Condensate draining for boiler?

[Lobster]

I'm looking at the installation instructions for a Worcester-Bosch combi, in particular the pipework layout for ducting away the condensate. PDF file (5.6Mb, sorry!) is available here:

(or )

On page 11, in several of the diagrams, it seems to me that the condensate waste pipe connects to the system in the house without a trap, or connects to the pipes on the wrong side of an existing trap, meaning that foul air is connected directly to the atmosphere in the house.

I can't believe that I'm interpreting it right. Any able to clarify please?

Thanks David

[Andrew Gabriel]

There's probably a trap in the boiler (at least, there is with my Keston). If the wastepipe is shared with something else (e.g. a sink, bath, washing machine, etc) which can empty out at a good rate, I would suggest making sure an air admittance valve is fitted at the furthest such item from the sewer, so that when one of these finishes emptying out, the slug of water going off down the pipe doesn't have any tendancy to suck the trap dry in the WB.

[Lobster]

Well I was thinking that, but looking at the diagram in the manual, they show the condensate feeding into a tundish near the boiler, and that is what seems to be open to foul air.

David

[Andy Hall]

You should certainly have some form of trap before the foul drain. I did that and also put a tundish next to the boiler as an air break. Although there is a trap inside the boiler as well, one does not to have any risk of it emptying because there may be the risk of escape of fumes into the room.

[PeterK]

For some reason I can't view the pdf but the manual for a 30/40 CDi conventional also has condensate pipework on p11. Skipping on to P40 in "inspection & servicing" there is "To clean the condensate trap" ( the trap is shown as item 16 on the boiler layout diagram on P7) . This process ends with "fill the condensate trap with approx 1/4l of water and refit..." very strange this is not required at commissioning - boiler shipped "wet"?.

PeterK

[Andy Hall]

On the WB web site, go to the installer section and then enter CDI in the search. Navigate using the Literature tab.

The front cover of the manual describes the CDi conventional as a condensing boiler, hence the condensation trap.

Whether the piece about filling the trap should be part of commissioning, I don't know. The trap should fill with condensate anyway when the boiler is heating from cold, but it does seem inconsistent.

[Matt]

No, its not shipped wet. When you fire the boiler for the first time (or after being completely switched off for an extended period) the boiler fires at minimum for 15 minutes in order to fill the condensate trap.

The LED display usually alternates between -II- and the flow temperature while this is in progress.