Purmo Low Temp Rad Report

[Jon Glanfield]

Has anyone seen the report from Purmo recently which suggests that there is a 15-25% improvement in efficiency when using rads over UFH, due to the slow response and overshoot engendered in an UFH system.

It is not written purely from a HP perspective but does make reference to them and the study was carried out in Sweden so presumably may have included some systems using HP's.

I'd be interested in others views of the survey, as it is not specifically aimed at HP's its relevance to the technology is perhaps suspect, but it does allege that the difference in COP due to higher temps with rads is offset agains the efficiency losses due to overshoot and lack of control.

Cynically too it's published by a rad manufacturer!

It is downloadable from here: http://www.purmo.com/en/clever/cleve...ions-movie.htm

[Bigfreeze]

There are no overshoots where weather compensation is employed. Only where cheap ass stats control everything.

They were careful not to mention heat pumps there as they wouldn't be able to show a saving against ufh. They just said low temp systems, which could just as well be a condensing oil burner vs a standard.
At the 45C flow they stated, the COP of a HP would be down 20% plus as against a ufh system. Add to that the fact you have no thermal storage and I can't see how that could be construed as a good thing where a mechanical motor and its necessitity to cycle on and off is involved.

Just goes to prove that you can take any study and if you word it carefully enough you can make it mean anything you want in your favour. Just look at the way the Fracking companies are doing just that to justify their businesses at the moment.