Excess Prssure In Hot Water Boiler

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Old 12-26-07, 07:42 AM
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Excess Prssure In Hot Water Boiler

The high pressure relief valve has been going off at 30 lbs pressure and this matches on the pressure gauge so it looks like it is working correctly. My contractor told me I have a leak in the indirect water heater coil allowing pressure to come back through the coil into the system. To check this he told me to draw down the pressure to 15 lbs and close the input valve from the house supply coming into the input pressure valve. I did this and the system remained at 15 labs for 3 days. After 3 days he decided it was not the water heater coil leaking but the input pressure valve leaking. He replace the input pressure valve and now the perssure is back up to 30lbs and the pressure relief valve is going off. Any sugguestion as to why when the system is in a closed loop it is working but when I open the valve coming from the house pressure it lets the system go back up to 30 lbs? Could the valve he replace be defective also?
 
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Old 12-26-07, 08:47 AM
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It sounds like the new valve may be defective but let's try something else before blaming it for the trouble.

Check the expansion tank. Manually push the schraeder valve (on the air side of it). If it leaks water instead of letting air out, there is your problem. Additionally, if air does come out of it, get a tire gauge and check the pressure in it...it should be between 10 and 15 psi (12 B&G recommends), but no more than that.

Hope this helps.
 
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Old 12-26-07, 09:14 AM
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Excess Pressure On Hot Wate Boiler

Tank looks good, air pressure is at 15 pounds.
 
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Old 12-26-07, 10:31 AM
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You talk about an "indirect water heater". Is this a stand alone unit next to the boiler? or is it perhaps an "immersion coil" inside your heating boiler?

How high do you have the boiler's high limit switch setpoint set at?

Get close to the feed valve and see if you could hear the water trickling thru it. What's the brand and M/N of it?
Since you have shut it closed and the problem ceased, this is the problem...whether a defective valve or improperly adjusted.
 
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Old 12-26-07, 03:20 PM
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The indirect heater is a seperate unit from the boiler and is set up as a seperate zone off the boiler with it's own zone control and thermostat on the heater itself. I checked the setting on the boiler and I found only one switch with I believe is the aquastat and this is set to 180 although the boiler does go to 190 before turning off. The inlet pressure switch is a TACO, model # 329-3 with a setting from 10-25 and the tag on it says it is set for 12 lbs. Not sure what you mean by M/N on the inlet valve but hope you have enough info. As far as hearing a leak through the valve this may be very hard to do. It takes amost 24 hours for the pressure on the pressure gauge to go from 15 up to 25-30 lbs.
 
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Old 12-26-07, 03:36 PM
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Originally Posted by boats View Post
Tank looks good, air pressure is at 15 pounds.
Did you isolate the tank ? The water side of the tank has to be at atmospheric presssure in order to read the air charge in the tank. If you don't do this, what you will read on the tire gauge is the pressure in the boiler, NOT the air charge in the tank.
 
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Old 12-26-07, 07:11 PM
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How do I isolate the tank? I believe the tank has a bladder in it. It is a blue tank with a release valve at the top and the valve to read the air pressure on the bottom. Feeling the tank it is warm at the where it hooks into the pipe and cool at the bottom where the pressure read valve is.
 
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Old 12-26-07, 09:03 PM
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Got a digital camera ? Can you snap some pics and post them on www.photobucket.com (free) and provide a link here so we can see ? Much easier that way ...
 
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Old 12-27-07, 07:43 AM
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I'll try to borrow a camera. To try to give you a picture of the system I'll do my best to discribe it. Coming from the boiler there is a galvanized pipe that looks like it is about an inch and a half in diameter going into an American Air Purger union which has a hump on the top of it. Connected to the top of the hump is a TACO release valve (It is a small tank looking thing with a relief valve on the top of it). Connected to the bottom of the air purger is the expansion tank which hangs down. It is a Amtrol model 30 with the pressure valve on the bottom where I read the 15lbs. Why would the expansion tank make a difference whether the input to the system is open through the input pressure valve or whether the input to the pressure input valve is shut off. If the tank is waterlogged would it not act the same in a closed system as it would if high pressure is coming pass the input valve. If the tank is waterlogged and the boiler pessure is at 25 or 30 could I expect to read this at the pressure valve at the bottom of the expansion tank? Right now the water from the house to the input pressure valve has been shut off after I drained the system back to 15 lbs and the system has been sitting at 15 lbs rock solid for the past 24 hours. The top of the expansion tank is hot near where it is connected to the purger union and the bottom is cool.
 
