Need some boiler advise and education

[Matt10]

First I have a Thermo Dynamics S series oil fired boiler about 25 years old.
There are three heat zone lower level den small zone, 1st and second floor large main zone and upper level bedroom small zone
The problem I've been having for the last three years is no heat on the second floor of the main zone. seems the pressure was too low too push the water up to the second floor. The issue was compounded by the fact that the pressure part of the gauge never changes from about 12 and I believe it isn't functioning. In the past by playing around with the pressure regulator valve for the water, it seemed as if it was stuck and not letting any water enter. after messing with it I felt the cold water flow in and after bleeding, the heat began coming up on the second floor.
Again this year I had the same issue and result except that the boiler expansion tank valve has pissed off some water 2 or three times in 2 days. I would like to solve this issue. I went out and got a test gauge that I was able too hook into one of the lines where there had been a plug so I could monitor the pressure. There is no doubt the original gauge is broken.
When the boiler isn't running but is on, the new gauge reads zero when the boiler goes on and heats up it hits about 26 or 27 lbs which seems normal. not sure why it let out water??
I would welcome any ones thoughts on this whole matter. Thanks Matt

 

[Dana]

The expansion tank has to be functioning, and properly pre-charged to the system's operating pressure -0/+3 psi. So if the system is intended to operate at 12psi, with the tank isolated from the system with no pressure on the water side of the tank (you may have to unscrew it until it starts to dribble) the air has to be pumped to at least 12 but not more than 15 psi.

When you say "...boiler expansion tank valve has pissed off some water..." are you talking about the air valve on the expansion tank, or do you mean the pressure relief valve opened up? If water is coming out of the expansion tank's air valve the internal diaphragm is shot and the tank needs to be replaced.

 

[Sponsor]

 

[Matt10]

The expansion tank has to be functioning, and properly pre-charged to the system's operating pressure -0/+3 psi. So if the system is intended to operate at 12psi, with the tank isolated from the system with no pressure on the water side of the tank (you may have to unscrew it until it starts to dribble) the air has to be pumped to at least 12 but not more than 15 psi.

When you say "...boiler expansion tank valve has pissed off some water..." are you talking about the air valve on the expansion tank, or do you mean the pressure relief valve opened up? If water is coming out of the expansion tank's air valve the internal diaphragm is shot and the tank needs to be replaced.

You can see what I have. I don't really see any way to tell which one the water came from as the drain line is common. It now seems I have a slow steady drip from that line Qt. an/hr. I can say that I heard what I believe was the pressure valve release a quick burst of water twice.
Also it seems to running between 2o and 26 lbs depending on the temp. I just watched it, at 22 the boiler came on it rose to about 26 and shut off. The pressure valve did not let off any pressure.
Any way too tell which one the drip is coming from?
I was thinking to lower the pressure at the regulator valve?

 

[Dana]

There's no source of water on the bottom side of the expansion tank- it was the pressure relief valve that spit the water. Most pressure relief valves on 1-3 story residential boilers are set to open up at 30 psi, which isn't too far away from the pressure you've been running the boiler.

When the valve opens up even a hint of grit in the valve seat would cause it to continue to drip. Sometimes you can get it to spit the grit and re-seal by manually opening the valve with the lever.

But first you have to get the pressure down to something reasonable and check/adjust the air charge on the tank. Unless the top of the highest radiator on the system is 45 vertical feet above where you're measuring the pressure it doesn't need to be 20psi. Simple math that works 99% of the is 0.433 x vertical feet, plus another 3psi to deal with the pressure differentials that happen while pumping. At less than 10 psi there can be flash boil at the boiler, so in most cases 12psi would be the minimum pressure at the boiler to give it some margin. Almost all 2 story and some 3-story houses do just fine at 12-15 psi, measured at the boiler. The fact that the broken gauge was stuck at 12psi is a clue that you probably don't need more than 12 psi. A system that measures 20 psi at idle (no pumping) is NOT normal or typical- it's the exception. So unless you have crazy-tall ceilings or something and it really IS that far to the top radiator, drop the pressure to 12-15 psi.

The regulator valve /auto-fill valve usually has an isolating valve (hopefully a ball-valve, not a corroded old gate valve) between the regulator and the potable supply. In normal operation that can and often should be closed. Like the pressure relief valve it can pick up grit and not seal tightly, slowly overfilling the system over time. If the isolating valve is an old gate valve, those too often seep when closed.

 

[Matt10]

There's no source of water on the bottom side of the expansion tank- it was the pressure relief valve that spit the water. Most pressure relief valves on 1-3 story residential boilers are set to open up at 30 psi, which isn't too far away from the pressure you've been running the boiler.

When the valve opens up even a hint of grit in the valve seat would cause it to continue to drip. Sometimes you can get it to spit the grit and re-seal by manually opening the valve with the lever.

