Correct size of replacement boiler

jkgray

Stop tap in house already opened to map, stop tap on water meter in road now on max (was already almost on max).

Have filled a larger container this time and repeated several times to ensure better accuracy.

New readings are:

Flow out of kitchen cold water tap (if no other tap on) is now approx. 13 l/min

If cold tap on bath is also on then flow out of kitchen cold tap is 10 l/min but out of the bath cold tap is approx. 5 l/min?

I have done it many times so reasonable sure these are right as I thought there must be a mistake given the 'extra' 2 l/min appearing but these figures definitely seem correct

jkgray

On a separate point, the person we're likely to go with said he does not power flush before installation just magnaclean with filter aid x900 and inhibitor x100. Any thoughts?

That being said the existing system seems to be mostly microbore so powerflush would not work anyway? (though neither he nor any of the others looked at the radiators so none would have realised this)

gas4you

A magnetic filter is NOT a replacement for a proper flush.

Doesn't necessarily need a 'power flush', but definitely a proper chemical flush, then flush through each rad with mains pressure water.

Don't look at anything more than a 28Kw combi with your flow results.

jkgray

What about the microbore issue? Does that have any relevance?

unclebulgaria

You really have to get both pressure and flow tested with a flow cup and pressure gauge. There can be problems if your water pressure drops too low when two taps are open simultaneously, the combi can be fooled into believing that the hot tap has been turned off as the pressure drops too low to operate the water pressure switches inside the boiler.

southcoastrgi

jkgray wrote: »

What about the microbore issue? Does that have any relevance?

microbore means the pipes are smaller so it's even worse if you have sludge as they can block easier, look at any MI & they will tell you the system needs a chemical flush BEFORE the boiler is installed, failure to do so will invalidate your boiler warrentee

jkgray

is this a potential solution to my low flow rate?

ecoTEC plus 937 storage combination boiler

http://www.vaillant.co.uk/stepone2/data/downloads/f4/42/00/ecoTEC_plus_937_sales_brochure.pdf

http://www.plumbnation.co.uk/site/vaillant-ecotec-plus-937-power-store-combi-boiler-natural-gas/

Thanks

gas4you

No.

You need a minimum of 20 l/m flow to make the 937 worth while.

If you are loaded, you could look at getting an accumulator fitted.