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Discuss General advice -retro fitting wet UFH in the Water Underfloor Heating Installations area at PlumbersForums.net


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Hi all
Newbie here who has joined to try and learn from your collective wealth of experience! I am a homeowner and not in the trade. You will see this from my lack of technical terms, Trying to do as much research as possible so we get it right - this is a one time opportunity and we need to avoid costly mistakes.

Planning major refurb downstairs of 20 year old barn conversion. Large area of approx 91 square metres open plan lounge/diner/kitchen plus separate small utility.
Concrete sub floor with approx 110mls of screed etc on top currently.
We have an oil fired boiler. Low pressure system. Also removing an oil fired aga so need to ensure we compensate for the heat loss from that.
We are getting conflicting advice so looking for others experience.
1) The boiler ( so far we have not been advised to change it) will be altered to be a sealed system - we are querying whether the increased pressure needed for UFH will be detrimental to the existing pipe work fitted to other areas of the ground floor ( several other rooms where we are not refurbishing) . The pipe work to the rads etc are all underfloor- so any leaks would be hard to resolve. How much of a risk is this ? I can’t find much information on this?

2) If we do decide to go ahead with the major work and expense of retro fitting UFH , any thoughts on whether we would be best to dig out the current floor ( currently getting quotes) to fit traditional UFH or fitting the overlay systems such as Lo pro Max? We are prepared to invest in digging up and know we would have to cope with the mess but if the overlay wet systems are now just as effective then we would look at this instead.

Thanks in advance for your views and experience!


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Get someone in to test the existing pipework th 5 bar.
If it holds, then it should be ok.
The maximum any heating system will achieve without the PRV releasing is 3 bar.
For that matter get it tested to 6 bar - double the maximum relief valve setting.
The heating system will only operate between, say 1 - 2.5 bar, depending whether the water is being heated

Craig Watson

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You do always risk leaks when converting gravity systems to sealed systems. It would really depend how old the system is and what protection the pipe work and system have had to judge how much of a risk it is.

With your underfloor heating, if your going to do it, do it properly. Insulation is key with these systems so dig up your floor and allow for 100mm insulation at a minimum, also contact the manufactures with your plans and get them to design the system for you and make sure your installer is familiar with UFH systems.
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