Secondary Circulation - switching on/off

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Jock Spanners

Jock Spanners

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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?
 
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
 
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.
 
Ermintrude said:
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.
Click to expand...
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.
 
Make sure you don't use plastic pipe/fittings on the secondary return.
 
croppie said:
Great minds and all that!
Click to expand...

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.
 
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.
 
Killy Bing said:
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.
Click to expand...

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.
 
If PIR in hall way. 30 second lead, toilet 120 second lead. By that time secondary is hot.
 
And you're all forgetting he has to fit a smart pump any way as per EUP.................
 
then its a dumb pump anyhow :) wont a pir in a halllway just turn on the pump everytime anyone goes by??
 
Last edited by a moderator:
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?
 
lame plumber said:
then its a dumb pump anyhow
smile.png
wont a pir in a halllway just turn on the pump everytime anyone goes by??
Click to expand...

My point exactly.

No matter how sporadic the lads bathroom visits are the grundfos will build a suitable database of optimum run times.
 
croppie said:
My point exactly.

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

Really? The pumps not just going to spaz and just run or not run?
 
Surely the pump will be damaged if it`s running against a closed head or am I just old school?
 
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.
 
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
 
It won't withstand the constant temperature. It specifies this on JG if I recall.
 
rpm said:
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.
Click to expand...

But it's not a closed head it's a pressurised open circuit unless nrv packs up. .
 
Ermintrude said:
But it's not a closed head it's a pressurised open circuit unless nrv packs up. .
Click to expand...

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

How do you earn a living then
 
I asked about the Grunfoss comfort at the merchants and he reckons their phasing it out? Any one got a heads up on that?
 
It really is a shame that so many plumbers stay away from them, 90% of call-outs are wet wipes nowadays. In and out in around an hour, really is easy money but then I wouldn`t know where to start on the stuff you guy`s do. As I say horses for courses and I`m learning loads from you guy`s.
 
Ch4 plumbing said:
I asked about the Grunfoss comfort at the merchants and he reckons their phasing it out? Any one got a heads up on that?
Click to expand...

Hadn't heard that now. Possibly because the Alpha2 has a stainless steel body and can do both heating and potable water.
 
rpm said:
It really is a shame that so many plumbers stay away from them, 90% of call-outs are wet wipes nowadays. In and out in around an hour, really is easy money but then I wouldn`t know where to start on the stuff you guy`s do. As I say horses for courses and I`m learning loads from you guy`s.
Click to expand...

And I now where to find a decent plumber when I need one :crowngrin:
 
rpm said:
It really is a shame that so many plumbers stay away from them, 90% of call-outs are wet wipes nowadays. In and out in around an hour, really is easy money but then I wouldn`t know where to start on the stuff you guy`s do. As I say horses for courses and I`m learning loads from you guy`s.
Click to expand...

Mate. you couldn't pay me enough to even contemplate your job.
 
croppie said:
Mate. you couldn't pay me enough to even contemplate your job.
Click to expand...

First six months is the worst mate, apart from the one`s in the height of summer which have been left switched on for a few days, even now I need to step outside for some fresh air. But no exams no licence no expensive tools like you guy`s.
 
have no tools - 24" stilly which are like a multi tool, Hammer screwdriver. Combustion analyser , tape measure.

I only got train tickets?
 
croppie said:
Hadn't heard that now. Possibly because the Alpha2 has a stainless steel body and can do both heating and potable water.
Click to expand...


Just checked Grundfoss site and the standard Alpha 2 pump is for underfloor and heating and the Alpha2n and Alpha2ln are for hot water?
 
Ermintrude said:
have no tools - 24" stilly which are like a multi tool, Hammer screwdriver. Combustion analyser , tape measure.

I only got train tickets?
Click to expand...

Still got my 24" stillys with slip on scaffold pipe, No.2,3 & 4 copper & hide mallets, all the spanners and large sockets from the old days in Battersea power station amongst others mate just never need them now but can`t bring myself to throw or give away.
 
Wow you worked at battersea? It's a immense building was supposed to go to see prodigy in mid 1990s but didn't make it mates did. It's a massive . The genny halls are huge!

I could spend years looking round old industrial buildings.
 
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