Hot feed to another cylinder - any issues?

[recursives]

Hi.

We have an annexe which has an issue with the length of time that water takes to run hot from the tap.

One of the solutions we are looking at is to install another direct cylinder (approx 112l) closer to the annexe so that hot water is almost instantly available.

My question is whether there are any issues with using our existing hot feed as the supply to the new cylinder. The theory being that there will be 112l of hot water instantly available but if that is all used then there is another x hundred litres (sorry can't remember the main tank stats) available from our primary cylinder. There would be approx 5l of cold water in the pipework before hot water enters the cylinder - that should mix in quite quickly.

The 'main' cylinder has all the necessary mixer/filter controls and essentially the 'second' cylinder is just a storage vehicle. Obviously it will still need a TPV etc but as the feed will already have passed through primary filters etc I can't see that it would need a second one.
That's the issue really, as there could be a problem sending already hot water into the mixer/filter messing with the wax (I think).

Anyone ever done this or has knowledge of building control regs on this?

Your thoughts would be much appreciated.

Dennis

 

[AWheating]

fit a secondary return to existing hot water system.

 

[recursives]

fit a secondary return to existing hot water system.

Thanks for the reply. We have discounted a secondary return as too wasteful - the water requirement in the annexe will be very low and/or intermittent and it makes no sense to effectively create a radiator in the roof void (no matter how well insulated).

 

[Old Account]

If I were you I would consider a secondary return.

The Grundfos UP 15-14BA circulator pump is a secondary hot water service circulator with Auto Adapt.

It's designed for the following:
domestic hot-water systems in single and two family house
small heating system
cooling and air-conditioning systems
However, the Grundfos COMFORT Pump range is high in energy-efficiency hot water recirculation in domestic homes. It has a very quiet running motor to due to a noise permanent magnet motor, the energy consumption is reduced to as little as 5-8 W. The autoadapt function ensuring that the pump runs only when required which means it minimises both heat and power waste. So you will achieve the best result for maximum comfort with a minimum of water / heat and electricity.

The pump is suitable for vented and closed systems but it must be installed indoors and should only be fitted into pressurised hot water circulation systems.

 

[Dilalio]

Secondary return and just stick a timer in to control the pump for periods of demand.

 

[Welder]

Recursive.
If the secondary cylinder is directly fed from the first, there is no need for separate controls as the heating of the water will take place in the primary.
That said, as you've said the water usage is "very low and/or intermittent", you'll gain no benefit whatsoever because the cylinder will cool down without it continually being refreshed. When you need it the whole cylinder will need to be refreshed (bottom in top out) instead of just a little in the pipework.
The advice you've already been given re a secondary return is the correct advice in every sense - even though you may think differently.
FYI, insulating the pipework correctly and setting the pump to operate correctly will see you lose less heat than an unused cylinder. This means the circulation pump is actually the least wasteful option.
As always, a little understanding can be a dangerous thing.

 

[SimonG]

Secondary return, well insulated and only pumped when required. Timer or pir.

 

[Stigster]

+1 for the secondary return with PIR. That is an ideal setup for what OP is trying to achieve.

 

[Dilalio]

If you have the cabling access then yes, that is a perfect solution - depending on where you locate the sensor.