Manifold system versus hot return system

[Russdl]

18 hours ago, PeterW said:

So if you were to go with bronze as your choice (not that I agree with Wilo and they have been wrong before...!) then you can switch it if you want but I think you’re spending money you don’t need to.

You make a convincing points Peter. At the stage when I was convinced it was absolutely the wrong pump I had planned to change it. The plumber who told me that it was the wrong pump also told me that the pump in the Willis circuit was a crap pump so I was going to replace the reported ‘crap’ pump the current Wilo and get a bronze Wilo for the hot return. Has the plumber sold me a dummy or is it a crap pump? (Water softener pipes in the way. I’ll get a better picture in a bit)

I should add, he wasn’t trying to sell me a replacement pump. 

 

Edited February 25, 2021 by Russdl
Added last sentence

[PeterW]

Pumps are pumps - I have a pair of £35 DAB pumps running in my attic that have been there for 10 years, one of which is running 18 hours a day on a 72°C thermal store and hasn’t missed a beat.
 

Downside..? It chews 45W and is getting slightly noisy but at 1p a day cost for the pump to date I’m not really worried...!!

 

What would I replace it with ..? Wilo now, but that’s because they are pretty robust and low power and are not overly expensive. 
 

TBH, your new plumber reminds me of a number of IT professionals I’ve worked with, and the analogy that no-one ever got fired for buying IBM..!! He has no interest in selling you the best value item based on what it is being used for, and knows that he can “flog on fear of failure” to you with named brands. 
 

If that’s how you want to install stuff then your choice but I would suggest that your new plumbers bills will be significant for a gold plated solution which is pretty pointless. 
 

I also know that here are a lot of OEM products in this market, and I bet your plumber will not even know what they are .... but I bet he’s best mates with the Reps at Wolseley... 

 

 

 

[SteamyTea]

Is cavitation a problem with pumps?

https://www.thermal-engineering.org/what-is-cavitation-in-centrifugal-pumps-definition/

[PeterW]

1 hour ago, SteamyTea said:

Is cavitation a problem with pumps?

https://www.thermal-engineering.org/what-is-cavitation-in-centrifugal-pumps-definition/

Yes if you run them too hard and there is any air in the system at all. Hence why having automatic air vents is ideal - if you look above the Willis there is a bottle vent which is highest point in the system. 

[SteamyTea]

41 minutes ago, PeterW said:

any air in the system at all

Cavitation also happens when there is no air.  It creates a vacuum 'bubble' which then collapses under the water pressure.  This micro hammering causes wear.

[Onoff]

3 hours ago, SteamyTea said:

Is cavitation a problem with pumps?

https://www.thermal-engineering.org/what-is-cavitation-in-centrifugal-pumps-definition/

 

Hell yes! Try operating a hydraulic pump at 2500psi when the pump is part full of air. Sounds like a horde of angry dwarves with hammers trying to escape!

[markc]

2 minutes ago, Onoff said:

 

Hell yes! Try operating a hydraulic pump at 2500psi when the pump is part full of air. Sounds like a horde of angry dwarves with hammers trying to escape!

Thats a pretty good description

[Onoff]

Ref Salus, our very own @Jeremy Harriswas using (and rating highly) Salus gear if I remember correctly. He was no mug either. 

 

 

 

 

[Onoff]

1 minute ago, markc said:

Thats a pretty good description

 

Wait until a filter housing next to your crown jewels disintegrates at the same pressure. Then it sounds like a 6'5" bloke screaming for his Mum & praying nothing vital's been hit. Ask me how I know! ?

[Onoff]

I've re-read this thread and you appear to have had one electrician and THREE plumbers on the job but the plumbing pictures show it looking unfinished? What are you doing to get through so many plumbers, you're not Zoot in disguise are you?  ?

 

(I still can't fathom "potable hot" btw).

[Russdl]

@Onoff it’s been unfinished for a good long time for reasons best not gone into here. It is now much closer to finished, water softener in, accumulator in, still have one dead Wilis heater but the system works fine on the one serviceable Wilis. Plumber No1 didn’t often show up, months between visits and we couldn’t put up with it any longer. Plumber No2 couldn’t fit me in. Plumber No3 could and he has got everything up and running. No’s 2 & 3 had opinions which they expressed and I repeated them here. The electrician who did most of the first fix but then stopped working for plumber No1 was back as part of his solar PV day job and he diagnosed the knackered Wilis heater. And expressed an opinion. 
 

Things are moving forward nicely now after many months in the Doldrums. 
 

@PeterW Thanks for your comments earlier, taken on board. 

[garrymartin]

On 24/02/2021 at 11:51, PeterW said:

@Russdl That’s not a cast body - it’s a resin body by the looks of it so I would query the model number on the front as a resin body pump is suitable for potable water instead of a bronze body (and Wilo confirm this)
 

And Hep2O can be used as a hot water return circuit. You have (incorrectly) read the guidance and don’t understand the BS/ EN definitions and I have had this confirmed by Wavin.

