new CH system advise reqd

[Jeff]

I have spent the best part of today trawling throught the archives and am more confused than ever :-(

(I feel as though i know IMM personally)

the situation will be 4 bed semi with bath/shower room and ensuite shower room + ground floor granny bedroom and ensuite bathroom

2 adults, 2 teenagers + 1 OAP

OAP bathes once a week other occupants shower daily with very occasional bath

we are used to a triton 9.5 kw shower and pretty poor bath filling due to the cold water tank emptying if using hot and cold together (conventional antique system)

the archetect specced an unvented cylinder but the plumber says the cold water main is not up to the job (15mm lead)

I have concerns about fitting 2 electric showers (2x40amp out of 100 don't leave alot) I had a bad experience with a combi 20 years ago, forever to fill a bath, but am looking at the Bosch Worcester 40he plus combi or maybe a high recovery tank maybe with a shower coil Central heating will be replaced as is very old single pipe system

Totally confused and looking for advise please

done some flow timings :-

time taken to fill 5 litre container

20 secs = kitchen sink mains

30 secs = kitchen sink mains with bathroom sink tap on full

17 secs = bath cold from header tank

23 secs = bath hot from cylinder

so, I am getting at least 15 litres / min out of the kitchen mains tap and

10 litres / min with 2 taps fully open

I am used to a hot water flow of about 12 litres a min

does this mean that a combi with 16 litres/min flow will work ok ? and does it also mean that a mains pressure cylinder would also be ok ?

I would rather do without the expence and aggro of replacing the service pipe

Regards Jeff

[Doctor Evil]

That is nice.

Replacing the service pipe is the ideal solution as it gives you more scope. Also it is lead, so it NEEDS replacing. Forget what an architect says, they know sweet nothing about water systems.

If the mains pipe is replaced and you get around 25-30 litres/min then either:

1. Install a high flowrate combi. Alpha CB50, W-B Greenstar 40kW, W-B Highflow, are ideal for you as you only take showers most of the time. The likelihood of you running a shower and drawing a bath is slim.
2. Install a Powermax. A "one box" floor standing solution run from the mains. High flowrates.
3. A heat bank and separate condensing system boiler. High flowartes, and will runs two showers no problem at all. and one shower and one bath at the same time.

If the mains pipe stays at 15mm then:

1. An accumulator. This is a vessel with a large beachball inside which acts a cushion. It charges up with water from the mains at the static pressure. Static is when no water is drawn. Dynamic, or working, pressure, is measured when the taps are on. You may have a high static pressure, but the small pipe reduces dynamic pressure considerably. An accumulator stores cold water and releases it at the static pressure with volume. Once the pressure drops after use, it then charges itself back up from the mains again.

It can be mated to an unvented cylinder. Cost is expensive. If you can get the mains pipe sorted out, it would be much cheaper than the accumulator. They are fine in poor flow water areas, like villages and end of lines.

1. A combi cylinder (combined cold tank and cylinder) heated by a combi. The cylinder provides all the water in the house except the showers, which the water section of the combi provides.

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[Owain]

"Jeff" wrote | the situation will be 4 bed semi with bath/shower room and ensuite | shower room + ground floor granny bedroom and ensuite bathroom | 2 adults, 2 teenagers + 1 OAP | OAP bathes once a week

That could change if incontinence sets in :-)

Also a shower is considerably easier than a bath from a mobility point of view, so assume/provision for a shower there too.

Owain

[Jeff]

Thanks for that, I will look into replacing the main, more for the lead aspect ( will phone ST water tomorrow )

just done another test, with both taps full on i'm getting

kitchen sink 10 litres / min bathroom sink 16 litres / min

without meaning to appear thick does this mean that i have in excess of 26 litres / min available at the moment ? And with regard to the above figures what would I have at the taps with a 16 litre / min combi ?

Regards Jeff

[Andrew Chesters]

In case you hadn't spotted it, IMM has had a name change. He is a bit like the pop Prince in that respect. You would do well to KILLFILE Dr Evil (AKA Drivel).

[John Rumm]

If you have reasonably hard water then the lead is less of a problem that you might expect, since the inside of the pipe tends to acquire a coating that will limit contact between the water and the lead.

