Secondary return hot options. Which way would you do it

[bigspark17]

Have a house to 2nd fix which has a hot water loop system off the immersion this has a pump onit ready for me to utilise. Standard system boiler set up.

Option 1
Install timeclock adjacent to pump.

Option 2
Install timeclock and pipe stat so that once the water has looped around once the pipestat will detect this on the return and stop pumping. Not wasting heatloss in pipe.

Option 3
Have the pump energised off the DHW side of the 2 channel programer, meaning return pump will be on while programer calls for heat.

Option 4
Have the return pump energised off the cylinder stat satisfied conection, pump will pump while cylinder is full of desired hot water.

Or any other way of doing it?

 

[PEG]

Hi,how big is the loop,and,most importantly,how thoroughly is it insulated?

 

[davesparks]

Normally I’d put it on its own timeswitch so that it can be set to run when it is needed, assuming the occupier of the property understands what it is and how it works.

Adding the pipestat is an interesting idea but will it ensure that the hot water delivery time meets the requirement?

Switching it on with the DHW channel of the programmer may not work as that should be timed to come on and heat the tank before the hot water is required for use, not necessarily whilst it is being used.

Having it connected to the satisfied terminal of the cylinder stat also relies on it being on at the programmer when hot water is required, not just when it is being heated.

 

[bigspark17]

Hi,how big is the loop,and,most importantly,how thoroughly is it insulated?

Roughly 50m loop, & pipes are mostly installed in insulated wall/floors.

 

[bigspark17]

Normally I’d put it on its own timeswitch so that it can be set to run when it is needed, assuming the occupier of the property understands what it is and how it works.

Adding the pipestat is an interesting idea but will it ensure that the hot water delivery time meets the requirement?

Switching it on with the DHW channel of the programmer may not work as that should be timed to come on and heat the tank before the hot water is required for use, not necessarily whilst it is being used.

Having it connected to the satisfied terminal of the cylinder stat also relies on it being on at the programmer when hot water is required, not just when it is being heated.

@davesparks i would normally install a timeclock also & inform the client to time as required after the cylinder has had adequate time to heat up. I just see this method abused when the customer doesnt fully understand the system and its left on permanently.

The ideal of a timeclock/pipestat setup is it can still be timed on, & once the loop has been filled to desired temp it would turn the pump off until temp drops below set temp on stat? Not tried it in practice tho.

Would be interested to hear @Leesparkykent thoughts/previous installs.

 

[Leesparkykent]

@davesparks i would normally install a timeclock also & inform the client to time as required after the cylinder has had adequate time to heat up. I just see this method abused when the customer doesnt fully understand the system and its left on permanently.

The ideal of a timeclock/pipestat setup is it can still be timed on, & once the loop has been filled to desired temp it would turn the pump off until temp drops below set temp on stat? Not tried it in practice tho.

Would be interested to hear @Leesparkykent thoughts/previous installs.

Hi mate, I usually just put it on a single channel programmer or mechanical timer.
I connect the common of the timer/programmer to the normally open terminal of the cylinder thermostat so the secondary return will only work if the cylinder is up to temp and the programmer is timed to come on.

The only down side of the mechanical timer is no battery back up.

 

[davesparks]

The ideal of a timeclock/pipestat setup is it can still be timed on, & once the loop has been filled to desired temp it would turn the pump off until temp drops below set temp on stat? Not tried it in practice tho.

The possible issue I can see is that parts of the loop could cool down faster than the section with the pipe stat on it, particularly assuming the pipe stat would be in the vicinity of the hot water cylinder which is usually quite a warm location.

I’m probably over-thinking the issue though

 

[PEG]

No,i agree,the idea is to put the tank,next to every outlet,which only works if tank and loop,rise and deplete,together.
This was the reason behind my insulation comment.

Without proper,continuous insulation to the return loop,it merely becomes another heat loss whilst pumping,and a cold dead-leg,when not.

I have assisted in fitting sensors,flow controls and other monitoring arrangements on systems such as these,and a reliable,efficient set-up is impossible,without A1 insulation to the full return pipework.

 

[Leesparkykent]

No,i agree,the idea is to put the tank,next to every outlet,which only works if tank and loop,rise and deplete,together.
This was the reason behind my insulation comment.

Without proper,continuous insulation to the return loop,it merely becomes another heat loss whilst pumping,and a cold dead-leg,when not.

I have assisted in fitting sensors,flow controls and other monitoring arrangements on systems such as these,and a reliable,efficient set-up is impossible,without A1 insulation to the full return pipework.

Not just the return....the whole hot water pipework needs to be insulated as it obviously draws from the cylinder. There is a requirement for a secondary return if the HW won't reach 50~C in 30 seconds from a hot tap.

 

[PEG]

Not just the return....the whole hot water pipework needs to be insulated as it obviously draws from the cylinder. There is a requirement for a secondary return if the HW won't reach 50~C in 30 seconds from a hot tap.

I see your whole hot water pipework...and i raise you...the cold water pipework,too

Invariably,the cold feeds follow the same route,and with secondary pipework forming a secret heat loop,nobody likes to brush their teeth with tepid water...

 

[bigspark17]

Not just the return....the whole hot water pipework needs to be insulated as it obviously draws from the cylinder. There is a requirement for a secondary return if the HW won't reach 50~C in 30 seconds from a hot tap.

On most presurised system you have built into the cylinder stat an overload linked in series to the stat, i dont recall there being a satisfied terminal on these? How do you get around that?

 

[Leesparkykent]

On most presurised system you have built into the cylinder stat an overload linked in series to the stat, i dont recall there being a satisfied terminal on these? How do you get around that?

They have a satisfied terminal as you can still pipe it as a Y-plan. you just have add an extra 2 port on the cylinder coil flow for the series connection of the the cylinder thermostat.

Terminal 3 on a megaflow is satisfied.

https://www.heatraesadia.com/-/medi...n-manuals/megaflo-eco-installation-manual.pdf Page 21, 2nd diagram.

 

[bigspark17]

They have a satisfied terminal as you can still pipe it as a Y-plan. you just have add an extra 2 port on the cylinder coil flow for the series connection of the the cylinder thermostat.

Terminal 3 on a megaflow is satisfied.

https://www.heatraesadia.com/-/medi...n-manuals/megaflo-eco-installation-manual.pdf Page 21, 2nd diagram.

So on a y plan your saying youd have to add another motorised valve? I cant see this being an option.

Pic below of standard overheat/cyl stat on standard pressurised system.

 

[Leesparkykent]

So on a y plan your saying youd have to add another motorised valve? I cant see this being an option.

Pic below of standard overheat/cyl stat on standard pressurised system.

Yes you can. On a 3 port mid position valve you obviously have 3 ports....AB is Flow from boiler, A is to radiators and B is to the cylinder, between port B of the 3 port and the cylinder flow connection, this is where the two port motorised valve goes. Normally closed of the cylider thermostat connects to the brown of the two port valve, normally open of the cylinder thermostat connects to the grey of the three port valve and HW off, on the programmer like normal. All the two port valve does is work like a kind of fail safe so in the event of a fault on the three port and it starts letting by then the two port is closed blocking the flow to the unvented cylinder. It's a G3 requirement of a Y-plan system with unvented hot-water storage.

 

[bigspark17]

Wouldnt it be a whole lot easier to convert to s plan? I wired today a presuried cylinder s plan and noticed no satisfied terminal on the cyl stat. Y plan seems old fasioned and no brnefit to s plan apart ftim giving priorety to DHW.