For info the below is the definition they (Wavin) use for a hot water return circuit which you don’t meet on 2 of the 3 criteria so you have no issues. 
 

 

 

 

 

@PeterW

 

Just wanted to add to Peter's excellent advice with the following graphic from the Hep2O Technical Manual as an additional resource for when people come across this thread in the future. It specifically mentions the design differences between locations and that domestic systems operating intermittently at less than 65 degrees are approved.

 

[sharpener]

For those who don't like the idea of a plastic bodied pump this is the best value bronze one I have found. Can also be turned down to much lower power consumption than the Wilo, see the graphs in the link.

[weslev]

On 01/10/2020 at 07:40, Nickfromwales said:

Just to clarify;

The HRC is added to the manifold system, it doesn’t ‘replace’ it. I still would steer well clear of series plumbing with T-offs for each room and go with radial ( off manifolds ) for the best results.

 

FYI, you simply add a 3rd manifold which accepts the hot return pipe runs. That is required for when you need to isolate a hot supply to a particular outlet, as if you didn’t have that then the outlet would get back-fed from the other hot return outlet connections ( as they would still connected via the common HRC connection at / before the HRC pump so at full hot pressure ). 

Remember that if you go away from

manifolds then you have to increase the size of the hot water pipe work, significantly, at the start of the DHW pipe run to cope with multiple outlets drawling from the same common connection. 
 

Thread title says VS but it should read “hot return or not?”  

@Nickfromwales apologies for resurrecting an old comment on an old thread but...

 

Am just embarking on my own H&C installation and have landed on a manifold system as the preferred option, have also settled on the fact that three of my hot outlets may or should be on a HRC as they are some way off from the manifold setup (and id like hot water to come out of the taps fairly quickly), those being two bathroom sinks and the kitchen sink (all roughly 15m). If you don't mind, my general questions on the HRC are: -

• Firstly is it actually necessary, then...
• I would be installing in hep2o and am fairly sure that the HRC is ok to be done in the same barrier pipe, is this correct?
• Flow and return both in 10mm hep2o or should the flow be larger? does it matter?
• My design for this set up would be to feed the whb's and sink from the main hot manifold but reduce to 10mm, have the HRC come back via 10mm to a return manifold specifically for these three returns, then from manifold run to an isolation valve, followed by a non return valve, then my secondary pump, a final isolation valve and then into UVC somewhere in the upper portion of it if at all possible. Is this logical.
• To save faffing on any technical controls, run the HRC from a programmable pump.

Hopefully I've explained my intentions correctly and would really appreciate any guidance you could offer.

 

KR

 

[Nickfromwales]

On 12/03/2024 at 10:36, sharpener said:

For those who don't like the idea of a plastic bodied pump this is the best value bronze one I have found. Can also be turned down to much lower power consumption than the Wilo, see the graphs in the link.

Excellent price too. Cheers, not seen that one before tbh as I just run to Grundfos Comfort these days. 👍

[Nickfromwales]

Hi @weslev, see below  
 

• Firstly is it actually necessary, then...
• < Up to you, cost vs comfort. At 15m you’re just on the tipping point tbh. 
• I would be installing in hep2o and am fairly sure that the HRC is ok to be done in the same barrier pipe, is this correct?
• < Yup.
• Flow and return both in 10mm hep2o or should the flow be larger? does it matter?
• < I’d do the lot in 10mm if the hot return is on and left running vs pulsed via a PIR etc. If pulsed, then flow in 15mm and return in 15mm too otherwise it takes a while to get ‘there and back’. 
• My design for this set up would be to feed the whb's and sink from the main hot manifold but reduce to 10mm, have the HRC come back via 10mm to a return manifold specifically for these three returns, then from manifold run to an isolation valve, followed by a non return valve, then my secondary pump, a final isolation valve and then into UVC somewhere in the upper portion of it if at all possible. Is this logical.
• < The HRCs need to come back to individual manifold ports, each with their own isolation valves, same as the hot out manifold; so each pair of hot and hot return can be isolated. This avoids having 3x isolations and a lot of exposed pipework at the basins. 
• To save faffing on any technical controls, run the HRC from a programmable pump.
• < Doesn’t need to be technical. It’s on or off / timed, or triggered by a motion sensor in that room. Typically I work on houses where we’ve installed a decent chunk of solar PV, so I just set these to run all day (if clients are retired / working from home) or on sensors / timed for all other situations. For the retired / other folks the system reverts to the sensors at night, and runs constant through the day, as losses are largely offset by PV anyways. So if you get up to go for a pee, by the time you’ve done the deed and want to wash your hands, the hot water is sat at the tap waiting for you. 

Resurrecting old threads is fine, good to blow the dust off them tbh. 

[Nickfromwales]

1 minute ago, Nickfromwales said:

Yup

Based on it being tempered or not running 24/7. 

