Can I join vent and cold water feed?

[redconker]

Hi there,

I'm running out of options on my CH header tank overflow (please see below linked issue), so can I join vent and cold water feed?

//www.diynot.com/forums/viewtopic.php?t=170391

I understand the vent pipe is there in the case the boiler thermo goes, surely with the vent pipe and feed pipe joined, the boiling water / steam will still have somewhere to go so it should be okay?

any help would be great?

thanks.

 

[bengasman]

constant overflowing shows there is something wrong with the system, so taking out the overflow pipe is not a solution.
If you can't find the problem, get a RGI to sort it out.

 

[Fluffster]

The vent pipe and cold water feed both act as feed and expansion pipes to accomodate the increase in volume when water is heated.
By restricting an open vented system you have a higher possibility of pumping over continously.

However some manufactures list this method as an option on their boilers.

If you are still getting pumping over you may still have a restriction, did you cut out the old cold water feed where it meets the heating circuit as a powerflush will not always shift this?

Pete

 

[redconker]

Thanks. I'm comfortable the system is flowing around well enough and there isn't a blockage or restriction in the cold water feed.

If I try joining the vent to the feed, can I do this at the boiler or does it have to be done high - i.e. in the loft?

thanks.

 

[bengasman]

How did you assess the flow is correct throughout the entire system?

 

[Gasguru]

As has been said before cut out the feed and vent connections and clear the blockage between them.

On this boiler you can convert to combined feed and vent but it is masking the problem.

Just curious but what pumps are being used? what non-return valves are being used and how is the pump overun controlled?

 

[redconker]

Just curious but what pumps are being used? what non-return valves are being used and how is the pump overun controlled?

I have two Grundfos UPS 15 -60 pumps. I don't have non-return valves and the controller controls the pumps in order to control the CH or HW or both. They run most of the time the heating is timed to come on.

Thanks for the help.

 

[Gasguru]

So presumerably all the returns join at the boiler return connection...otherwise it may not work properly.