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Keep old boiler or upgrade for new UFH


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I am looking for a little bit of advice before I get a plumber involved.

I’m looking at adding 20mtrs underfloor heating to my property.

I currently have a 15+ year old Vaillant ecotec-plus-937.

My question is, is it worth upgrading the boiler to something newer that maybe more compatible with todays controllers and can modulate better, or does it not matter?

I hear horror stories connecting old boilers to work with UFH (electronically)

Any advice welcomed.

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If you boiler is serviceable use it. It will turn down to about 12kW. Which is quite high, but if you are in a leaky (heat) house that maybe ok.


All boilers benefit from a long run time and you really need to minimise zoning (remove as many thermostats as you can) to keep system open, otherwise you will get short cycling. Short cycling basically consumes loads of gas for very little heat output and shorten the boiler life.


Assume you will mix UFH with radiators? If so use an Ivor mixer for the UFH or electronic (expensive). Most other mixers are rubbish.


You may benefit from adding weather compensation to the existing boiler, then run the whole system on WC, use the existing trv's as limit stops (set a couple of degrees above target temp) and the UFH on continuous on a set low flow temperature.

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