Water Heating Question

With this number of bathrooms and outlets, your average instantaneous combi won't be keeping up if you use multiple outlets at the same time.

You'll need either one of the following:

1. Just lump it and only use one shower at a time and scream at people not to use the hot taps.
2. Get a storage based solution.
3. Get a combi with more capability.
4. Get a Dr Drivel second combi for one of the bathrooms.

Which solution is optimal depends on many variables.

As to the issue with the downstairs (presumably kitchen) taps starving the showers, you might consider a local electric heater. They're fine for handwashing and even doing the dishes, and will prevent the upstairs shower running cold.

Christian.

Heat recovery devices on the showers may help a little, as well as reducing cost.

We have a Worcester 350 which is also running 14 (soon to be 15) radiators. Wonder if there's a larger capacity boiler easily available? Interested in the Dr Drivel! What's that about?

It's also the utility room taps - but plenty of shouting currently accompanies most showers!

Thanks.

Switch all your laundry appliances (i.e. dishwasher/washing machine) to cold fill only, if they currently use any hot.

Turning down the isolator valve for the tap to reduce flow rate can help with the taps. Stops them taking all the hot water, although will obviously increase sink fill times.

Christian.

In case you're new to this NG, there is a frequent poster currently calling himself 'Dr Evil' (an inadvertent anagram of 'drivel') to whom the answer to any question is to install one or more combi boilers. His views are disregarded by the more discerning contributors!

The problem which you are going to have with *any* system producing instant hot water is that - unless you have a very large capacity cold mains supply - turning on *any* tap will reduce the mains pressure and have repercussions elsewhere in the house. This is regardless of the number of independent heating devices - because they are *all* fed from the same mains supply.

In your position, I would be seriously considering a hot water storage system - probably using instant hot water from the combi for the kitchen tap only. With suitable zone valves etc. you can make the CH side of the combi heat both the radiators *and* a tank of hot water.

Thanks for the useful advice - time to start planning my attack on this one I think. I used to be a regular visitor to this NG, but have been too busy with other things (the house mainly!) in recent times. I'll watch out for Dr Evil. I had already concluded the limitations of our cold water supply. As you say, stored seems to be the way to go.

Note that if there is insufficient water actually entering the house, you'll need to either fix the cold supply, or install huge loft tanks (and pumps if you want a decent shower).

Christian.

This could probably be added to current boiler, perhaps retaining the combi hot water for nearby usage, or the upstairs shower where higher pressure than loft tank might be an advantage, and using a hot water cylinder for everything else.

Sounds like all the water is provided off the mains? Think you'd have to upgrade this considerably to provide enough flow for all this lot.

Have you space in the roof void for a cold water storage tank? That and a stored hot water system of suitable size would get round the problems of everything interfering with everything else - if the pipe sizes are carefully calculated. You'd obviously keep mains feeds to cold water taps where it might be used for drinking, and could keep the combi supplying the kitchen.

That is unfair, he also has suggested at various times installing 15ft of rockwool in the attic, Prescott in the Monarchy, and Tony Blair as arcbishop.

Not to mention magic magnetic water softeners.

Its full moon tonight so he is probably under restraint somewhere - or roaming the streets drooling.

What I wrote is not untrue - just incomplete!

IMM. IMM is now Dr. Evil.

You can set up a hot water storage cylinder to operate from the heating circuit of a combi boiler. I've done it and it's not very hard. However, it is unusual, wiring diagrams aren't published and is likely to cause much head scratching by the 'always done it like that' type plumber.

Also, the disadvantage with electric showers is that they're limited to 9 or 12kW. If you do the maths, this doesn't convert to much of a flow rate when you calculate the gpm heated from 10 to 40 degC. The old shower may be past it, but a new one will still have a similar kW rating and produce a similarly inadequate flow rate. Electric water heating is expensive; I disagree with the suggestion to change washing machines to cold fill.

The way to a decent flow rate is a storage system, which will accumulate the required kW of hot water, or a combi oversized for the heating load, say 30 or 40kW. I don't like combis, but they do have their uses.

A modern machine will barely use any of the hot water from a hot fill. By the time hot water has actually come down the line, the fill is complete. This leads to the water being heated first by gas and then again by electricity, whilst there is now hot water in the lines needlessly cooling down. In most circumstances, then, cold fill is actually more energy efficient.

Christian.

The snag is many modern machines use so little water it wouldn't run hot by the time it's filled. You could, of course, run the hot tap beside the machine until the water is up to temp then start the machine, but for the amount of electricity it uses to heat from cold it sounds an awful faff.

The combi sits above the washing machine and we always run the utility hot tap before switching it on. A tip from my mother many years ago! I had quite a search for a washing machine that still accepted a hot fill!

Thanks for the tip though.

There's no need. A modern machine uses only a tiny amount of water, so even if you do manage to heat by gas, you save very little. This is why modern machines are getting increasinly cold fill only, particularly the more environmentally friendly (i.e. efficient in water use) ones.

Christian.

Add another combi. Highly cost effective.

One does upstairs CH with a stat/programmer and one does downstairs - two separate timed zones using less fuel. One does one bathroom, one does the other. Divide and rule and one shower doesn't influence the other when showers are taken, or other taps drawing off hot water. Combine the outputs for the baths only, where high flows are required, by using two check valves and shoick arrestor - simple.

You get:

- two separate timed CH zones, upstairs and downstairs

- no water storage so no standing heat losses,

- not running out of hot water at any time

- liberating space in the house

- eliminating a cylinder,

- no tanks in the loft to give off water vapour promoting condensation up there.

- high pressure showers.

- fills a bath very quickly as the outputs of two combi's are directed into the hot water.

The best solution.

If he is going to do it,. he may as well do it right. Electric hand wash heaters when you have cheap to run gas around is very silly.

Oh my God. All he has to do is fit a flow regulator on the appliance hot feeds. A washing machine does not need to fill quickly. use cheap water heated by gas which is 3 to 4 times cheaper than electricity.