how much does size matter in feet?

scatgo

PSI and Fahrenheit not working on my furnace gauge. the only needle that moves right now is marked Ft. Now I am trying to find a new gauge but can someone please explain the whole feet thing to me. its been about 30 years since i went to vocation school for hydronics so the details have been forgotten

Alan (California Radiant) Forbes

Feet x .433 = psi

scatgo

https://forum.heatinghelp.com/discussion/comment/1870038#Comment_1870038

OK. I did come across that information but how is that useful info to me?

Alan (California Radiant) Forbes

What feet is the needle pointing to? Multiply that number of feet by .433 to arrive at pressure.

mattmia2

it is measuring pressure in feet water column instead of pounds per square inch. it was mainly used to tell when the system was filled up to an open expansion tank.

scatgo

https://forum.heatinghelp.com/discussion/comment/1870043#Comment_1870043

Right now it says 20.

mattmia2

8.6 psig

EBEBRATT-Ed

An easy rule of thumb that you can always remember (although not perfectly accurate but usually close enough is) 2'=1psi

so your 20' simplified is 10psi

The correct way is .433 x20=8.66 psi

or 2.31feet/psi=20/2.31=8.65psi

scatgo

https://forum.heatinghelp.com/discussion/comment/1870045#Comment_1870045

Ok. The strange thing is i do have a open expansion tank that is mounted in the ceiling above the furnace. My guess is about eight feet from the floor to the tank. 8 times .433 = 3.464. The gauge reads 20.

mattmia2

open tank or a sealed compression tank with no diaphragm but closed? i don't see how an open tank can be below the emitters.

scatgo

https://forum.heatinghelp.com/discussion/comment/1870225#Comment_1870225

Expansion tanks - Structure Tech Home Inspections

I have the old school style open tank. Its not a open air style. Open air type must be above the emitters. The link above gives more detail on that.

mattmia2

we're missing something here because if an open expansion tank is below the emitters the water would run out of the tank.

scatgo

https://forum.heatinghelp.com/discussion/comment/1870234#Comment_1870234

No. The drain valve on the tank stays closed. Read this link…………

Expansion tanks - Structure Tech Home Inspections

mattmia2

it showed all 3 styles of expansion tanks, open tanks, compression tanks, and bladder tanks.

Jamie Hall

How are you sure that it's an open tank, @scatgo ? I sounds to me like a regular steel compression tank.

EBEBRATT-Ed

It is not an open tank it is a bare steel compression tank

scatgo

https://forum.heatinghelp.com/discussion/comment/1870270#Comment_1870270

Bingo! My bad. Sorry people total brain fart on my part.