Should I change to a combi boiler?

[DP]

Isn't the only advantage of open-vented that the radiator circuit pressure will be lower, so is less likely to leak immediately if it's on its last legs? Otherwise, if the pipes and radiators are in OK condition, why would anybody want to stay open-vented?

Why take a chance?
Such a system is bound to weep after it is cleaned when under pressure
If the pipework is corrected to conform with OV setup, do not see any issues.
Have fitted suitable combis to what was open vented, retained as open vented.
Do I want to be constantly running back to address the problem of dealing with micro leaks on system where I have converted to sealed system? Not if I can help it.
If present system is sealed, no problem, will keep it like that.
Can immediately recall two open vented systems easily 35 plus years old now have a combi working as open vented- zero issues.

 

[Mottie]

My heating system was converted to sealed a few years ago. Original system since house was built in early sixties. Still had three of the original rads fitted. Was chemical and power flushed. One leaked straight away when system was filled so was changed, one leaked a week later so that and the remaining other rad was replaced. No trouble with the pipes though.

 

[winston1]

We have heard of an advantage of an open system. What advantage does a sealed system have?

 

[Mottie]

No F&E tank in the loft so no crap can get in system so system is kept cleaner. No pipes needed in loft (if boiler not in loft) so no chance of freezing. If you sprang a leak while not at home, only a set amount could leak out and that would take ages once the pressure had released. With open system water will just run and run. That’s all I can think of.

About 10 years ago our neighbour died so her house was unoccupied for some time. The pipes in loft froze, split and when it thawed it run and run for ages we assumed. My bat-eared wife heard water running one night and I had to break in to turn the water off. Both ceilings completely collapsed, carpets, bathroom, beds, kitchen cabinets, floors absolutely saturated and when the house was sold it needed completely gutting and took months to dry out.

 

[DavidLewis]

No F&E tank in the loft so no crap can get in system so system is kept cleaner. No pipes needed in loft (if boiler not in loft) so no chance of freezing. If you sprang a leak while not at home, only a set amount could leak out and that would take ages once the pressure had released. With open system water will just run and run. That’s all I can think of.

Also, related to your first point, no way for extra oxygen to get introduced into the system water through the (non-existant) F&E tank so much less opportunity for internal corrosion. No chance of pumping over.

 

[JohnD]

It is a mistake to think that all unvented systems are combis.