[JohnMo]

58 minutes ago, Nickfromwales said:

Excellent price too. Cheers, not seen that one before tbh as I just run to Grundfos Comfort these days. 👍

 

On 12/03/2024 at 10:36, sharpener said:

idea of a plastic bodied pump this is the best value bronze one I have found

That is what I use, but the model with a timer. Set it to come on morning and evening and set the return temperature to about 35. Only runs for a couple of minutes time. There are two sizes, you just have to watch the head required, the small one is a very low head output.

 

 

[weslev]

1 hour ago, Nickfromwales said:

Hi @weslev, see below  
 

• Firstly is it actually necessary, then...
• < Up to you, cost vs comfort. At 15m you’re just on the tipping point tbh. 
• I would be installing in hep2o and am fairly sure that the HRC is ok to be done in the same barrier pipe, is this correct?
• < Yup.
• Flow and return both in 10mm hep2o or should the flow be larger? does it matter?
• < I’d do the lot in 10mm if the hot return is on and left running vs pulsed via a PIR etc. If pulsed, then flow in 15mm and return in 15mm too otherwise it takes a while to get ‘there and back’. 
• My design for this set up would be to feed the whb's and sink from the main hot manifold but reduce to 10mm, have the HRC come back via 10mm to a return manifold specifically for these three returns, then from manifold run to an isolation valve, followed by a non return valve, then my secondary pump, a final isolation valve and then into UVC somewhere in the upper portion of it if at all possible. Is this logical.
• < The HRCs need to come back to individual manifold ports, each with their own isolation valves, same as the hot out manifold; so each pair of hot and hot return can be isolated. This avoids having 3x isolations and a lot of exposed pipework at the basins. 
• To save faffing on any technical controls, run the HRC from a programmable pump.
• < Doesn’t need to be technical. It’s on or off / timed, or triggered by a motion sensor in that room. Typically I work on houses where we’ve installed a decent chunk of solar PV, so I just set these to run all day (if clients are retired / working from home) or on sensors / timed for all other situations. For the retired / other folks the system reverts to the sensors at night, and runs constant through the day, as losses are largely offset by PV anyways. So if you get up to go for a pee, by the time you’ve done the deed and want to wash your hands, the hot water is sat at the tap waiting for you. 

Resurrecting old threads is fine, good to blow the dust off them tbh. 

Thanks, thats really helpful.

 

They say, a little knowledge is a dangerous thing, and thats all ive got at the moment so places like this are really useful for asking some of the finer details.

 

If i go for the HRC i'll go 15mm and control it so that its not on all the time.

[Nickfromwales]

On 15/03/2024 at 11:06, weslev said:

Thanks, thats really helpful.

 

They say, a little knowledge is a dangerous thing, and thats all ive got at the moment so places like this are really useful for asking some of the finer details.

 

If i go for the HRC i'll go 15mm and control it so that its not on all the time.

Cool. Just with 10mm there and back, or even just back, vs 15mm there and back, the delay in getting the cold water (dead leg) gone eg getting the loop to circulate hot water from the tank to the tap is quite significant.

[Nickfromwales]

5 hours ago, weslev said:

Thanks, thats really helpful.

 

They say, a little knowledge is a dangerous thing, and thats all ive got at the moment so places like this are really useful for asking some of the finer details.

 

If i go for the HRC i'll go 15mm and control it so that its not on all the time.

Insulate both runs with at least 19mm wall insulation. FYI, you don't really need the more expensive black neoprene stuff as the thermal values are pretty much the same as the cheaper grey stuff. Just try to leave seams unbroken and slide the insulation down the pipe wherever possible as that save a mountain of awkward taping up along the lengths. Tape joints well, gaps are bad.

[Iceverge]

@weslev

 

I had the issue of a long run to the kitchen tap. 10mm pipe is fine for hot water. I have the "times to hot" in the below post. 

 

https://forum.buildhub.org.uk/topic/18834-unvented-cylinder-installation-spot-the-problem/?do=findComment&comment=377078

[weslev]

On 16/03/2024 at 20:59, Nickfromwales said:

Insulate both runs with at least 19mm wall insulation. FYI, you don't really need the more expensive black neoprene stuff as the thermal values are pretty much the same as the cheaper grey stuff. Just try to leave seams unbroken and slide the insulation down the pipe wherever possible as that save a mountain of awkward taping up along the lengths. Tape joints well, gaps are bad.

Thanks for the tips NFW.

🙌

[weslev]

On 16/03/2024 at 23:37, Iceverge said:

@weslev

 

I had the issue of a long run to the kitchen tap. 10mm pipe is fine for hot water. I have the "times to hot" in the below post. 

 

https://forum.buildhub.org.uk/topic/18834-unvented-cylinder-installation-spot-the-problem/?do=findComment&comment=377078

Thanks, interesting reading. 

 

I like the manifold straight out the top of the UVC, simple and effective.

 

KR

 

wes

 

[Iceverge]

2 hours ago, weslev said:

Thanks, interesting reading. 

 

I like the manifold straight out the top of the UVC, simple and effective.

 

KR

 

wes

 

 

It really helps. A tip from our Welch wizard. @Nickfromwales