Boiler decision - getting fed up now.

[monkey73]

Hi All

I have been trying to decide on a new boiler system for weeks now since moving into our new house. We are having the electrics done next week and would like the boiler done not soon after to minimise the upheaval so that we can move in properly and unpack.

So many engineers have said so many different things. Here's the facts:

We have a water softener
Static pressure is 2.8-3bar
Static flow from mains is 12-13 l/min
Static flow from water softener is about 11 l/min

We want a combi for it's benefits but don't want it's negatives (who does?!).
We live in a 3 bed detached with 1 bathroom, but likely that another tap is on while shower is being used. We like powerful showers and currently have an Aqualisa Aquastream pumped which will need to be changed if we go mains pressure for our system.

Currently have back boiler with hot water cylinder.

I'm know a combi won't be AS good but what I don't know if how much I will be losing by fitting one.

Recently came across discussions around fitting an accumulator to smooth out the pressure and give us a better flow into the boiler. Is this possible?

I really need to make a decision so that I can stop spending all my time researching this and move on to other things!

Any advice appreciated.

Thanks

 

[Agile]

I have never seen a static water flow!

Regardless a combi will only properly serve just one outlet.

How many live there is also relevant.

Your incoming flow rate is likely to be totally inadequate for a combi.

My advice is to keep a cylinder fed from a loft tank. With a pressure pump if you like!

Tony

 

[monkey73]

well I meant the flow rate when nothing else is running.

But yes, I am coming to the same conclusion. Probably put a system boiler in the loft, and keep the cold water cistern and the hot water cylinder (though maybe increase the size as we like long showers), and replace our current faulty pumped aqualisa with a new Mira pumped or something like that.

 

[D_Hailsham]

Static flow from mains is 12-13 l/min

Did you measure that at the kitchen cold tap?

It might restrict the flow, so check again at the garden tap.

 

[monkey73]

That was measured from the kitchen tap, pressure was measured from the outside tap.

But surely it doesn't really matter if the flow rate from the softener is 11 anyway, as that is what we will be using.

 

[TCCHeating]

Have a look at this:

http://uk.grundfos.com/products/find-product/home-booster.html

They are not cheap but it would sort out your poor flow rate.

You could then get the benefit of a high powered combi. But i would go with a system boiler and an unvented cylinder for the best system.

 

[monkey73]

But everywhere I read says to warrant an unvented cylinder you need 20 l/min+

Is that not true?

 

[TCCHeating]

But everywhere I read says to warrant an unvented cylinder you need 20 l/min+

Is that not true?

Did you not look at the link??

You can get up to 30lpm if you use the homebooster pump i posted the link for

 

[monkey73]

Sorry I thought you were making 2 separate points. So what you mean is that you would fit the Home Booster AND then fit a system/unvented?

That makes more sense but actually like you said, that cost is way above what we can justify.

I think looking at all the options, the only benefit we would gain from the Combi is hot water whenever we wanted it. Everything else seems to be pointing to system/vented.

 

[TCCHeating]

That makes more sense but actually like you said, that cost is way above what we can justify.

Yep, i agree! That was my money no object best solution!

To keep costs down get a decent sized vented cylinder fitted to a system boiler and fit a good shower pump.

Make sure you have plenty of cold water storage in the loft to make sure the pump doesn't run dry.

 

[monkey73]

Yep, thanks for your help, finally come to a conclusion. Now to get some quotes!

 

[Dan Robinson]

I have never seen a static water flow!

perhaps it happens when you detemper a pipe?

 

[roguetrader]

In fairness a combi and home booster wouldn't be that much different to a system boiler, unvented and all the extra pipework.
If that's what you wanted.

 

[D_Hailsham]

But surely it doesn't really matter if the flow rate from the softener is 11 anyway, as that is what we will be using.

Is the flow from the softener restricted, so it can't be any more than 11, whatever the mains flow rate?

 

[monkey73]

I don't know if the flow is restricted, can't see anywhere where it would be unless its internal to the softener.

And can you explain why the system would be the same as a combi with home booster if all my pipe work is already there for a tank etc?