combi-boiler - worcester bosch - water is hot and cold? (4 years old/no cover)

wakkaday

hi guys
i had this issue before over a year ago and i think i just took the air out of the radiators and its fixed the issue, but this time it doesnt seem to work
is there any diy steps i can take to remedy the problem.

the water from the taps (kitchen, bathroom) goes from hot to lukewarm and then re-heats again and its really annoying me.

my combi boiler has one of the mag-tek adaptors connected to it, i did take that off to check if that is clogged, but only water came out of that adaptor and it seemed fine, so connect that back up.

ive taken air out of the radiators 

the pressure is on 1.5 which is fine

but the water is still changing between hot and cold...


what else can i try?

thanks

ariarnia

i'm wondering if this might be better on the diy forum? 

Ectophile

First check if it's still under warranty.

There's a chance that the problem is a clogged heat exchanger.  That can happen if the boiler was retro-fitted to an old heating system, or if the installer forgot to add corrosion inhibitor to the system when installing it.  If the heat exchanger is blocked, the boiler can't transfer the heat to the incoming cold water, so it overheats and then shuts down.  Unfortnately, that's a job for a plumber.

Miser1964

Probably the hot water plate heat-exchanger is partially blocked with limescale from the cold-water feed. That's not something a filter on the CH flow can change. 

HumberFlyer

Do you have the eco (preheat) on or off on the boiler

wakkaday

I have turned off the eco and the pre heat it was on yeh , it’s not clear whether it’s off on the panel

i checked the guarantee and it’s up to april23 , but the issue I haven’t had it serviced every year and they will want proof of that

I don’t have anything to show them if they ask …

macman

Your warranty is void if you cannot provide evidence of an annual service, so you'll have to pay for the repair yourself.

HumberFlyer

We have had a worcster bosch for 16 yrs and replaced last december with a new wb. On both of them we find that if the preheat is on it does possibly what yours is doing, and makes sense that it is doing it. The tank in the boiler is kept hot ready for "instant" hot water.... when you turn on the tap it gets pushed through so hot at the taps but then it gets replaced by water that hasn't been preheated so it is only warm till it has built up enough flow to become hot again. May or may not be the issue you have described. We was advised by the installer to keep it off as it just wastes gas constantly flaring up 24/7 just to keep a few litres of water hot in the boiler.

[Deleted User]

macman said:

Your warranty is void if you cannot provide evidence of an annual service, so you'll have to pay for the repair yourself.

I agree. Most boiler manufacturers also exclude sludge or debris from their warranties if the system wasn't flushed through properly when the boiler was fitted. The process of draining down; fitting a boiler and re-filling the system can disturb deposits of sludge in the radiator system.  

shiraz99

I've always had the preheat function turned off on mine (Hot water is set to Eco), it's a waste of energy and doesn't make a huge difference as the hot water doesn't take that long to heat up fully if I want it really hot, for example doing the dishes or running a bath. Sounds like this could well be you issue as you initially get a burst of how water but once this runs out, it goes back to warm until it reheats back up again.