Looking for an explanation

[Steelmasons]

You were previously told that the hotter the water the higher the pressure. That is not correct.

 

[picasso]

Think we might be waiting a while.

 

[Steelmasons]

Indeed.

 

[Steelmasons]

Agile has a habit if disappearing when being asked for an explanation regarding the mis-leading advice he gives.

 

[Steelmasons]

The guys in the combustion chamber are waiting with baited breath as to how Agile managed a 10:1 turndown ratio on a Vaillant Turbomax.
Possibly Agile won't disclose this information due to the R&D which is understandable.

 

[Agile]

If you have 2 bar in an unvented cylinder when the water is at 20c what do you think the pressure will be at 60c ?

The pressure inside the cylinder when no water is being drawn is irrelevant to the user. Since there is normally no gauge, the user does not even know what it might be.

Immediately any water is drawn off then the pressure falls to a maximum of the set value of the pressure reducing valve on the cold feed [ or any lower pressure which may be supplied from the mains ]

Tony

 

[picasso]

I cant be bothered to argue with you.

 

[Steelmasons]

The pressure inside the cylinder when no water is being drawn is irrelevant to the user. Since there is normally no gauge, the user does not even know what it might be.

Immediately any water is drawn off then the pressure falls to a maximum of the set value of the pressure reducing valve on the cold feed [ or any lower pressure which may be supplied from the mains ]

Tony

Whether irrelevant to the user or not this thread was focused on water discharging from TPRV due to pressure issues.
I'm not sure how water being drawn from the cylinder has any relevance whatsoever???

 

[ianmcd]

Whether irrelevant to the user or not this thread was focused on water discharging from TPRV due to pressure issues.
Edited for being a twot , it is Friday after all

 

[Steelmasons]

Hey Ian , my name isn't Tony...

 

[ianmcd]

sorry Steel quoted the wrong post will sort accordingly

 

[picasso]

The pressure inside the cylinder when no water is being drawn is irrelevant to the user. Since there is normally no gauge, the user does not even know what it might be

This is a strawman argument, used by people that are losing a discussion, if the pressure inside the cylinder is greater when at a higher temp then the expansion vessel will also be at a higher pressure, open a tap and the flow/pressure will be greater until the ex vessel gives up its energy, hence the higher the temp the greater the pressure.

 

[Agile]

In a normal scenario when the cylinder is reheated before it is completely cold there will be little internal increase in pressure.

Even if it has somehow been allowed to become completely cold and then reheated without anyone ever turning on any hot tap, then the increased flow from the EXV would only be from about 9 litres and that would run out within a minute at a typical tap flow.

Tony

 

[picasso]

So now you agree that there is an increase in pressure and flow from the higher water temp ?

 

[Mottie]

We've not long been converted to an unvented hot water cylinder. It don't half flow out fast for the first five seconds or do when you first turn on the tap. Reading this thread has explained why - I think! Is it that as the water is heated up, the pressure cylinder stores the pressure of the expanding, heated water and then when you first open the hot tap, it forces the contents back into the system and out of the tap until the pressure reduces to whatever the cold water intake pressure is?