DHW secondary recirculation advice

[Andypeeps]

Hi,

Same old problem of long draw off, I decided to put a recirculation loop in. A bit new to this and probably should have researched a bit better. I've looked for similar problems on this forum but can't see anything similar. Apologies if I've missed it.

As I am refurbishing it was easy to put a return pipe from the furthest sink back to the loft. I did this by connecting it up to the cold inlet pipe via a NRV. First question: Is that OK or does it have to be a secondary connection into the tank? I also put an NRV into the cold feed so no danger of it feeding back to anywhere else.

Also, rather than having the pump running all the time wasting hot water, I was thinking about putting 'on-demand' buttons outside bathrooms/ kitchen etc that would only turn the pump on for a few minutes when hot water was required. The buttons would be like the light switches one presses that will turn on for a few minutes and then turn off. Is this a dumb idea? We have unusual usage timings and i didn't want the pump running constantly

The other question is what pump I need, that's not going to cost the earth? I'm UK based. I know Grundfos do 'comfort' pumps but these are £200-300 and was hoping for something a bit cheaper.

The tank is in the loft and I was planning on putting the pump by the last sink on the ground floor which is about 16m of pipe run (each way), so a long pipe run. I bought a pump from Amazon but its not drawing the water off and I think it's not powerful enough: https://www.amazon.co.uk/Circulator.../B079Z832FD/ref=psdc_1938160031_t1_B07QGLKJVD

Any advice on the best way of doing this now I've half done it would be much appreciated.

Cheers

 

[oldbutnotdead]

The push for hot water isn't going to work. It takes time for hot to be pumped from tank to end of leg, more time than will elapse between pushing a button at the door & wanting some hot.
Having the return coming into the cold feed is fine as long as there's an NRV in the cold feed before your return tees into it. Make sure the cold feed is insulated from the tee to the cylinder.
Is all your DHW pipework insulated? If not, insulate it (including the return). This will mean the water being moved by your low volume pump will still be warm when it gets to the far end of the loop.
You often get what you pay for from one of the worlds biggest tax avoiders. There is no mention of what head that pump can deal with (nothing to do with max operating pressure). You have 32 metres of pipe with many bends, each bend equates to 0.5 metres of pipe and each metre of pipe exerts drag on the water which the pump has to overcome. Google it. Then buy a pump that is up to the job.
Control- timeswitch and a pipe thermostat. Timeswitch to set overall operating times, pipe thermostat on the return pipe at the farthest point from the cylinder set to activate pump when pipe temp drops below 40 deg C to start with, play with it til it works for you.
You have put the pump in the return haven't you? Pumping in the correct direction? ( The uphill drag to the loft won't be helping,)

 

[dilalio]

Hope you haven't used standard barrier pipe (pushfit plastic) for any of the DHW flow and secondary return.

 

[muggles]

Buttons to press are easily forgotten. I prefer to fit motion sensors in the rooms with hot water outlets - that way they activate as soon as you walk into the room. A pipe thermostat can be used to prevent the pump activating when the loop is warm. If you want a crap circulator then this will fit your requirements https://www.pumpsalesdirect.co.uk/c...mp-240v-direct-replacement-of-ups-15-50n.html

The old mantra of "buy cheap, buy twice" apples though. Personally I'd rather go for a good quality one from the start

 

[Andypeeps]

Many thanks for your responses. It sounds like I may have to bite the bullet and spend big!! The pump I have bought (I since found out) has a 1.8m head. Doesn't sound enough now given your rough calculation (which is helpful) but I thought as it's circulating, I wouldn't need much.

Grundfos has a comfort pump with a built in thermostat so that may be an option. https://uk.grundfos.com/products/find-product/comfort.html Yep I put the pump in the return (in the right direction) and all the pipework (will be) insulated just haven't got around to it yet. All the pipe is soldered copper. Call me a traditionalist but I can't be doing with this new fangled plastic malarkey. Lot more expensive but so are leaks!!

Motion sensors is an interesting idea, although wouldn't work in the kitchen as we're in there most of the time without needing hot water. I'll have a look at your suggested pump and similar.

Any specific requirements for a separate pipe thermostat? Doesn't need to be particularly fast acting but would like not to put too much hot water back up the return if possible.

Thanks again.

 

[oldbutnotdead]

Pipe stats- can't find the thread now but someone on here pointed me to brewing thermostats at The Worlds Biggest Tax Avoider- think they were £10, have adjustable set points and adjustable hysterisis (the temp gap between satisfied and call for heat).
Quick experiment for you- do yr insulation, get a decent pump etc, tune system so it gives you what you want then leave hot water system running 24 hrs without heating on & without using any hot water. Read gas meter at start & end and cslculate daily running cost. Then decide if you can bear that cost

 

[Andypeeps]

Thanks for the tips @oldbutnotdead. I will investigate. If you do come across the thermostats please let me know. I had a quick search but couldn't find anything that matches your description. Cheers

 

[Bodd]

Hope you haven't used standard barrier pipe (pushfit plastic) for any of the DHW flow and secondary return.

Could do it with Buteline.

 

[dilalio]

Could do it with Buteline.

I know what it can be done with.
My post was hoping OP hadn't used what you can't.

 

[Bodd]

I know what it can be done with.
My post was hoping OP hadn't used what you can't.

... Sorry.......

 

[dilalio]

... Sorry.......

Its cool

 

[Bodd]

Its cool

 

[Andypeeps]

Could do it with Buteline.

Is this what all the 'cool kids' are using these days? I did have a quick look at it but wasn't sure about the longevity and the cost of the tools/ connections. Given the cost of copper and irritations with soldering, perhaps I should have considered it more seriously. Is it available in 22mm and 15mm?

 

[Bodd]

Is this what all the 'cool kids' are using these days? I did have a quick look at it but wasn't sure about the longevity and the cost of the tools/ connections. Given the cost of copper and irritations with soldering, perhaps I should have considered it more seriously. Is it available in 22mm and 15mm?

I like it far better than push fit. You have to work with it in a different way, you have to think different. I have both the manual and cordless tools.
problems are:
Lack of merchants that stock it
Having to get the cordless tool re-calibrated.
16mm is not such a problem fitting the stuff, its when someone in the future wants to add to it.
I worked for a fella in Australia, where they mainly use press fit of many different brands. Problem he had was having to buy all the tools to add to the system.
Cost a fortune.