Having said that you may find the water company are prepared to meet some of the cost of replacing the lead, which may make upgrading the pipe more appealing.

It would appear that way.

Assuming the tap can support the flow (which a bath tap should even if the sink does not) 26 lpm of tepid water, or about 14 lpm of water hot enough for a bath at this time of year, more in the summer.

[Jeff]

Thanks John - so it would appear that in this situation the WB Greenstar 40 HE Plus Combi will do the job i.e.

take up no room - fitted on gable end in loft provide a good shower - thermostatic valve provide hot water to a similar performance as at present be a lot more efficient than present traditional antique system ( £80 / month gas bill ) No tanks in the loft No pilot to blow out

Regards Jeff

[John Rumm]

Yup that is fine, but you will need flooring, lighting and a guard rail.

Should be very good on the shower...

For bath filling you will probably find it a little bit slower than with the stored system because the 15lpm of water you will get from the combi will be at bath temperature, so you wont be adding and cold to the mix. With the cylinder you probably have the water stored at a higher temperature and hence fill the bath with a mixture of hot and cold which should add up to a bigger flow rate (at least until the cistern runs out ;-)

You did not mention what your current boiler is, but if we assume it is a few years old and only manages 70% efficiency, then you can expect that to go up to a best case of 90%. However you may not see quite that much gain since your current radiators may be a little undersized to allow you to run the condensing combi at optimal flow temperature, but it is a modulating boiler so most of the time it ought to make a fairly decent job of keeping itself running at a good efficiency.

You can also take the opportunity to upgrade the other system controls like adding thermostatic rad valves anywhere they are not currently fitted (apart from the bypass rad). You could also add a programmable thermostat which will also improve overall comfort levels in the house.

Although you will be getting more heat per pound spent on gas with the new boiler, remember that you will be shifting your showers from electricity to gas, so may not see an actual fall in your gas bill (although at 80/month I would expect you will unless the house is very poorly insulated). It will also hack a lump of the leccy bill so you should still be ahead.

Probably a good thing, unless you are in an area that gets frequent interruptions to the mains water supply.

True.

Possibly a few radiator lockshield valves to need replacing if they leak when the rads are converted to running as a sealed system.

[Doctor Evil]

I am the said Doctor Evil. Quiver in your boots.

As you added no value whatsoever, you a candidate for the kill. I am only Doctor Evil, a part time world-wide playboy.

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[Doctor Evil]

If that is simultanwoulsy then 26 l/min. BUT!!! There may be peaks and troughs. The mains delivery will fluctuate with demand. The houses with the

15mm pipe teed off will suffer most in fluctuations. You may go down as much as 10 l/min at peak times.

Best get a new 25mm mais pipe.

Make sure the gas pipe from the meter is sized correctly. You may need a length of 28mm from the meter and 22mm all the way to the boiler

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[David M]

I'm not 100% sure here as it's not clear if the bathroom sink is off of the main or cold water tank.

It's a bit unusual to have a higher flow rate in the bathroom sink compared to the kitchen,

Does you water main enter the house in the kitchen? Are you sure that your stopcock is fully open?

cheers

David

[Jeff]

Yes I was surprised the bathroom sink tap delivered more, but put it down to size, traditional tap versus quarter turn mixer in the kitchen - they are both mains fed and stopcock is fully open and in the kitchen, pipe run between the 2 taps is only about 10 feet

Regards Jeff

[Jeff]

Very true, at the minute we cannot fill with hot and cold for that reason

Floor standing Thorn (asbestos flue) in the old outside loo with hot water cylinder in ajoining coalhouse so probably 50% efficiency

then you can expect

complete system will be replaced as its very old and i believe a single pipe system, feed at top of rad return at bottom, might keep my 10 foot long curved rad that fits the bay though

Thanks for your help

Regards Jeff

[John Rumm]

(a new inlet valve like a fluidmaster or torbek on the cold cistern would probably fix that BTW)

Most of those on the sedbuk database are listed at 65%, there were a couple of models (m54) listed at 55%

[Doctor Evil]

This man is mad as should be killfiled by all, ASAP

-- Doctor Evil