27kw combi doesn't nromally give you 27kw of heating INPUT, most would say be 24kw. Even the Worcester 40kw combi only gives 30kw of heating power consumption (output is lower).
For two bathrooms I sugest a Worcester hiflow if you want a combi or get a hot water system and a system boiler.
You must have a VERY large house if you need 27 kW of heating just for UFH.
UFH typically provides a maximum of 70 watts/m sq. That means your house has 450 sq M. Thats 45 average size bedrooms!
I dont believe that. In any case if your house is so large with even just 12 bedrooms then you should be able to afford a proper heating consultant as the house would be in the £1M-£3M price range.
The consultant would have told you that a combi boiler is sized for the hot water output NOT the heating output. You need about 24 kW of water heating per bathroom if you are happy to wait to fill a bath in 15 minutes, with three thats 75 kW and a commercial boiler as the largest domestic is only about 35 kW.
You will also need a water mains supply capable of giving 40 litres per minute, four times the norm and requiring a 35 mm supply pipe.
I just do not understand why you dont get a competent heating consultant to visit you and discuss your requirements. But that will cost you some money and perhaps you are very mean and think that you can get free advice on a £16,000 installation off the internet without a visit and it will work to perfection.
Nerds like you who judge without the facts get right up my nose. If you cannot comment without petty snipes, please do not bother. I am sure other contributors with common sense can be far more constructive in their comments.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local