Should I decrease pipe spacings

[Robs931]

I have DIY installed my UFH system a couple of weeks ago and I'm now waiting for the screed to be poured in a few days time. The layout was designed by the firm I purchased the UFH kit from with 150mm pipe centres throughout the entire ground floor, which I adhered to thinking everything was fine. I have since been in contact with some ASHP companies to get quotes and one of them mentioned a lot of UFH companies don't perform proper heat loss surveys and just use 150mm centres as a default and I may need 100mm centres in some rooms.

 

I have since carried out my own heat loss calculations to the best of my ability using the NRG online calculator, and as far as I can see the only room that might be an issue is the kitchen due to the reduced heated floor area as there's no pipes under the kitchen units. The room has a total floor area of 26.2m², a heated floor area of around 20.3m² and a total heat loss of 1446W according to the NRG report. There is a lot more glass in this room compared to any other which I assume is the reason for the higher heat loss compared to all the other areas of the house. If I understand the UFH output chart correctly, at 150mm centres a MWT of 35°c will give a heat output of around 60W/m², which over 20.3m² gives 1218W, a short fall of 228W. But if I went to 100mm centres at the same water temp it would output around 70W/m², which over 20.3m² only gives a shortfall of 25W. 

 

The room has 2 loops, one 64m and the other 78m. My question is, as I have a fair roll of pipe left, should I be thinking about closing the pipe spacings up to 100mm on the 78m loop and replacing the 64m loop with new pipe at 100mm centres too? Or would the system be ok left at 150mm and just be a little less efficient to run? Ideally I don't want to rip up what I've already installed, but if leaving it means the kitchen will never get warm then I need to do something about it now whilst I still can.

 

Thanks in advance.

[JohnMo]

Is this a new build or retrofit?

 

What's below the UFH pipes?

[marshian]

Not sure I'd want to start again - I'd add a radiator sized to cover the shortfall in watts running at the same flow temps as the floor?

[Conor]

Your fridge will make up the shortfall....

 

And remember that shortfall is on the coldest day of the year. And you've other heat sources in the house, and air movement from other areas. It'll be fine. Move on to the next job.

[Robs931]

11 hours ago, JohnMo said:

Is this a new build or retrofit?

 

What's below the UFH pipes?

Yes new build. Block and beam, 150mm PIR and 75 screed.

[JohnMo]

Im running 300mm spacing without issue, wouldn’t fret too much. I have 1x 100m pipe doing main bathroom, then it does hallway by front door and then kitchen diner

[ProDave]

26 minutes ago, Robs931 said:

Yes new build. Block and beam, 150mm PIR and 75 screed.

I would be surprised if the kitchen heat loss is really 1.4kW  that would be more than half my total house heat loss at -10 outside.