CH PUMP LOCATION

[madjeff]

About to upgrade to to unvented HW System, but keeping vented boiler system. Previously my pump was fitted to the return line upstairs near cylinder (boiler installed on ground floor) The logic in fitting to return line was the temperature was lower, thus allegedly pump duty/life longer, seems reasonable to me. However current thinking is to fit it close to boiler on hot feed side. Can anyone tell me why. On a closed loop system can't see it makes any difference so why put it at the highest temperature spot.

Appreciate your expert views

 

[gas4you]

Fitting the pump on the flow, after the open vent, then the cold fill (that order is important, creates a positive pressure system.

In theory you then have less chance of anything being sucked in by the pump.

Change it to this system and keep it all up to date.

The temp of the water through it won't make any difference to its life cycle, but the cleanliness of the system water will.

 

[madjeff]

[Fitting the pump on the flow, after the open vent, then the cold fill (that order is important, creates a positive pressure system.]

Thanks for that good point, what do you mean by after the open vent then the cold fill? Normally this is just a single pipe with the fill or vent teed off isn't it.

 

[seco services]

what do you mean by after the open vent then the cold fill? Normally this is just a single pipe with the fill or vent teed off isn't it.

pipe comes from boiler then the vent tees off then the cold feed tees off then the pump.

 

[Paul Barker]

Also pays to expand the flow at the open vent by sizing up one then back down. the reasoning for this is the pump draws a vacuum at the T where the open vent is taken from, which makes it hard for air bubbles to float up the open vent. Expanding the water at this same point counters that effect freeing the bubble to be released.

there is of course a part which also does this job called an Air Jeck.

 

[madjeff]

Thanks for info guys understand the message now. Unfortunately i'm a pipe short as currenly the vent is teed off the HW return at the cylinder up in the airing cupboard. (gravity system)The feed is in 22mm which runs to the boiler pump for CH so I could use that for the new vent, but would be difficult to run a new pipe for feed (assume 15mm) from attached garage to loft. The other alternative is to go fully non vented, but reluctant to go that route as pipes in concrete below ground floor and who knows how good a job that was when it was done. Any ideas on alternative position for feed I currently have 2x28mm coming down from airing cupboard and 4x22mm coming from upstairs and downstairs heating circuits + the 22mm cold feed I mentioned earlier.

 

[Agile]

A combined vent and feed pipe is quite acceptable and I would say usually less prone to problems.

Putting the pump on the return can suck air into the system through leaking pump valves and that will do a lot of damage to the system.

Tony

 

[madjeff]

A combined vent and feed pipe is quite acceptable and I would say usually less prone to problems.

Thanks for that, one problem out the way. If I run the 22mm to vent and tee off for the feed at upstairs floor level (about 3 metres below tank) would that be the best position?

 

[gas4you]

Get an aerjec as previously suggested. Should only be about £10-£12.

Problems and installation solved in one go.

 

[Agile]

If I convert to a combined feed and vent I usually connect a 15 mm feed via a horizontal pipe just below the bottom of the F&E tank.

This prevents pumping over and overcomes any blocked feed pipe on the old pipework.

Tony

 

[madjeff]

Ok thanks very much for help, much appreciated.