System boiler enough for my house?

[menie13]

Hi

We need to change the boiler in our house. We have a 4 bedrooms house with 2 bathrooms.
We do want to have pressure for the hot water from our taps and showers.
I am not sure if that the right system for us that's why I am pretty keen on getting advice/suggestion from you guys:

1/ Worcester Bosch 7715430441 White Greenstar 42CDI Floor-standing Boiler
2/ Heatrae Sadia Megaflo Eco SystemFit Indirect Unvented Hot Water Cylinders 150L
3/ http://www.scaleout.co.uk/ or http://www.worcester-bosch.co.uk/homeowner/system-solutions/greenstar-system-filter

Thanks in advance

Cheers
Mel

 

[Dan Robinson]

42 kW is far too much.

150 litres might not be quite enough.

 

[menie13]

HI Dan

Thank for teh feedback.
should i look at 30kW? and for the water cylinder 250L? It might use a lot of energy to heat the water ?

Cheers
Mel

 

[Dan Robinson]

Depending on the exact size of your house 18 or 24 kW might be more suitable.

As for the size of the cylinder it depends on your usage; however, they lose very little heat, so over sizing will not be significantly wasteful.

Really, though sizing of the boiler and cylinder are best left to the installer.

 

[menie13]

Great I will check that with him. But is the system we provided will be efficient and providing good water pressure?

Cheers
Mel

 

[Dan Robinson]

The pressure is governed by the quality of the plumbing rather equipment you have chosen.

 

[D_Hailsham]

Use Whole House Boiler Size Calculator to find out what size boiler you need. I would set the Domestic Hot Water Allowance to 3kW.

You mention a floor standing boiler. Is this essential? There's a much greater choice available in wall mounted boilers.

As for the cylinder, as Dan says, 150L may not be enough. It depends on the reheat rate and the demand (two baths at the same time?).

You say you want good pressure; you also need a good flow rate. Have you measured it? The garden tap is the best place. Use a litre-marked bucket and a watch with second hand. You need at least 20 litres/min. Check when kitchen cold tap is on, then when it is off.

You can reduce hot water demand by having cold fill only on washing machine and dishwasher.

Make sure you have maximum loft and cavity wall insulation. It will reduce your requirement by 20% or more. Installing Double Glazing is a good selling point, but it has a long payback time. Use the above calculator to see the effect of insulation.

 

[Mark Br]

As well as speccing your boiler, Your installer should also check the pressure and flow rate to ascertain the suitability of installing an UV cylinder.

Ps - Megaflows are expensive compared to other cylinders available that do the job equally as well.

 

[ALEC1]

I should think the coil is only about 15kw, and the house has 12 rads.. why a 42kw boiler??

 

[Dan Robinson]

Probably because the OP used one of those daft "boiler selectors" on a couple of manufacturer's websites.

Not the fault of the OP of course, but they are cack.

 

[menie13]

Looking at boiler I might go fo a system boiler as it seems that kind of boiler removes the need for a feed and expansion cistern.

Regarding the hot water cylinder, any well known ones which are good to go for?

Cheers
Mel

 

[Agile]

You obviously know virtually nothing about boilers or hot water systems.

A system boiler and unvented is the best solution but so much depends on your dynamic flow rate and that can only be measured at your property.

You should engage a competent engineer and let him spec a system for you. THEN you can ask here what we think if you have any doubts.

I would have lots of doubts if he did not know what a dynamic flow rate is or did not measure it as the first step.

An 18 or 24 kW boiler is likely to be the largest you need!

42 kW is madness!

Tony

 

[menie13]

Ok we have a quote:

Megaflo_Eco_210I_Unvented_Indirect_Hot_Water_Cylinder
IDEAL LOGIC SYSTEM PLUS 30HE
Upgrade to fully pumped (inc grundfoss pump, controls and wireless room thermostat)
Vertical flue system
Install combi Mate Scale Reducer
Instal soak away (safe disposal and neutralization of condensate waste water)

BILL: £6570

Seems pretty expensive as I looked at the price of the boiler and cylinder and I can get them for less than 3k

 

[Weedrip]

Then why don't you offer to source your own component's and work out what's needed and take responsibility for any faulty equipment that may arise.

That way we could all just work for wages.

Sorry but if you don't like the price for the work quoted find some one who will do it cheaper. There is always someone who can do it a tenner less than the last guy's quote.

good luck

 

[doitall]

I would definitely be getting another 1 or 2 quotes going on that