Increasing operating pressure on an unvented cylinder

[cushy81]

Hi all,

I have a 300L Telford Tempest unvented cylinder in my basement. I live in a tall 4 storey Edwardian semi-detached - the height of the property does affect our water pressure to the bathrooms on the 2nd floor - the water is having to travel a hell of a long way!

The water pressure coming into the property is 4.5 bar. However, the Tempest cylinder is constrained to an operating pressure of 3 bar. By the time the water gets to our showers its running at around 2 bar of pressure and a flow rate of 10 litres/minute.

Id like to increase the operating pressure of the unvented cylinder to 4.5 bar to improve flow rate. I know this will void warranties etc but is it actually possible or advisable? I know most steel cylinders are pressure tested to 15 bar, so it I guess the cylinder shouldn't split - but has anyone actually tried this successfully in larger properties? Or is there a better way so I don't have to void every warranty I have? The Tempest is cylinder is about 4 years old.

Any advice gratefully received!

Cheers,

Tom

Mods note:

To comply with regulations in the UK unvented cylinders of this size can't be altered from the manufacturers specification in this way.

Whilst unlikely the potential damage from a cylinder is similar to a gas explosion therefore we will not allow posts about modifying them on the forum.

Regards

Mod

 

[dilalio]

Increasing pressure will not increase flow.
You need larger bore pipework.

 

[MeldrewsMate]

The simple answer is that you must not adjust the operating pressure.
I don't know why you had the Tempest installed in the basement, but moving it to the 1st or 2nd floor will give you better pressure at those levels and, being closer to the main points of hot water use, give less time lag for the hot to come through.
How does the safety relief discharge get to the outside if the cylinder is in the CELLAR ??

 

[Dan Robinson]

moving it to the 1st or 2nd floor will give you better pressure at those levels

Care to explain?

 

[picasso]

Have look at fitting an accumulator.

 

[oilboffin]

Fitting it upstairs won't give more pressure

 

[bernardgreen]

Fitting it upstairs won't give more pressure

If the cylinder at 3 bar is in the cellar then the pressure at a higher floor will be 3 bar minus the "head" of the height of that floor above the cylinder.

If the cylinder at 3 bar is in the loft then the pressure at the lowest floor will be 3 bar plus the "head" of the height of the cylinder above the floor.

1 bar is the head created (or lost ) by a height of 32 feet

 

[cushy81]

The simple answer is that you must not adjust the operating pressure.
I don't know why you had the Tempest installed in the basement, but moving it to the 1st or 2nd floor will give you better pressure at those levels and, being closer to the main points of hot water use, give less time lag for the hot to come through.
How does the safety relief discharge get to the outside if the cylinder is in the CELLAR ??

The cellar has steps going up to the garden so the pipe for the safety relief discharge is drilled through the wall into a drain outside. Boiler, tank and expansion vessel are all in the cellar (which is tanked etc).

 

[cushy81]

The simple answer is that you must not adjust the operating pressure.
I don't know why you had the Tempest installed in the basement, but moving it to the 1st or 2nd floor will give you better pressure at those levels and, being closer to the main points of hot water use, give less time lag for the hot to come through.
How does the safety relief discharge get to the outside if the cylinder is in the CELLAR ??

So will a Tempest steel cylinder not operate at 4.5 bar even though it's been pressure tested at 15 bar? I ain't moving my whole set up upstairs but cheers for the advice!

 

[cushy81]

Have look at fitting an accumulator.

Thanks will do

 

[cushy81]

Have look at fitting an accumulator.

I've also investigated a Stuart Turner flomate pump but I would still be restricted by the operating pressure in the cylinder. The problem is the height of the house. The water has to travel 4 floors so my understanding would be more pressure would help increase flow rate to the showers on 2nd floor. I could be wrong though.

 

[dilalio]

OP said....

By the time the water gets to our showers its running at around 2 bar of pressure and a flow rate of 10 litres/minute.

2 bar pressure at the outlets is ample.
10 lpm is not.
Problem is distribution pipework.

 

[endecotp]

It sounds like you have a pressure gauge. I’d be interested to know what happens to the incoming mains pressure (e.g. at the kitchen cold tap, outside tap etc.) when the upstairs hot tap is on.