat wrote:I'm not a fan of a permanent install. The device needs to be calibrated before each use and you can't do that while connected.

+1

It's easiest to just run a couple inches of metal tubing thru the pipe so that it can be pulled out at will to tweak the mano to zero and clear the probe of any fly ash accumulation.

titleist1 · Post by **titleist1** » Tue. Feb. 21, 2017 11:26 pm

This is what my fitting in the flue pipe looked like after 3 years...so yes, they do need to be cleaned occasionally.

I calibrate mine by taking the rubber tubing off the port on the manometer and returning it to zero, maybe once per month or if I am messing with the blower restrictor plate.

guysnydr · Post by **guysnydr** » Wed. Feb. 22, 2017 4:43 pm

Thanks for the help guys, much appreciated.

I've never heard of bending the pipe downward inside the flue as Sunny Boy suggests. Wouldn't there be more tendency to have fly ash dust suck onto the tube if it was bent down? Maybe not, just wondering. Seems like most folks (from what I have read, just have the tube straight into the flue. I don't know what is right though obviously - LOL

2biz · Post by **2biz** » Wed. Feb. 22, 2017 5:24 pm

I believe Sonny Boy is saying the opposite... "Bend the brake tubing so that it faces slightly down stream inside the pipe." Down Stream would indicate the tube is bent slightly so it points in direction of flow....

Thanks for starting the Thread...Being a Newb.....I had the same questions about the Manometer and fittings...

guysnydr · Post by **guysnydr** » Wed. Feb. 22, 2017 6:00 pm

Ahhh! You are right, I must have misread that! Thank you!

titleist1 · Post by **titleist1** » Wed. Feb. 22, 2017 6:25 pm

2biz wrote:Thanks for starting the Thread...Being a Newb.....I had the same questions about the Manometer and fittings...

Dont worry about asking newbie questions you won't get a condescending attitude here like I have seen on other forums. We are happy to help out.

guysnydr wrote:tendency to have fly ash dust suck onto the tube if it was bent down

The exhaust air flow should be pulling a vacuum on the manometer probe so fly ash should not get sucked into the probe.

guysnydr · Post by **guysnydr** » Wed. Feb. 22, 2017 8:06 pm

Okay, I got the Dwyer Mark II hooked up below my barometric damper (high side open with a short piece of tube dangling and low side attached to flue pipe with 3/16 steel brake line. I was able to get the tubing that came with the manometer over the 3/16.

I was going to try and adjust my barometric damper tonight but I am a little confused about where it should be reading. It is currently reading about +.02 right now. It's probably around 45 degrees outside right now and the fire is at a lower burn rate. This reading is taken from the flue pipe below my barometric damper.
Captcaper mentioned in a previous post that I should look for a .4 to .6 reading. Did he mean .04 to .06 by chance? Now for the real confusing part.... the Harman manual says I want -.06 to -.08 (negative readings). I am confused I'm afraid. What am I looking for here, positive readings I assume is correct or am I missing something.... again

??

Maybe I should just wait for a colder day too?

Thanks again!

lsayre · Post by **lsayre** » Wed. Feb. 22, 2017 8:35 pm

In order to take advantage of the full scale range, the Mark II is connected up such that negative readings are read on the positive side of the manometers scale.

Setting it up to where it just starts to crack open at -0.05" (which will be seen as +0.05") is a good starting point, and will likely serve you well. When draft is below this level it will remain closed.

Post by **Lightning** » Wed. Feb. 22, 2017 8:37 pm

Okay, sounds like you did a fine job setting up the mano. A section of 3/16 brake line is what I use also. We normally set up these gauges backwards, so that they read negative values on the positive side of the scale, just for the simple reason that there is more gauge to work with on that side.

Most hand fed coal stoves will be happy anywhere between -.02 and -.05. With weaker draft the fire will be slower to respond to primary air supply and a little sluggish to recover after reloading. I run mine between -.03 and -.04.

Just keep in mind that we're reading negative values on the positive side of the scale

Post by **Lightning** » Wed. Feb. 22, 2017 8:47 pm

Also I wanted to add that it's common for the draft to get pretty weak during warm spells with a cool fire idling along. I've ran mine at -.01 for long periods of time with no problems. What you don't want is to see it with a zero reading OR a reading on the other side of zero in the negative side of the scale. This would indicate a draft failure or even a back draft which is potentially dangerous because of carbon monoxide.