Posted by: @jamespa

↑

Posted by: @ngillam

↑

@jamespa I tried to discuss with kids, I got a couple of eye rolls....and one tutted!

 

Exactly.

It strikes me that grey water recovery might be a simpler and more robust way to 'save' the water.  There is still some heat lost though.  A smart tap that turns the pump on but then only turns the tap on when the water comes through hot is the ultimate solution.  Are we overthinking this problem?

A shower directly next to the HW tank......or a shower head off the tank 😀 

Posted by: @ngillam

↑

A shower directly next to the HW tank......or a shower head off the tank  

Which is exactly how houses used to be designed (and I suspect mass designed houses still are).  Put all the plumbing as close together as possible.

I have a recirculation pump that we had fitted when the house was renovated 5 years ago; at the same time, we had our ASHP installed which provides DHW via our Daikin 'thermal store' (posh water tank). The thermal store is at one end of our single-story 300 sq m house; the master bathroom and our son's bathroom are at the other end. We were scared off using the recirculation pump by our installers who said 'it will use a lot of energy' but that was, we think, a ruse to get us to drop the requirement as the builders were scrapping with the plumbers about payment at the time (as subcontractors).

Anyhow, we re-visited the recirculation pump a few months back found it worked a charm. Prior to using the pump, our DHW was set to 55C and was always just warm enough in the morning, to the extent that the shower handle was on max; we have Grohe (Cosmopolitan 310) rain shower heads and we would wait a couple of mins (or more) for the hot water to arrive - at 9.5l/min we were wasting 80 or more litres of water a day waiting for hot water (2 showers a day in summer for three people - obvs if someone showers immediately afterwards somebody else they are not waiting around, so it was 4 'shower events').

With the pump now running the hot water is instant, and we were able to reduce to the DHW temp to 50C and it still feels hotter at the shower than when set to 52 without the pump. So, we are saving electricity on heating the water, and up to 80l of water a day. I checked the daily electricity consumption which I can see on an hourly basis and the morning (4am) DHW spike is less if anything - previously the spike was around 2.8kwh (incl background, non-DHW) and now its around 2ish kwh.

My setup is that the recirculation pump (a Dab Evosta2) is controlled by a mechanical DIN rail timer which I have set to run from 6-10am, and in the evening from 6-8pm. If I get round to it I may replace this with a digital daily timer so I can accommodate the shift in shower times at the weekends.

@marzipan71 Morning, it looks as though it's a very much a "must have" in spaced out residences, do you witness the same temp drop from DHW tank on initial start up of pump as the pipework is primed?  I can drop as much as 5 degrees typically, I may heat the tank to 50degs and set the circulation pump to 24hrs to see how fast the heat from the tank dissipates without a reheat over say a 12hr period.

I think my family want me to stop tinkering.......

Thanks,

Neil.

Morning @ngillam hmmmm don't think I've measured that tbh. I should probably do a test with a cup and thermometer at the shower and see what the temp diff is between what the ASHP sees in my thermal store (DHW tank) and the shower water temp  both with and without the pump running. I'm actually going to drop the DHW storage temp again (to 48, which will mean I've dropped 7C from where we were without the pump) as I'm a few notches below running the shower at max temp (my shower valve does not have a safety temp limiter - it really doesn't) when showering and my understanding is that the optimal scenario is to not have to blend cold water at the shower. Also looking at a Shelly DIN rail timer which would allow me to ask Alexa to run the recirculating pump on demand - like when someone randomly decides on a bath. It would be interesting to know how long it takes from starting the pump to get to temp in the master bath.

FWIW I had an (apparently) excellent conversation with ChatGPT about this subject (and, indeed, about setting up and fine tuning my ASHP for this winter cycle.

Hi,@marzipan71 I plan to use my melcloud output to show a day of circulation pump switched off and then a day of it on 24hrs and watch how quickly the temp trace drops throughout the day.  I just need the family members to obey which rarely happens.

Hi @ngillam I don't have anything as sophisticated for data with my Daikan alas - I've a digital controller that looks like my car stereo display ca. 2002 and that's about it. While you're consulting melcloud, I'll be in the bathroom with a cup and a thermometer. Bless my installers.