Pumped tank water to combi boiler.

[Shednight]

Hi people

Called out to a boiler service today and came across a Nocchi jetinox 45/43 pump that was fed by the tank in the loft then to the cold inlet to the combination boiler.

I know you're not allowed to pipe up the cold from a tank to a combination boiler but is this set up allowed?

I know from past experience working in schools and flats that you have break tanks and pump sets but in a domestic situation is this really allowed?

I look forward to hearing your views on this one.

 

[steadyon]

I've seen it done before. If you think about it, the FOV into the tank acts provides the air gap. The pump provides the pressure which would otherwise come from the mains. The only issues are:

a. Making sure the output pressure from the pump never exceeds what the boiler can cope with at the inlet - pressure reduction valve on output?

b. What happens if the tank gets emptied, although this is no different from a mains failure, and the boiler should cope.

 

[Centralheatking]

Shednight - your post is really good - combis and water pressure /tanks are right in my
ball park - see my profile.

A 4 inch air break is the spec - ie wcs tanks etc it is a wras specification and has been
enscrined in water law for the last 100 years or so - so a water tank with a ball valve
feeding a pump that feeds a combi is all ok.

The real question is why ? would anyone have a tank fed combi -it is nuts CHK

 

[stevetheplumber]

theres no reason you cant feed a combi from a tank provided you have the head i know at least one that runs happily on a tank
well how was we to know the electric shower was tank fed the tank is several floors above

 

[Mike Jackson]

Shednight - your post is really good - combis and water pressure /tanks are right in my
ball park - see my profile.

A 4 inch air break is the spec - ie wcs tanks etc it is a wras specification and has been
enscrined in water law for the last 100 years or so - so a water tank with a ball valve
feeding a pump that feeds a combi is all ok.

The real question is why ? would anyone have a tank fed combi -it is nuts CHK

I've done it in the past. Combi in a property with only 10 l/min incoming. Customer unable to have a shower as cold tap robbed the combi. 50 gallon tank in the loft and pump, problem solved.

 

[Shednight]

Shednight - your post is really good - combis and water pressure /tanks are right in my
ball park - see my profile.

A 4 inch air break is the spec - ie wcs tanks etc it is a wras specification and has been
enscrined in water law for the last 100 years or so - so a water tank with a ball valve
feeding a pump that feeds a combi is all ok.

The real question is why ? would anyone have a tank fed combi -it is nuts CHK

Yeah, I don't really have a problem with it and I guess if the tank emptied then the pump would just turn off as that's how it works. Was just seeing if it was really allowed by regs/manufacturer.

It's in a terrace house where around 7 houses share one water main so in full load at peak time the water pressure can get pretty low. The only downside of having the pump is its really loud.

thanks for everyone's views on this.

 

[Centralheatking]

Hiya MIke - I suppose my thinking is/was not to fit a combi in the 1st place. As you all know
I really doubt the combi system except installed in small homes and flats. Mind you we have
fitted many x 1000's over the years - but I still hate them CHK

 

[Shednight]

Yeah I'm not a great fan of combis either and this one was a ferroli aswell..