Boiler system suggestions to run 2 showers

getmore4less

If you want to zone have a look at evohome.

You also need to check compatibility of any control with the underfloor which has significantly different hysteresis over rad based heating.

Occupancy based control us unlikely to work.

abankerbutnotafatcat

Thank you once again for all your help.

We absolutely understand that a system boiler with a large tank is the best solution for a large family.

However, we are seeking the best compromise between an efficient boiler that only provides what is required for the vast majority of the time when there will only be two occupants showering one after the other, and one that can cope with two showers running at the same time when there are more people in the house.

Alex1983

You can have too combi's I see it quite regularly in big houses but remember you need to buy too boiler and maintain 2 boilers. You will possibly need a bigger gas meter. Pipework will not be to much of a problem as your starting fresh, you can still zone sections of the system with a combi.

C_Mababejive

ComicGeek wrote: »

Based on what? You can't make that statement without further qualification, it really depends on what boiler models, hot water usage amount and patterns etc.

A good combi boiler with high summer dhw efficiency must be more efficient in most normal scenarios than a system boiler and cylinder, there are fewer losses involved.

Yes i agree. In general , im a big fan of storage. Not excessive storage you understand.....optimal storage.

Combi's have their place but many Brits are somehow expected to suffer very average or poor water performance because they have a combi which they have been sold by default and are easier to bang in.

As an example, i have a heat only boiler with a currently rated input of around 10Kw. The cylinder holds enough to fill a bath then some more. The output temp at the tap is around 55c,,plety hot enough and would need cooling a little. The response time to get hot water at taps is very little. I have the programmer set to optimse fireing times so that HW is available when needed. Humans are creatures of habit.

In comparison one of vaillants biggest domestic combis, the843 has a max heat input of 43Kw to create similar outflows with temp raised a max of around 45c.

There are other issues such as strains on gas and water networks, environmental issues such as water wasteage due to heat up inertia etc.

Any heat losses from my cylinder are lost to the home environment. Energy loss with the combi due to heat up inertia on HW draw off are exported down the drain.

But i agree, it horses for courses,,i do think too many combis are sold inappropriately though.

Clive_Woody

As mentioned previously, we recently went for an unvented set up when we had our bathrooms replaced. We lost the old hot water cylinder and cold water tank. We now have a Joule cylinder which our plumber recommended as being cheaper but equally as good as Megaflow, the cylinder was installed in the loft which works well for us and frees us space where the airing cupboard was. By losing the cold water tank you are getting mains cold water from all taps, therefore drinking water from any cold tap in the house (not a deal maker/breaker, but a nice to have).

My daughter enjoys very long showers and I can shower at the same time in the other shower....so far I have not experienced any cold showers despite her best efforts.

Alex1983

If you do put 2 combi's in they need to be under a combine 70kw and gas pipework be under 35mm for your gas engineer to be able to do it under his domestic qualification. Any bigger and he will need commercial certification.

getmore4less

You may be better with a gas combined heater/tank rather than a separate second boiler, seems more common in the US.

No pumping hot water through pipes to heat a tank probably much more efficient.

Then separate boiler for the heating requirements which will be off for a lot off the year.

silvercar

We have one combi boiler and one conventional one. Enough hot water in the tank from the conventional boiler for general use and the combi supples the en-suite showers as well as heating the extension part of the house.

The system works well, so much so that when we called in engineers to consider combining it all to one boiler and a mega flow (or similar) they all agreed that what we had suits our needs better.

C_Mababejive

Alex1983 wrote: »

If you do put 2 combi's in they need to be under a combine 70kw and gas pipework be under 35mm for your gas engineer to be able to do it under his domestic qualification. Any bigger and he will need commercial certification.

Indeed and on another point, it will likely have to be 64Kw or under otherwise it will exceed the design load of your domestic meter.