Combi or Unvented or Something Else???

[andyinthevalley]

Hi
I am an ex-plumber who hasn't been anywhere near a system for 5 years so need a little help with what I expect is a common question...
I need to replace the heating system in my house. Current system is a vented Thorn EMI boiler fitted approximately 1983. The house has 1 bath, 2 showers, 3 WCs, 14 radiators. Having removed a few cold water tanks in my time and witnessed the gunge that can build up, I have a strong preference for removing the 2 cold water tanks (3 tanks if you count the header tank) in the loft. So, do I go for a powerfull combi system or an unvented system?
I have been recommended a Remeha/Broag 39kw combi but I am sceptical that the flow rate will be sufficient for 2 mixer showers and other appliances in the house at the same time. Any and all advice appreciated.

 

[Mike Jackson]

A 39Kw combi will cope with 2 outlets at once if flow restrictors are fitted. You could look at a Worcester Highflow 440 or Rinnai twinflow. If you've got the room and your pressure and flow rates are good I would go unvented every time though.

Mike

 

[andyinthevalley]

Thanks Mike

Unvented does seem to be the popular choice on most of the threads on this forum when considering a larger house. However, is the cost of installation not considerably greater than a combi? I also have to consider that the hot water cylinder currently in place would have to be replaced with a larger unit as it seems too small.

 

[Mike Jackson]

The installation costs aren't going to be hugely more expensive than a really good high flow combi. Another option to think about is to use a smaller combi, run the kitchen hot water off it and use an unvented for the rest of the hot water needs. Just need to fit an S plan.

Mike