Pressure readings wrong, thumping sounds

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Old 04-06-14, 02:38 PM
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Pressure readings wrong, thumping sounds

Hello. I've been reading through the posts about heating systems and learning a lot. Thanks for all the information. Heating systems are quite interesting. I just moved into a small ranch house an I'm having trouble with a gas fired hot water baseboard system that the previous owner installed himself about 20 years ago. I'm getting unusual pressure readings and loud thumping sounds about once per second that continue all night long. The boiler is a Weil McLain GV-5 Series 1 unit. It's also connected to an Amtrol Boilermate hot water heater. There are 2 zone valves, one for the house and another for the hot water heater.

When I moved into the house, I noticed loud noises coming from, I think, the heating system. The pressure reading on the tridicator was 40 psi when hot and there was some leakage from the boiler relief valve. The pressure seemed very high so I adjusted the regulator on the fill line until the pressure was 20 psi. That didn't help with the constant thumping sound. Then I measured the expansion tank pressure at the Schrader valve on the bottom and saw that it was zero and I also noticed that there was no hollow sound when I tapped on the bottom half of it. So I replaced the expansion tank and it now I get a hollow sound about halfway down so I think it's working ok.

After reading the sticky post about how to verify a boiler pressure gauge, I put a 100 psi gauge on a garden hose fitting and connected it to the drain valve for the house zone. I expect it to read about 20 psi but it reads zero! When I open the drain valve water comes out but slowly. If I lift the full pressure bar on the regulator, water comes out rapidly. Shouldn't I see water come out fairly rapidly even at 20 psi? If I connect the 100 psi gauge to the house cold water supply, I read 50 psi which seems reasonable. Could the heating pipes have some kind of blockage in them? The heat works OK. All the baseboard registers get hot but I'm confused by the zero pressure reading at the drain valve.

Thinking that the thumping sound was water hammer, I tried bleeding all the air out of the pipes by doing a power flush. That is, I closed the ball valve under the house zone valve, moved the house zone valve lever to open, and drained at least 10 gallons of water out of the system. Some bubbles came out initially but then they stopped. To push out as much air as possible, I lifted the full pressure bar on the regulator to give 50 psi (my full house water pressure) during the flush. Well, after doing that the thumping sound still occurs.

I also looked for bleed valves on the baseboards and there is only one on the baseboard farthest away from the circulator. I opened it until a small stream of water came out. That didn't stop the thumping either.

So I replaced the float type air vent (Amtrol 700-30) but the thumping still occurs.

I can't find any one place where the thumping is loudest. I even bought a stethoscope and tried to find the spot where the sound is coming from but I just can't localize it. The only thing I can tell is that it seems louder on the end of the house farthest away from the boiler. I traced the path of all heating pipes and wiggled them while the thumping was occuring and no amount of wiggling or moving them helped much at all.

I'd really appreciate any ideas on why my pressure readings are so odd (why does the extra gauge that I connect to the drain valve read zero?) and why I'm getting the thumping sound. I'm starting to think that the thumping sound may have more to do with temperature changes as the house cools off at night but the sound was really loud when the heating system was running full blast during the recent cold weather. The sound continues after the heat turns off. I wonder if water hammer can occur even if the circulator isn't on. If I leave the heat off for a few hours, the sound finally goes away. This is driving me nuts! Please help.

Bruce
 
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Old 04-06-14, 03:40 PM
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Hello and welcome to the forums...


If I lift the full pressure bar on the regulator, water comes out rapidly. Shouldn't I see water come out fairly rapidly even at 20 psi? If I connect the 100 psi gauge to the house cold water supply, I read 50 psi which seems reasonable. Could the heating pipes have some kind of blockage in them? The heat works OK. All the baseboard registers get hot but I'm confused by the zero pressure reading at the drain valve.
You should have a 12psi reading when the boiler is cold. IMO from reading your post you may not have enough water/psi in the boiler. You should not get a 0 reading..

Put the gauge back on that you made and lift the fast fill until 12 psi then stop...

