I know there’s a lot of good advice on this forum on this topic, so I’m hoping for any useful comments on the plan below for descaling my cast iron boiler. Thanks in advance!
The boiler is Potterton Netaheat Profile 50e, 25 yrs old and, for its first 24 years, never ever had any inhibitors added. I explained in a previous posting this was down to negligence on my part, as repeated modifications to the system were envisaged over the years, so inhibitor was never added! Then last year I flushed the whole system, used Fernox F3 for 4 weeks, then flushed and dosed just the heat exchanger with 13% sulphamic acid, and then after flushing everything refilled and added Sentinel X100 and X200 to the whole system. The system comprises 13 radiators (aged 3 – 15 years), HW cylinder, expansion vessel, Magnaclean.
Three months ago I noticed some kettling, not a lot, which must mean the heat exchanger is not as clean as I had hoped. 4 days ago I flushed the system and refilled using Fernox F3, as I’m getting a fair amount of magnetite in the Magnaclean. The F3 is currently in the system.
In order to make the descale as effective as possible I intend to apply possibly all of the following procedures, in sequence, to the isolated heat exchanger (not to the full CH/HW circuit):
1. Fill with 10% hydrochloric acid at 20C – 25C for 45 mins, drain and then repeated flush with cold water. (Fully aware of H & S risks and precautions).
2. If necessary, neutralise the residual effects of the hydrochloric acid with something like sodium bicarbonate.
3. Circulate 20% sulphamic acid at 70C for 2 – 4 hours, drain and flush.
4. Circulate 20% citric acid at 70C for 2 – 4 hours, drain.
5. Fill with 500g Fernox DS40 (one third of the box) at 70C for 1 hour, drain, and check the drained solution has not turned green from its original red colour. If it has turned green it means the DS40 has been used up in treating the scale/sludge, and more needs to be added.
Then, after carrying out the above, apply the following to the WHOLE system: drain and flush, refill using Sentinel X800, run CH and HW at max temp for 5 – 10 hours, drain and flush, then finally refill adding Sentinel X100 and X200. (The reason for using X800 here is to treat the radiators, with each radiator in turn being flushed as strongly as possible by closing off all the other radiators).
My question is, am I likely to do any harm to the heat exchanger by carrying out all of the above? And is 45 mins a sensible time for the hydrochloric acid to stay in the heat exchanger, given its potency and concentration?
Carrying out all of the above stages might be overkill, but my rationale is that since I can’t identify all the deposits lurking in the heat exchanger, I may as well presume they’re all in there and go for an attack strategy from all sides. I don’t envisage hiring a powerflush unit, but I will use a reversible circulating pump on the (isolated) heat exchanger.
The boiler is Potterton Netaheat Profile 50e, 25 yrs old and, for its first 24 years, never ever had any inhibitors added. I explained in a previous posting this was down to negligence on my part, as repeated modifications to the system were envisaged over the years, so inhibitor was never added! Then last year I flushed the whole system, used Fernox F3 for 4 weeks, then flushed and dosed just the heat exchanger with 13% sulphamic acid, and then after flushing everything refilled and added Sentinel X100 and X200 to the whole system. The system comprises 13 radiators (aged 3 – 15 years), HW cylinder, expansion vessel, Magnaclean.
Three months ago I noticed some kettling, not a lot, which must mean the heat exchanger is not as clean as I had hoped. 4 days ago I flushed the system and refilled using Fernox F3, as I’m getting a fair amount of magnetite in the Magnaclean. The F3 is currently in the system.
In order to make the descale as effective as possible I intend to apply possibly all of the following procedures, in sequence, to the isolated heat exchanger (not to the full CH/HW circuit):
1. Fill with 10% hydrochloric acid at 20C – 25C for 45 mins, drain and then repeated flush with cold water. (Fully aware of H & S risks and precautions).
2. If necessary, neutralise the residual effects of the hydrochloric acid with something like sodium bicarbonate.
3. Circulate 20% sulphamic acid at 70C for 2 – 4 hours, drain and flush.
4. Circulate 20% citric acid at 70C for 2 – 4 hours, drain.
5. Fill with 500g Fernox DS40 (one third of the box) at 70C for 1 hour, drain, and check the drained solution has not turned green from its original red colour. If it has turned green it means the DS40 has been used up in treating the scale/sludge, and more needs to be added.
Then, after carrying out the above, apply the following to the WHOLE system: drain and flush, refill using Sentinel X800, run CH and HW at max temp for 5 – 10 hours, drain and flush, then finally refill adding Sentinel X100 and X200. (The reason for using X800 here is to treat the radiators, with each radiator in turn being flushed as strongly as possible by closing off all the other radiators).
My question is, am I likely to do any harm to the heat exchanger by carrying out all of the above? And is 45 mins a sensible time for the hydrochloric acid to stay in the heat exchanger, given its potency and concentration?
Carrying out all of the above stages might be overkill, but my rationale is that since I can’t identify all the deposits lurking in the heat exchanger, I may as well presume they’re all in there and go for an attack strategy from all sides. I don’t envisage hiring a powerflush unit, but I will use a reversible circulating pump on the (isolated) heat exchanger.
.
