Hot water return in Hep2O? is this really a problem?

[Great_scot_selfbuild]

I've come across this statement:

“Hep2O should not be installed in Continuously operated re-circulating systems (Secondary Hot Water Circulation / Ring main installations).”

 

I was planning on using Hep2O pipework from the plant room to the end points, with the long hot water runs (20-30m) having a 10mm return line to enable circulation to avoid running taps, wasting water and waiting for the water to heat up.

 

I was sure I'd come across this approach by others - is this something I should be worried about? if not, why not?

[JohnMo]

Are you actually going to run continuously - I don't and wouldn't if I were either. Get a pump with a timer and thermostat and set a time or various time windows. The pump will run until the thermostat senses the return water at its set point pump then switched off. As the water cools the thermostat triggers the pump to start again.

[Great_scot_selfbuild]

55 minutes ago, JohnMo said:

Are you actually going to run continuously - I don't and wouldn't if I were either. Get a pump with a timer and thermostat and set a time or various time windows. The pump will run until the thermostat senses the return water at its set point pump then switched off. As the water cools the thermostat triggers the pump to start again.

I knew I was missing something!! @JohnMo Thank you so much for this. Just the advice / nudge I was needing 🤩 👏

[Nickfromwales]

31 minutes ago, Great_scot_selfbuild said:

I knew I was missing something!! @JohnMo Thank you so much for this. Just the advice / nudge I was needing 🤩 👏

You need to do the run in 15mm if you don’t want huge swings in the temp of the pipe.
 

You open the tap on such a long, timed loop, then you get tepid / warm / hot / warm / tepid / warm / hot / tepid / fully hot water (eventually).

 

If it’s for a basin for eg then you’ll be surprised at how hot you need this (entire) loop to (consistently) be to have an effective setup. For a bath or shower feed you’d just open the hot tap full bore and not give 2 fecks what temps you get before you get delivery of the water from the cylinder at that temp. 

[torre]

8 hours ago, Great_scot_selfbuild said:

Hep2O should not be installed in Continuously operated re-circulating systems

I'm a fan of Hep2O but that advice is direct from the manufacturer, so probably best heeded, Presumably doesn't like to be hot/expanded for too long

[-rick-]

2 hours ago, JohnMo said:

Get a pump with a timer and thermostat and set a time or various time windows. The pump will run until the thermostat senses the return water at its set point pump then switched off. As the water cools the thermostat triggers the pump to start again.

 

44 minutes ago, Nickfromwales said:

You open the tap on such a long, timed loop, then you get tepid / warm / hot / warm / tepid / warm / hot / tepid / fully hot water (eventually).

 

I thought the way to do this on a new install is to have sensors in the rooms with taps to switch the pump on (with heat based shutoff) when the rooms are occupied/light is on? Doesn't this avoid problems here?

[JohnMo]

4 hours ago, Nickfromwales said:

tepid / warm / hot / warm / tepid / warm / hot / tepid / fully hot water

Sort off. But you don't have cold water. It is fine and dandy for washing hands/face. Which is all you are doing most the time. We are pumping 20m and it's just fine. Room sensors are another way but more stuff to buy and wire in. Pump with integrated timer and thermostat easy and they are fit for purpose.

 

As you say shower or bath who cares, by the time you have removed your clothes etc it is ready to dive in to - recirculation or not, assuming you aren't using 22mm pipe that is.

[Alan Ambrose]

Curious - I can't think why it's ok for hot feeds but not for recirculating.

[-rick-]

8 minutes ago, Alan Ambrose said:

Curious - I can't think why it's ok for hot feeds but not for recirculating.

 

Hot is only really hot while the water is running. Then it will cool down. Constantly circulating hot loop will always be hot, and given the specs they have to assume the water will be 80C+ continuously.

[Nickfromwales]

1 hour ago, -rick- said:

 

Hot is only really hot while the water is running. Then it will cool down. Constantly circulating hot loop will always be hot, and given the specs they have to assume the water will be 80C+ continuously.

Eh? What spec is that?!

 

Hottest I ever recirculate is 55-57°. 
 

80° should never be allowed out of the water cylinder. Ever. 

[-rick-]

1 hour ago, Nickfromwales said:

Eh? What spec is that?!

 

Hottest I ever recirculate is 55-57°. 
 

80° should never be allowed out of the water cylinder. Ever. 

 

Max rating of the pipe. I didn't check before I sent it but I thought generally the plastic pipe makers were ok upto 80/90C. You wouldn't want to run like that* but they need to be able to stand behind the product if someone does.

 

* Older hospitals, hotels, etc, often have very hot loops and mix down near the consumers.