Unvented cylinder in house with low water pressure

[Agile]

Tony

That is absolutely what I mean, thank you.

But unfortunately John did not read it properly!

I will repeat it again in the hope that he will take a few minutes to read it again and hopefully comprehend it fully.

"""What ( I think ) Simon is trying to say is that an accumulator will boost the working pressure over what it would otherwise be when water is used!

An example is called for!

No acc. and if 10 li/min is taken from the mains then the dynamic pressure will fall to say 0.3 Bar.

Fit an accumulator and take 10 li/min and the dynamic pressure is "boosted" to say 1 Bar. With 4 li/min from the store and 6 li/min from the mains."""

Tony

 

[doitall]

You still don't understand Tony.

The dynamic pressure from the accumulator will always be lower than the standing pressure, yes it will increase the flow/volume as it is intended.

and in any case simond has changed his tune from last year, and is now going for a play on words. blubbering we call it.

According to simond's argument last year, is I fit an accumulator to an storage tank, I could supply the bathroom above.

 

[simond]

According to simond's argument last year, is I fit an accumulator to an storage tank, I could supply the bathroom above.

You've really lost me now. What storage tank?

I suggest you consider what Agile (and I) have said. At this point you may be able to claim a simple misunderstanding.

If we ignore your postings last year.

 

[doitall]

Must admit you have change your views on accumulators since last year,

You were adamant an accumulator would increase the pressure at the outlets above the standing pressure, having argued the point for weeks, are you now saying thats not what you meant.

 

[Balenza]

Agile wrote

No acc. and if 10 li/min is taken from the mains then the dynamic pressure will fall to say 0.3 Bar.

Fit an accumulator and take 10 li/min and the dynamic pressure is "boosted" to say 1 Bar. With 4 li/min from the store and 6 li/min from the mains.

Not a good example and shows how much simond knows when he agrees with it.
If the mains was supplying 10/L min with no accumulator fitted then why would it drop as low as 6/Lmin with an accumulator fitted and the store only capable of delivering 4L/min ?.
Stating dynamic pressures is irellevant in both cases if the flowrate remains the same.
An accumulator installation would be an expensive and pointless exercise with no benefit using the above explanation.

 

[WDIK]

Must admit you have change your views on accumulators since last year,

You were adamant an accumulator would increase the pressure at the outlets above the standing pressure, having argued the point for weeks, are you now saying thats not what you meant.

sorry I wont make sarcastic reference to the history, because that just not me and i know nothing of this bitter wrangle.
an accumulator could never boost pressure above the standing pressure of the incoming main only ever achieve static equalibrium.
the moment a draw off occurs then the pressure at the outlet is obviously reduced due to the restrictions to flow by the pipe work.
pressure continues to be supplied via the vessel as time extends.
clearly this pressure is not constant and probabley follows an exponential curve as the volume of the vessel becomes more depleted.
initial pressure would diminish back from full force down to a trickle over time and clearly is dependant upon the actual volume or capacity of the vessel.
a little like the linear expansion of a spring but as a negative reference being the base reference

 

[doitall]

The performance will start to dive the minute you open a tap.

As I said last year, an accumulator is ideal where the standing pressure is high, but the volume is low for whatever reason.

For example, we use them as top up vessels, where other means are not practical. you charge the vessel to 4 bar, and set the delivery to 1bar, and just top the accumulator up each year with its service.

 

[Agile]

If the mains was supplying 10/L min with no accumulator fitted then why would it drop as low as 6/Lmin with an accumulator fitted

An accumulator installation would be an expensive and pointless exercise with no benefit using the above explanation.

You seem to have chosen to miss the point!

In that example the mains was delivering 10li/min at a dynamic pressure of just 0.3 Bar.

With the accumulator sharing the load the same flow rate was achieved at a dynamic pressure of 1 Bar.

Tony

 

[doitall]

Tony, stick to repairing boilers

If the water in the accumulator is stored at say 1bar, the mains at 0.3bar will be static until the accumulator is depleted down to 0.3bar, therefore all the water will come from the accumulator.

 

[simond]

Half of Doitall's argument seems to be whether an accumulator boosts static pressure.

He says it does not. So does everybody else, including me. I am surprised we are debating a point that was never made in the first place.


If Doitall does agree that accumulators BOOST flowrate (in the same way that some of us believe the world is round), then WHAT EXACTLY does he think is pushing the water out of the taps faster?

