Too much pressure in system

dan holmes_2

Try turning the aquastat down 20 degrees it may just be off.As far as a new one the well it is in may be your only issus. What is the aquastat doing? Stright limit relay or booth? Is the burner i20 or low voltage?Dont ask the home depot guy for the aquastat.

Scott13

I have hot water heat with a boiler, base board heaters, and a few old radiators. Yesterday, my wife called me and told me there was a bunch of water all over our basement floor and the boiler was banging. I told her to turn off the boiler and I left work. When I got home, I found that the pressure releif valve was dripping, but there was a LOT of water on the floor, more than from just a few drops.

I switched on the boiler and right away the banging started. About three loud knocks, coming directly from the boiler. I checked the pressure gauge it was at about 14/lbs. The water temp was cold since the boiler had been off for a few hours. I let the system start to heat up, and as the water temp reached about 190, the releif valve really opened up, and hot steaming water started poring out instead of dripping. All this time the knocking persisted about every 4-5 minutes.

I shut the boiler off and went upstairs and opened each of the radiators and baseboard vents. There was a small amount of air in each one, but nothing major. Went back down and switched the boiler back on and it got up to 190 and started pouring out water again. Keep in mind the pressure had been at 14-15/lbs. steadily.

Next I isolated the expansion tank and drained it completly. It was full at about 30 gallons, with out a lot of pressure. When it was drained I opened the tank up again and the pressure instantly dropped to about 6/lbs. I thought I had solved my problem and that the tank was just water logged. I turned the boiler back on, hoping everything was okay, but I noticed that the relief valve was still dripping despite the drop in pressure and the cold water. The temp and pressure built in the system untill it got to 190 degrees and 14-15/lbs again and the steaming water started pouring out again.

Pretty frustrated I shut the system down for the night and sent my wife and kids to sleep at the in=laws (It's about 5 degrees at night here). After work today, I went to Home Depot and

Scott13

I have hot water heat with a boiler, base board heaters, and a few old radiators. Yesterday, my wife called me and told me there was a bunch of water all over our basement floor and the boiler was banging. I told her to turn off the boiler and I left work. When I got home, I found that the pressure relief valve was dripping, but there was a LOT of water on the floor, more than from just a few drops.

I switched on the boiler and right away the banging started. About three loud knocks, coming directly from the boiler. I checked the pressure guage it was at about 14/lbs. The water temp was cold since the boiler had been off for a few hours. I let the system start to heat up, and as the water temp reached about 190, the relief valve really opened up, and hot steaming water started poring out instead of dripping. All this time the knocking persisted about every 4-5 minutes.

I shut the boiler off and went upstairs and opened each of the radiators and baseboard vents. There was a small amount of air in each one, but nothing major. Went back down and switched the boiler back on and it got up to 190 and started pouring out water again. Keep in mind the pressure had been at 14-15/lbs. steadily.

Next I isolated the expansion tank and drained it completely. It was full at about 30 gallons, with out a lot of pressure. When it was drained I opened the tank up again and the pressure instantly dropped to about 6/lbs. I thought I had solved my problem and that the tank was just water logged. I turned the boiler back on, hoping everything was okay, but I noticed that the relief valve was still dripping despite the drop in pressure and the cold water. The temp and pressure built in the system until it got to 190 degrees and 14-15/lbs again and the steaming water started pouring out again.

Pretty frustrated I shut the system down for the night and sent my wife and kids to sleep at the in=laws (It's about 5 degrees at night here). After work today, I went to Home Depot and the guy there thought the over heating of the system was caused by the excessive pressure and that I needed to get my pressure down to about 10-12/lbs. He gave me a feed pressure regulator, thinking mine was broken. When I got home I went to look for my existing regulator and found that I don't have one. So I brought that back, thinking that if the system didn't need one up till now then that's not what's causing my problem.

The Home Depot guy agreed with that assessment and gave me some other advice. He told me to again drain the expansion tank, after the tank was empty I was to open it up again and wait for the pressure to start rising. When the pressure got to about 9/lbs. he wanted me to shut off the expansion tank and let the system run cold without the tank to see if the pressure stabilizes.

I did all this, and shut off the tank when it got to about 9/lbs, which took about 10 minutes. However, the second I turned off the tank, the pressure started to shoot up very quickly. When it got to about 14/lbs. again I opened the expansion tank back up and the pressure quickly dropped back down to about 9/lbs. I also noticed when the tank was closed I could hear the city water flowing into the system. This gave me the idea to turn off the cold water intake, so I did.

I've been running the system now for about a half an hour with the intake turned off. The water is no longer boiling out the relief valve because the temp has stabilized at about 185. The pressure is stable at about 10/lbs. However, the relief valve is still dripping. It drips slowly while the water is at about 180, and when it gets to about 185 it pours a little quicker until it cools back down a tad.

The pipes are slowly warming up, and I mean SLOWLY.

A couple of questions:

1) How long can my system run without the city water coming in? It's still leaking from the valve, so I've been opening up the city water as I empty out the bucket to replace what I loose. But I'm not going to let it stay open because then the pressure gets back up to 14-15/lbs.

2) Why is my valve still leaking even if the water temp is 60 degrees and the pressure is at 6/lbs? Do I probably need a new valve?

