Any chemists and/or metallurgists about?
14 September 2019, 11:24 PM
#1
Any chemists and/or metallurgists about?
Probably better posting this on Reddit but what the hell, I’ll paste it here too:
So I have a domestic heating system that holds about 400litres of water: 100 buffer tank, 120litre additional buffer, 16 big radiators (heatpump system, so multiple oversized rads in each room) and underfloor heating. I’ve had to re-plumb it all as it was a mess, everything was only four years old and mostly pex pipe, traces of inhibitor but yet it was full of sludge from the 4yr old mild steel radiators (Radson, so not cheap rubbish). So either there wasn’t enough corrosion inhibitor (likely) and/or the inhibitor used was ineffective (also possible as most are very vague on their active ingredients). Flushing out/neutralising flux wasn’t the issue as there was zero soldered fittings!
Anyway its now all flushed, cleared and ready for corrosion inhibitor...but this system is going to need about 4 to 5 bottle (manufacturers very vague on dosing levels, which makes me even more suspicious ), to add it will need to be partially drained again in the near future as some rads will need to be removed for decorators requiring more for topping up...which at £10 to £16 a 500ml bottle makes it very expensive when compared to say, automotive corrosion inhibitor, which can be had for about £3.50 a litre and also protects from freezing!
Some digging around has found me the cheapy stuff only contains benzotriazole which is more suited to protecting copper and brass, whereas the more expensive stuff (Fernox etc) also contains Sodium Molybdate which is better at protecting steel...the latter being the main cause of the sludge. Hence my suspicion that inhibitors using only benzotriazole maybe less effective in a mostly steel/pex system, so really I should be opting for the more expensive Molybdate based inhibitors.
Now here’s the rub...100grams of Sodium Molybdate concentrate can be had for £8. Now according to various scientific abstracts,100ppm gives good protection from corrosion, so that makes it enough to treat 1000litres.
So, £8 for the Sodium Molybdate, or £40+ for the Fernox/Sentinal?
So I have a domestic heating system that holds about 400litres of water: 100 buffer tank, 120litre additional buffer, 16 big radiators (heatpump system, so multiple oversized rads in each room) and underfloor heating. I’ve had to re-plumb it all as it was a mess, everything was only four years old and mostly pex pipe, traces of inhibitor but yet it was full of sludge from the 4yr old mild steel radiators (Radson, so not cheap rubbish). So either there wasn’t enough corrosion inhibitor (likely) and/or the inhibitor used was ineffective (also possible as most are very vague on their active ingredients). Flushing out/neutralising flux wasn’t the issue as there was zero soldered fittings!
Anyway its now all flushed, cleared and ready for corrosion inhibitor...but this system is going to need about 4 to 5 bottle (manufacturers very vague on dosing levels, which makes me even more suspicious ), to add it will need to be partially drained again in the near future as some rads will need to be removed for decorators requiring more for topping up...which at £10 to £16 a 500ml bottle makes it very expensive when compared to say, automotive corrosion inhibitor, which can be had for about £3.50 a litre and also protects from freezing!
Some digging around has found me the cheapy stuff only contains benzotriazole which is more suited to protecting copper and brass, whereas the more expensive stuff (Fernox etc) also contains Sodium Molybdate which is better at protecting steel...the latter being the main cause of the sludge. Hence my suspicion that inhibitors using only benzotriazole maybe less effective in a mostly steel/pex system, so really I should be opting for the more expensive Molybdate based inhibitors.
Now here’s the rub...100grams of Sodium Molybdate concentrate can be had for £8. Now according to various scientific abstracts,100ppm gives good protection from corrosion, so that makes it enough to treat 1000litres.
So, £8 for the Sodium Molybdate, or £40+ for the Fernox/Sentinal?
15 September 2019, 12:12 PM
#2
Just stick in the Fernox. Also have you got a magnetic filter on the radiator system?
Ive read that certain plastic pipes arent very good and allow oxygen to get into the system, creating sludge. Some pipes are better having a better oxygen barrier
Ive read that certain plastic pipes arent very good and allow oxygen to get into the system, creating sludge. Some pipes are better having a better oxygen barrier
Last edited by andy97; 15 September 2019 at 03:56 PM.
21 September 2019, 10:52 PM
#3
Normally I’d dump in the Fernox but with quantity required and the cost, it seems very wasteful to have to dump it down the drain in a few months time...and then do it again a few months after that.
Hence just using the active ingredients which is better than nothing.
Barrier pipe throughout, despite this the amount of sludge deposits was astonishing...the plate heat exchanger inside the heat pump succumbed quite badly which was probably the cause of high pressure alarm events on the refrigerant circuit (high refrigerant pressure is usually due to poor cooling of the compressed refrigerant ..the job of the plate heat exchanger). It appears to be behaving now after back-flushing loads of crud out of it.
Magnetic filters are now installed along with mesh inline filters, but that’s not enough on its own.
Hence just using the active ingredients which is better than nothing.
Barrier pipe throughout, despite this the amount of sludge deposits was astonishing...the plate heat exchanger inside the heat pump succumbed quite badly which was probably the cause of high pressure alarm events on the refrigerant circuit (high refrigerant pressure is usually due to poor cooling of the compressed refrigerant ..the job of the plate heat exchanger). It appears to be behaving now after back-flushing loads of crud out of it.
Magnetic filters are now installed along with mesh inline filters, but that’s not enough on its own.
Last edited by ALi-B; 21 September 2019 at 10:57 PM.