Upgrade to fully pumped questions

[Simon Dyer]

Hi, I am going to upgrade to a fully pumped system using a Honeywell smart fit y plan.

At the moment feed and expansion are connected to the H.W flow and return near the cylinder in 22mm pipe.

I plan to alter the pipe work so it looks like this picture titled " Cold feed & expansion configuration on a fully pumped system" http://www.gasman.fsbusiness.co.uk/picture gallery.htm but in 22mm not 28mm.

Is there any reason for the cold feed entering from the underside and being 15mm or can I come straight in from the top using 22mm?

I will fit a auto by-pass valve which will link in to the return which is about 150mm away, is that ok or does it need to be a longer loop (its a cast iron ideal boiler c 1985)
Thanks in advance

 

[gas4you]

22mm cold feed is better than 15mm as it helps prevent pump over due to the greater volume of water in it. I believe the cold fill should ideally hold about 3% of the system volume water.

I would fit an air seperator, such as the Myson aerjec, instead of just using a 'H' pipe work set up and keep the pump as close as possible to the aerjec.

The aut bypass return is no problem, its the total distance of the circuit between the boiler and the auto bypass that can often be stipulated by the boiler manufacturer.

 

[Simon Dyer]

So an Aerjec where the F+E pipes are in the picture would that be about right ?

 

[gas4you]

Extend the flow from boiler to a point higher than the 3 port valve, then fit the aerjec with the boiler flow going in the top horizontal connection. The flow from the aerjec will be from the bottom horizontal connection under the top one to the pump, then the T for the auto bypass, then 3 port valve.

Vent to f&e comes off top vertical connection on aerjec and cold feed goes in bottom connection on opposite side to the flow in and out.

All will become clear when you see aerjec instructions, as will other piping arrangements they give as an option.

I also always fit an auto air vent on the flow to the hw cylinder at the highest point, even if in theory there could be no air collect there.

Don't forget that all pipe work off hw cyl has to be insulated for at least 1m or until it dissappears through wall etc.

 

[Simon Dyer]

Just looked at aerjec instruction pdf. and all is clear now
Thankyou