Gravity circulation how powerful

[Goldspoon]

I'm not a "householder in distress" but maybe somebody can assist. I have recently obtained my Hetas qualification and am next endeavouring to learn as much about "wet systems" as I can. A colleague and I discussed heat sinks (he dislikes them because he likes to save every last bit of heat).

The scenario:

A large wood burning stove heats a thermal store via gravity 28's and the thermal store gets hotter and hotter. The rad circuit pump fails (powercut) and there is no specific heat sink rad designed in.

Question is: As long as the TRV's on the upstairs rads are open will they (or some of them) get hot via convection and dissipate heat? Note that for this discussion the main rads flow and return 22's DROP from the store and go under the floorboards before getting to rads via last bit of 15mm - drop is approx. 24" for return and 36" for flow.

He says they will get hot and therefore will act as heat sinks anyway - just choose your rad and make sure the valves cannot be closed. I do not know - my knowledge of convection suggests that cold water falls through lighter hot water (e.g. hot rises). however if this is the case then surely the DROP I mentioned earlier has cold at the bottom and hot at the top - so why would any kind of convection take place?

On another note - is a heat sink rad designed to prevent the stove and primary circuit boiling by preventing the gravity circuit slowing to a halt? Or is it designed to prevent the end result of everything boiling (everything being the stove and the thermal store which surely might eventually boil).

Any good reading on this subject?

Thank you in advance.

 

[tamz]

The scenario:

A large wood burning stove heats a thermal store via gravity 28's and the thermal store gets hotter and hotter. The rad circuit pump fails (powercut) and there is no specific heat sink rad designed in.

Your plastic F&E tank

I believe plastic, if WRAS approved F&E tank, can withstand boiling water for a minimum 500 hours...

would soften with the risk of collapsing, spilling boiling water everywhere

Some very basic questions here from a supposedly qualified engineer Did you get the HETAS qual for good attendance or don't they actually teach anything? One would think systems would be covered, even if only the basics.

Question is: As long as the TRV's on the upstairs rads are open will they (or some of them) get hot via convection and dissipate heat? Note that for this discussion the main rads flow and return 22's DROP from the store and go under the floorboards before getting to rads via last bit of 15mm - drop is approx. 24" for return and 36" for flow. He says they will get hot and therefore will act as heat sinks anyway

Think about that one. How can the heat travel DOWN by convection? Your collegue is not sounding too clever is he?

You have a large? thermal store being filled with boiling water from an overheating stove. http://www.youtube.com/watch?v=UtKADQnjQmc

 

[Goldspoon]

You wrote: Did you get the HETAS qual for good attendance or don't they actually teach anything?

Why do you feel a need to be so rude? The Hetas course I passed is for dry systems i.e. fitting a wood burning stove that is not connected to water. It was 2-days and very comprehensive. The exam surprised me in its difficulty.

I am discovering everything I can about gravity systems because I desire to be an experienced engineer.

 

[45yearsagasman]

You wrote: Did you get the HETAS qual for good attendance or don't they actually teach anything?

Why do you feel a need to be so rude?
Get used to it mate.Some people on here just can't help themselves.

 

[5TIMES]

common sense will tell you that that radiator isnt going to work if it drops back down!! (how is that gravity)?

come on! shape up or ship out

are you from a plumbing/engineering back ground, or out of an office?

 

[picasso]

http://www.arca53.dsl.pipex.com/index_files/cont3.htm

 

[tamz]

I wasn't being rude, just stating the obvious.

 

[roguetrader]

tamz is right, some fairly elementary questions there mr spoon. sounding a little on the dangerous side to be let loose on the public just yet. keep your head in the books and get some new colleagues.

 

[transam]

You will find that on solid fuel the feed & exp tank should be metal galvinised , this will also apply to the over flow , copper ect not plastic !

Logic might also dictate that if one were to use a metal feed & exp tank & overflow , due to the possibility of boiling water , than perhaps one should be required to make sure the overflow terminates safely , further to that it would be wise not to sight a feed & exp tank over say a bed !! the installation I believe should also contain a safety valve !

 

[Goldspoon]

Thank you for your input. I shall refrain from requesting advice again.

 

[5TIMES]

another happy customer

 

[transam]

Thank you for your input. I shall refrain from requesting advice again.

Why ??

 

[Servotech]

On another note - is a heat sink rad designed to prevent the stove and primary circuit boiling by preventing the gravity circuit slowing to a halt?
Any good reading on this subject?

Thank you in advance.[/quote]



Or is it designed to prevent the end result of everything boiling (everything being the stove and the thermal store which surely might eventually boil).

This is the puropse of the gravity heat leak.

HEATAS regulations state a heat leak radiator suitable to work on gravity must be fitted.
And here is a major problem the manufactures do not make a suitable radiator for gravity anymore so we fit a normal radiator expecting it to work properly.
Of course it won't - it may or may not get hot; but it won't circulate properly.
HEATAS won't really help you they simply say that you're the plumber it's your job to make it work.
After lots of problems my firmhave now totally given up installing solid fuel boilers.

 

[Andygasman2010]

Thank you for your input. I shall refrain from requesting advice again.

Why ??

Probably because he feels like he's been talked down too as well as recieving advice. A familiar story in here

 

[Norcon]

The Honeywell TS 130 valve (and similar, I think Watts make one) are approved by HETAS for dumping heat in place of heat leak rads.
They can flush cold water through internal coils fitted inside the boiler or through an external plate heat exchanger heat dump arrangement.

The heat leak rad can also be controlled by an AVTA cooling valve which works in the opposite way to a TRV.
So you can have a very reliable controlled heat dump above a certain pre set temperature thus saving energy.