Heat exchanger wrong size

Danny Mason · 6 Dec 2019

Hi, i ordered a heat exchanger which was advertised on ebay as compatible with my he35 ideal boiler. However it is half the size. It will still fit but suspect i shouldn’t? Kind of hoping someone tells me it will be fine? Common sence says no but i can hope

ianmcd · 6 Dec 2019

no you have the wrong part, I am guessing you have an Ideal Isar, if so the part number is 173545 and you will need 4 x new seals as well, if you can send it back get some one shot and clean your old one , it will be as good as new, you will still need new seals though

Danny Mason · 6 Dec 2019

Yeah so the guy who sent it me has sent me a new one out, i already purchased the seals so have them. Had to fit the old one back on for now i have flushed it out as much as i can. Still got the hot water issue so hoping its a failure of the part inside rather than a blockage. Easy enough to swap anyway so will try that first as iv already paid (not alot) for the part. If that doesnt cure it im not sure what it could be then any ideas?

basically the faster i run my taps the colder my hot water.

ianmcd · 6 Dec 2019

That is how it works, you need to measure the hot water flow rate, lets say your boiler is designed to raise the HW temp by 35 degrees at 11 Litres per min then in the summer say your water is coming in at 12 deg then at 11 L/min the outcome will be 47 degrees in winter the incoming might be say 5 deg so at 11 L/min outcome will be 40 deg but only at 11 L/min, if you run the tap faster than that then the outcome will be colder , you need to look at what your boiler should be set at and set the flow accordingly

Danny Mason · 7 Dec 2019

Ahh thats good to know. Iv had a play around with the flow and basically i can get the flow rate low enough to get boiling hot water downstairs but then upstairs its barely coming out of the tap... (too slow) if i increase flow rate so its a decent flow upstairs, it goes luke warm again. Cold water runs at 12 ltrs/min usually. Should it be 14.4 looking at the manual below? Im guessing if its still cold when im running water slower than reccomended... the problem deffo lies somewhere else as surely this should only make things hotter?

I really appreciate your feedback mate im learning alot

dilalio · 7 Dec 2019

When you get the new (correct) plate hex, don't throw the old one away... Clean it out using something like 1shot or spirit of salts (take necessary precautions when doing this) the reaction will tell you all you need to know about the internal state of the hex and once cleared you have a spare.
If you get nothing out then there are other issues at play.
And if badly blocked, you need to then consider doing something about the system water condition that is manifesting a blockage in the plate hex.

45yearsagasman · 7 Dec 2019

Make sure the CH flow pipe remains cool when in hot water mode. If it gets hot, then you may a faulty diverter valve.

shambolic · 7 Dec 2019

It’s probably diverter cartridge stuck.

Danny Mason · 7 Dec 2019

Well i already taken off to realise i had incorrect size and i cleaned it out there was only a bit of perrished seal in there really seemed pretty clean but my mate said they can fail aswell as get blocked so iv got another heat exchanger on the way anyway which paid £8 for.
However i now feel it might be a diverter issue as our house does not drop below 25deg even with heating switch off all night the rads stay mildly warm. Iv just powered the whole boiler down, waiting for rads to cool and then im going to switch back on with heating turned off and see if they heat up. If they do i suspect a new diverter valve is needed

Danny Mason · 7 Dec 2019

Ok so heres an update, can someone confirm if its the diverter valve i need to replace...

so i isolated the boiler, let everything cool off. Then switched back on with the Central heating switched off, and the pipe that im pointing to on the photo instantly gets hot (during which period only done a quick DHW pre heat and then i rsn the hot water so was demand for DHW. The one next to it only gets hot when i run my taps really slow.

dilalio · 7 Dec 2019

Better to feel if any rads (nearest to boiler) are getting hot when running hot water. That pipe may just get warm by convection but really hot if flow down it.

Danny Mason · 7 Dec 2019

Ok, well Does get very hot to be fair and rads were starting to heat up and all that happened was a quick pre heat and then DHW

shambolic · 7 Dec 2019

So the diverter cartridge is gubbed as said before. It’s behind the grey Honeywell box. And is a spring loads cartridge that should spring out for dhw. They get stuck with dirty water through time and the grease runs out. Easy to change the cartridge itself. 15-20 minute job.

shambolic · 7 Dec 2019

174200 I think the ideal part number is from memory.

shambolic · 7 Dec 2019

diynot

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Heat exchanger wrong size

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