Secondary Circulation - switching on/off

[Jock Spanners]

Hi Guys,

I'm planning a disabled bathroom for an incontinent child with severe problems. The client has specified secondary circulation as it's 20m from the unvented cylinder and they don't want to have to wait for the hot to arrive. Rather than put it on a single channel timer and have it circulate every half hour (and cool the cylinder) I was thinking of having a PIR in the doorway of the bathroom to switch on the pump for a couple of minutes. I would need a timer that could be switched on by the PIR to run the pump for 5 mins maximum. I can't seem to get an answer out of my sparky friends on how to do this. Has anyone here done it?

 

[chris watkins]

Hi Jock
I like your thinking but there may be a few issue around cool water in pipes if the bathroom did not get used for any length of time etc.
Can I suggest the Grundfos Comfort Autoadapt which remembers patterns of use & has safe guards built-in it may be a good solution.
Grundfos Comfort | Grundfos

 

[Ermintrude]

Easy, lag pipes. Standing loss will be low. You only need a 15mm return.

Run in copper to prevent any legionella. I would set up a timer in parallel with the PIR.

Set it so timer runs once or twice a day - get up go to bed.

PIR in hall way en route to bathroom. Fit the tmv3's on the legs otherwise you will be cooling return all day long. Seen a few on secondary circ!

Wire all neutrals common. Wire s/l from PIR and timer to l on pump.
Make sure PIR, programmer and pump are fed from same supply.

Cylinder will need to be on 24/7 to ensure always avail.

Set PIR to have over run of 15mins.

 

[chris watkins]

Easy, lag pipes. Standing loss will be low. You only need a 15mm return.

Run in copper to prevent any legionella. I would set up a timer in parallel with the PIR.

Set it so timer runs once or twice a day - get up go to bed.

PIR in hall way en route to bathroom. Fit the tmv3's on the legs otherwise you will be cooling return all day long. Seen a few on secondary circ!

Wire all neutrals common. Wire s/l from PIR and timer to l on pump.
Make sure PIR, programmer and pump are fed from same supply.

Cylinder will need to be on 24/7 to ensure always avail.

Set PIR to have over run of 15mins.

Sounds a lot of work to me, if water usage is roughly the same times each day me thinks the Comfort wins.
I would certainly go with you on the insulation (legal requirement) of F&R & not plastic pipe for this system (don't like the high oxygen).
Even if you still go for the PIR still go for one of the other Comforts (or other makes) with temperature control built-in & of course they are EuP directive complaint.

 

[Ermintrude]

No a huge amount of work . 2 hrs? Comfort ok, not fitted one

 

[helpsy]

Make sure you don't use plastic pipe/fittings on the secondary return.

 

[Ermintrude]

Make sure u just don't use plastic.

 

[Dotty]

Hi Jock
I like your thinking but there may be a few issue around cool water in pipes if the bathroom did not get used for any length of time etc.
Can I suggest the Grundfos Comfort Autoadapt which remembers patterns of use & has safe guards built-in it may be a good solution.
Grundfos Comfort | Grundfos

Great minds and all that!

 

[Killy Bing]

Great minds and all that!

However due to the customers needs i don't think it will be suitible, use will be totally random as such the pump wont be able to learn a routine as there wont be one.

the timer and pir sounds a good solution.

 

[rpm]

Slightly off topic but if fitting a macerator in this room then do not use a Saniflo, I say this from experiance of a customer who caused me a real headache until I realised that something in his medication was reacting with the rubber components.