What are these??

Ross_24

These are on an old oil-fired, hydronic system. They have me stumped. What are they?

Seem to be something for expansion but they have coin vents on the end of the pig tail which makes me think air elimination.

Mark Eatherton

I think it is an early style of water hammer arrestor. The vent is not to let air out, but to let air in, which is compressible. The spring design, theoretically, will absorb any hydraulic shock caused by quick closing solenoid valves (dish washer, clothes washers ice machines, etc). They are normally connected to the potable water system,and not the closed loop hydronic system.

ME

Ross_24

Mark Eatherton said:

I think it is an early style of water hammer arrestor. The vent is not to let air out, but to let air in, which is compressible. The spring design, theoretically, will absorb any hydraulic shock caused by quick closing solenoid valves (dish washer, clothes washers ice machines, etc). They are normally connected to the potable water system,and not the closed loop hydronic system.

ME

Thanks, Mark! It's very odd, because this is the second home lately where I've seen these on the hydronic system not the domestic.

ChrisJ

Perhaps they are being used for thermal expansion instead of a single compression tank?

Robert O'Brien

Mark Eatherton said:

I think it is an early style of water hammer arrestor. The vent is not to let air out, but to let air in, which is compressible. The spring design, theoretically, will absorb any hydraulic shock caused by quick closing solenoid valves (dish washer, clothes washers ice machines, etc). They are normally connected to the potable water system,and not the closed loop hydronic system.

ME

Correct, quite common around here. The vent is for draining them as they fill with water over time

Mark Eatherton

Ross said:

Mark Eatherton said:

I think it is an early style of water hammer arrestor. The vent is not to let air out, but to let air in, which is compressible. The spring design, theoretically, will absorb any hydraulic shock caused by quick closing solenoid valves (dish washer, clothes washers ice machines, etc). They are normally connected to the potable water system,and not the closed loop hydronic system.

ME

Thanks, Mark! It's very odd, because this is the second home lately where I've seen these on the hydronic system not the domestic.

Strange Ross... Can't really see it doing any good on a hydronic system unless there was hammering, like when happens with Honeywell valves are installed backwards... The applications I've seen were domestic.

ME

Ironman

The remnants of Grandpa's still?

Mark Eatherton

ChrisJ said:

Perhaps they are being used for thermal expansion instead of a single compression tank?

Now THAT would really mess with the PONPC. I've seen jobs that had two expansion tanks on it. One in the basement near the mechanical package and one in the attic. The pumps kept switching between positive and negative discharge. I eliminated the tank in the attic and pumps started working as they were supposed to, providing all positive pressure differential.

I seriously doubt that these devices would react much with a slow pressure increase, as opposed to stoping mechanically induced water hammer.

ME

ChrisJ

Mark Eatherton said:

ChrisJ said:

Perhaps they are being used for thermal expansion instead of a single compression tank?

Now THAT would really mess with the PONPC. I've seen jobs that had two expansion tanks on it. One in the basement near the mechanical package and one in the attic. The pumps kept switching between positive and negative discharge. I eliminated the tank in the attic and pumps started working as they were supposed to, providing all positive pressure differential.

I seriously doubt that these devices would react much with a slow pressure increase, as opposed to stoping mechanically induced water hammer.

ME

Well, they do allow room to expand without pipes bursting, so I donno?