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Old 12-27-07, 08:00 AM
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What's the city water pressure over there? Notice below (the manual from Taco for the feed valve you have) that the max. inlet pressure should not exceed 100psi.

This is a long shot, but I'm running out of suggestions

 
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Old 12-27-07, 08:41 AM
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Could not get the manual to display on my system but I am on my own water supply and the top pressure is 40lbs. Any ideas on my last post about internal closed system verus input from house to inlet pressure valve. If the system is closed and the pressure remains at 15 can I rule out any problems within the system itself (like compression tank)and pretty much point at the input pressure valve?
 
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Old 12-27-07, 08:53 AM
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I'd agree with you on the feed valve (inlet pressure valve as you call it) being the source of trouble
 
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Old 12-27-07, 03:55 PM
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I tend to agree that the reducing valve seems to be at fault also. Is there by any chance a 'fast fill bypass" piped AROUND the pressure reducing valve ? If so, then that fast fill valve could be leaking through.

Since you are on a private water system, there is also a good chance that when the valve was changed, the plumber did not flush the lines, and some debris got caught in the new valve. (I'm on a private well myself, and I have similar problems from time to time).

Let me make sure I understand something though:

You close the manual feed valve. Reduce boiler pressure to say 15 PSI. With the boiler firing normally now, you see the pressure remaining within say 4-5 PSI of that initial number from cold to hot ?

I initially didn't address the pressure problem, only stated that you can't measure the tank pressure without isolating the tank.

You still should check the tank in any case though. It should be done routinely every couple years, because air WILL leak through an intact bladder at about 1 PSI per year. So, if your tank hasn't been charged properly in say 5 years, then you will be appx 5 PSI low. With low pressure in the tank, your pressure swings from cold to hot will be higher than need be, and if it gets too low, will open the safety relief valve.

You can check the pressure without removing the tank, but you need to drop the boiler pressure to zero. You don't need to drain it, only let enough water out until it reads zero. THEN put your tire gauge on the tank fitting. If it's less than 12-15 PSI add air.

A tire pressure gauge on the tank fitting will read the HIGHER of two pressures, either the air charge in the tank if the boiler pressure is below the tank pressure, OR the boiler pressure if it is higher than the tank pressure.

As I said though, this may or may not have anything to do with your existing problem. But it does bear checking... you may have a bad valve AND low tank pressure.

Even if a tank is waterlogged, it will feel warm only at the top, because the hot and cold won't mix by themselves. Hot water is more buoyant, and will stay at the top of the tank. Feeling the tank is no indication of whether or not it is waterlogged.
 
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Old 12-27-07, 08:38 PM
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The expansion tank was changed about a year and a half ago. To answer your question about the pressure. Once I drain it down to 15 and turn off the input water to the system It stays at 15 for days throughout the boiler going up and down in temp. Tomorrow I am going to call my heating contractor and have him change the input valve again and check the tank. This time I am going to have him flush the line prior to putting in a new valve. Like you say there may be dirt,etc in the line that may be clogging the valve. It may be a couple of days before he gets here so I will let you know how I make out. When the water shut off the boiler is working fine and holds the pressure. I am letting him do the work because I am covered by a maintenance contract for the season and his work and parts are covered under it. Sure appreciate the feedback I have been getting.
 
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Old 12-27-07, 08:42 PM
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I forgot to mention in my last note that the input valve has a open/auto lever on it and it is in the auto mode. There are no other lines around the input valve. All water going into the boiler has to go through the input valve.
 
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Old 12-27-07, 09:05 PM
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Yep, given your explanation, it's almost without a doubt that the tank is fine (like you say though, ask him to check it anyway) and the new valve got some crud in it... thank heaven for service contracts, eh ?

Good luck!
 
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Old 01-07-08, 06:29 AM
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Well the heating contractor came back and brought two techs with him. They replaced a zone control valve a month or so ago and decided there was an air block in the system from when the valve was changed. So they ran water through the whole system and removed the air. They then felt the pressure/temp gauge was reading too high and the relief valve was going off too low so they replaced both of those. So I don't know whether it was an air block in one of the zones or the temp gauge or the pressure release valve but it has been working for 4 days now and hopefully will continue to do so.
 
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Old 01-07-08, 04:34 PM
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OK then... so what's the new pressure gauge reading from cold to hot boiler ? just curious ?

You can't argue with success, but you did say in your first post that the gauge was reading 30 PSI when the relief valve opened... how weird a coincidence is that, that they both just happened to be "off" by the same amount, in opposite directions ? color me skeptical ... sorry ...
 
