Hot water loop woes

[Jenni]

Hello.

(My self build continues at a rather slow pace . . . .)

 

ASHP fitted April 2021. Tank and pump for the loop was fitted back then and has just been waiting for me to catch up and need it.

Plumbing went in last year. The unvented cylinder is next to bathroom (radial pipework there). I ran 15mm plastic pipe with 25mm climaflex insulation to the furthest tap (utility room, approx' 25m away from tank), via kitchen, then a 10mm return to tank. 

 

Have just come to get the pump up and running, it's a Wilo Star-Z NOVA T (https://wilo.com/gb/en/Products/en/products-expertise/wilo-star-z-nova/star-z-nova-t)

My first annoyance is that the special "Wilo connector" to get this powered up has gone AWOL in the intervening time, Wilo do not sell this stand alone. My sparky thinks we can probably get over that one way or another.

 

The bigger issue is it doesn't look like the pump will do what I wanted it to do. From what I can tell, it will run continuously within 3 separate time periods, which can be specified. 

I was initially planning on 'pulsing' the pump (for eg, to run for 2 minutes in every 15 minutes, within a specified timescale). But I've just had a look back on some threads on here and see that this isn't necessarily the recommended way of doing it.

Life is a bit variable here, I would like warm water to be at the taps from around 7am-10am and from 4pm-10pm.

This would mostly be for hand washing so warm (ie, if water had been pulsed but was in a cooling moment) would be fine, and when washing up - waiting for the hotter water to follow the warm wouldn't be too much of an issue, (and far preferable to putting hot on top of cold leg as I do currently without the loop pump working.)

But I also want a 'boost' button, for when warm/hot water is required outside of these times. I don't especially mind waiting as such, just cant bear to see all that cold water just running through while I wait!

 

Can anyone see a way I can achieve all or any of that with my current supplied pump? If not, any pumps that will?

 

Many thanks

Jenni.

 

[JohnMo]

Switching on off like you are proposing may not be the best way to do it. All you will be doing is getting just enough heat into the system and then loosing it repeatedly.

 

You may be better running a pipe stat, set to a warm temperature and let that control the stop starts, not sure if you would need an external timer. All are pretty cheap to pickup.

 

There are other ways around it and other things to sort out, but it depends on the exact plumbing of the cylinder, do you have a mixing valve on the hot water outlet, it limit outlet temperature?

[Jenni]

Hello @JohnMo

I run my ASHP in eco mode at the moment, it means my cylinder holds the hot water around 43c this is warm enough for most of what I need, for washing up I don't add any cold water to that. I may raise it a few degrees at some point in the future. 

I could certainly use the Wilo pump to run continuously 7am-10am and from 4pm-10pm. But this strikes me as a bit wasteful regards to electricity use, but I'm not against it, if that's the consensus on here. But I can't see any way to run a boost button with it, and I would really like that functionality. 

[Jenni]

1 hour ago, JohnMo said:

There are other ways around it and other things to sort out, but it depends on the exact plumbing of the cylinder, do you have a mixing valve on the hot water outlet, it limit outlet temperature?

 

To answer this directly, no - the cylinder has no restriction / mixing valve on the hot water outlet.

[Jenni]

Is anyone able to shed some light on this please?

 

I'm sure others have had other triggers to get the pump running outside of programmed times, via occupancy sensors etc. Surely a boost button is possible?? 

[JohnMo]

Could you put a pipe stat on the pipe as it comes back towards the cylinder, to cut and start the power to the pump? Then use the pumps time clock or an external one?