Automatic Bypass Valve

[lloyda]

Does it matter if all the pipework to and from an automatic bypass valve is fully lagged? Or to put it another way, is the purpose of the abv to ensure circulation, or to circulate and lose some heat?

 

[Mike2007]

Its to route back to the boiler should all the radiators be closed, raising temperature in boiler (stopping it) .

 

[lloyda]

Well yes, I understand that. But that does not really answer my question.

 

[Mottie]

I thought the point of the auto bypass was to allow the boiler temperature to reduce when the boiler switches off and the pump runs on for a while. Lagging would inhibit the heat loss, wouldn’t it? Is the boiler fitted outside?

 

[polesapart]

Or to put it another way, is the purpose of the abv to ensure circulation

A good way to kill a pump is to run it in a "no-flow" situation.

 

[muggles]

It's to maintain a minimum flow rate through the boiler when the pump is running and the system has closed off. It should be insulated

 

[lloyda]

It's to maintain a minimum flow rate through the boiler when the pump is running and the system has closed off. It should be insulated

Thanks. Boiler is in the loft, and all pipework there is lagged, but I've got a section of unlagged flow/return in the airing cupboard (where the pump and abv are) which means it is getting very warm. I want some warmth in there, but it seems excessive so I'll add some insulation.

I've recently had my system converted from y-plan to s-plan as part changes required to change to an unvented dhw cylinder. I'm not sure is this was happening before the change or not, but I think the bypass is allowing flow when just the dhw is on - is that normal, or has the abv been opened too far?