Shut the water feed off and run the system.

Let us know...


Thinking that the thumping sound was water hammer, I tried bleeding all the air out of the pipes by doing a power flush. That is, I closed the ball valve under the house zone valve, moved the house zone valve lever to open, and drained at least 10 gallons of water out of the system. Some bubbles came out initially but then they stopped. To push out as much air as possible, I lifted the full pressure bar on the regulator to give 50 psi (my full house water pressure) during the flush. Well, after doing that the thumping sound still occurs.
Pics would help here as all systems are different. Even if you bled the system correctly, are your air eliminators working? Show us where they are located..

Did you leave the screw cap on top loose?

The only thing I can tell is that it seems louder on the end of the house farthest away from the boiler.

Where are your zone valves and circ located? It can just be hammer from the zone valves closing from inproper location/install...


but the sound was really loud when the heating system was running full blast during the recent cold weather. The sound continues after the heat turns off.
Well you may have temp issues too... The boiler should not go higher then 180f.. If the aquastat is faulty it can go higher. Verify the boiler temps. Possibly you need a new gauge for that also. High temps will cause all kinds of sounds...

lastly the boiler may be filled with sediment... Well? City water?


Lets start there...
 
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Old 04-06-14, 04:25 PM
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I put a 100 psi gauge on a garden hose fitting and connected it to the drain valve for the house zone.
A 100 psi gauge is way too high a range to get any kind of accurate readings. Get a gauge that reads 30 or 60 psi maximum. (You DID open the drain valve after attaching the gauge, didn't you?)

You need to REPLACE the "tridicator" gauge so that you KNOW what pressure is running in the system.

You need to check the air pressure in the expansion tank when the tank is isolated from the system or when the system pressure is zero. Measuring the air pressure when there is system pressure on the other side of the diaphragm will give an erroneous reading.

Tapping on the expansion tank is NOT an acceptable method of determining anything.

You need to replace the safety valve on the boiler. This should routinely be replaced every five years.

Lots more, please post pictures of your installation.
 
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Old 04-06-14, 04:55 PM
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Thanks for your reply. Yes, I will replace the tridicator. I didn't want to do that since I thought I would have to drain the system but it looks like maybe I can just close off the ball valves to the boiler. I'll post some pictures. I measured no pressure at all at the Schrader valve on the expansion tank. A new tank was only $28 at Pex Supply so I replaced it to eliminate that as a problem. Good idea about replacing the relief valve. I'm pretty sure it's over 5 years old.
 
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Old 04-06-14, 05:10 PM
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Thanks for your help. I'll try lifting the fast fill lever until I measure 12 psi on the gauge I made. I replaced the old air eliminator with a new one and made sure the cap was unscrewed 2 turns. The zone valves are right next to the boiler feeding the baseboard supply line and the hot water heater. I'll post some pictures. My zone valves are Honeywell V8043F. I read that they sometimes close too fast and removing the short spring (leaving the long one connected) will slow them down. I tried that with both zone valves and it made no difference so I put the short spring back in each zone valve. The boiler heater does turn off at 180 deg according to the tridicator and the aquastat setting inside the boiler case is set at 180. I tried putting it to 170 yesterday but I still had the thumping. I'll try a lower setting tonight. The boiler is getting city water. The boiler is about 25 years old and it very well could be filled with sediment. Would that cause continuous thumping sounds? The sounds are very regular and spaced just about a second apart.
 
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Old 04-06-14, 05:14 PM
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It could just be thermal expansion wher the pipes to the baseboard come up through the floor. Try grabbing those pipes and move them around some. See if the noise changes or goes away...
 
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Old 04-06-14, 05:21 PM
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I'll put this question to the forum since I am not familiar how to investigate or solve.

"The sounds are very regular and spaced just about a second apart."

Could it be the flowchek valve with low flow causing the flapper to bounce on the seat?

I have one that "clicks" for that reason. Not sure if I would call it a "thump" but the sound does travel throughout the system when the pump is running.
 
