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Here you will find all about PDHW.

Priority Domestic Hot Water

This is an area for all things PDHW. From the principle of how it works to the various types of PDHW, to diagrams for specific models.

Blog posts

July 30, 2022


Lets look at 4 pipe vs 2 pipe The boilers referred to in this article all have the functionality to control the diverter valve from the software in the boiler, ie there are some terminals to attach the DV valve cables to.  Not all boilers have this (Ideal and Vokera being a good example) however these  boilers can still be …
July 22, 2022


There are various ways to implement PDHW. Some  manus  get  the boiler to control the DV situated  inside the case just like a combi does. (will talk later about ways of doing PDHW with a boiler that doesn’t control the DV) In fact its often the same combi DV  that you add to a system boiler to make it PDHW.…
July 9, 2022

PDHW Pt 1 Why new S&Y plan systems should be BANNED

This is Part 1 of a series of PDHW articles I am writing. This is a general background. Putting a brand new, high efficiency boiler onto an S or Y plans system is like putting triple glazed windows into a rotten wooden frame. All of the performance benefits of the new window are lost as cold air enters via the…

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