Draining down a Combi boiler, any tips??....VENTED OR NOT???

[dude_diy]

Hi any advice is much appreciated. I have a Baxi 105 HE boiler and will shortly be needing to drain the central heating system down to reposition a few rad's as my kitchen is being extended. Ive taken a chance before and drained the system down and re filled on my own without problems before but, my questions are:

How do I know if I have a vented or unvented system?
Whats the difference?
Is there a difference when draining / re filling vented and unvented?
Is there any special precausions I should take or do?
Any additional advice?

Any advice, comments or pointers are greatly appreciated, last thing I want to do is cock my central heating system up.....the Mrs really would KILL me!

Cheers in adavnce

Dude diy

 

[Goldspoon]

I would say not to worry - it's straightforward.

How do I know if I have a vented or unvented system?

Combi's are unvented

Whats the difference?
:

Unvented means heating system is sealed. Vented systems are open to air via 22mm copper pipe that goes up into loft and overflows into a tank if pressure builds up. If pressure builds up in an unvented system there are safety devices to release it.

Is there a difference when draining / re filling vented and unvented?
:

Procedures are different because the kit is different (e.g. re-fill combi using filling loop but re-fill vented by switching a gate valve or iso valve on or untying a ball valve in your F&E loft tank. Basically the principle is the same. More likely to get airlocks when re-filling vented.

Is there any special precausions I should take or do?
:

Switch boiler off and take fuse out if chance of somebody else switching it on.

Any additional advice?
:

Check the FAQ's on this site or do a search on this site "drain combi" or similar

 

[kevplumb]

Combi's are unvented

no they ain't you can fit some combi's on a vented system

 

[AshaDPlumber]

The combi is the system, so how exactly do you fit a combi to a vented system? Are you sure you know what your talking about

 

[wilhelm]

read the mi.s

.....

 

[wilhelm]

oil boiler I hasten to add. Berty worster heatslave.

 

[dude_diy]

Thanks for all your help so far guys, its really appreciated. Also very useful. Im still not 100% if my system is vented or not. I do however have a 22 mil copper pipe coming out of my side wall which looks like a type of breather cap. Does this mean i have a vented? any replies and your time are again appreciated.

What does anyone think?

 

[dude_diy]

Just wanted to add, when I re-filled the system before i used a valuve under the bolier which i use to top up pressure if i ever needed to...is this correct?

 

[corgiman]

The combi is the system, so how exactly do you fit a combi to a vented system? Are you sure you know what your talking about

OLd dad is right Asha you certainly can fit a combi on an open vented CH system, it wont need the system kit built in to it would it?

Cant see any occasion as to when you would want to though

 

[AshaDPlumber]

Yeah i see what you mean now, but like you say cnat see why you would want to.