thescruff wrote on Jul 31^st, 2009, 9:07pm:


Not at all, like this you mean...  

That example has a bigger head than the one before it  

Not if Bill.  

Draw a storage tank.

Drop a cold pipe say 3mtrs to a bath tap, so the distance between the two points is 3m, now to increase the head I have to increase the distance between A, the tank and B, the outlet, I can do that by raising the tank, or lowering the outlet. Think of the top of the cylinder as a big shower rose.

See my first drawing on page one, and how The distance has increased between A, tank and B, highest point.

Now go back to the cylinder, the head is the pipe coming out of the cylinder, because it is the highest part of the system, if I could increase that distance I will increase the head.

The next highest point is the pipes on the roof joists, so if I could lower the top of the cylinder to the joist level, I have increased the head.

Look at the Monsoon pdf it explains it quite well.

Quote:



Never in a million years  

What bit don't you understand.

ok where am I going wrong,

house 1  
cws tank in loft
hot water cylinder on first floor

head at  bath tap 0.2 bar
head at kitchen sink 0.5 bar
head at basement sink 0.8 bar

house 2
cws tank in loft
hot water cylinder on ground floor

head at bath tap 0.2 bar
head at kitchen sink 0.5 bar
head at basement sink 0.8 bar

house 3
cws tank in loft
hot water cylinder in basement

head at bath tap 0.2 bar
head at kitchen sink 0.5 bar
head in basement 0.8

the head is determined by the distance between the tap
and the cws tank, I still cant see how moving the hot water cylinder
makes a difference to this ,


lemmings dont commit suicide, its an old wives tale

Quote:


As you can see by this example (I think)  .

The higher the outlet the lower the head.

Consider the next bit very carefully, the hot water pipe from the cylinder is an outlet the same as a tap.

Keep thinking, if you could lower that outlet a 1mtr  

Because the top of the cylinder is the maximum available head, it's where the hot water comes from.

If you connect a hose to the bath tap, 0.2 bar and say 10 Ltrs/min.

What do you think will happen in the kitchen, would you expect 0.5 bar and more than 10 Ltrs per min, you can't get more than the maximum.

The pressure for the whole house is determined by the length and size of the cold feed in the bottom of the cylinder, less the height of the cylinder.

Better add, if the top of the cylinder was below the pipes in the loft, then the pipes would be the head and not the top of the cylinder.

That's how it work, if all you get out of the top of the cylinder is 10 Ltrs/min, then that is the maximum anywhere in the system, whether its in the basement or the bathroom. Try to get more out and you suck in air, which would be likely if you exceed the head, your basement for example.

The original question, if you can think back that far, gave you the opportunity, to either lower the top of the cylinder to below the highest service pipes, raise the storage tank, or both.