testing equipment

[alan m]

hi there
im going to build a manometer to test my dc system.
im finding it hard to find dc related manometers. they are all about gas appliences, and carberetters

mine will probably be just some 1/2" clear pipe cliped to some ply and a ruler

how much pipe do you think i would need
is the end open or sealed up. what stops the dc sucking all the water out if it is open

thanks alan

[guy48065]

If the DC air is choked off the vacuum created could suck the water out--if the manometer is built to measure static pressure Less than your DC static pressure.

You should be able to find a manometer intended for filter monitoring easily enough.  I found dozens of Dwyer manometers on eBay.

[BernardNaish]

A "U"loop of plastic with each vertical arm 24" long should do it. I doubt if any DC will pull more than 24" of water vacuum. If it does make both limbs longer.

Fill with water colored with a little red dye to half way up and mark this point as zero. Remember that it is the difference between the levels in the two arms that we need hence 1" difference in this level will equal 1" of water vacuum. It is much easier to mark up a scale from zero every half inch. Then each division of the scale will equal one inch because one side will go up the same distance as the other goes down.

The left hand loop is traditionally connected to the container being measured and the right hand limb left open to the atmosphere. We are measuring inches of water pressure compared with atmospheric pressure.

Looking forward to hearing the result. Thanks for trying.   Bernard

[alan m]

i built a manometer today.
not sure is it corect or not yet. il post pics tomorrow
i got some 10mm inside diameter clear hose and cliped it to ply in a U shape
i attached the end to a 6"blank end

i am getting 3.5 "diference in height at both the first and last dc ports.
and about 7" just after the6"seperater

is this normal

[BernardNaish]

Alan, I look forward to seeing the pics. Please add a sketch of exactly where you took the measurements.

Regards,   Bernard

[Rick T]

Alan, this might be helpful to you. http://www.science-house.org/index.php/flight/109-build-a-manometer
I haven't made one but these folks should know what they are doing. Note the angle required to negate gravity etc.
Good luck.

[BernardNaish]

The link above is to a manometer designed for use in measuring air velocity not pressure. It is perfectly valid for that application but not for measurement of the pressure above and below the Thien baffle. Hence the manometer arms must be kept vertical to measure these pressures and NOT angled as it must be for air velocity measurement. I do not think we can measure the air velocity in a DC system using this sort of manometer because the air will be too turbulent but I would love to be proved wrong. If someone can try it and tell us all if it will work then we might gain the use of a valuable tool.

[alan m]

1st off . dont be afraid to say this is wrong. im not sure if its right or not

[alan m]

its very hard to see the red liquid (you woulnt think it thow ,its very clear)
the end of the hose is attached to an end cap with 2 air line fittings . a male threaded one on the outside and a female one on the inside

[alan m]

the red line is the no vacum position.
the middle lines are 3"apart. they are taken on the first and last ports. there was almost nothing between the 2

the farther away lines are straight away after the seperater. and 7" apart


i just put the end cap onto the fitting with a short pece of pipe and taped it up

[alan m]

i drilled a hole at 90 degrees into the small section of pipe. and mounted the pipe to that. the liquid didnt even move.
the air line fitting sticks in about 1.5"into the pipe





what do you think . is it working corectly

[BernardNaish]

Alan, I think it is working. Now we need to know the distance between the water levels with the manometer connected to your collecting drum. That is underneath the Thien baffle!!!!!

Regards,      Bernard

[alan m]

i will try that the next time im out there.
i didnt want to drill a hole if the thing wasnt working properly



also what do those figures iv got mean in reality

[BernardNaish]

Alan. Sorry I have not replied earlier. The pressure reading in your collecting duct is an indication of how well your DC is working and might well increase as your filter blocks. I am not too sure about that as it might decrease whatever, as the kids say, it is an indicator of DC health.

What I would really like to know is the difference between pressures above and below the baffle plate.

I have also bought some plastic hose as it is a great idea and a good deal cheaper than a ready built manometer and just as good. I intend to build two manometers today and try it on our DC.

As my wood work is done in a club workshop, an old stable built about 1810, I have to act respectfully when making changes so it will be a while before I get agreement to add a Thien TH to our system. I have sketched some plans and sourced the materials. I am also itching to build.

Regards from Wessex, Wiltshire, England.   Bernard

[alan m]

i had a feeling you were on this side of the pond

so is a high no better or worse.

iv been a bit busy getting ready for the paddys day parrade. il test the pressure in a few days when everything is put away