System Boiler or Heat Only

[dfairclough1]

Apologies if this has been done to death elsewhere - Looking for some advice on changing our boiler.

Current set up is an Ideal Mexico FF460 Floor Standing boiler which was originally on a HW gravity feed. I installed a pump and converted it to Y-Plan about 4 year ago. HW tank was found to be leaking and this was changed at the same time.

Now looking at refitting the kitchen and would like to change the boiler to wall mounting but still want to keep the hot water tank so ruled out combi.

Heat load using whole house method is about 18Kw (4 Bed Detached in Lancashire)

Looking at Veissmann, Vaillant and Worcester Bosch (in that order) but can't decide between a system boiler or heat only.

Apart from having less components in the system (ie. Expansion Tank, Pump, 3 Way Valve, Programmer) all of which are relatively new, are there any other benefits to commend a sealed system over an open vented system.

Would just like a bit of advice in advance before getting some quotes.

Cheers

 

[BingoBongo]

look at the viessmann 4 pipe setup,depending on location of your existing cylinder and how much repiping is involved

 

[adlplumbing]

i prefare sealed systems but just prefrance
mainly easyier to rmove airlocks and it you have leaking rad it will tell you by perssure gauge

 

[Happyplumber]

you can use system boiler or if you larger house then use heat only boiler and pressurize the whole heating circuit separately.sometimes one needs a 18 to 24 litre expansion vessel .

A system boiler is usually a stripped down combination boiler with the secondary heat exchanger and the water side removed ,thats why they are realtively cheap compared to heat only boiler which has to be made specially

with heat only you are not tied to certain manufacturers parts at premium price the pump,valves and expansion can be readily sourced at very competitive prices

generally heat only unit is smaller as well because essentially its gas valve and burner and small control board

 

[dfairclough1]

BingoBongo - HW Tank is off upstairs landing approx 3.5m horizontally from the boiler which is in kitchen on the ground floor. Pump , Mid Posn Valve , Bypass Valve and programmer are all located with the HW tank in the airing cupboard.

Currently only connections to boiler are Gas, Flow / Return and supply LEN from junction box (also in airing cupboard)

adl and happy thanks for the info.