Secondary heating loop?

[Post and beam]

What are the benefits, or reasons to avoid or include in my install please?

What effect does this configuration have on efficiency.

 

Thanks as always in advance for wise words

[JohnMo]

Do you mean secondary return loop on DHW?

 

If not done correctly can deplete the cylinder heat pretty quickly.

 

Pipes in full system need to be well insulated.

 

You need to limit when the system runs, so ideally have on a timer or a trigger of some sort. Ideally have a thermostat at the suction of the pump so it knows when the system is hot, then can cycle the pump on off to limit circulation flow.

 

If you have small bore pipes from a manifold to consumers, it may add little advantages but could be an energy drain.

 

It can limit the water draw off volume before hot out of tap.  Good for water conservation 

 

We have it but it's just on in the morning now. Evening is showers, so nearly hot by time you have undressed anyway.

[Post and beam]

Yes dude, secondary return loop for hot water. 

The pipe is insulated colour coded MLCP. I have been reading up quite a lot about it today. Due to the cost it adds to my first fix quote, posted here yesterday, i am minded to not bother.

[Andehh]

Def run one, and just insulate very thick and meticulously.

 

Was a lifesaver for us as the kitchen ended up about 25 seconds to draw hot water from the cylinder, reduced to about 4 seconds with the hot loop.

 

Bathroom towers are even quicker.

 

 

[sharpener]

The typical killer is the 22mm pipe to the bath. Make sure the washbasin taps are piped separately all the way from the tank in 15 or even 10, then you won't need secondary recirculation or pumps or stats or timers which can all go wrong.

 

 

Edited February 5 by sharpener

[Post and beam]

1 hour ago, sharpener said:

The typical killer is the 22mm pipe to the bath. Make sure the washbasin taps are piped separately all the way from the tank in 15 or even 10, then you won't need secondary recirculation or pumps or stats or timers which can all go wrong.

Thanks, that all sounds very sensible.

[Nickfromwales]

I do the showers, baths, and (if they’re less than 12m away) the kitchen and utility hot feeds all in 15mm on radials without the HRC feature. 
 

I then fit a second manifold via a TMV, which feeds to all wash basins ONLY, on 10mm flow (<12m) or 15mm flow (>12m) and always on 10mm returns to the HRC pump.

 

This means the recirculated water is never over 46°c, so you can use Hepworth (without voiding their warranty) and the dT is much lower than sending 50-55° DHW direct off the primary UVC TMV, thus reducing losses to the point it’s not worth crying about; but obvs the pipes are all insulated too!

 

An HRC is a brilliant luxury I would afford myself in a heartbeat, especially if I had solar PV > UVC all summer and an ASHP for cheap as chips DHW  in the first place. 
 

Defo include! 

[marshian]

12 minutes ago, Nickfromwales said:

I do the showers, baths, and (if they’re less than 12m away) the kitchen and utility hot feeds all in 15mm on radials without the HRC feature. 
 

I then fit a second manifold via a TMV, which feeds to all wash basins ONLY, on 10mm flow (<12m) or 15mm flow (>12m) and always on 10mm returns to the HRC pump.

 

This means the recirculated water is never over 46°c, so you can use Hepworth (without voiding their warranty) and the dT is much lower than sending 50-55° DHW direct off the primary UVC TMV, thus reducing losses to the point it’s not worth crying about; but obvs the pipes are all insulated too!

 

An HRC is a brilliant luxury I would afford myself in a heartbeat, especially if I had solar PV > UVC all summer and an ASHP for cheap as chips DHW  in the first place. 
 

Defo include! 

 

Any chance of schooling me in what a TMV is?

 

Long time bug bear of Mrs "Alien" is the amount of water she has to run off in the kitchen before she gets hot water - despite the VC being directly above the kitchen the Hot feed takes the long way round via bathroom first in 22 before reducing to 15mm going 2.4 m down a boxed section to feed first the downstairs toilet then utility room and down 1.0 m and then 6m across the house under the floor to get to back up to the kitchen sink

 

All the pipework runs are insulated.......

[Nickfromwales]

Thermostatic mixing valve. 

[marshian]

Just now, Nickfromwales said:

Thermostatic mixing valve. 

 

OK and radials - a loop of pipework without a pump (so reliant on convection currents?)

[Nickfromwales]

Just now, marshian said:

 

OK and radials - a loop of pipework without a pump (so reliant on convection currents?)

Nope. 
 

Radial runs from the hot water cylinder vs series run (which is what you have which sucks lol). 
 

So each hot and each cold has its own pipe from a hot or cold manifold at the cylinder.

 

[Nickfromwales]

These were all short runs, kitchen and utility very close, most bathrooms directly above, so no hot return required. 
 

Furthest basin was piped in 10mm and was less than 5-6 secs to get premium temp hot water out of the tap. 
 

Far right manifold was 4x wash basins and if you follow the pipe work back you’ll see it is fed via a TMV to cap the max temp at the basins. 

[marshian]

1 minute ago, Nickfromwales said:

Nope. 
 

Radial runs from the hot water cylinder vs series run (which is what you have which sucks lol). 
 

So each hot and each cold has its own pipe from a hot or cold manifold at the cylinder.

 

 

ahh OK so in doing that you "hopefully" minimise the distance to travel and with the pipe size minimise the volume of water that needs to be displaced before you get HW at the tap

 

No pump?

[Nickfromwales]

Just now, marshian said:

 

ahh OK so in doing that you "hopefully" minimise the distance to travel and with the pipe size minimise the volume of water that needs to be displaced before you get HW at the tap

 

No pump?

Yup. 

 

And nope, not on that job as it wasn’t necessary. 

[marshian]

Just now, Nickfromwales said:

These were all short runs, kitchen and utility very close, most bathrooms directly above, so no hot return required. 
 

Furthest basin was piped in 10mm and was less than 5-6 secs to get premium temp hot water out of the tap. 
 

Far right manifold was 4x wash basins and if you follow the pipe work back you’ll see it is fed via a TMV to cap the max temp at the basins. 

 

We posted at the same (or similar times) thanks for the further explanation even before I'd asked the question