But first you have to get the pressure down to something reasonable and check/adjust the air charge on the tank. Unless the top of the highest radiator on the system is 45 vertical feet above where you're measuring the pressure it doesn't need to be 20psi. Simple math that works 99% of the is 0.433 x vertical feet, plus another 3psi to deal with the pressure differentials that happen while pumping. At less than 10 psi there can be flash boil at the boiler, so in most cases 12psi would be the minimum pressure at the boiler to give it some margin. Almost all 2 story and some 3-story houses do just fine at 12-15 psi, measured at the boiler. The fact that the broken gauge was stuck at 12psi is a clue that you probably don't need more than 12 psi. A system that measures 20 psi at idle (no pumping) is NOT normal or typical- it's the exception. So unless you have crazy-tall ceilings or something and it really IS that far to the top radiator, drop the pressure to 12-15 psi.

The regulator valve /auto-fill valve usually has an isolating valve (hopefully a ball-valve, not a corroded old gate valve) between the regulator and the potable supply. In normal operation that can and often should be closed. Like the pressure relief valve it can pick up grit and not seal tightly, slowly overfilling the system over time. If the isolating valve is an old gate valve, those too often seep when closed.

By manually opening the valve with the lever I got the drip to stop. I went to the regulator valve and following the instructions ( Taco 329-3 ) I turned the adjustment screw 1.5 tuns CCW. I lowered the pressure to 0 and let it refill it went to about 18lbs but on heating it climbed to 22 lbs. I am going to attempt to lower the valve pressure some more.
I am beginning to think the Taco valve is faulty. Can I turn it all the ways CCW and work my way back?
The boiler instructions say too leave the feed valve open when the boiler is operating?

 

[Matt10]

There's no source of water on the bottom side of the expansion tank- it was the pressure relief valve that spit the water. Most pressure relief valves on 1-3 story residential boilers are set to open up at 30 psi, which isn't too far away from the pressure you've been running the boiler.

When the valve opens up even a hint of grit in the valve seat would cause it to continue to drip. Sometimes you can get it to spit the grit and re-seal by manually opening the valve with the lever.

But first you have to get the pressure down to something reasonable and check/adjust the air charge on the tank. Unless the top of the highest radiator on the system is 45 vertical feet above where you're measuring the pressure it doesn't need to be 20psi. Simple math that works 99% of the is 0.433 x vertical feet, plus another 3psi to deal with the pressure differentials that happen while pumping. At less than 10 psi there can be flash boil at the boiler, so in most cases 12psi would be the minimum pressure at the boiler to give it some margin. Almost all 2 story and some 3-story houses do just fine at 12-15 psi, measured at the boiler. The fact that the broken gauge was stuck at 12psi is a clue that you probably don't need more than 12 psi. A system that measures 20 psi at idle (no pumping) is NOT normal or typical- it's the exception. So unless you have crazy-tall ceilings or something and it really IS that far to the top radiator, drop the pressure to 12-15 psi.

The regulator valve /auto-fill valve usually has an isolating valve (hopefully a ball-valve, not a corroded old gate valve) between the regulator and the potable supply. In normal operation that can and often should be closed. Like the pressure relief valve it can pick up grit and not seal tightly, slowly overfilling the system over time. If the isolating valve is an old gate valve, those too often seep when closed.

The expansion tank has me baffled. When I tap the bottom it sounds empty when I tap the top it sounds empty but when I tap anywhere on the sides it feels full?
I tried testing the pressure but the pin in the air valve did not want to move. not with my finger or the gauge so I left it alone lest I mess it up?

 

[Dana]

The bottom half is filled with air, the top with water. There is a rubbery diaphram separating the air side from the water side. As the system water heats up it expands, and the tank gives it a space to fill into.

But in order for it to fully do it's job the air-side has to be pre-pressurized to the target system pressure when there is no pressure on the water side. On the botttom of the tank there is a schrader valve (same as a car tire's air valve) for pumping air in or releasing pressure to adjust it to the target system pressure. The pre-charge on the air side can be 2-3 psi higher than the target pressure, but not lower than the system pressure or it may not have sufficient space for the water to expand into.

 

[Matt10]

The bottom half is filled with air, the top with water. There is a rubbery diaphram separating the air side from the water side. As the system water heats up it expands, and the tank gives it a space to fill into.

But in order for it to fully do it's job the air-side has to be pre-pressurized to the target system pressure when there is no pressure on the water side. On the botttom of the tank there is a schrader valve (same as a car tire's air valve) for pumping air in or releasing pressure to adjust it to the target system pressure. The pre-charge on the air side can be 2-3 psi higher than the target pressure, but not lower than the system pressure or it may not have sufficient space for the water to expand into.

The schrader valve appears to be inoperable?
Maybe at 25 years old I should just change it? Looks pretty easy
The pressure release valve is still dripping. I'm running right at 20lbs.
It is winter here. I have plenty of heat, in 6 weeks it should be safe for me to work on it

 

[Dana]

You tried putting a tire pump on it and couldn't get any air into or out of it?

