boiler

[sanang]

Hello, I have had a new Combi boiler fitted, but I find I am only getting hand hot water. Engineer says a Combi will give about 90 ltrs of hot water then it will go luke warm and you need to wait about 20 mins, for hot water again. I find this incredible. My 20 year old immersion tank was more effective. Is this really how Combi boilers work - if so I have made a big mistake spending so much money.

[tamborine]

can you feel the hot tank to assess the hot water capacity?

[LCDMAN]

Its a combi Tam, there is no hot water tank!!!

Sanang, not sure what drugs your "engineer" is on, but a combi boiler will keep producing hot water while ever a hot tap is open. You open a hot tap, the boiler ignites and heats the water (coming from the mains supply). You turn the tap off, the boiler stops. Simples!!

He's talking rubbish! Get him back and tell him to sort it!

[LCDMAN]

http://www.muswell-hill.com/foxandco/pages/boi lertypes.htm

"The big advantage with a combination boiler, or a "combi" as it is usually called, is that it not only delivers continuous hot water, but more importantly delivers it at mains pressure too."

"Combis are also considered to be amongst the easiest systems to install, because they eliminate the need for both an expansion tank in the loft and a hot water cylinder in an airing cupboard."

[coccinelle]

Turn the thermostat up of the water, what this does is slow down the rate the water goes through to get heated so you get hotter water. I also find by not opening the tap full on this does the same.

[terence7556]

you have,nt made a big mistake but possibly a lesson in how a tradesman thinks and operates.
a combi is easier and therefore quicker to fit than the system boiler you used to have so a tradesman can fit more and make more money, cynical but true.
yours needs to be set up properly to produce hot water at a reasonable amount,but even your system boiler would eventually run out of hot water, so call hin back to do it

[gucciman]

i suspect your engineer is not an engineer at all but rather an installer, what he has told you is total rot.

and most combis do not deliver water at mains pressure especially the low power ones, they usually incorporate a water throttle to slow down the flow of water through the boiler to a level that the boiler can handle. the only system that will give you mains pressure hot water is an unvented mains pressure system.

first thing i need to know is the make and model of the boiler and most importantly the power of the boiler i.e. is it a 24kw, a 28 kw etc you should find the info somewhere on the boiler or in your instruction manuals.

next i need to know what size of gas pipe he has used to supply the boiler. if you look under the boiler at the pipework the gas one should have a yellow tap where it enters the boiler or it should have adhesive tape on the pipe marked "gas". is it 15mm diameter or 22mm diameter pipe? is the gas pipe the same size all the way down or does it reduce in size? did he run a new gas supply from the meter to the boiler or not?

my next step would be too measure the flow of water from the tap with a weir guage and the temp rise, i would then compare these results to the spec in the instruction book to see if the boiler is doin what it is meant to or not.

next i would check the burner pressures or gas rate if is a zero governer to see if those are in spec or not.

any actions i then take would depend on the results i obtained.

to sum up, if your hot water isn't as good as you would like, then your biler could be underpowered, your gas supply could be undersized, your burner pressures could be wrong or you could just be expecting too much from a combi because your used to a conventional cylinder and tank system.