Worcester 24i - dhw flow reduction problem

[Devlin31]

Hi,
Hoping to get some help with oldish boiler - Worcester 24i RSF.

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 restrictor? – is this a simple enough job? My worry is I have read with these boilers is that it is hard to get a water tight fitting again due to odd 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!


Approx How much would someone charge to descale the heat exchanger properly? (I am south west London area)


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 – “scalemaster magnetic gold) on the boiler water feed, could this be blocked/restricting flow? Don’t know anything about them, or if they need to be changed/replaced periodically. The boiler has never had a servie service other than legal annual safety check.

Any help/advice/recommendations gratefully accepted.

Cheers guys
D

 

[SafeGasInstall]

24kw boiler will deliver about 8L of ht water per minute .

suggestion : dont play with boiler if you are not happy then call the HA and complain of poor flow of water , after 5 complain they will come and fit you a new boiler anyway

 

[Devlin31]

Thanks for the reply.

Thing is the housing association did send a guy who said the water flow was "okay" - ignoring the fact it is half as good as it was! As I said he increased the heating system pressure when it was a dhw problem! Obviously if he says no issue with boiler then we are stuck. HAs don't want to do anything in this climate

Not a mains pressure issue as cold is same as ever (good)

I'm not intending to mess about with gas, but if it is was a simple case of cleaning a filter say or removing the flow restrictor on the water input side then it saves the girlfriend hours of arguing with the HA and guys coming and saying no problems.

 

[SafeGasInstall]

removing flow restrictor will make more water going true the boiler and boiler is only limited to 24kw so will not heat up the high flow water

 

[Dotty]

Unfortunately nothing you can do without taking the case off. And because the case forms part of the combustion seal it is illegal for you to remove it.

Afraid you're going to have to keep on at the HA.

 

[Nostrum]

If you remove the restrictor you'll likely have problems in the winter with Luke warm water.
You seem fairly technically minded so your better off being there's he the engineer comes around, ask him to measure the flow rate. I have had this problem with these boilers although the flow rate didn't drop. The boiler should modulate down even if the flow is restricted to keep the water temp at 55 there abouts.

its hard to say without doing all the relevant checks but it could be a problem or even two problems, some being gas related so I won't go into detail.

long and short is you need someone who's gives a toss to come around and try and fix it. If there are children in the household I would suggest playing the health and safety card with regards to scalding. H.A's tend to respond better to anything that is likely to see them in court.

 

[Nostrum]

Unfortunately nothing you can do without taking the case off. And because the case forms part of the combustion seal it is illegal for you to remove it.

Afraid you're going to have to keep on at the HA.

to be fair croppie it does not on this boiler, the hydraulics are accessible without removing the combustion chamber cover. That said there isn't much point pulling the boiler to bits before doing the type of tests a qualified gas engineer would do to determine what the cause is.

 

[Devlin31]

If you remove the restrictor you'll likely have problems in the winter with Luke warm water.
You seem fairly technically minded so your better off being there's he the engineer comes around, ask him to measure the flow rate. I have had this problem with these boilers although the flow rate didn't drop. The boiler should modulate down even if the flow is restricted to keep the water temp at 55 there abouts.

its hard to say without doing all the relevant checks but it could be a problem or even two problems, some being gas related so I won't go into detail.

long and short is you need someone who's gives a toss to come around and try and fix it. If there are children in the household I would suggest playing the health and safety card with regards to scalding. H.A's tend to respond better to anything that is likely to see them in court.

Thanks for the info.

I have read about people having a clogged/blocked/damaged restrictor or blocked gauze filter (the inlet side of the flow switch) that can affect flow so I thought it was worth a check. As said this does not involve any access to the combustion chamber.

I will use a thermometer and bucket to do a crude flow and temp test, however, the flow has got worse over couple of years so something has changed. The dhw water running hotter than it was, I'll see what the exact temp is.

I think I am probably going to have to try and find a decent local gas engineer to have a look, local independent guys seem quite rare in the Richmond area - I do suspect the heat exchange is scaled so that is a job for them, but I'm no expert on boilers (marine electrics is my trade). Pretty crap we may have to pay out when it is a HA flat and "their" boiler, but not much else to do, their culture is repair something when totally buggered, pretty poor approach and costs them more in the long run.

I might try a post in the "looking for a gas engineer" thread!

 

[buckley plumb]

a simple test just to check the hot water flow rate so you can put the engineer to shame on the next visit is to open the bath hot tap fully and then put a bucket under it and time for 1 min then remove - using a measuring jug one jug at a time measure how many litres are in the bucket after the min - this is the flow rate if its less then req 8 litres from previouse post then there is a flow problem and you have proved this -

 

[Devlin31]

If you remove the restrictor you'll likely have problems in the winter with Luke warm water.
You seem fairly technically minded so your better off being there's he the engineer comes around, ask him to measure the flow rate. I have had this problem with these boilers although the flow rate didn't drop. The boiler should modulate down even if the flow is restricted to keep the water temp at 55 there abouts.

its hard to say without doing all the relevant checks but it could be a problem or even two problems, some being gas related so I won't go into detail.

long and short is you need someone who's gives a toss to come around and try and fix it. If there are children in the household I would suggest playing the health and safety card with regards to scalding. H.A's tend to respond better to anything that is likely to see them in court.

So on full flow the temperature of the hot water should be no more than 55?

 

[buckley plumb]

35-40 degrees more than cold inlet water temp on full flow

 

[Devlin31]

35-40 degrees more than cold inlet water temp on full flow

Thanks - I'll post up when I have tested flow and temperature.

 

[Ermintrude]

If flow bad enough and water comes out at 65c plus council may arrive pretty quickly. Especially if a child has recently scaled hands? Not saying reduce the water flow at stopcock or anything like that... Or all edge a scalding?