No Water in gravity system upstairs radiators

haunt

The system is a 1920's gravity flow (?) gas fired hot water with cast iron radiators in a 2 story house. The complaint was no heat upstairs. I tried to bleed the up stairs radiators. I got a short hiss of air, then nothing. At the boiler feed, I found a combo PRV & relief valve. The water feed valve to the combo valves and the boiler was turned off. When I opened the water valve, both units were leaking badly. I replaced the combo unit and turned the water back on. Went back upstairs. opened one bleeder valve and got a good steady hiss of air. With a big grin on my face, I went to all the radiators and opened all the bleeders at the same time. Each hissed out air for a little while then they all stopped. I was back where I started from. No water and no heat in the upstairs radiators. I tried to increase the water pressure by adjusting the prv but it didn't help. When I tried the fast fill feature on the prv, the water just rushed out of the adjoining relief valve. So, I then capped of the relief valve drain (temporarily) thinking that I would force the water to the upstairs radiators with line pressure. Went back upstairs to bleed again and nothing! I am stumped. Any idea what is going on?

unclejohn

You most likely have a bad relief valve, But your gonna have a bad life if you don't remove the cap on the relief valve now. Also replace the pressure temp. valve while your at it.

haunt

Thanks unclejohn. Yeah, that cap was removed as soon as I figured out that it didn't help.

Paul48

I get the impression you have something backwards on the regulator/backflow preventer?

haunt

Hi Paul48,
Thank you for taking the time to read about my problem and trying to help figure it out. I appreciate it.
It wouldn't be the first time that I did something backwards. But in this case, unless the arrow indicating direction of flow which is cast into the body of the unit is wrong, then I am innocent of all charges.

Paul48

What's the pressure set at?

haunt

original setting was at 15 lbs and I raised it to 18 lbs

Paul48

With the supply open, and at 18 psi, you can't bleed the air?

bob_46

First the acronym PRV is ambiguous . I believe what you have is in the attached picture. There can be NO valve between this device and the boiler. What kind of expansion tank do you have ?
Is the tank in the basement or possibly on the top floor or in the attic? Measure from the gauge on the boiler to the top of the highest radiator in feet ,multiply by .433 and add 5 . That's the pressure you need in the boiler. It sounds like you may have a restriction between the combo fill/relief and the boiler or a grossly inaccurate gauge. 18 lbs would raise the water approx. 41 feet.

haunt

Again, thank you gentlemen for taking the time to read my post and offer your advice.
Paul48-yes, can't get anything out of upstairs radiators.

bob- you are exactly right. That is the type of device. It is a WATTS 1450F Fill and Relief Valve. There IS a valve between the device and the boiler which is open. It looks original to the installation of the gas boiler. I wouldn't be surprised that the gauge is not accurate. The instructions with the Fill & Relief Valve stated that it was pre-set at 15 lbs, which should have been enough pressure in the first place. There is a tank in the basement between the floor beams. Old green riveted steel tank.
I was reading on this site about orifices that used to be installed on upstairs radiators to balance the systems. Is it possible that orifices are installed and delay the pressure getting to the upstairs radiators?
Clogged orifices?

bob_46

I doubt it is clogged orifices . If that is a gate valve between the device and the boiler the gate may have fallen off the stem . Is the gauge on the boiler ?

Paul48

No, the orifices restrict flow not pressure. The pressure would be the same in a 6" pipe or 1/8". And your system is completely pressurized. Any orifices would only be at the valve, the return pipe is wide open. Bring the pressure up to 20, and try to bleed one radiator. If that doesn't work, go to 22, and so on. This is going on the possibility of your gauge being wrong.

JUGHNE

Is there a chance that the HO fiddled with valves before you got there? The rad valves often were 1/4 turn on to almost off, (small port to prevent freezing). Water would fill very slowly.
Basement valves if any would probably not shut off the entire 2nd floor.

There is a good chance that the old green compression tank in the basement is water logged, and the 2 nd floor rads with their air chest on the top was doing the work of air tank. You will know it if you get them filled.

haunt

I don't believe that it was a gate valve but I will have to check the next time I am there. There was also a drain valve below that, so I could probably check for pressure at that point.The gauge is on the boiler, original equipment. I wish I took some pictures to post. And had some information on the make and model of the boiler. It is a huge, approx. 4 ft x 4 ft x 6 ft tall grey beast
I get the orifice thing now. I should have stuck to trying to bleed the one radiator as Paul48 suggested, instead of opening them all up at the same time.
There was one thing that I saw that I had no idea what it was. Again, I wish I had thought to take a picture. Attached to one of the pipes near the boiler was a metal box, maybe 2 inches wide, 2 inches deep and 6 inches long. Red plate on the front with a knurled knob on it and said something like "...Heat Controls". It was electrical because there was a BX cable coming out of the bottom of it which went to an on/off switch.

Paul48

If the valve is broken, when he bleeds one radiator the pressure will fall off and go to zero. We know he got pressure to the rads upstairs, but not enough to get water.

haunt

Thanks Junge, good point on the radiator valves. I did try one of them which was stuck pretty good and, at the time, didn't want to open another can of worms . I agree on the waterlogged tank. It had a valve to shut it off from the boiler and a drain valve on the other end so i could drain it out.

JUGHNE

The "heat controller" box may be the water temp thermostat. (Maybe a strap on type). It would be a real surprise if there was a zone valve on a gravity system of that vintage, not impossible, but most were put in without electricity needed.

haunt

I will have to investigate this device further and post a picture to help identify it. I didn't want to disturb the asbestos pipe covering at the time. Hope to get back there in a week or so.

JUGHNE

Must not be very cold there

Mark Eatherton

haunt said:

I will have to investigate this device further and post a picture to help identify it. I didn't want to disturb the asbestos pipe covering at the time. Hope to get back there in a week or so.

What you are describing is the high limit control. Your problem sounds like a complete or partial rust blockage/stoppage between the makeup and the boiler.

Finding and fixing it could be a major job if it is difficult to get to. Gravity systems rarely have enough isolation on them to do an easy job, so it may entail a complete draining, refilling and re-purging. Also, unless you are faster than the Green Lantern, you'd best just bleed one radiator at a time, and you'd be wise to keep an old towel in your hand to clean up what's going to come out of the vent valve. In fact, bleed into the towel. The old guys called it black gold. I call it something that is impossible to get out of your clothes or carpet or paint once it's on there...

ME

haunt

Thank you Mark, I am sure that the system has not been cleaned out in the last 60+ years. So accumulation of rust and crud in the system sounds like a sure bet.

hot_rod

I think there is a fine mesh strainer under the brass cap on that fill valve, maybe the Watts brand too.

If the system is not filling or filling quickly, check the strainer.

Get a gauge that screws onto a hose connection and connect it on the boiler drain to confirm pressure.

You can buy one or build a test gauge up with hardware store parts.

haunt

Thanks for the picture. I'm sure that I have everything I need to put one together and check the pressure at least at 2 points where there are drains. The instructions also state that there IS a screen in the fill valve. I'll check that if the pressure isn't good.

SWEI

A partially clogged strainer will read pressure but still not flow. Look for a pressure drop when the valve opens.

haunt

Good tip, Thanks.