System Pressure

[trumpeterb]

I have a question regarding system pressure with my Eko 40 boiler setup. I have read and been told that the system should be set around 12 pounds of pressure. Does this mean 12 pounds when the boiler is cold or hot? Currently, I have 12 pounds of pressure when the boiler is hot, and when it is cold, the pressure drops to 0. If I boost the pressure to 12 pounds when it is cold, it jumps to between 25-30 pounds of pressure when it is hot.

 

[Nofossil]

I hope someone with actual plumbing knowledge answers this, but it sounds to me like your expansion tank is undersized or waterlogged. I don't think you should be seeing that kind of pressure variation. I'd be happy with 10-15 cold and 15-20 hot.

 

[Singed Eyebrows]

I have a question regarding system pressure with my Eko 40 boiler setup. I have read and been told that the system should be set around 12 pounds of pressure. Does this mean 12 pounds when the boiler is cold or hot? Currently, I have 12 pounds of pressure when the boiler is hot, and when it is cold, the pressure drops to 0. If I boost the pressure to 12 pounds when it is cold, it jumps to between 25-30 pounds of pressure when it is hot.

I'm far from being a plumber, that said, how much water is in your system & how much expansion do you have? I start with about 8 psi & go to about 13 with 750 gallons total with about 120 gallons expansion acceptance. I do this to stay under 15 psi. The 12 pounds you hear is cold pressure. Cold is relative though & depends where you are starting from & going to temp wise as to how much ex. tank you need along with system volume. The Amtrol charts always give a starting temp & end temp. As the Mod. says it sounds like not enough tank or waterlogged tank. Run the numbers at www.amtrol.com, Randy

 

[stee6043]

Another factor here is pump performance. I highly doubt the circ pump(s) you have are designed to run at anywhere near 0psi.

I find higher pressures will tend to help with air elimination in your system. Currently I'm running 17psi cold and I expect I'll hit 26-27psi at full temp. Last year I ran 14psi cold and typically maxed out at 25psi with 180+ water in both tanks. I have 120+ gallons acceptance on my expansion tank...

 

[in hot water]

On a closed loop, pressurized system, with the boiler cold, you need enough pressure to assure few psi at the highest point in the system. Typical residential systems fill to 12- 15 psi. If cannot hold 12 psi cold, you may have a small leak? Does the pressure relief valve ever discharge? You may have an undersized or waterlogged expansion tank. With the system at 0 psi, charge the expansion tank to the pressure you intend to fill the system to.

 

[jebatty]

If the pressure is dropping to 0 when the system is cold, the air scoop/vent likely also is admitting air into the system due to the vacuum being created as the system cools. You don't want to be admitting air into a closed system due to corrosion issues. You need a positive pressure remaining when the system is cold. Good advice in previous posts.