Radiator / furnace problem

[ransley]

problem.http://www.bellgossett.com/Press/BG-proper.asp>

leave it at 10 psi cold, you only need more if top floor radiators are cold, I have a 3 story boiler is 12lb cold.

[Big_Jake]

The B & G fill valve that I see on most installations is an auto fill valve with a lever for fast fill, and a screw to adjust the fill pressure. I would agree that the "fast-fill" lever shouldn't be left open, but would disagree that the water supply leading to the fill valve should be left off. Why even have it in place if it is only used to fill the boiler manually when the pressure is low. It would be nearly the same amount of effort to open a valve while watching the gauge on the boiler when you needed to fill it.

Of course, if I posted this at alt.hvac, they would be laughing their collective asses off, whether I was right or wrong.

JK

[Edwin Pawlowski]

I did say "the same problem" didn't I?

I had a problem this past winder with the packing nut on the feed valve. I didn't get around to fixing it for some time, but it did not leak when turned off. The noise from air in the system was very loud, especially after being off all night and going back on first thing in the morning. It woke me before the alarm went off. I finally replaced the valve, left it open, problem went away once the air self purged. There is a valve on top of the Extrol expansion tank for this purpose.

Sorry if my real life factual situation differs from your opinion. The feed valve is still open, but I'll probably close it until heating seasons starts again. Then it will be open, same as it has been for the 29 years this house has existed.

[Doug Miller]

[snip]

I'm not questioning your experiences -- I just don't think that you've quite understood the OP's situation. As you said, it's perfectly normal for the pressure to go up or down due to expansion and contraction as the system cycles on and off. What's *not* normal is the need for frequent bleeding and replenishment.

OTOH, if you're having to purge air, and add water, every few days like the OP does, then -- I'm sorry, but you have a leak too. A properly functioning hydronic system has no need for frequent air bleeding and water replenishment.

[Edwin Pawlowski]

No, Doug, I don't have a leak. All my tubing is either visible or in a place a leak would be evident, especially after 25 years. No pipes or tubing in concrete. You are welcome to come and inspect at any time.

[Doug Miller]

And do you tell me that you have to purge air, and add water, every few days?

[Edwin Pawlowski]

Not if I leave the feed water valve open. No pair to purge then. Only after it has been closed and runs a couple of cycles. I'm sure you'd like to see this in operation. What time can I expect you? Bring your leak detector.

[Doug Miller]

Water doesn't just disappear. If you have to keep putting water in, that means water is getting out.

[Edwin Pawlowski]

As the water cools, it contracts and air is sucked in to replace it. If the system is sealed, a bladder tank is going to counteract these actions in a perfect world. In an imperfect world air gets sucked in. I know what works for me. I know I have no leaks.

[Doug Miller]

If you have to keep putting water in, that means it's getting out somehow. Your last sentence should be revised to "I have no leaks that I know of."

[dpb]

I keep wondering how the system keeps cooling water indefinitely w/o it finally freezing solid... :)

[Edwin Pawlowski]

The heat is not on. The valve is open. No water has passed. The invitation is open for you to come and search for the alleged leaks. I'd bet you money, lots of money on that. Here is your chance to make thousands of dollars, just by finding a simple leak.

[hvacrmedic]

You don't have an air buffer. What do you think the purpose of the expansion tank is? It's supposed to have air in it. If you'd quit letting the air out of it, then your problem might take care of itself.

[Doug Miller]

If no water has passed, then you're not adding water.

The system has a finite volume. It is simply impossible to keep adding water to a finite volume, unless it's getting out somehow.

[Edwin Pawlowski]

Not so much adding water as it is eliminating air Taco makes valves to eliminate air

Once air is in the system, it must be purged. The only way to truly purge the air it to keep the feed water valve open to replace the air that is moved out of the system. If the system is opened for any reason, repair a circulator, change a fitting, whatever, air is introduced. Simply opening a drain does not eliminate it all,

Air, or course, has greater compressibility so when the water expands it easily compresses the air. Some will be eliminated by the Taco valve, but some will still be getting by if there is no feed water to take its place. Once the system cools, the air is still there and with the pressure drop it may even be possible to draw in more. As you introduce fresh water, you are also introducing dissolved oxygen, thus making the air problem worse.

The only way to finally eliminate all the air is to keep the feed water valve open until all the air is purged from the system. It may take some days depending on the number of cycles, temperature, size of system. If you keep closing the valve, you will never evacuate all the air. Having air in the system does NOT mean you have a leak.

I replaced a circulator a few months back. It took two or three days for the air to finally be fully evacuated and the heating system to be quiet again when circulating.

[Edwin Pawlowski]

I'm not letting air out of the tank, it is in the water side of the system. The only way to expel air is to add water or something else to replace it. The expansion tank is to allow for the change in volume of the water as the temperature changes, but does nothing to expel air from the copper tubing. I'm sure you know better.

Description: Series FV-4M1 Automatic Vent Valves are used in commercial and residential hydronic heating applications to provide automatic air venting for hot or cold water distribution systems. It consists of a brass body construction with female NPT connection, brass cover, air vent with silicone rubber seal, polyethylene float with valve plug, and automatic vent. Series FV-4M1 has a high temperature rating and is ideal for use with glycol systems or for use as an anti-vacuum device. It can also be installed to permit the separation and dispersal of air while fluid is circulating in the system. Can be disassembled for inspection and cleaning. Maximum Pressure:

150psi (10 bar).

[Doug Miller]

Yes, I know. I understand all that. My point is simply that if you keep having to add water, over and over and over and over, there *must* be a leak somewhere.

[Edwin Pawlowski]

Every time you introduce water, you are introducing oxygen. If you close the valve, it becomes a gas and does not leave because there is nothing to replace it You are not adding water over and over, you are getting a proper purge of the air and that will not happen as long as the feed valve is closed.

Getting back to the original question: My point is that the OP has the valve closed and is never truly eliminating all the air and is probably sucking some in when the system cools. It does not mean there is a leak as you insist.. If he leaves the feed valve open for a while, it will correct. Mine did.

[Doug Miller]

That does *not* mean you can keep adding water indefinitely. It's a closed system. If there is no point at which water can leave the system, it eventually *must* become full when water is repeatedly added, and when that point is reached, no more water can be added. If water *can* be added indefinitely, it *must* be escaping somewhere.

If there is a point in the system where air can be sucked in, there is a point where water can escape.

I would define a point at which water can escape as a leak.

That's because your problem was nothing more than excess air. *His* problem, OTOH, is a leak.

[Edwin Pawlowski]

Not necessarily. Check valves and refielf valves can keep water from leaving but allow air to get sucked in under a vacuum or pressure differential. That may be the OP's problem.

Your opinion, not mine. He is doing the same thing I did when the feed valve was shut off. Mine had air in it for a few weeks until I finally got around to repairing the valve so it could be left open and the air properly purged. Right now he is not purging the system properly and air is still in the system. Perhaps the OP will get back to us and let us know what he found.