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Old 04-06-14, 05:26 PM
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Here are some pictures of my boiler. There's a picture of the overall system, the zone valves, the expansion tank and the old air vent that I replaced, and the controller board and circulator.
 
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Old 04-06-14, 05:43 PM
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Here are some pictures of my boiler.
Oh... One of those... Although efficient they were problematic...)

Can you post pics to a image hosting site so we can get them larger and zoom in?
 
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Old 04-06-14, 06:01 PM
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Ha ha, yeah I guess it's a lemon but it does start up reliably and I'm happy for that.

I just tried your suggestion about lifting the fast fill lever until the pressure goes up to 12 psi. It sure looks like my tridicator reads about 15 psi high. The fact that the boiler relief valve didn't start to open until the tridicator showed over 40 psi confirms that. But thing are getting stranger and stranger - when I brought the pressure up to 12 psi on my homemade gauge, the thumping sound started up again even though the boiler had been off for at least an hour and the temperature was under 100 degrees!!! Now I'm starting to think that the sound I hear is water dripping onto something that acts like the head of a drum. The sound is very regular like dripping would be. I don't see water anywhere but I'll look more closely now. It seems that a pressure of more than 5 to 10 psi makes something start to drip. That's my latest theory. I'll try to find out tonight if my theory is all wet (literally).
 
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Old 04-06-14, 06:54 PM
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The check valve right after the feed water valve does leak a little bit when I close the feed water ball valve but if the sound was coming from there I would likely hear it when I put my ear or a stethoscope on it. The thumping sound isn't coming from anywhere near the boiler but mostly from the other end of the house about 100 feet away.

So far no luck finding any water dripping from the heating pipes. Looks like my theory is drying up.
 
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Old 04-06-14, 07:18 PM
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Here are some larger pictures. I compressed the jpgs more to get them under 50K. Hopefully, they're better than the small pictures. The first picture shows the boiler supply and return (supply on the bottom). The second picture shows more of the piping. The third picture shows the city water input, check valve, and regulator. The fourth picture shows piping to and from the baseboards. The top center pipe going over the gray iron pipe and facing out of the picture is the supply to the baseboards. The pipe to the right of it is the return from the last baseboard.
 
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Old 04-06-14, 07:36 PM
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I just tried your suggestion about lifting the fast fill lever until the pressure goes up to 12 psi. It sure looks like my tridicator reads about 15 psi high.
OK so you know your gauge is off... try this..

With your new gauge reading 12psi shut the water feed off to the boiler. Keep a eye on your new gauge. Possibly minutes? Hourly? See if the boiler holds pressure. If it stays ay 12 psi for some time you know there is no leak.

If it drops to 0 psi... start a looking....
 
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Old 04-06-14, 08:53 PM
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Yes! I'll try that and let you know what I find tomorrow morning.
 
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Old 04-07-14, 10:03 AM
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Lawrosa, I ran the test you suggested and found that I have no leaks. With your help I now know that the gauge on my boiler is off by 15 psi and that no water is leaking from my heating pipes. I finally found the source of a lot of the thumping sound. The previous owner tried to finish the basement and nailed 8 foot long wooden planks across the joists to make a ceiling over about a third of the basement area. The heating pipes were bracketed tightly against the planks in two places. I removed the two brackets and now there is much less noise. When the heat went on, the planks expanded and pulled on the nails securing them to the joists. When the heat went off, the planks contracted and pushed the nails back into the joists. That's why I was getting noise even after the circulator turned off. I'm surprised at how regular the thumping was. I suppose over a long time the nails loosened in a pattern that allowed them to pull in and out of the joists quite evenly. It sounded almost like a clock or motor was making the noise. But I know that wasn't the case because I turned off all electricity to the house and the noise continued. I was planing to take down the partially finished ceiling and walls in the basement anyway since I want a large open space to use as a workshop so I will do that now and find all the places where the heating pipes are hung incorrectly. I think that will get rid of the small amount of noise remaining.

Thanks a lot to you and others for your comments.

Bruce
 
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