Changing the schrader valve is a lot cheaper than changing the tank. It's the same tool and part as swapping it out on a tire.

Before doing anything at all with the tank, with no pumps running with the boiler idling somewhere near the low-limit temp (not at it's max temp), bleed drain water out of the system to get it down to 15 psi, see how it behaves. If it was pre-charged a dozen+ years ago to 12 psi it might still be about that, or a bit lower. Running the system at 20 psi with a pre-charge of 10 psi the diaphragm is already substantially pre-stretched, with far less expansion volume left for the water.

 

[Matt10]

I attempted to take a pressure reading with two different gauges . Neither one got a reading never thought maybe there is no pressure at all? I am going to try putting some air in. I have a new schrader valve and the tool If it come to that.

You tried putting a tire pump on it and couldn't get any air into or out of it?

Changing the schrader valve is a lot cheaper than changing the tank. It's the same tool and part as swapping it out on a tire.

Before doing anything at all with the tank, with no pumps running with the boiler idling somewhere near the low-limit temp (not at it's max temp), bleed drain water out of the system to get it down to 15 psi, see how it behaves. If it was pre-charged a dozen+ years ago to 12 psi it might still be about that, or a bit lower. Running the system at 20 psi with a pre-charge of 10 psi the diaphragm is already substantially pre-stretched, with far less expansion volume left for the water.

If I drop the pressure to 0 psi and allow it to refill at idle and it repressurises to 20 even though I have turned the valve 3.5 times CCW does this not indicate the valve is not functioning properly?

 

[Dana]

Stop trying to use the auto-fill valve's setting to hit the right pressure, and stop draining the system down to where it reads 0 psi. Draining it to zero too often draws air into the system, which then has to be purged. Auto-fill valves are something a "solution problem", creating as many problems as they solve, and were never designed to be precision instruments. It's there as a convenience to the boiler tech, and when they're out of calibration, broken or the valve seat leaks they become the opposite of "convenient". If the thing is simply stuck, sometimes monkeying with the fast-fill levers can free it up, but you really don't need the auto-fill. (Mine has been off-calibration for years, sometimes is sticky, and I just don't even bother adjusting it.)

Instead, turn off the isolating shut off valve between the auto-fill and the potable supply, then bleed down the system to 12-15psi and stop. If the pressure continues to creep upt despite the isolation valve being closed, the shut off valve is probably seeping, and that IS worth fixing.

 

[Matt10]

Stop trying to use the auto-fill valve's setting to hit the right pressure, and stop draining the system down to where it reads 0 psi. Draining it to zero too often draws air into the system, which then has to be purged. Auto-fill valves are something a "solution problem", creating as many problems as they solve, and were never designed to be precision instruments. It's there as a convenience to the boiler tech, and when they're out of calibration, broken or the valve seat leaks they become the opposite of "convenient". If the thing is simply stuck, sometimes monkeying with the fast-fill levers can free it up, but you really don't need the auto-fill. (Mine has been off-calibration for years, sometimes is sticky, and I just don't even bother adjusting it.)

Instead, turn off the isolating shut off valve between the auto-fill and the potable supply, then bleed down the system to 12-15psi and stop. If the pressure continues to creep upt despite the isolation valve being closed, the shut off valve is probably seeping, and that IS worth fixing.

Ok brought it down to about 12 isolating valve off will wait and see!
What about the pressure relief valve having a constant leak?

 

[Dana]

If you can't get the relief valve to stop dripping you'll have to replace it. As it drips eventually the system pressure will drop low enough to pull air into the system from the vents or flash-boil on the heat exchangers. The flash boil makes it less efficient and makes a lot of noise, so you really wan't to have it set up where you don't have to check the system pressure every day due to a chronic slow leak from a dripping pressure relief valve.

Try flushing it a few times by opening it with the lever. If it's grit on the valve seats it can often be purged and it'll stop dripping, but if it's pitting/corrosion it's hopeless- time to buy a new one.

 

[Matt10]

Looks like a pretty quick easy replacement. Any particular brand also the also the automatic air vent any brand recommended

 

[Dana]

Watts tends to have middle-of-the road decent stuff for things pressure reliefs and other boiler fittings, and are usually available at box stores, but there are others.

What type of vent are you replacing, and why? Got a picture?

 

[Matt10]

Watts tends to have middle-of-the road decent stuff for things pressure reliefs and other boiler fittings, and are usually available at box stores, but there are others.

What type of vent are you replacing, and why? Got a picture?

It's been dripping from the top for quit some time figure it's due, as long as I'm doing the pressure valve.

I tried flushing it a few times no luck

 

[Matt10]

The watts valve at lowes and HD is the female version. Use a nipple or a different valve?

 

[Matt10]

Just a follow up due too a leak in a pipe to a radiator I had to shut the system down. So I changed the expansion tank and PRV . When I turned the water back on there was none. Upon closer examination the water valve was clogged all up so I changed that. Boiler up and running. Radiator is plugged off so that's next. Thanks