3) Any idea why this may have happened all of a sudden?

4) What's with the banging coming from the boiler?

5) The pipes on the second floor are still ice cold. Is 10/lbs. of pressure enough to get hot water up there?

6) Could this be a problem with the circulation pump? The banging seams to be coming from it's vicinity, but it's hard to tell.

Yeah, I know that's a lot, but it's been a pretty stressful and scary couple of days. We just got this house about a year and a half a go. The boiler worked fine last winter, now this winter (after the warranty ran out) it's killing me. I have no money, so replacing it is a pretty scary thought, considering I've heard they cost like 5 grand to get done. That would take me months to save.

I really know NOTHING about plumbing/heating. Everything I just typed I wouldn't be able to yesterday morning, but I've been reading like crazy on here and similar forums trying to learn. I'm usually a pretty quick study and I'm not afraid to try and fix things I know nothing about.

So... any ideas?

Scott

blackoakbob_2

I'll try to start at the beginning......

you must have a tight system, so replace the water that is being lost and correct the leak. I believe that the pressure relief has failed since it has not stopped dripping. So you need a new one. Also, I really don't believe your pressure gauge is accurate anymore due to the extreme difference in pressures that you related. So, you need a new one. These two things will allow you to start to find out "What happened?". Since you have drained the expansion tank twice and it refilled and caused the relief to pop it's leaking and is bad. So you need a new one. This may be the cause of all of the trouble. Replace it with a diaphram type tank. Then begin with filling the system to 12# cold, vent the upper floor radiators and start up the boiler. Check for water flow from the pump by noting any temperature rise thru the boiler and system.
The pressure should raise to 18-22 # at 190 and you may still have to bleed the areas that don't warm up, making sure to maintain water pressure at the correct coresponding temperature. If the pump is not working the temp will rise in the boiler rapidly but the aquastat should trip it out before the relief valve will open. If not, you will need a new one. I'm at a loss to explain why you would have full city water pressure on the system before, but it must be regulated down or turned off and filled manualy. I found one like this last month the gauge was spun around, the safety did not work and the old hydralic gas valve was stuck and the house was at 90 degrees! I told them..... you guessed it.... you need a new one! I hope this helps. You don't need a complete new one but you need some good maintenance, bad.Best Regards

Scott13

Need an aquastat

I changed the pressure feleif valve so the system is now sealed. I filled up the tank and the pipes and let everything start warming up. The boiler heated up pretty quick but some of the pipes upstsirs were still cold so I bled them some. Then they got warmer. The boiler stayed steady at about 14/lbs. and 190 degrees. No problems. But after a while the boiler started to get hotter, above 200 and close the 210 and the valve opened up. I switched off the boiler and the valve shut off again, so I'm good there.

I guess I need a new aquastat to keep my boiler from getting too hot. Anyone know where I can get one for an old boiler? It's a 1975 AO Smith model #MW100 P750.

Scott13

Dan,

I took some pictures of it. The thing that confuses me is that it doesn't seem to ever come in contact with the water or tank. It just has a gas line running through it. Am I looking at the wrong thing?

http://img449.imageshack.us/img449/7100/serial8ka.jpg

http://img449.imageshack.us/img449/3716/aquastatfront3rs.jpg

http://img449.imageshack.us/img449/8315/aquastatside1dn.jpg

dan holmes_2

scott I service and teach about gas heating but am not good with this comp Icant get your pictures to show.Does this unit have a name?

Scott13

If you copy the text of those links into your browser address bar the pictures should come up.

The boiler is a AO Smith "Copper" Hydronic Boiler. Model #HW100 P720. Serial # 720A D75 30377.

After further inspection I found that the aquastat has a small wire that wraps around the boiler and connects to what looks like a sensor that projects into the boiler. It's a Honeywell aquastat with the following numbers printed on the side: T5001A V5155a17303-3 CU3

The system is comprised of the boiler and two expansion tanks. One is an old Hercules Copper Bearing Range Boiler 30 gallon tank hanging from the ceiling. The other is a small Fill-trol pressurized tank with a diaphragm that sits near the ground right next to the boiler.

Here is a shot of the overall system:

http://img384.imageshack.us/img384/1843/boiler2vk.jpg

Here's the Hercules expansion tank:

http://img384.imageshack.us/img384/8453/tank9ug.jpg

Here's the circulation pump, which I still suspect is bad since after I got the boiler up to 190 degrees the pipes 8 feet away from the boiler were still cold, even after bleeding the upper radiators:

http://img384.imageshack.us/img384/9123/pump3vy.jpg

Do they even make pumps to replace one like this anymore?

dan holmes_2

scott its going to be a long winter. You have a burkay type water heater used as a boiler. the circulater is a b&g 100 very common any circulator will replace it. If it is spinning it is ok. Did you oil it? The aquastat you will not find hope it is ok.Have not found many of these over the years but removed one last week.

dan holmes_2

The tank in the ceiling does now or did once make your hot water. Isee a second flue in the picture you must have a water heater?

Scott13

Yeah, I have a hot water heater, the tank in the ceiling just services the boiler.

I have a guy coming tommorow to replace the pump. I also found the same aquastat online, so I'll replace that later.

Thanks to you all for your help. I've learned a lot about my system from reading this site and the help that you guys gave me.