Position of UVC expansion vessel?

[lakelandfolk]

Hello, Does an expansion vessel have to be fitted above the top of the cylinder? Could it be fitted lower down, say at half the height of the cylinder or even level with the base of the cylinder?

[JohnMo]

1 hour ago, lakelandfolk said:

Does an expansion vessel have to be fitted above the top of the cylinder?

Generally I would say no,

1 hour ago, lakelandfolk said:

Could it be fitted lower down, say at half the height of the cylinder or even level with the base of the cylinder

You end up with a few head aches, due to the position of the combination valve and the relief valves. Generally the expansion vessel will be directly attached to the combination valve and piping to the expansion vessel will rise from the Combination valve set.

 

The other thing that affects the position of the combination valve, is the relief piping and the limitations on piping length before and after tundish. You have a max of 600mm before the tundish and you are required to a minimum 300mm straight length below it before any bends

 

A typical install instruction says

 

"Expansion Vessels Installation

To prevent water stagnation and particulate accumulation affecting water quality, it is recommended that the expansion vessel be installed in the vertical orientation so that the fitting accommodating thermal expansion or a pressure surge is:-

1. bottom fed and upright; and

2. that the connecting pipework to the fitting:-

- rises continuously; and

- is kept to a minimum;

 

 

[ProDave]

The expansion vessel tees off between the outlet of the control group and the cold inlet to the cylinder which is at the bottom.

 

I can see no operational reason why it would not function correctly lower down, BUT it would mean you would have to partly drain the cylinder if the expansion vessel ever needs replacing.

 

Is there a legislative reason it cannot be mounted low down?  

[lakelandfolk]

Many thanks, The cylinder is going to be just 1165mm high so I can see that the correct positioning of the tundish will pretty much rule a lower position for the EV

[Jenki]

4 hours ago, JohnMo said:

Generally I would say no,

You end up with a few head aches, due to the position of the combination valve and the relief valves. Generally the expansion vessel will be directly attached to the combination valve and piping to the expansion vessel will rise from the Combination valve set.

 

The other thing that affects the position of the combination valve, is the relief piping and the limitations on piping length before and after tundish. You have a max of 600mm before the tundish and you are required to a minimum 300mm straight length below it before any bends

 

A typical install instruction says

 

"Expansion Vessels Installation

To prevent water stagnation and particulate accumulation affecting water quality, it is recommended that the expansion vessel be installed in the vertical orientation so that the fitting accommodating thermal expansion or a pressure surge is:-

1. bottom fed and upright; and

2. that the connecting pipework to the fitting:-

- rises continuously; and

- is kept to a minimum;

 

 

That course was worth it's money👍. Nailed it.

[ProDave]

What I am failing to understand is the height of the EV can be lower just by teeing off the pipe between the control group and the cylinder water inlet boss a bit lower down.  That does NOT affect the positioning of the control group or the tundish or any other pipeowrk.

 

So I ask again from any of the professional plumbers on here, what harm does it do if you tee off the cold pipe lower down and mount the EV alongside the tank?  Everything else being equal, EV mounted upright with connection at bottom etc.