Open vent boiler , no rising vent ??

[Gez2312]

Hi , I've been to see a job today to discuss fitting underfloor heating.

The customer has a new (5 month old) Vaillant heat only boiler fitted in the garage .

Pipe work leaves top of boiler is elbowed down underneath the boiler and then goes to pump then three x two ports valves (up heat, down heat and DHW)

The cylinder cupboard is upstairs. I expected to see a filling loop and expansion vessel. But was shocked to find that was not the case , the fill and expansion is connected to cylinder circs (as in old gravity system)

I know that the expansion should rise from top of boiler to header tank. But obviously this is not the case , the expansion is now after a lot of downward pipe work and after a two port valve.

I told the customer I would touch the system until it was re-piped or expansion vessel fitted and to contact the installer.

My question is was I right in saying this and how serious is the problem ? My theory is once the zone valve is shut for hot water the only expansion is up the return and through the cylinder !

Your thoughts and opinions gratefully received !

 

[Last Plumber]

Definitely sounds wrong from your description .

Like you said, re pipe or concert to sealed.

 

[gas tec]

Did you check the loft, ive seen exp' vessels and filling loops in there using the old cold main feeding the tanks and then using the heating cold feed or open vent pipe. Pain in the backside just to top up the system.

 

[Chriswareham]

dose the boiler have an auto air vent on the top this will make sure it is full of water it can fill and vent from the hot water cylinder the vent is there to releasle pressure this can sill be done vir the cylinder its normally done just before the pump so that it doset pump over ? it has a release be it vir the return

 

[Last Plumber]

Did you check in the loft or just presume?

 

[billy77]

Hi
as with most modern boilers this appliance incorporates a high limit thermostat
with this device installed the flow and return can drop first without the need for a rising open vent.
it is good practice to fit an automatic air vent to stop the collection of air in the appliance heat exchanger.
also as all modern central heating boilers are now fully pumped it will not be detrimental to the system for the open vent not to continually rise, it may however cause problems with venting any gases's though.