Re circulation line - DHW

[desktop987456]

Hi,

I have 160 litre vented DHW cylinder. I am trying to put a re-circulation line from cylinder to farthest fixture which would be going through two bedrooms till it reaches the farthest fixture.

I have bought a recirc pump Grundfos comfort BA 15-14 BA which i would be putting on re-circulation line. I have attached schematic for recirculation line for convenience. Couple of questions:
- Do I put the pump pumping into the cylinder (in cylinder, just as shown in picture?) or pumping away to farthest fixture?
- Is it worth putting extra money on 50ft copper pipe when the recirc pipe will be going through to the bedrooms to get to the fixture? I was thinking of getting away with cheaper alternatives than copper. Am I right in my thinking or should I stick to copper.
- can I put PEX or normal PPR pipe for recirculation line? pros or cons.
- the outlet of recirculation line is 3/4", can I put a narrower pipe 1/2" for recirc line?
Thanks

 

[Exedon]

Pump on return
Pipework needs to be copper or MLCP (plastic with a aluminium core)
We use tectite metal with tectite classic fittings and correct insert ,mainly because it's standard 15mm and 22mm and not 16mm.
Do not use standard plastic barrier pipe its not designed for the constant temperatures on re circulation systems.

 

[desktop987456]

Thank you. Understood pump on return. The length of the recirc line is 50ft to the hot water recirc inlet, Whereabout on the re-circulation line should I be putting the pump at the start of line from farthest fixture or near to the HW cylinder.

 

[muggles]

Install it near the cylinder. You can use plastic pipe provided it's not running continuously although MLCP / copper is a better option. Make sure it's well insulated. I'd use a motion sensor to control it so it only comes on when that room is occupied

 

[Elsa TLC]

Install it near the cylinder. You can use plastic pipe provided it's not running continuously although MLCP / copper is a better option. Make sure it's well insulated. I'd use a motion sensor to control it so it only comes on when that room is occupied

Id be talking to the manufacturers. To see if their position has changed.
Buteline used to say that their pipe and fittings can be used for a secondary return. They now don't recommend it.

Pumps with auto adapt and timers go wrong so cant be relied upon.

From my experience its the plastic fittings and not the pipe that's the problem.
One manufacturer said to use brass fittings with their pipe, however your out on your own if it goes tit's. Id stick to copper for the complete circuit.

 

[desktop987456]

From my experience its the plastic fittings and not the pipe that's the problem.

Thanks. I agree.

Install it near the cylinder.

Thank you.

I'd use a motion sensor to control it so it only comes on when that room is occupied

Which motion sensor to use for Grundfos comfort series pump?

 

[Elsa TLC]

Thanks. I agree.

Thank you.

Which motion sensor to use for Grundfos comfort series pump?
View attachment 388838

Ive used these before. They supposedly find your patterns to give you the right performance.

However people do tamper with these things and maybe cheaper less intelligent pumps get fitted as replacements.

However you seem up on this so you should be ok.

 

[desktop987456]

Thanks. The pump didn't come with the sensor, where can I source the sensor for this pump?

 

[Elsa TLC]

Thanks. The pump didn't come with the sensor, where can I source the sensor for this pump?

Its all as one.

The sensor is coiled around the end. The red bit on the side is the sensor. It should pull out.

 

[Exedon]

From my experience its the plastic fittings and not the pipe that's the problem.

On secondry circulation systems it is the pipe that's the problem.
Standard barrier pipe is designed to carry hot water then cool again. On a recirculation system that's run continuously it never cools and the inner part of the tube can strip out.
When the plastic pipe manufacturers stopped its use of barrier pipe on recirculation systems probably 10 years ago we switched to MLCP
have had zero problems.

 

[Elsa TLC]

On secondry circulation systems it is the pipe that's the problem.
Standard barrier pipe is designed to carry hot water then cool again. On a recirculation system that's run continuously it never cools and the inner part of the tube can strip out.
When the plastic pipe manufacturers stopped its use of barrier pipe on recirculation systems probably 10 years ago we switched to MLCP
have had zero problems.

You are right. It was just that the pipe I found failed inside the fittings.

 

[desktop987456]

Its all as one.

The sensor is coiled around the end. The red bit on the side is the sensor. It should pull out.

The sensor is missing on mine, I shared the generic picture of the pump for reference.

 

[Elsa TLC]

The sensor is missing on mine, I shared the generic picture of the pump for reference.

Talk to Granfos they should be able to set you straight.

 

[desktop987456]

Re-circulation line laid from farthest fixture to water heater, used aluminium layered PEX pipe 16mm. Insulated the pipe and buried it in a plastered wall, plaster to be done. I have laid an electric wire in a separate conduit from bathroom to the pump.
Also installed a non return valve from where the recirculation line starts (from farthest fixture) to prevent back flow from pump; as the T or X model of comfort series has non return valve built in, this one doesn't.
- Before commissioning the line, I want to install an occupancy sensor that will run the pump when bathroom is occupied. I have never installed a motion sensor so how do I wire it to the pump?
- The occupancy sensor would kick off the pump but what would stop it once hot water is through in recirculation line?
- Can I put a Tee on recirculation line to supply to another bathroom from recirculation line?
Thanks in advance.

 

[Razor900]

There are a couple of ways. You can either have the occupancy sensor trigger a timed relay or more usually use a sensor with a timer built in to run the pump for a set period

Yes you can run multiple loops from one pump

Oh and use preinsulated mlcp. One transition fitting at either end with almost no joints. By far the easiest way