The Efficient Home Forum

Hi,

I've had evohome wireless for a number of years now without realising that DHW priority was a thing since my controller hadn't received any firmware updates since I had it. Anyway, I now have the latest firmware which has the DHW priority setting, which I have enabled.

Due to a retrofitted cyclinder and connection to the heating circuit, I have no zone valve to isolate the heating circuit and my DHW 'loop' is essentially just like any other zone/radiator, but controlled by a 2-port valve.

Everything has worked as it should for a number of years (both hot water and heating work great on their own schedules), albeit without the hot water priority. Now I'm trying to use it, it doesn't seem to work that I can tell. I assumed that when there was demand on the hot water, all my radiator HR92's would close allowing all the flow to be diverted through my hot water cylinder. In reality, the radiators stay open as well as the hot water. I have an old heat only oil boiler which from memory is 18kw and it works great for my home. My cylinder is a fast recovery one with an 18kw coil in, so I wanted to push all the flow through it when there was demand.

Resideo support told me that the heating schedule should 'pause' if there is demand for hot water whilst also demand on the HR92's. They had me factory reset the controller and unbind my BDR91's, etc but that made no difference.

Anyone know anything I can try?

Here's a crude diagram of my system (I have more radiators, but all on HR92s):

I thought (but happy to be proved wrong), that priority HW only worked with OpenTherm, which I presume your oil boiler does not have.

lloyd wrote:I thought (but happy to be proved wrong), that priority HW only worked with OpenTherm, which I presume your oil boiler does not have.

I was just about to say this. If you don't have OpenTherm, PDHW is pretty pointless.

Thanks for the replies.

That's not how I understood it that it had to have OpenTherm.

Why is it pointless without OpenTherm? If my boiler output is for example 18kW and my cylinder has an 18kW coil, then 'pausing' the heating for 20 minutes whilst the cylinder recovers makes perfect sense to me, especially if the heating has only just come on in the morning or evening.