primary flow with cold feed and vent into it?

[mutley racers]

Hi guys, today my boss has told me to pipe up a boiler with the primary flow having the vent pipe and cold feed going into it.

Is this ok?

The pump is on the flow pumping downwards. He says that if the cold feed goes into the return then the pump will pump the water through the coil and back up into the F& E and then it will all heat up and boil in F&E.

Is this correct or can you have the the vent at the top of primary flow and cold feed into the return?

Thanks for your help

Regards

Lee

 

[stevetheplumber]

close coupled near the suction side of the pump is normal

 

[mutley racers]

Does that mean they cal all go into the primary return then?

 

[Bernie2]

Have a look at J Mac Pump, Technical guides for vent and feed positions. Also Randell Grundfos do a good guide as well. Basically the traditional way is cold feed on return and vent on flow before the pump.

A lot depends on what the boiler manufacturer recommends.

After all, if you do it their way and the boiler goes pear shaped you've got a claim.

Do it your own way and you have got to prove it didn't upset the boiler.

 

[radswilldo]

On moden open vent systems the advice is for a h system/plan(i think thats the term) with the pump, vent and cold feed all on the flow, the vent is first then cold feed(maximum gap between both 150mm) followed by pump. This system is favoured due to positive pressure, The pump should be horizontal or pumping up, pumping down is frowned upon due to the possibillty of air entering the pump.

 

[Plucky]

This system is favoured due to positive pressure, The pump should be horizontal or pumping up, pumping down is frowned upon due to the possibillty of air entering the pump.

I have always been taught pump down,

How could you possibly make an H pattern with the positive side of the pump facing up. The Vent and feed need to be in the negative side of the pump.

 

[newbie1]

rads is right pumping down raises the possibility of airlock though not written in stone better to have pump drawing from primary flow and then pumping up then round to the 2ports or 3 port

 

[Plucky]

I could say pump up could increase chance of pump over. If you have the pump up then it is not an H pattern. Its called an H pattern because the pipework is in the shape of the letter H

 

[radswilldo]

Its called h pattern because of the vent and cold feed connection, the pump is after. In the real world (cylinder cupboard) you may not have the space to put pump on horizontal, that leaves up or down, its still a h plan. The cold feed is the neutral point, between the cold feed the pump is under negative pressure, from the pump to the cold feed there will be positive pressure. By placing the vent before the cold feed within 150mm will locate the vent also at the neutral point. This has been tried and tested. If you go beyond 150mm,then the vent will be under positive pressure. Read any plumbing design guide, i'm sure you have some. Ring grundfos, willow etc about pump installation.

 

[Plucky]

Yes I understand that. Here is a typical H pattern with pump facing down. And I have never heard of any issues with drawing air in woth this set up although I can see why you might think it could happen.

 

[Bernie2]

Its the way recommended for high pressure systems.

 

[radswilldo]

I said frowned upon, not declared outlawed. As I said, seak to pump manufacturer's, visit website or ring the tech if your an APHC/Ciphe member