boiler not filling with water problem...


Hello,
My name is David and I have a boiler problem I was hoping to could help me work thru?
I have a peerless Natural Gas boiler (boiler number mmw-115-wc, serial number mmw-18429) and it doesn't stay heating the 2 bedroom apartment that its in. I have check the gas it runs the pilot light stays on and light the fire at 180 degrees. And shuts off at around 220 degrees the motor runs and circulates the water in the pipes. The valve connected to the expansion tank works when I manually press it (it takes both hands though. Is that normal?) the expansion tank could be bad because I can't seem to charge it with air (12PSI) but I did grain it completely and reinstalled it. I filled the pipes with water and purged the air the little automatic air valves open and close once and a while with air only. and the boiler psi fluctuates between 12 and 20 PSI. Yet it still runs out of water and the heat stops. What should I check to make sure it adds water when it needs it? Is the expansions tank bad is? And if it is would that prevent it from adding water when it needs it?
Thanks for your help.
David
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D.L.,
It sounds like it should be working to me. How do you know that it's "out of water"? Where does the water go? Your system should have an automatic fill valve, and if it were truly out of water, the pressure gauge would not read 12 psi.
Does this boiler only heat these two rooms, or does it heat other areas too, and are those areas OK? (it's hard to tell from your message)
Here's two likely possibilities. One is that your system is air locked. I know you bled the air out of the lines, but there's right and wrong ways to bleed lines. Maybe these two rooms are on their own zone, so while you took care of the rest of the system, you might have not handled this particular set of pipes.
It could also be the circulating pump itself. Maybe the impellor is brokes, or maybe the motor coupling is loose. It might look like the pump is functioning, when it really isn't.
The reason I suggest these is because it sounds like your boiler is working. If it really were running out of water, that water should be showing up somewhere.
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When the rooms get cold it shows 0 PSI. I don't know where the water goes but I know it lasts for a few days and then nothing. It doesn't add any new water to the system.

Its a simple system that heats all the rooms one after another on one line. Then goes back into the boiler. The basement has its own line but it doesn't heat it because the zone has been shut off.

I could get it up to 15 PSI the return line was hot everything was working. But it seems to just go into the air or something.

It seems to be circulating the water ok. But I will check it after I figure out where the water is going.

No leaks except the automatic relief valves but they only purge air and shutoff when water enters it.
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D.L. Man,
OK I believe you! For some reason, the pressure drops to zero. The water just can't disappear, it must be going somewhere. Is it possible your T&P valve is piped directly to a drain, and you're unaware of a leak? Is there anything else you might suspect?
The next question is why doesn't your boiler automatically refill. How do you add water to this boiler? Isn't there a fill valve?
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There was one leak in the pipes from where a fitting came apart. We resealed it once and have marked it again. Its a pin hole size that drips unto the the cement wall. The drip evaporates before it gets down 2' on the wall so it might not be top on our list right now. But there is a leak:(

There is an expansion tank/combination purger valve that connects to the water line. That looks like this one.(Its at the bottom of the page) http://store.yahoo.com/furnace-airconditioner/casirhotwatb1.html
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UPDATE
I fixed the problem. I wasn't sure but I back tracked the water to the inlet line and it was a fill trol mod110 expansion tank. It was the kind with the automatic water feeder. I checked the pressure on it and I couldn't get a reading. I tried to add air and I couldn't get a peep to go in. I unscrewed it and it was full of water. After somemore looking at it I knew it was broke I had to do some research to find out WTH a expansion tank really did first. It wasn't suppose to have water in it at all. And it was suppose to have 12 -whatever PSI of air in the other end.
I bought a new unit for way to much and had everyone and their momma try it screw it in for me. I decided to save something bigger for the pros and not waste both of our time.
I screwed it in and heard the water rush in after turning back on the water inlet valve. That is something that I never heard it do before too. The system filled to about 15 PSI with it unplugged and without adding water manually. I began to bleed it by shutting off one end of the valves and opening the valve until the bubbles stopped shut the valve and opened up the shutoff to one side and closed the other then did all over again.
I plugged it in and checked that the automatic air valves were open a little bit. My dad thinks they are to be closed tight all the time so I checked. The heater turned on and started to flow. The return line got hot as the out line and I watched it to make sure it stayed that way. And now I figured it works.
Thanks for all your help. I will be lurking in this group from now on and I told everyone this FYI.
Now I have to fix that leak in the pipe.

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