Converting open vent to sealed system...whats required?

[martyc]

Hi,
Been advised (here!) that convertin to a sealed system might not be a bad idea.
http://www.diynot.com/forums/viewtopic.php?p=743604#743604

I like the sound of this as i assume the system would be pressurised and less likely to ever have air in it and i suppose it will be quieter??(can be noisy on heat up and cool down)

Can someone advise me on the general steps taken to convert to a sealed system?...so i can see if its worthwhile doing now or if i should leave it till after the winter.

My hot water cylinder is also open vent...would i have to change this aswell?

Many thanks,
MArty.

 

[chrishutt]

First you must ensure that your boiler is suitable for a sealed system. Does it have an overheat stat? Do the manufacturers approve its use with sealed systems?

Don't expect a sealed system to solve every problem with your system. You may need to flush it out and chemically clean it, so best left till the warmer weather.

No need to alter the hot water set-up, but the heating system will operate under higher pressures and this may lead to leakage on old rad valves and other weak points in your system, including possibly the heat exchanger coil in your hot water cylinder.

 

[martyc]

Not sure if the boiler is compatible...will check!(its an ideal classic NF 50)

I just did some reaind and understand you need an expansion tank that "absorbs" the increased pressure when system is heated.

I suppose what i really would like to know are the advantages of such a system over a vented system before i look into it any further.
Cheers,
Marty.

 

[bengasman]

Better heat exchange, at least theoretically.
No evaporation, no limescale build up and up and up.
No continuous access to oxygen, less sensitive to corrosion, though still need inhibitor.
Once the air is out, it will never get back in.
Due to pressure, any airlocks are easy to get out unless design or installation is really bad.
Often better flow.

 

[ChrisR]

I told you in the other thread that you have to have a kit fitted to the boiler (by a corgi reg'd engineer) first.
That's if it's not obsolete.

Then see the boiler instructions, about the pressure vessel, filling loop and pressure relief valve you'll need.
If the pipes/rads/rad valves are old, you're liable to get leaks.

You can't seal a normal HW cylinder;, needs a special type, again fitted by a registred engineer, this time for Unvented systems. Not DIY!.