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Old 01-12-08, 12:47 PM
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You were right to be skeptical, the pressure is going up over 30 again and spilling out the pressure relief valve. Only getting about 1/2 cup each day. The pressure gauge hits 30 and the valve opens so they are in sync. Only does it when I bring the boiler up in the morning. The rest of the day it goes up to just under 30 and the valve stays shut. It has 4 zones and I bring them up about 5 degrees one at a time. The first one seems ok but by the time I get to the second or third it is up to 190 and 30 lbs. At cold it is at 140 and 20 lbs. Any sugguestions?
 
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Old 01-12-08, 01:43 PM
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I still think you have two problems! I think the charge in the expansion tank is LOW ... (did your service guys check it ? do they even know HOW ?) ... AND, you've got some grit or crud sticking the pressure reducing valve open (you ARE on a well system after all...) and causing a slow increase in pressure.

The reason it's only doing it in the A.M. is because when the boiler cools overnight, and the pressure drops because it's cooling, the fill valve is adding water. When you first fire it, the pressure increases and blows out the extra water. From there, as long as the boiler stays HOT, and the pressure stays high, the fill valve isn't adding any more water. But, let it COOL again, pressure drops, fill valve adds water.

Here's what you should do, BEFORE calling them knuckleheads back again.

1. Turn off boiler. CLOSE the manual fill valve.

2. Let system cool to under 100*F (cooler is better) (this is important!)

3. Leaving the valve between the boiler and the expansion tank OPEN, drain boiler pressure to ZERO with a hose and drain valve. You don't need to actually drain the boiler, only let out enough water that the pressure goes to zero.

4. DOUBLE CHECK the air charge in the expansion tank! With the boiler at ZERO you should have 12-15 PSI in the expansion tank. Remember, you can NOT check the pressure in the tank with ANY pressure on the water side, you will not get an accurate reading. If the pressure is below 12 PSI, add air to the tank until it is at 12-15 PSI.

5. Once you are certain that the tank is properly charged, open the manual fill valve and re-pressurize the boiler to 12 PSI. CLOSE THE MANUAL FILL.

6. Re-start the boiler. Let it get all the way hot... all the way up to 180-190*F (turn the thermostats up to 80* if you have to). Watch the pressure gauge on the boiler as it's heating up. It should increase maybe as much as 5-10 PSI , and the relief valve should NOT go off. Tell us what the pressure goes up to.

7. Run the boiler this way for a week, and check the pressure gauge daily.

8. Now... if it has run fine this way for a week with the manual fill valve closed, and you KNOW the expansion tank has the proper air charge, what else can the problem be ? Call the knuckleheads back and make them change the valve again... don't let them b.s. you ...
 
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Old 01-13-08, 07:28 AM
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Thanks, will get back.
 
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Old 01-14-08, 08:37 AM
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Decided not to touch the furnace I paid them big bucks for a service contract that I do not want to give them any reason to cancel, especially with the problems I am having. They are coming back tomorrow. Just one question, When the pressure on the boiler reads above 15 lbs should the pressure on the expansion tank read the same. I checked the pressure on the expansion tank with an air gauge and it read 26 lbs which matched the pressure gauge on the boiler.
 
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Old 01-14-08, 03:40 PM
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YES, if you put a gauge on the tank when there is pressure on the boiler, that gauge will read the BOILER pressure, not the pressure of the air charge in the tank.

(Unless of course the pressure on the air side of the tank happens to be HIGHER than the boiler pressure).

Let me re-state what I just said.

When you put a gauge on the air valve on the expansion tank, you will read the HIGHER of two pressures, either the boiler pressure, or the air charge in the tank... whichever is HIGHER.

The air charge in the expansion tank can only be read accurately if there is NO (or very little) pressure on the water side.

If the knuckleheads measure the tank air pressure with pressure still on the boiler, you will _know_ they are knuckleheads.

In fact, as a test, why don't you drain down to like 8 PSI in the boiler... they'll never know... check the air charge... if your gauge reads 8 PSI, you will KNOW that the tank needs air. If you wanna let them do it for you, that's fine, but forewarned is fore ARMED !
 
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Old 01-26-08, 02:23 PM
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I got them back out here and made them draw down the pressure on the boiler and guess what, very very low pressure in the expansion tank. There was no water coming out of the valve and it looks like when they replaced the expansion tank late last year they did not check the pressure in the tank when they installed it. They put pressure back in at 12 lbs and it has been working for a week with no problems and the pressure on the boiler is staying at 20. I hope this is it. Thanks for all your help and for increasing my knowledge of my system. Greatly appreciated.
 
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