lacnob wrote:

Speedy Jim wrote:

lacnob wrote:

Speedy Jim wrote:


lacnob wrote:


have a very old (I'm guessing 45 years) oil fired hot-water boiler.
My problem is two radiators (not steam type) on my second floor
(bedroom & bathroom) don't get hot. If I crank up the thermostat to
76 degrees, one of the radiators will get warm about ¼ of the way up
(I normally keep the thermostat at 68), the other remains ice cold.
There is a large radiator with an automatic bleeder on it which throws
off a lot of heat in another bedroom on the second floor. I tried
turning that radiator off- didn't help. The bathroom radiator with the
automatic bleeder is cold. The pressure on the boiler show 20 when cold
and 23 when hot. When I bleed the bedroom radiator, air comes out but
no water. All radiators on the 1st floor have been bled & water comes
out. Last winter, the pressure was at 10 & I had the same problems, so
I put on an automatic bleeder on the bathroom radiator to no avail. Any
suggestions appreciated.



Not enough boiler pressure.

Have another look at the gauge. Is the "20" in Feet?
That's probably just shy of what's needed to get to
the bath.


Thanks for the input.
The 20 is pressure. The "red zone" starts at 30. From what I've read,
12 to 18 PSI is adequate so 20 to 23 should be more than adequate.


That's correct. 20 psi should be good for damn near 40 Ft
elevation. Of course, it *is* possible that the gauge
is inaccurate.

With 20 psi at the boiler, you should be able to get
a powerful stream out of the highest rad vent.
Jim


Could it be that on the cold radiators the bleed valves are slightly
corroded so air might be getting in through the valves? Should I try
radiator blanking plugs?

lacnob


No. With adequate boiler pressure, the bleed valve will
always have pressure behind it trying to force water out,
so air can't get in.

If the boiler gauge is accurate, then maybe there is
a large accumulation of air in that part of the system
that you just haven't bled off yet.

One thing that *can* happen is if the boiler pressure
drops a lot (like at night during shutdown), the system
will have a vacuum at the highest rads and air then
*can* be sucked in.
Jim