I have a boiler that feeds a closed loop radiator system - (not steam) when the system is cool the pressure gauge reads 15 PSI - as the system heats up, the pressure rises to 18-19 PSI - I understand that water expands when heated, and it's the job of the expansion tank to compensate for this expansion.

I kind of remember the pressure gauge staying right around 15 PSI not matter the temperature, but now I am noticing it near 20 PSI while running.

If any one has any thoughts, or if you can check the pressure gauge on your boiler while it is running, kindly let me know.

It was suggested that the expansion tank was full or waterlogged, so I shut off the valve to the tank, and just to be 100% sure, I removed the drain valve and emptied the tank, but it still rises to about 19 PSI when heating. This could be normal, just not sure. Thanks for any input.

Jim

 

Is there a level guage on your expansion tank?

Where is the guage at that your reading? You could have some air in your lines, there should be a bleeder at each radiator, you could try that. If youre heat is working fine, I wouldn't really worry about it. Im an HVAC mechanic too btw...mostly work on industrial stuff though.

 

You have air in the line. You'll need to flush the air and at the same time pump water into the line to charge. If you don't have the equipment to do it, it's best to let a professional.

Your unit will be more effiecient when it's done.

Joey

 

No, there is no level gauge on the tank - the tank holds 20 gallons, and each time I drained it, about 6 gallons came out, I was using a one gallon container to catch the water.

The gauge I am reading from is on the main outlet pipe directly above the boiler - it has a temperature gauge and a pressure gauge.

The system is working fine - I just don't recall the pressure rising up in the past as it is now, that's why I pose the question. I recall after I installed the boiler the gauge always read 15 - just something I noticed, and intend to keep an eye on.

Jim

 

jward,

Last week I opened the bleed valves on each radiator, and only a tiny amount of air escaped on the upper floor radiators. I also connected a garden hose to the lowest drain valve on the boiler and while street pressure was active, I let the boiler drain until no more air bubbles came out of the hose. (like bleeding brakes) There is no noise in the system while running - I have heard air in the lines before, almost sounds like marbles rolling around the pipes, but I no longer hear any of that.

Can you outline a procedure for purging air from the system?

Jim

 

That's basically it.

I don't believe you're getting enough pressure from your hose, though. A pump is normally used to put more psi into the closed loop. I think that's why you're seeing the fluctuation.

I don't think 4 or 5 psi on the high side is hurting anything. You're safe. If it's heating like you are used to, leave it be.

Joey

 

If the feed valve on your boiler is a Watts S1156F, it's set between 12 and 15psi. These feed valves don't last forever. If they fail in the open position then you can excessive pressure. Your pressure relief valve should be set at 30psi. I've worked on several hydronic systems and 20psi seems to be safe. I've even seen them a little higher withough blowing the pressure relief.

I worked on a system the other day. They had air in the system. I had to replace a couple air eliminating devices (high vents). I opted to replace the feed valve because I know they fail when they have been in service for a while. Well, after draining the system, doing the work, then purging the system I let the system run. This was a cold start mind you. The pressure at the beginning was 12psi. I let it run for a while and the pressure went up near 30psi. This will happen with a cold start. I just bleed off the excess pressure untill it stabilized. It must be ok because I haven't been called back on it. I suppose I could have changed the pressure tank, but I don't like throwing parts at a problem. I know that a cold start can cause the pressure to rise higher than normal.

It sound like you have a monoflow system. A monoflow system consists of a main with feed and return branches serving each convector. You can purge most of the air at the purge station at the main by connecting a hose to the drain, closing off the vlave just below the drain and opening the drain. You will have to add water to the system as you remove it. I try to have at least 10psi in the system at all times. If your feed valve is the Watts there is a lever at the top of it that actuated the "fast fill". If the feed valve is going to fail, it will usually fail after actuating the fast fill.

Like I said, this procedure will remove "most" of the air. On a monoflow system you also have to bleed each convector. On a continuous loop system, this isn't necessary.

You might also want to make sure that your air eliminating devices work. There are many different types, so I'd need to know what type you have to know what to do. Many new system us something like a Spirovent, which shouldn't need maintainance. Many systems I see use the high vent type. Thats a cylinder shaped thing with an 1/8 thread on the bottom and usually a small cap on top. Sometimes if water leaks out of the cap, people will close the cap, but then no air will escape. These high vents are usually installed on the air scoop on the feed side of the boiler, on the top of the boiler it's self and sometimes on the top of the return pipe, usually at the top of the vertical pipe above the circulator.

I know. I'm not being all that clear. I don't think you have to worry at this point. I would just keep an eye on the pressure. It's a good idea for all of us to keep an eye on our heating systems in the winter. That way if there is a problem you can solve it quickly.

Good luck!

 

wittom,

The feed valve is a B&G - it's stamped 15 PSI - I undid the union coupler, and temporarily connected a pressure gauge, I am getting just under 15 psi street pressure.

The boiler itself has a 30 PSI blow off valve. The system is indeed a monoflow.

I purchased this boiler 3 years ago from a plumbing supply house, and installed it myself. I called my sales rep today, and asked if the pressure should remain constant, or rise as the water is heated. He told me working pressure is between 9 and 22 pounds and it will vary with the water temperature, so its acting as it should.

Thanks for the input!

Jim

 

So, it sounds like your OK.

I know that when it gets really cold the pressure on a hydronic system will often be higher than it is whith average outside temps.

I like the hydronic systems. My house now has an old hot air furnace. I plan on changing it to a hydronic boiler. Some might say that I should just replace the furnace with a newer, more efficient one. I know the hot water systems better and I'm equipped to do the entire install myself. The HVAC folks are better equipped to do sheet metal work. I also will be using a zone to heat the domestic water.

It sound like you will get years of service out of your heating system. Being that you've installed the boiler your self, maintainance should be a breeze. You'll have a better understanding of the system than someone who paid a contractor to install it.

 

We moved into this house in 1994 and did major renovations. We were contemplating changing over to baseboards, but my wife liked the look of the tall radiators (the house is 98 years old) so we kept them - and am I thrilled we did. They hold heat a long time, and the rooms warm up quickly.

Several years back I got laid off, and soon after my boiler sprung a bad leak, it was too old (45+ years) to fix, and I got quotes between 5k and 8k to replace it. That was way out of my budget, so I went to a plumbing supply house, filled out a worksheet to see how many BTUs were needed, and left with a high efficiency, pilot-less boiler for $1600 - it took me 2 days to install. Nothing overly difficult. I pulled a permit at town hall, and had them inspect the job when I was done. The worst part was getting the new boiler to the basement, and then getting the old one out. The new one was 330 pounds, the old one was over 400. We had to break up the old one into 3 sections, and even then it was a bear. Yep, I did learn a lot about the system, and while I had it all apart, I added some quarter turn shut off valves to the main line so if I ever need to change the pump, or any pressurized parts on the boiler, I can isolate the boiler from the house loop and not loose more than a few gallons of water. Standard practice now days, but they weren't on it before.

Jim