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.

 

[Dotty]

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.

No it isn't.

The time taken for the secondary to come up to temp as soon as the pir detects movement you might as well turn the tap on as soon as you enter the bathroom.

 

[Ermintrude]

If PIR in hall way. 30 second lead, toilet 120 second lead. By that time secondary is hot.

 

[Dotty]

If PIR in hall way. 30 second lead, toilet 120 second lead. By that time secondary is hot.

assuming of course this bathroom isn't en suite.........

 

[Dotty]

And you're all forgetting he has to fit a smart pump any way as per EUP.................

 

[Ermintrude]

Smart pump work the same just set it on constant head

 

[lame plumber]

then its a dumb pump anyhow wont a pir in a halllway just turn on the pump everytime anyone goes by??

 

[Ermintrude]

Set sensor so it's en route to bathroom ?

Could always fit a high velocity pump set? Fit one that shifts 30lpm and you have circulated pipe volume three times in the time it takes to do a tom tit.


Power it off light switch? Remember when pumps used to run all day long?

 

[Dotty]

then its a dumb pump anyhow

wont a pir in a halllway just turn on the pump everytime anyone goes by??

My point exactly.

No matter how sporadic the lads bathroom visits are the grundfos will build a suitable database of optimum run times.

 

[Ermintrude]

My point exactly.

No matter how sporadic the lads bathroom visits are the grundfos will build a suitable database of optimum run times.

Really? The pumps not just going to spaz and just run or not run?

 

[Dotty]

For a couple of weeks yeah. after that no.

 

[Ermintrude]

For a couple of weeks yeah. after that no.

Really they are that good?

 

[rpm]

Surely the pump will be damaged if it`s running against a closed head or am I just old school?

 

[Ermintrude]

Surely the pump will be damaged if it`s running against a closed head or am I just old school?

Closed head? It's a secondary hot water circulator

 

[Dotty]

Really they are that good?

yep, the ones I've fitted have been anyway.

Surely the pump will be damaged if it`s running against a closed head or am I just old school?

It's a secondary loop we're talking about here but the capacity to reduce pump pressure against increased resistance is built into them too.

 

[rpm]

I just don`t like any pump running against a closed head no matter how short a time it is and didn`t know about capacity to auto reduce pressure guy`s that`s why I asked - Thanks for the update.

 

[Irish]

please excuse my ignorance here lads, why no plastic on a secondary return? I'm working in a house and they've got issues with their secondary rtn and its in plastic well most of the house is in polyplumb

 

[helpsy]

It won't withstand the constant temperature. It specifies this on JG if I recall.

 

[IDCHAPPY]

Late to the thread, but don't use plastic on Returns :lol:

 

[Ermintrude]

I just don`t like any pump running against a closed head no matter how short a time it is and didn`t know about capacity to auto reduce pressure guy`s that`s why I asked - Thanks for the update.

But it's not a closed head it's a pressurised open circuit unless nrv packs up. .

 

[rpm]

But it's not a closed head it's a pressurised open circuit unless nrv packs up. .

I realise that now mate, at the time I thought it was a flow system to the bathroom and talk of the pir turning the pump on before demand was required was why I posted, also I didn`t know these pumps could auto adjust the outgoing pressure. Please remember how I earn a living and whilst I`m here to help others with my knowledge I`m also here to learn.

 

[Ermintrude]

Sorry wasn't having a dig was trying to explain ! Respect every one equally on this forum as everyone knows something u dont!

 

[Gray0689]

I realise that now mate, at the time I thought it was a flow system to the bathroom and talk of the pir turning the pump on before demand was required was why I posted, also I didn`t know these pumps could auto adjust the outgoing pressure. Please remember how I earn a living and whilst I`m here to help others with my knowledge I`m also here to learn.

How do you earn a living then

 

[rpm]

Sorry wasn't having a dig was trying to explain ! Respect every one equally on this forum as everyone knows something u dont!

Thanks, appreciate that.

 

[rpm]

How do you earn a living then

Macerators, service & repair

 

[Ch4 plumbing]

I asked about the Grunfoss comfort at the merchants and he reckons their phasing it out? Any one got a heads up on that?