Change from System and tank to Combi

[DP]

That assumes that the delayed HW is solely due to lack of water flow. With a combi boiler and HW on demand, the water flow is limited by the capacity of the boiler to heat it dynamically. Speed up the flow too much with a secondary pump and the HW will just be lukewarm.

Secondary pump on an unvented cylinder NOT a combi boiler
OP has a heat only boiler and cylinder.

 

[ericmark]

Winter second pump maybe a good idea, but in summer, any heat into the house means AC runs for longer, so don't want the second pump. And it is not just a second pump, but flow and return, so extra pipework as well.

To lag the CH and DHW pipes together may again work in the winter, but not in the summer. Also to was hands 10 mm pipe work is ample, but not to run a bath. Even then down to boiler size, if the boiler can't deliver full bore with a 28 mm pipe, no point in having it that big.

I wash my hands likely 5 times a day after going to the toilet, but shower is instant electric, the washing machines (clothes and dishes) are cold fill, so between each use the water has gone cold. And often I will not wait for the hot, so that water drawn into the pipes just heats the house.

I like the reservoir of water, be it a tank, cylinder, or cistern does not matter. If the water goes off, I still have enough for a week or two. But I would if starting from scratch, likely have a different system. Smaller pipes for sure. But not starting from scratch, so will keep it as it is, not really worth changing.

 

[Echo the husky]

Secondary pump on an unvented cylinder NOT a combi boiler

The local council were fitting special combi boilers that had a built in secondary return a few years back. I haven't seen one since then, and I can't remember the brand.

My combi boiler has a small hot water reserve that can be kept hot for faster hot water delivery but I quickly switched that feature off when I moved in as it kept briefly firing the boiler at frequent intervals through the day and night to keep the reserve hot. When the boiler is BER I intend to replace it with a heat only boiler and adding a cylinder.

 

[DP]

The local council were fitting special combi boilers that had a built in secondary return a few years back. I haven't seen one since then, and I can't remember the brand.

My combi boiler has a small hot water reserve that can be kept hot for faster hot water delivery but I quickly switched that feature off when I moved in as it kept briefly firing the boiler at frequent intervals through the day and night to keep the reserve hot. When the boiler is BER I intend to replace it with a heat only boiler and adding a cylinder.

Secondary return pump is essentially required for larger properties that have remote hot water requirements. When this tap is run, there would be significant delay before hot water gets there. A hotel is a prime example= hot water on tap is quite quick to arrive. Combi on the other hand is intended for smaller properties which often consists of bathroom, kitchen and perhaps a shower room, therefore pipe run often is short so almost every hot water point thus defeating the need for secondary pump.

Be interested in further details of combi with secondary return pump. Another point of note is the secondary pump is connected between most remote hot tap and inlet pipe to the cylinder ( which is stored hot water ). There is no such storage in a combi so am at a loss to understand need for secondary pump in a combi boiler. Two pump combis have been produced in the past, but the pump in it does not act as secondary return pump but is there to replace the diverter valve

Please do post the boiler details you quote in your post