using combi for hot water with system drained

[Simon F]

was wondering if it was possible to close flow and return to a combi then drain down to still use hot water. read some previous posts where the suggestion was to fit a loop between flow and return.
what purpose would the loop serve? would it not work to just close the flow and return prior to draining to maintain pressure in the boiler?
If an open loop would be needed for some reason, how will that correspond to new requirements for zoning?

 

[wazzer]

I have left the like that over night

 

[Halesowen1]

The boiler will not work unless it has correct water pressure in system, it is a safety feature, so by fitting a filling loop and connecting the flow and return you can then keep pressure up to allow for hot water use only.
I suppose the loop will also stop any chance of any problems if it fired up for heating, lets say for instance it fired up for anti frost etc.

 

[wazzer]

If its under pressure and he isolates flow and return drains off the boiler will still be pressured

 

[Halesowen1]

What if it looses pressure, you will need to repipe the lot just to put some back in.

 

[davebigpipes]

But if for any reason the ch struck up it would damage the pump and get hot quick

 

[Simon F]

But if for any reason the ch struck up it would damage the pump and get hot quick

thanks Dave, that makes good sense. it would have occurred to me to turn off the controls for Ch, but someone else could come along and turn it back on.

 

[wazzer]

I Assumed he was not going to leave it like that for ever thought it was while he did some work ...if it had a built in loop that would be handy...and so it dose not fire up remove link

 

[Simon F]

its not for any specific job, was a general question. I recently did a job were the system was to be drained for a few weeks while work was on going. it would have been useful to keep the hot water but not vital as the house was empty at the time. I had wondered about the possibility of keeping the boiler working for hot water, but wasn't sure so played safe and drained it all.
Thanks for the replies so far.

 

[dancinplumba]

intergas boilers operate with no ch water, like a multipoint if required

 

[Halesowen1]

Still not fitted one of these Intergas, I cannot get anybody to have one when I quote.

 

[Simon F]

But if for any reason the ch struck up it would damage the pump and get hot quick

got to rethinking this one, as most combi's are supplied with the internal bypass would that not act to protect the pump.
obviously you would not want it firing up for ch so would turn controls off anyway. but if it did fire up and was isolated at flow+ return would the bypass protect the pump and boiler from damage?

 

[AWheating]

putting a loop of pipework in will help keep the boiler working and give the pump somewhere to circulate heated water. If you do not give the boiler somewhere to remove some heat then it may overheat/not fire up.

the internal bypass may protect the pump but you are not removing heat, it would be safer to link in a loop or rad. you could drop a coil of speedfit on after an amount of pipework for example. Personally i would not rely on a machanical valve that could not be working or fail, air on the side of caution.

 

[davebigpipes]

I guess the auto bypass would save the pump from instant breakage but would still put it under quite a lot of load

 

[stevetheplumber]

you need tke loop as a heat dump for pump over run after dhw stops

 

[jtsplumbing]

Stevetheplumber has right answer !!😛unk: