Convert to Combi or unvented system?

[NHW]

3 bed detached, 1 bath room, 1 en-suite shower (dont have bath + showers at the same time so not having hot water to multiple locations at same time isnt too much of an issue)

Currently in the process of getting some quotes in for getting the boiler replaced and some are saying combi will be better and some are saying unvented would be better? i've looked at the advantages and disadvantages of both and still cant seem to figure out which one would be best.

our system is currently open vented (tank in loft) and one of the main reasons that we wanted to change to either the combi or unvented is because there is literally no pressure coming out of the shower at the moment, i believe that changing to either system will mean that the water will be fed from the mains instead of relying on the gravity between the loft tank.

Have already decided on which boiler:

Atag A325EC (Combi)
or
Atag A320s (unvented)

the only other benefit i can see from going to a combi would be that there would be no need for any tanks which would mean some free space in what is currently the boiler room.

In terms of cost i believe that the combi might cost slightly more to install as it would require a conversion? whereas going from open vented to unvented isnt as complicated?

 

[Plumber90]

Cylinder and heat only boiler every time, much more practical as long as you have good enough water pressure and flow rates.

Cost wise I would have said that a boiler and cylinder would be more expensive.

The price you pay also depends on your location, less up north, more down south/london

 

[Classic40]

Totally agree, cylinder every time!

I think I would be tempted to stay with a cylinder if the water pressure/flow was low because you can always add a pump to a vented cylinder.

Same with a combi, if the flow/pressure are low it will not work half as good as a vented cylinder with a pump.

 

[NHW]

Ah right, i see what you mean.

Oh i forgot to mention that another issue i actually have is the amount of hot water available, its basically 2/3 of a bathtub of hot water max a day.

e.g. if someone did the washing up at 4pm using hot water, even if you waited till 5pm to use the hot water again there would only be 1/2 a bath full of hot water and the tap just stops giving any water after that point. not sure if i have a specific issue somewhere to do with the tank but im guessing thats not normal?

 

[Classic40]

My 120L vented cylinder (Just a normal one with the blue foam; not a high rate recovery) takes approx 30 mins to reheat from cold to 60c.

What times is your programmer set to run?

 

[Plumber90]

The reason it doesn't heat the water back up very well could be if its a very old very scaled up cylinder.

 

[PotatoHead]

If you're only ever running one tap at a time there's an argument for fitting a combi. Generally a cheaper installation, cheaper running costs. and I wouldn't say it's any less reliable when you consider there's plenty of parts to go wrong on an un-vented cylinder.

 

[mfarrow]

May I ask for the reason to not retain the existing boiler? The two together will be quite costly but depending on the age and condition of your existing boiler you may have a good life left in it yet.

 

[Whitespirit66]

Two other questions.

You say that your tanks are in the boiler room. Where in the house is the boiler room?

When the hot water runs out, do you get cold water, or does the hot tap just run dry?