Converting to sealed system and expansion vessel vessel sizing

[westyvip]

Hi,

I have just started a job where the system requires converting to a sealed system as customer wants to remove tanks from loft. I am just wondering where the expansion vessel is best fitted? Boiler is in garage so plenty of space. Does it need fitting on return? Never actually converted a system before so just a bit unsure! Also, how do i calculated the required size of expansion vessel? what size should i fit?

 

[SimonJohns]

Dont do anything til you have read MI and see if boiler is compatible with sealed system

if it aint, DONT BOTHER

 

[westyvip]

it is, its only a few year old glowworm ultacom hxi. Im confident doing the work, just not on sizing the vessel!

 

[westyvip]

MI actually states to fit on flow near inlet of pump..

 

[desrob]

MI actually states to fit on flow near inlet of pump..

i have had this conversation on here and got accussed of not been competant because i asked the question should expansion go on flow or return,mi said flow but the return seemed to be favourable to most as for sizing there are sizing charts etc to use not to difficult

 

[SimonJohns]

id bet on about 18L
you can buy kits that come with combined prv, filling loop and expansion vessel

 

[westyvip]

any downside to oversizing vessel? Reason i ask is because gloworm ultracom 2 sxi system boiler only has 8 litre expansion vessel in.

 

[SimonJohns]

any downside to oversizing vessel? Reason i ask is because gloworm ultracom 2 sxi system boiler only has 8 litre expansion vessel in.

Won't hurt anyone. Just take up more space

 

[tamz]

You will probably find an 8 or 12 litre will do most houses.
You can work it out roughly from here.
http://www.google.co.uk/url?sa=t&rc...sg=AFQjCNGayyU7so__xBy_TpLrPiZV2XjEWw&cad=rja

 

[Mbear]

It matters not a jot where it goes tbh.

My general rule of thumb though is always put it in the return or if it's going on the flow then id fit it between boiler and zone valves. Ie not after the zone valves on the flow

8litre does most 2/3 bed flats/houses, if it's quite a large house then I'd go for 12litre

 

[tamz]

Fitted on the return keeps the heat off it a bit and helps the diaphragm last a bit longer but it can be fitted on the flow or return doesn't make much odds.

 

[Best]

Yea, fit it on return if possible - less heat & also recommended often by expansion vessel makers who usually say " on return, on suction side of pump & no valve to be put on pipe to vessel. " Also, some say to use an auto vent on pipe to vessel if it is on a high position, where air cannot get out.
Better the vessel is close to boiler & PRV should be at boiler always. Use the kit as has been said & that may make it simple, but the filling point can be anywhere handy on system, provided a pressure gauge is there too.

 

[GQuigley67]

also if the vessel is slightly oversized, then there will be little or no increase in pressure