Why isn't my hot water hot?

[Twitterqueen]

New Potterton Gold Combi HE boiler put in this past Jan.
We've had hot water previously but for some reason it is now just tepid.

I have to boil the kettle in order to wash up.
The shower provides hot(ish) water, but I have to have it turned up to the max.
The tap in the bathroom provides the same lukewarm water as in the kitchen.

Any ideas / suggestions would be very much appreciated. My 3 teenagers are SO not happy (and neither am i)

Sometimes if you turn the flow down low (ie not much water coming out of the tap) it gets hotter - ours was like that at the old house. If the tap was on full it would just be tepid but low it would get really hot. Took years to run a bath though.

turn the radiators off and let them get cold. Turn the hot tap on. Do any of the radiators start to get warm?

I mean, turn off the heating at the timer/programmer and/or the room thermostat, not at the radiator knobs.

Thanks PigletJohn
I'll try that one. I've tried turning off the heating and leaving on the hot water but that hasn't made any difference.
I will try it now and get back to you later today.

Hi PigletJohn
I ran the tap for 5 mins and no hot water came into the radiators at all.
The boiler hot water light and gas light are both firing up, and the temperature is fluctutating around 80-90 degrees, but no hot water from the tap and nothing in the radiators .

can't understand that. I wonder where the heat is going. From your test it doesn't sound like the divertor or bypass. I suppose you would have noticed, if hot water was pouring down the outside wall behind the boiler. If it was the flow switch it would not have fired up.

Was it a new boiler put on old radiators? do you live in a hard water area?

I can't see any alternative to calling in a mender.

p.s.

is there (as rumberlina mentioned) a great deal of water coming out of the hot tap? Like 2 gallons a minute?

Could be the heat exchanger. Is the water getting a bit warm and then going cold alternately?
Did you have a magnetic filter out on when the new boiler was installed?

Has someone accidental turned the switch off for the electric pump?

Do you have a power cut atm?

Maybe the pump has gone?

If you feel the pipes coming out of the boiler, do they feel hot? What about the ones coming back in again?

Thanks all

New boiler in January of this year, on old radiators
I do live in a hard water area
No power cut
Don't know about a magnetic filter
Just one pipe feels hot - I don't know whether it's coming in or going out
The flow is 5ltrs per minute from the hot tap - it doesn't appear excessive to me but I know nothing.

I would contact the installer but last time I rang (when it first lost pressure) he called me an effing c* and never to darken his doors again.

I have a feeling it may have started when I last repressurised it, but I've drained some water from the radiaotrs and then respressurised and it hasn't made any difference

I've rung Potterton & an engineer is coming out tomorrow thank goodness!

You should see if its possible to fit a magnetic filter now as it will keep some of the junk from the old radiators out of the new boiler. A filter will cost about £150.

new boiler on old radiators is very prone to blockages from old dirt and sediment lying around. The installer is supposed to clean it out, usually with a powerflush, which takes about half a day to do properly, before fitting the new boiler. Sadly a boiler guarantee does not cover blockages or other damage caused by sludge or sediment, and cleaning is always specified in the manufacturer's instructions.

If your heat exchanger is blocked it will probably be possible to unblock it with an acid cleaner, or it might have to be replaced.

I strongly advise fitting a system filter, especially when you have old radiators, because there will be an unknown amount of old dirt in them. Even a powerflush will not get it all out. A filter costs the installer about £100 and is not much work to fit when the boiler is going in.

I have no way of knowing how thorough a job your installer did, but he seems to lack charm so I doubt he will get many recommendations.

Thanks again Piglet
I had a power flush when the new boiler was fitted - the men were amazed at just how disgusting the water was in the old system.
So perhaps this is the problem.
At least I'm prepared for when the engineer calls tomorrow.

Your installer wasn't called Mick by any chance?

The lovely Heateam for Potterton have now fixed my boiler and I have hot water again.

I don't know why I waited 2 weeks before contacting them... (well actually I do, it was fear of something major wrong requiring lots of additional money).

Anway - sludge and scale was the reason. New heat exchanger installed.

And I'm recommended to get a Combimate scale reducer, which I will do asp.

I really appreciate all the help here. Thank you.

Did he not recommend a filter as well?
A filter helps keep out the sludge.
I think all fitters should recommend filters when fitting new boilers to old rads.