Worcester 280 RSF HW heat exchanger - made of what?

[mbga9pgf]

I have what I suspect to be a calcified heat exchanger on my 280 RSF. I have the one with the flat, box like water-to-water heat exchanger.

Symptoms:

The exchanger isnt blocked I dont think - the flow rate through the taps is fine. unfortunately, after the tap is turned on, it takes ages - I reckon about 2 minutes to get hot water through the tap, and even then, we are talkingabout 1 litre a minute! Obviously, something is not right. The boiler is working fine - central heating is working great and all the rads are quite hot after 5 minutes of the boiler being on. I am planning a descale of the loop at some stage, probably next summer, however, I cant go on without hot water supply to the taps. The manual recons it can heat 11 litres of water by 40 degrees C - and we are well short!

We are in a hard water area in gloucestershire.

I want to descale, but unfortunately, as I dont know what the secondary HE is made of, I am unsure of what to use in it. I am going to knock up a basic system to flush the heat exchanger through, using a drill powered water pump, a vat of the reagent, and some hose pipe to and from the boiler secondary heat exchanger whilst it is still fitted to the boiler. I am going to tap into the mains supply and return pipes using the hose pipe, then pump the fliud round using a drill powered water pump, from the container of reagent.

Now, I have a couple of options as to what to use. (from least reactive to most)

Heated pure vinegar (works great on the kettle)
Kettle descaling liquid
Dilute HCL
Fernox DS3

I want to go straight for the fernox as its what you guys swear by, but does anyone know what the secondary heat exchanger on the 280 RSF is made of? I dont want to flush an aluminium HE with HCL or DS13 one would imagine.

any other tips/tricks? I am absolutely skint at the mo, I would pay for a new heat exchanger if I could, seems a bit of a waste as I reckon this is down to excessive limescale.

 

[kevplumb]

but does anyone know what the secondary heat exchanger on the 280 RSF is made of?

copper

use the ds3

 

[mbga9pgf]

but does anyone know what the secondary heat exchanger on the 280 RSF is made of?

copper

use the ds3

Sweet. Thanks for the rapid reply. No problems with corrosion of the HE with the DS3 then?

 

[kevplumb]

no actually its ss with copper /brass unions

if it will take being soaked in hydrochloric im sure ds3 won't damage it

 

[mbga9pgf]

no actually its ss with copper /brass unions

if it will take being soaked in hydrochloric im sure ds3 won't damage it

From the symptoms would you say this is caused by a furred up HE or something else? The primary has history of Fernox anti corrosion treatment and I am going to give it another rinse through with treatment and anti corrosion. I suppose it is costing so little to try and sort its worth a go.

I almost got a new boiler but heard the 280 RSF is a pretty solid beast - bearing in mind I am in a hard water area and on LPG, I would prefer a little inefficiency over a boiler made of string and pritt stik and is likely to break down every 5 minutes. Or am I being unfair to modern build standards?


Final question, are the supply/return feed pipes to heat exchangers standard dimensions on these and can I get similar sized unions/pipe down the plumbers merchants, or are they a special size?

 

[Agile]

You said the hot water flow rate is fine and then you said its only one litre per minute ( which is not fine! ).


Far better to take it out and use DS40 on the primary side and then 10% HCl on the secondary IF you are competent to use acids safely.

DS3 is not very soluble in water and to be effective needs to be heated to about 80°C.

HCl can be used cold.

Tony

 

[mbga9pgf]

You said the hot water flow rate is fine and then you said its only one litre per minute ( which is not fine! ).


Far better to take it out and use DS40 on the primary side and then 10% HCl on the secondary IF you are competent to use acids safely.

DS3 is not very soluble in water and to be effective needs to be heated to about 80°C.

HCl can be used cold.

Tony

I can turn the tap on at quite a good flow. Unfortunately, its stone cold. I can get a decent rise in temp, but only at 1 litre a min.

Hope that clears up the confusion.

Was hoping not to have to bother to drain down the system, purely detach the supply and return hw pipes, connect up my pump and heated bucket and crack on!

 

[Agile]

There is another way but thats at the extreme end of DIY.

Make up your solution of DS3 and disconnect the mains water from the boiler.

Set the boiler on heating! Then by gravity use your tubes to pour the DS3 solution so that it flows SLOWLY through the DHW coil of the boiler.

All you need is some hose and two jugs to do the pouring/collection.

It can take some time, perhaps an hour or two of pouring! Thats because DS3 is a slow reaction. HCl at about 10% concentration used COLD with the boiler OFF would be far quicker, perhaps 10 min! But you need gloves and eye protection.

Tony

 

[mbga9pgf]

There is another way but thats at the extreme end of DIY.

Make up your solution of DS3 and disconnect the mains water from the boiler.

Set the boiler on heating! Then by gravity use your tubes to pour the DS3 solution so that it flows SLOWLY through the DHW coil of the boiler.

All you need is some hose and two jugs to do the pouring/collection.

It can take some time, perhaps an hour or two of pouring! Thats because DS3 is a slow reaction. HCl at about 10% concentration used COLD with the boiler OFF would be far quicker, perhaps 10 min! But you need gloves and eye protection.

Tony

Hmm, I like your ideaof turning on the CH loop to heat the DH3... will give that a go instead of heating the bucket of stuff on a stove!

Fingers crossed I will get some hot water back....

Will standard sized union fittings go on the HE with 22 mm Copper pipe or are the bolts on these usually a bespoke size?

 

[Agile]

It may well be 1/2" iron threads but its a flange and washer connection. Not so easy for a DIYer to put together.

The alternative is to connect to the DHW in/out under the boiler and use a hose to above the boiler to establish a gravity flow route.

Still a flange connection but you could cut the pipes and use standard plumbing connectors.

Tony