Unvented heating and hot water c/h system has hot water tank?

fezster

Because of the fast recovery times of modern unvented cylinders and the low heat loss from them, you can leave the hot water on if you anticipate multiple showers, and it's unlikely the hot water will run out. I can use my shower 24 hours later (with the boiler not having come on in between) and the water in the tank is still hot.

littlerock

I am finding this very interesting because I have never had a hot water tank for the last 20 years at least and I have never missed it. And I am puzzled about combi boilers only delivering warm water in very cold weather as I have never experienced any problem. How cold does it have to be again for this to happen? Sometimes if it is very cold outside, we have found running the bath taps a bit slower gives the water a chance to heat up, but that is all. But as before, I live in the centre of a southern city, which like many urban cities has its own micro climate, so we do not really experience severely cold weather these days.

Alex1983

You’ve answered your own question, in the very cold weather you’ve slowed the flow down to get adequate hot water. This isn’t as much of a problem with high powered combi’s but more with low powered combi’s which can’t give a high flow rate and temperature rise. You end up putting a combi in which is far more powerful then required to run your heating system to gain the better flow rates.

If you designed the system correctly you’d probably only need a boiler half the size as the combi you have and you’d have the best flow rates and high temperatures.