Worcester 24i - dhw flow rate problem

[Devlin31]

Hi,
Hoping to get some help with a crappy Worcester 24i RSF. (http://www.worcester-bosch.co.uk/installer/literature/discontinued-product-literature/discontinued-gas-boiler-literature/24i-discontinued-november-2004-literature)

This is in my girfriends flat, think was put in about 2003. Over the last few years the pressure on the DHW has dropped by about half (still just about useable for shower) and also the water temperature is very high due to this slower flow (no adjustable temp control on these, set by boiler I think)

I’m thinking is probably the heat exchanger scaled up – we live in a hard water area (sw London) and the hotter the water this will keep getting worse.

The service manual above mentions a flow restrictor and also a gauze filter in the flow switch – is it worth checking to see if these are blocked, or remove the flow restictor? – is this a simple enough job? My worry I have read with these boilers is that it is hard to get a water tight fitting again due to odd/rubbish fibre washers used!

Really this should be sorted for her – it is a housing association flat, but the contractors who came out just said the flow is okay (despite her making the point that it has reduced by half, the water is almost scalding hot and this will get worse) – she isn’t very technical and couldn’t say much (I work away in thr week so wasn’t there) – he reassured her he will improve it by “increasing the pressure” i.e. in the heating circuit!!!!

How much would someone charge to descale the heat exchanger properly? SW London prices and all that : (

I know she shouldn’t have to, but anyone who has dealt with council/social housing providers knows that unless something is exploded they don’t worry too much about efficiency and it is hard to get them to do anything – even if I suggested it needs a descale, doubt they would do it till water reduced to a trickle.

My other thought is that there is a “scale inhibitor” (looks like made by daw enterprises from what I can see) on the boiler water feed, could this be blocked/restricting flow? I attach a pic – any thoughts? Someone has painted over it helpfully.

Don’t know anything about them, or if they need to be changed/replaced peridically.

The boiler has no service other than legal annual safety check.

Any help/advice/recommendations gratefully accepted. Driving me mad to be honest!
Cheers guys
D

Untitled

• Devlin31
• 6 Oct 2013
• 1

 

[Devlin31]

Anyone?

 

[Agile]

So this is for a housing association tenant who is going to pay for the work?

It would be unusual for the boiler to be lime scaled up UNLESS there were dripping hot taps. Where there?

In my area I would charge about £175 but its messy and easier where boiler is not fitted too high up.

Tony

 

[Devlin31]

Thanks for reply.

As wrong as it is when it is a rented ha flat looks like she will have to pay herself as they wont do anything unless boiler is truly buggered

The chap who the ha sent, said it was okay, ignoring being told flow has substantially reduced and water very hot, and then told her that he has increased the pressure on the ch circuit - so good advice then ?!

There has been some leaking taps over the years but these have been fixed in reasonable time.

I thought scaling in hex was common in hard water area with this model. But it could be corroded gauze filter or flow restrictor on the water flow switch?

Boiler is in bathroom cupboard at waist height.

 

[Agile]

It should be obvious to you that you can measure the flow rate and compare it with the makers spec. With a normal mains pressure the boiler should pass about 9 litres per minute!

Unfortunately there are some very dim people working in the plumbing trades. Particularly those who have to work for the social housing contractors!

Then are the unhelpful ones who just give you bullshit like that.

London water is not particularly hard and does not cause any problem to boilers unless there are other factors involved like leaking taps!

Tony

 

[Devlin31]

Thanks.

Yes the HA contractors are often pretty clueless, or far to rushed to do a good/thorough job.

It is hard to get the HA to do anything and the contractors they use know this also.

I will test the the flow rate with the bath tap fully open. Any idea what temperature the 24i should be heating the dhw to? Can't seem to find it in the servicing and installation manual - it is set by the boiler, consumers temperature control for heating only.

Would it be worth getting a engineer myself to check the flow restrictor and filters?

The input valve for the mains to the boiler can be adjusted (about 3/4 open at the moment) - but this could cause problems when the weather is colder and mains is much cooler coming in?

 

[Agile]

This is probably too technical for you!

The boiler will heat 9 litres per minute by 35 C .

Any other flow rate and different temperature rises will apply.

If the inlet valve is partially closed then why are you complaining about a low flow rate? Its only to be expected!

Tony

 

[Devlin31]

This is probably too technical for you!

The boiler will heat 9 litres per minute by 35 C .

Any other flow rate and different temperature rises will apply.

If the inlet valve is partially closed then why are you complaining about a low flow rate? Its only to be expected!

Tony

I've never claimed to be a technical expert on boilers! I presume you mean a temp rise of 35 C above the incoming cold temp and the boiler will heat a max of 9l in this way in a minute.

I had a look at the cold water inlet valve yesterday. Yes it is not fully open, but it has never been touched or adjusted in the years my girlfriend has lived at the flat (so it is not linked to the change in dhw output) I presume it was set up this way when installed - the mains pressure in the area is very strong and would presumably be to much for the boiler if valve fully open.

I'm away for a bit with work now, but I will confirm the flow rates of the hot and cold and the exact temp of the hot. No weir gauge but a bucket and litre jug will give reaonasable approx.

 

[Agile]

Better to think of the flow rate and what temp rise the boiler can achieve on that!

Tony