Dilemna....new boiler

[thornton_chris]

OK,
I have a very old concorde WRS boiler which has an F&E tank in the loft. We want to replace it with a more modern efficient unit. The other problem we have is that there are 5 of us (Me, wife and 3 kids) and with our current setup we run out of hot water after just 2 showers.
I got a plumber round yesterday to quote on a new boiler and he came up with some problems. Can any of you solve them???

1). I put a pumped shower in last year which we love however we have quite low mains water pressure. He says that a combi will work on it but that the pump will need to be removed and therefore the shower will be very week. Is there anyway of rectifying this?

2). The gas pipe which feeds out current boiler is 15mm. He says that all boilers are now 22mm and this would require a new 22mm pipe run from the front of the house to the back which is going to be nearly impossible! Is this true, does anyone know of any new boilers which run on 15mm gas pipe?

Any help would be much appreciated.

Chris

 

[simond]

One solution would be to change the boiler for another heat only boiler (eg: if it were my job it would be; Viessmann 100 Compact/Broag remeha Avanta 18v/Vaillant 400 series/Worcester Ri).

The last two aren't ideal because the Vaillant 400 is a cheapy Glowworm dressed up, and the Worcester may need your larger gas pipe, for no tangible benefit.

Then put in a larger HW cylinder, either vented or pressurised (unvented). If you are tight on space an ACV tank in tank cylinder will reheat very quickly and store water at a higher temp. This effectively gives you a better HW store.

 

[mikej2005]

When I was researching a new boiler last year, I didn't find any boilers that used a 15mm gas connection - all the ones I looked at required 22mm. If you were to go for a more powerful combi, you might even find that you need an even larger diameter tube, depending on the distance and bends involved.

Could you relocate the boiler closer to the meter ?

If you keep running out of hot water then a combi would be a possible solution, however you have to think about how many hot water outlets are likely to be used at once. A more powerful combi will lessen the effect of a hot tap being turned on whilst someone is in the shower (for example) but it will require a good mains cold water flow-rate, which it sounds like you may not have.

If you want to investigate this yourself, open a cold tap fully into a bucket for a set length of time and work out your flow-rate in litres per minute, then compare that with the output of the combi. A combi can't put out what it's not getting in !

One last thing - many people don't like electric showers, but they never run out of hot water !
___________________________________________________
Not a pro - just a DIYer passing on his thoughts and experiences

 

[simond]

There are plenty of smaller domestic heat only boilers that only need 15mm gas inlet. 'Research' on the internet is often not the best way to find out what is what.

 

[gas4you]

If you decide to go the combi route then you will need to probably change the gas pipe to AT LEAST 22mm, possibly 28mm some of the way depending on the distance from the meter.

Your main decision point should be whether you will get an acceptable shower from a combi.

I feel from what you have said I would agree with Simon and go for a heat only boiler, be it an open vent or a system boiler is immaterial at present.

I would also recommend changing your current H/W cylinder to a fast recovery model that will re-heat the contents in around 10-15 mins, so you will not have to worry about running out of HW so much, if at all and keeping your shower pump. An 85 litre unit should do, but you could always fit a 120 litre version if that makes you feel happier. They are sold as big enough for a 2 bathroom property.

If your HW cylinder is as old as your boiler this should, in a perfect world, be replaced anyway. It could also be that it is half full of scale if you live in a hard water area.

 

[mikej2005]

There are plenty of smaller domestic heat only boilers that only need 15mm gas inlet. 'Research' on the internet is often not the best way to find out what is what.

Oops - I should have mentioned that I was after a powerful combi.

 

[doitall]

The poor mains pressure rules out the combi of any size, and more so if you're expecting 2 or more showers at the same time.

The gas pipe will most certainly need to be 22mm minimum, and in most cases (front to back) 28mm

 

[Agile]

An 85 litre unit should do, but you could always fit a 120 litre version if that makes you feel happier. They are sold as big enough for a 2 bathroom property.

The standard recommendation is for a HW storage of 50 li per person.

For five people that would mean a 250 litre cylinder or larger. Thats what I would recommend to ensure it would never run out in normal circumstances.

That will be far cheaper with a small heat only boiler like a Worcester 15 Ri or similar. That might work on the restricted 15 mm gas supply.

Tony

 

[thornton_chris]

Just thought that I would update you with the result.

We went with a combi in the end. It's a Valliant as recommended on this site.

The shower water pressure is just as good as when we had a pump and of course now we will never run out of hot water.

Well chuffed!

 

[sturharv]

Have you tried running two showers at once!

 

[thornton_chris]

We've only got 1 shower.