Is an expansion tank needed for the heating

[miketurner]

Hi

I'm obtaining a few quotes from different local plumbers.

Do I need an expansion tank for the heating if the hot water cylinder has internal expansion and does not require one ?

I’m looking at having an Ideal Logic Max Heat only 24kw boiler fitted to replace my existing one and a Halo WiFi thermostat.

I’m looking to have the existing vented water tanks removed from the loft and have a mains fed unvented system, with a Gledhill Platinum unvented internal expansion 180 litre hot water cylinder. My water flow is around 18 and 4 bar water pressure (tested by one of the visiting plumbers who said those figures were good).

Will I still need an expansion tank for the heating ?

Any advice appreciated, thank you.

 

[flameport]

A sealed heating system must have an expansion vessel. It can be a separate item, or some boilers have them internally.

An unvented hot water cylinder must also have one, either as part of the cylinder or an external item. It's unrelated to the heating, as the hot water from the taps is separate from the water inside the radiators.

 

[miketurner]

Thank you for the info.

 

[MeldrewsMate]

Be aware though, that most internal expansion vessels (integral to combi boilers and system boilers) are only around 8 litre capacity, and your heating system may require an additional external expansion vessel to be fitted.

 

[miketurner]

I will probably end up with a hot water cylinder and two expansion tanks to make things simpler. Good to know though. Thanks.

 

[dilalio]

How many rads do you have?

A heat only boiler will require an external EV and a pump and a bypass.
With a system boiler, you would get these built into the boiler and therefore under that boilers warranty. Beware though that some boilers manufacturers do not consider certain components as warranty items.

 

[miketurner]

Hi, I have around 14 radiators. The plumber said there would be less pipework needed (fewer walls to damage) if he changed my existing heat only boiler for another heat only one. Thanks for the info.

 

[Mottie]

24Kw seems a lot for 14 rads. How big is your existing boiler?

 

[miketurner]

Our existing boiler is a glow worm 24hx We have around 14 rads and water underfloor heating in one room.

 

[dilalio]

Do a heat loss calculation.
Including cylinder I'd predict 10-15kw.