Is the flow going into bottom of hot water coil better?

[Readingplumber]

Hi,

I have been thinking based on the science - heat rises -

1) Would there be more benefit of connecting the flow to the bottom of the cylinder coil rather than the traditional top on a pumped central heating system? - only draw back i can think of is will be a bit more fiddly to plumb in?

2) if you connect a radiator same way - flow bottom return out the top opposite corner would that be more effiicent - i know it would look ugly!

Thanks

 

[WHPES]

1, flow should come in at the top - you want the water hottest towards to the top of the cylinder.

2, no because the top corner above the bottom inlet would not heat up properly as the hot water would rush to the diagonal corner. I have a customer with all the rads done in this way and one top corner is always cool. Rads are most efficient if hot comes in at the top and out at the bottom at the other side. How ugly depends on your skill in pipe bending and neatness.

 

[charlie frederi]

1, flow should come in at the top - you want the water hottest towards to the top of the cylinder.

2, no because the top corner above the bottom inlet would not heat up properly as the hot water would rush to the diagonal corner. I have a customer with all the rads done in this way and one top corner is always cool. Rads are most efficient if hot comes in at the top and out at the bottom at the other side. How ugly depends on your skill in pipe bending and neatness.

Hi
I agree with WHPES

 

[Billy Bob Bob]

Hi,

I have been thinking based on the science - heat rises -

1) Would there be more benefit of connecting the flow to the bottom of the cylinder coil rather than the traditional top on a pumped central heating system? - only draw back i can think of is will be a bit more fiddly to plumb in?

2) if you connect a radiator same way - flow bottom return out the top opposite corner would that be more effiicent - i know it would look ugly!

Thanks

dont want to be rude or insulting mate but why?flow goes to the top for a reason,why would you want to?

 

[sparky]

Telford tempest unvented cylinders flow is in through the bottom of the coil and the return out through the top. Not sure why.

 

[oldplumber]

heats up more of the water in the cyl to max temp

 

[LIFES A GAS]

Servowarm piped most of their clyenders that way (flow at bottom) not sure if there are any advantages or not.
Martin

 

[migoplumber]

and most european rads are pipe up flow-return to bottom and top opposite corners - ever so slightly more effieceint but so much more uglier. the difference is printed on most radiator data sheets.
the same applies for cylinders flow at bottom, but because the heat rises, exits at the top of coile quicker - less heat transfer.
bit weird the cylinder coil one. dont like it myself, physics dont work that way in my brain - hoping for a better post below mine!!

 

[WHPES]

Think Stratification (i.e. the nearer the top of the cylinder the warmer the water.

Therefore you want to bring the water at the top up to temp first rather than bring the water at the bottom of the coil warm and take longer about it as water being heated at the bottom convects upwards and mixes with the cooler water above. Putting hot at the top heats up the water working downwards which is what you want.

 

[stevetheplumber]

on a fully pumped sealed system i dont think it makes much diffence realy its a hangover from gravity fed systems only difference is its easier to pipe as you get the air vent in at the top and more space for motorised valves

thinking about this in theory flow in the bottom would actually be more efficent as theres greater heat transfer the greater the temp difference
ie the hot flow against the colder lower part of cylinder in practice i doubt its a meausable differenc

 

[Renewable M]

Hot in to the TOP of the coil. The reason is simple..... the system water is cooled as it travels around the coil to the bottom of the cylinder. So the return is cool.

If you pipe it up in reverse, as the cylinder cools the boiler return will have a proportionately higher temperature (pulling heat out of the cylinder) so toward the end of the heating cycle, boiler cycling is very likely, and as we all know that a bad thing.

Theres your answer.