Worcester Greenstar 24I System NG Part Issue

Our boiler (see above picture) which I've identified using the GC Nr needs a new main heat exchanger. Advised by heating engineer, excess heat over time has caused damage to the outer aluminium case.

I'm assembling all the relevant parts he requires for this procedure prior to booking him for another visit. The heat exchanger is proving to be problematic as there are two types (visibly almost identical)


As you can see from the above picture it's either Heat Exchanger Old Sump (Before FD887) or Heat Exchanger New Sump (After FD888). So it seems the only difference is a design change to the clip on black plastic sump assembly.

Heat Exchanger Old Sump (Before FD887) - Part No 87161157400
Heat Exchanger New Sump (After FD888) - Part No 87161157410


According to Worcester website (see above picture) the data badge pre July 2010 (boiler commissioned Sept 2009) provides the FD number as the 11th, 12th, 13th digits.


Therefore glancing at the serial number (see above picture) you'd expect this to be 989. Hence Heat Exchanger New Sump (After FD888) would be the correct part to order.

Can someone who is familiar with these boilers just confirm what I've stated is correct. I'd just rather be 100% sure, not order the wrong part and end up having to pay the engineer for a wasted trip.

Any responses much appreciated

In what way is the casing damaged?
It's not unusual for it to become ribbed due to the differing expansion rates of the inner aluminium heat exchanger and the outer tubular stainless steel shell.
Providing the rolled edge sealing at the top is not leaking it's not normally considered much of an issue.
Is the boiler performing ok otherwise?
It would often be a better deal to see if Worcester would do the job on a fixed price or even replace the heat exchanger under warranty.

So the damage was originally ribbed effect, he acknowledged this was fairly common. But now a small split has appeared in the casing at the top with evidence of leakage albeit minor. I've observed this while he had the cover off, it's fairly apparent the heat exchanger has seen better days. Incidentally he's not trying to pull a fast one on me, actually a friend and will likely charge me very little for the work. I'm really just trying to source the items to make his visit as painless as possible.

Warranty sadly expired (7 year warranty). Worcester quote £400+ for the part alone not including fitting. Reconditioned heat exchangers are available from reputable eBay sellers for £65.

The boiler is functioning just fine, if you cast your mind back I replaced the synchron motor about a month ago after you correctly diagnosed the previous issue. I'm just acutely aware this if left unresolved will in time likely end badly. For the sake of a reconditioned heat exchanger, new gasket and slipping him a few quid for his time seems very much worth it.

Thanks for your response @Gasguru

You cant recondition that heat cell, what is on sale is one that has been pulled from a boiler removed and replaced, not reconditioned, get a Worcester fixed price repair and they will supply and install a new heat cell

Poisonata said:

Reconditioned heat exchangers are available from reputable eBay sellers for £65.

Click to expand...

Noooooo....you can't recondition these heat exchangers. You can sometimes partially clean the waterways but none of the seals can be replaced.
Over the last couple of years many many boilers parts are now being described as reconditioned when they are just polished second hand parts.
I've contacted ebay several times but they are such a corrupt company they show no interest.
Very few boiler parts can genuinely be refurbished.

Slide out the plastic tray cover under the boiler (if it's still fitted) and post a picture looking up.
The earlier heat exchanger models have a rectangular condensate trap on the lower LHS, the later models have a "bottle" type trap more towards the centre with a circular cap at the base.

Thank you once again for your response. The picture below shows it seems to be the bottle type trap


hence my initial thoughts regarding the later model of heat exchanger (according to the serial FD number) with the new sump appear to be correct.

Your response was incredibly useful @Gasguru as everything falls into place now.

When these boilers were first released there was a big drive by the government encouraging people to convert to condensation type (grant of some sort). Several years on a glaring problem arose during a particularly cold winter, those boilers not fitted with a wide enough, insulated exterior drain pipe were prone to freezing up due to the slow drip, drip discharge of water generated by the boiler. In response to this I'm sure Worcester designed this reservoir syphon arrangement (bottle trap type) in order that water was discharged in a larger volume all at once reducing the risk of freezing exterior pipes. Also exterior drain pipes were recommended to be of a greater diameter. This is why there has been a revision to the sump was made I'd conclude. Correct ?

Now confident its the Heat Exchanger New Sump (After FD888) - Part No 87161157410 I'm taking your advice / ordering a new heat exchanger from Worcester. By reconditioned I had assumed this meant used heat exchanger, cleaned, still serviceable with new rubber gaskets. Apparently not the case.

Once again, thank you so much. More than happy to stick you a small gift in the post as your advice on this / other matters has been invaluable. Best wishes.

I forget the name but the earlier trap design was patented and sold/licenced by a company called Altecnic.
Back in the early days of condensing boilers many many boiler manufacturers adopted that trap design and variants of it.
It then became apparrent that the traps have little debris holding capacity and other shortcomings...hence manufacturers brought out much improved designs.

I had a 24ri and paid Worcester Bosch a one off fee of about £300 to fix my boiler last year, they replaced the heat exchanger and a few other parts for no extra charge.

Sorry to resurrect this old thread. I too need to now replace my heat exchanger, I suspect mine is the old sump type. ( GREENSTAR 28i Junior ID no 7716130142 & GC number G20 47 311 87. I can get a far better price on the new Part No 87161157410 and was wondering is there any reason why this could not be fitted - is there any other technical reason it cant be fitted ? I had the condensate trap replaced and the new one is a completely different shape and design but fits perfectly. Also I note the "sump" part of these heat exchangers are also a consumable part. If for any technical reason the Part No 87161157410 could not fit, could my plumber not simply swap over the sump from my existing heat exchanger onto the new unit which has a different design.