Could it be PRESSURE? And if it is not PRESSURE what is it?

The Romans understood this principle, it is proving challenging to get the message across in 2008. Please put your ego to one side and admit you are wrong, then we can all move on.

 

[simond]

What I did say (about year ago) was that the accumulator would achieve a static pressure of the highest available to it over a time period.

In other words, if you found that the static pressure on Thames Water's network went up overnight, then the stored charge in the accumulator at 8am in the morning would be equal to the highest recorded pressure before the last drawoff.

In this instance the accumulator would hold a pressure higher than the water main at that point in time.

If Doitall has any further misconceptions I suggest that he reads the three page article on accumulators in last months 'Gas Installer' (the internal CORGI trade publication delivered to registered operatives).

Alternatively, if he is passing our area (on his horse, presumably) I will show him the raise in dynamic pressure on an accumulator fed system over a mains delivered one.

 

[Agile]

Hi guys, the static pressure at the outside tap (at ground level) as measured by the little pressure gauge I bought is just over 2 bar. Flowrate with the kitchen tap fully open is about 12 litres per minute,
Steve T

Although I did not repeat the static pressure I had based it on the OP's situation.

With the accumulator initially charged to 2 Bar then the mains might give 4 li/min and the accumulator 6 li/min when the accumulator has given up part of its output and has 1 Bar charge pressure left thus sustaining a dynamic pressure of 1 Bar at the shower outlet.

Why do so many people have so much difficulty understanding how these things work?

I also wonder why so many people immagine the whole volume of the accumulator is available for use. In reality the mostly useful volume is only about 1/3 of the total. Thats based on using it for a shower where a dynamic pressure of at least 0.6 Bar is required to give a proper velocity.

Tony

 

[doitall]

Half of Doitall's argument seems to be whether an accumulator boosts static pressure.

If Doitall does agree that accumulators BOOST flowrate (in the same way that some of us believe the world is round), then WHAT EXACTLY does he think is pushing the water out of the taps faster?

Could it be PRESSURE? And if it is not PRESSURE what is it?

The Romans understood this principle, it is proving challenging to get the message across in 2008. Please put your ego to one side and admit you are wrong, then we can all move on.

The accumulator is not boosting the pressure, it is adding more volume to the poor flow rate.

As you nor Tony can't grasp, the pressure is existing, through undersized or restricted pipes the flow is poor, if the installation pipework, within the building is capable of an higher flow rate, then an accumulator can increase the existing flow, but at the existing pressure.

The OP has 2 bar delivering 12 Ltrs, Now lets assume the installation pipework in the building is not restricted and can deliver more than 12 Ltrs, then the accumulator can add say another 6Ltrs, The pressure however will still be 2bar.

As I said Tony stick to what you're best at.

 

[Balenza]

Agile wrote

In that example the mains was delivering 10li/min at a dynamic pressure of just 0.3 Bar.

With the accumulator sharing the load the same flow rate was achieved at a dynamic pressure of 1 Bar.

The same flowrate ??.
If the dynamic pressure has risen to 1 bar then why has the flowrate not increased also ?.
What would be the point of fitting an accumulator if the flowrate remains the same ?.
Seems pointless to me.
Aah I see.
It allows other taps to be used simontaneously with say the shower running.

 

[Balenza]

Half of Doitall's argument seems to be whether an accumulator boosts static pressure.

If Doitall does agree that accumulators BOOST flowrate (in the same way that some of us believe the world is round), then WHAT EXACTLY does he think is pushing the water out of the taps faster?

Could it be PRESSURE? And if it is not PRESSURE what is it?

The Romans understood this principle, it is proving challenging to get the message across in 2008. Please put your ego to one side and admit you are wrong, then we can all move on.

The accumulator is not boosting the pressure, it is adding more volume to the poor flow rate.

As you nor Tony can't grasp, the pressure is existing, through undersized or restricted pipes the flow is poor, if the installation pipework, within the building is capable of an higher flow rate, then an accumulator can increase the existing flow, but at the existing pressure.

The OP has 2 bar delivering 12 Ltrs, Now lets assume the installation pipework in the building is not restricted and can deliver more than 12 Ltrs, then the accumulator can add say another 6Ltrs, The pressure however will still be 2bar.

As I said Tony stick to what you're best at.

You need to learn how to apply the Bernoulli's principle Doitall.
Its the only way you will ever unlock the secrets of the accumulator.