Secondary return???

[myatix]

Hi All, i have a Quick question with regards to a secondary return. I am in the middle of installing an ASHP with a Heat Geek high performance unvented cylinder.
I have a question with regards to where to join the secondary return.
1. Directly into the cylinder
2. Into the Hot water run close to the cylinder?

The reason for asking is because I could imagine that going directly into the cylinder Would cause more mixing and therefore reducing stratification in the cylinder.

I have 28mm cold water mains into the cylinder and was planning on using a 15mm pipe for 7m secondary loop. I presume 15mm is sufficient?

Thanks for any help.

 

[Madrab]

A secondary return would normally feed back into the cylinder's secondary return tapping. The bronze pump would usually live by the cylinder and pump the HW back up into the cylinder. With the HG unvented it should be the same would need to check.

15mm will be fine - usually a pipe size smaller than the main run for the secondary return and makes sure it's all well lagged.

 

[cross thread]

And what pipe are you using for secondary return? Copper ok some plastic not.

 

[Exedon]

Standard barrier type plastic cannot be used its not intended to run at constant hot temperatures. .
All the manufacturers stopped it's use probably 10 years or more ago.
We use tectite metal (aluminium core) on secondary return hot water systems.

 

[polesapart]

Adjacent cylinder makes no sense to me: how would the heated water find its way into the loop?

 

[myatix]

The pipe is 15mm stainless steel. I am an expat living in Denmark and copper is not really used much any more.

I am planning to increase the pipe size to 22mm just before before it enters the cylinder (1/2 meter) to reduce the flow. One of the main goals of the Heat Geek cylinder is to use stratification to improve efficiency and having a 15mm jet of water flowing into the secondary return is bound to mix things up in the cylinder.

 

[Madrab]

One of the main goals of the Heat Geek cylinder is to use stratification to improve efficiency and having a 15mm jet of water flowing into the secondary return is bound to mix things up in the cylinder.

Maybe they thought about that when they placed the secondary return where they did??

 

[dilalio]

The pipe is 15mm stainless steel. I am an expat living in Denmark and copper is not really used much any more.

I am planning to increase the pipe size to 22mm just before before it enters the cylinder (1/2 meter) to reduce the flow. One of the main goals of the Heat Geek cylinder is to use stratification to improve efficiency and having a 15mm jet of water flowing into the secondary return is bound to mix things up in the cylinder.

Why not just call them and ask?

 

[Elsa TLC]

The pipe is 15mm stainless steel. I am an expat living in Denmark and copper is not really used much any more.

I am planning to increase the pipe size to 22mm just before before it enters the cylinder (1/2 meter) to reduce the flow. One of the main goals of the Heat Geek cylinder is to use stratification to improve efficiency and having a 15mm jet of water flowing into the secondary return is bound to mix things up in the cylinder.

REHAU I would Imagine is available in Denmark.
Check to see if this can be used.
Buteline from NZ can be used for secondary return, as long as you have it on a timer.

 

[dilalio]

Recirc is going to be detrimental to SCOP. Radial circuit off manifold would be better.

 

[myatix]

@dilalio The plan is to create a radial curcuit from the manifold to the cylinder which is 7m. Creating a secondary loop between the bathroom and manifold is not an option as all pipe goes underfloor construction (concrete)

 

[dilalio]

@dilalio The plan is to create a radial curcuit from the manifold to the cylinder which is 7m. Creating a secondary loop between the bathroom and manifold is not an option as all pipe goes underfloor construction (concrete)

Manifold to cylinder.... Radial?
Sketch?

 

[myatix]

Manifold to cylinder.... Radial?
Sketch?

Sorry have no idea what you’re saying here???

 

[dilalio]

Sorry have no idea what you’re saying here???

I was asking if you could upload a sketch/diagram because I couldn't understand what you mean by radial circuit from manifold to cylinder!

When I said manifold for hot water with radial circuit, I meant individual pipes to each hot outlet, thus reducing pipe runs and heat up time to the furthest away...
If cylinder is central to them.... Not always feasible I know.

 

[myatix]

Hi again,

The cylinder is not central at all it’s a retro fit so is located in a room away from the original combi boiler and manifold. The original manifold is somewhat central but that means there is a 7m run from the cylinder to the original manifold and then the manifold runs out to each individual tap/ shower etc. (Furthest being about 12 meters away)

The customer already feels that waiting 1 minute for hot water to the bathroom furthest from the manifold is annoying. Adding another 7m of 28mm pipe to the manifold is by no means improving that situation so running a secondary return from the existing manifold to the new cylinder ensures it doesn’t get any worse.