Gravity Hot Water

[pault123]

Doing some work in a utility room - owner has oil fired boiler with gravity HW & pumped heating.
He wants to raise height of door opening which would involve raising Primary Flow & Return to cylinder, this would create an inverted loop of say 100 mm near the boiler for the width of the door frame before dropping down to the original pipework (which then has a near horizontal run of about 10 metres) to the cylinder.
Whats the best solution bearing in mind I can't get another pipe through from here to the cylinder (laminate floors etc).
Was thinking AAV's at high points - and either a two pump system with HW pump on return near boiler and non return valve on Heating (Flow ??), or 2 2port valves and 1 pump fitted on returns near boiler. Concerned about best layout to avoid pumping over or pulling air in. Also they always say don't fit motorised valves to return, but if pump is after them whats the problem ?
OV is off primary flow and cold feed off primary return as standard.
I presume there is no chance of the gravity circuit working with an inverted loop and longish horizontal run.
Do I need to check with manufacturers that the boiler is suitable for pumped primaries (not sure what boiler it is at the moment)

Thanks
Paul

 

[Billy Bob Bob]

cant quite picture whay you meen but flow and return must never drop into a u then rise again on a gravity circuit,or fully pumped coming off a boiler

 

[pault123]

That is what I'm being asked to do. I know its not ideal but with AAV's its not so much of a problem on fully pumped surely ?

 

[Billy Bob Bob]

not unless the boiler ever trys to vent and cant,you then have a oil powered rocket!!!, potentially

 

[pault123]

Just to clarify the heating flow & return leave the floor standing boiler and run down under the ground floor to later rise to 1st floor somewhere else in the property. The primaries rise from boiler over door frame and then 10 metre horizontal run to cylinder on 1st floor.

not unless the boiler ever trys to vent and cant,you then have a oil powered rocket!!!, potentially

This is why I'm asking - surely if the boiler stat fails for example it will still vent through an inverted loop and any trapped air is released by the AAVs ?

 

[Billy Bob Bob]

Just to clarify the heating flow & return leave the floor standing boiler and run down under the ground floor to later rise to 1st floor somewhere else in the property. The primaries rise from boiler over door frame and then 10 metre horizontal run to cylinder on 1st floor.

but vent and cold feed on the primaries this is were your problem is,they cant drop and rise

 

[pault123]

I was told some time ago by a Potterton (I think) tech support guy that it was OK on a fully pumped system but that may have been in connection with a boiler with an overheat stat !
Would you agree with that ?

 

[Billy Bob Bob]

I was told some time ago by a Potterton (I think) tech support guy that it was OK on a fully pumped system but that may have been in connection with a boiler with an overheat stat !
Would you agree with that ?

yes baicaly o/heat stat would give protection you can also pressurise if one of these fitted

 

[pault123]

So basically I've gotta tell him it can't be done and he'll have to continue to stoop to get through the door !
He was talking about a new boiler a while back, but apparently may be looking to move after this work is completed. A new boiler would give him more flexibility with pipe arrangements.
No other options ??

 

[Billy Bob Bob]

So basically I've gotta tell him it can't be done and he'll have to continue to stoop to get through the door !
He was talking about a new boiler a while back, but apparently may be looking to move after this work is completed. A new boiler would give him more flexibility with pipe arrangements.
No other options ??

tell him a new boiler and de scale will make it more sell able,people are not stupid first thing they will see=clapped out old boiler

 

[pault123]

Ok thanks for replies I've been asked to do this before & said it couldn't be done, but was put on the spot with a phone call the other day.
Initially said yes but then started to think more about it afterwards. I'm pretty sure this boiler won't have an overheat stat.
So will break bad news to him tomorrow !
Cheers
Paul

 

[WHPES]

Perhaps I'm mistaken but could you retrofit an overheat stat to the boiler and convert it all to a fully pumped S plam system?

 

[pault123]

Perhaps I'm mistaken but could you retrofit an overheat stat to the boiler and convert it all to a fully pumped S plam system?

That may have been a possibility, but to be honest I think it was going to be an aggro job anyway, so told client there could be safety issues.
He was disappointed about his short door frame, but against that he's saved some money, and he's happy there are no potential comebacks when he sells 😉.

Thanks for the input though.