Hot water recirculation system efficiency.

With more homes looking to save energy, many are moving to heat pumps which could see a massive reduction in instantaneous hot water systems (combi boilers)—bringing back the cylinder to your client’s homes. But looking further into a cylinder-based hot water system might have some hidden benefits that your clients might not have considered.

“Heating” hot water

Did you know every time a gas combination boiler has to heat water, the efficiency of the boiler drastically drops whilst generating hot water. This is because you have to push your flame rate in the boiler up, causing it to fall out of the condensing mode. You are dropping the efficiency to as low as 70-80%. A system-style hot water system relies on storing water, removing these peak demands. Match this then to a heat pump, and you can operate four or even five times the input energy.

Reducing water use

This comes down to this article’s point, which is a recirculation loop. By looping the hot water back into the cylinder and pumping this, you can massively decrease water usage, whereas a combi boiler (that cannot really have a secondary loop) has to heat up water, pipes, and heat exchanger, and then send it through the pipes around the house. Then, finally, you get your hot water. This is frustrating to wait that long and can waste as much as 12 litres of water every minute of running. By recirculating, you eliminate this issue by having hot water when you need it (which is also a massive time-saving).

However, a few things to consider to minimise energy loss.

Insulate your system

The larger the system (including the pipes), the more energy you lose to use up the reheat. You can be losing as much as 30w/m on a simple 15mm bit of pipe. Compare this to 7w/m if this was insulated. So make sure both your cylinder and pipework system (both hot water flow and return is insulated as much as possible). Remember, we do pre-insulated pipe to save time!

Install a timer

When you are asleep, the chances are you are not using hot water, so why not install a timer on the secondary pump for your customer? Therefore at night, you are saving the energy you would have lost through the pipe system (even if it is lagged). Why not go even more fancy and hook it in with a PIR sensor, so any time someone is in a WC, the pump turns on…

Type of owner

If you have a larger family that uses hot water daily, a cylinder is for you. However, if you are out most of the day and live on your own, an instantaneous water heater is better for you. So consider the occupier of the house. This is because storing anything (no matter how good the insulation is) does always lose energy. The longer the period the system is not used, the more energy is lost.

As always, if you have any questions, our friendly team is here to help! Give us a call on 01245 227630 or email [email protected].

Secondary Recirculation Systems

Why You Should Use Secondary Recirculation Systems

As houses get bigger and clients demand even more from their installer, one of the biggest issues is delivering hot water quickly and efficiently to the hot water taps. The only way to efficiently do this is by setting up a circulation loop from the cylinder to the tap emanating the dead leg between the two – known as a secondary recirculation system. Although there are no legal requirements to fit one, HSE’s best practice is to deliver 50°C water within 1 minute to a tap; this is for legionnaire control.

How Does a Recirculation System Work?

The idea is you have your primary hot water pipe flowing through your house. Besides this, you have a “secondary recirculation pipe”, which travels beside the hot water primary pipe to the extremities of the system. The secondary pipe taps into the primary to join the two pipes. The cylinder then has a hot water circulation pump (normal heating system pumps will not work). The pump is set to push the water through the primary pipe to the tap, and it then returns on the secondary pipe, thereby keeping your hot water hot all the way to the tap.

Limits of a Secondary System

With 60-70°c water flowing through it for most of the day, the secondary pipe has a hard life. A heating system can flush through the water’s pH and impurities. However, you cannot do this with a recirculation water system. Also, you are transporting oxygenated water, which can harm parts of a system. This is why all plastic pipes made under BS 7291 cannot be used on these systems. However, because of how our pipework is made, MLCP can be used with recirculation systems as Multipipe MLCP is made to a different standard than plastic pipe. See our MLCP range here

Our Top Recommendations for Secondary Recirculation Systems

  • Where possible, insulate as much of the pipe with good quality, thick insulation. This will limit the heat loss going back to the cylinder.
  • Only use a WRAS-approved pump specifically designed for hot water circulation.
  • Fitting a timer to the pump is a great idea for energy efficiency to stop the circulation when not needed.
  • You can use a rule of thumb of 2 sizes smaller than the flow pipe for sizing the right pipe.
  • If you have reduced flow rates at your tap, you might need to fit a flow restrictor on the secondary pipe to push water to the tap.

Towel Rails

Did you know fitting a towel rail on the secondary circuit can be done? This is great because they keep constantly hot! (as long as the timer runs). Ensure you consider the heat loss to your cylinder, but also, they *MUST* be WRAS approved and made of stainless steel or copper. Lastly, the towel rail should only be fitted to the return circuit of the hot water system.

If you have any questions about secondary recirculation systems, please email our technical team who will be happy to help: [email protected].