Converting open vented heating to sealed
Discussion
My annual boiler service was this week. The engineer that was sent out has been out to me a couple of times, on one occasion it was for a boiler issue that subsequently turned out to be circulation problems. Spent a few minutes picking his brains after he’d finished and he mentioned that going to a sealed system and getting rid of the header tank should solve the issues I’ve got with air locks after draining the system and should reduce the amount of sludge. He mentioned something about a DIY kit to replace the upper vent and add an expansion vessel, pressure relief valve and filling loop.
I can’t find anything suitable in either Screwfix or Toolstation. Has anyone else attempted something like this? Is this actually practical?
I’d mentioned that I was planning to get power flushing done, he said that was pointless with microbore pipe work. Does this sound about right? I’ve got one radiator that doesn’t heat up at all, pretty sure there’s a magnetite blockage in the flow side pipework somewhere.
I can’t find anything suitable in either Screwfix or Toolstation. Has anyone else attempted something like this? Is this actually practical?
I’d mentioned that I was planning to get power flushing done, he said that was pointless with microbore pipe work. Does this sound about right? I’ve got one radiator that doesn’t heat up at all, pretty sure there’s a magnetite blockage in the flow side pipework somewhere.
We changed from header tank to pressurised and it exposed that we had a small leak which meant that the pressurised system lost pressure every week or so. The pipes were buried in concrete (1970's bungalow) so difficult to find where the leak was. So we spent about £2,500 running new pipes in the loft which come down from the ceiling (unsightly)
miniman said:
Is he talking about converting a vented system into an unvented system by adding bits? They are completely different tanks, one being suitable for very high pressure.
If I’ve understood properly, his suggestion was to leave the hot-water as-is, but remove the heating header tank (leaving the cold water header in-situ, complete with the steam vent from the hot water tank), cap off & remove the steam vent from the heating circuit to the heating header tank, fit an expansion vessel in the airing cupboard above the hot water tank, then add a filling loop in place of the existing feed from the heating header tank. The heating system through the radiators and the water tank coil would then be pressurised to 1 bar or so.I’d never heard of doing that, only converting vented systems with tanks to combis when the boiler was replaced, which is obviously a more radical bit of plumbing, hence me asking.
gmaz said:
We changed from header tank to pressurised and it exposed that we had a small leak which meant that the pressurised system lost pressure every week or so. The pipes were buried in concrete (1970's bungalow) so difficult to find where the leak was. So we spent about £2,500 running new pipes in the loft which come down from the ceiling (unsightly)
Was that a full switch to a combi or just the heating circuit? How was it done?miniman said:
Is he talking about converting a vented system into an unvented system by adding bits? They are completely different tanks, one being suitable for very high pressure.
I think he's talking about the circulating system not the consumable hot water.If the system tends to leak a little, it will have lost any inhibitor and accumulated chalk etc.
Over years of poor maintenance, 'open' systems lose water by evaporation anyway, and dust/dead pigeons etc fall in the header tank.
Plumbers don't bother to add inhibitor or refresh it as needed.
I would suggest the best way forwards might be to clean the system, install a filter if there isn't one already and ascertain whether it leaks or not.
Then run it with decent inhibitor and a cover over the header tank to keep the mice and spiders out.
Changing to a sealed circuit will increase the pressure, which will perhaps make any leaks more obvious.
Microbore will benefit from cleaning a system at least as much as other pipework.
Unfortunately, cleaning a CH system effectively is quite time consuming, even with special equipment.
It's quite DIY-able, but then it's even more time consuming with the potential to make a terrible mess!
How old is the boiler? If it's quite old and turns out to be the part that's leaking, then replacing it soon makes sense in the face of the cost of hours of work.
But the system still needs to be cleaned properly, and any leaks found and dealt with.
alangla said:
OutInTheShed said:
Sounds like the OP has two problems.
1) his plumbing is full of s
t
2) his plumber is likewise.
The first is definitely true, despite my best efforts to get rid of it.1) his plumbing is full of s
t2) his plumber is likewise.
The second is what I’m trying to establish in this thread.
I can't see what making the heating loop presurised would do other than add potential for more leaks.
If you have air locks, then surely that condition will still exist. Maybe adding an automatic air valve at the highest points on the loop might deal with that.
Cleaning it out would be the first step.
A bit of mechanical action would probably bring a load out - just make sure you have a magnetic filter first. You can buy a rubber 'bit' that goes on an SDS drill to vibrate the radiators.
Spiders taking a bath in the header aren't that big a problem - it isn't drinking water. But as OITS says, a proper lid stops debris and reduces evapouration.
I don't really understand the 'love' for sealed systems. Expansion vessels, PRVs, tundishes, filling loops and an annual maintainance liability from someone who is certified.
For reference, I am not a plumber, but have recently been through a major redesign/overhaul of an 'old' vented system. I have pulled a load of rads out and changed to UFH, I will also be pulling the hotwater tank out and swapping for a heat store in due course. Heating is staying open loop.
To be fair, a sealed system pressurised can avoid issues with the pump cavitating if it's struggling to suck thick 'water' through a small tube.
If the system leaks under pressure, it needs sorting anyway, as it probably leaks a bit due to thermal cycling and might be likely to get worse soon.
Paying white van man to sod about with old boilers, pumps etc can be a mug's game, compared to getting a new boiler with a 10 year warranty.
If the system leaks under pressure, it needs sorting anyway, as it probably leaks a bit due to thermal cycling and might be likely to get worse soon.
Paying white van man to sod about with old boilers, pumps etc can be a mug's game, compared to getting a new boiler with a 10 year warranty.
Boiler is 5 years old and is the one bit that does appear to function as it should. The radiators themselves are fine, they’ve all been off the wall and been cleaned out with a hose, most of them were pretty clean after last year’s clean.
Header has its lid on and is wrapped in a jacket so hopefully nothing much other than the odd bit of dust or insect getting in via the steam vent pipe aperture.
Magnetic filter is fitted next to the boiler and was cleaned when the radiators were cleaned in the spring.
I’m not aware of any leaks but the plumbing in the house (1999 built) is awful, so anything is possible.
The fundamental issue seems to be that I’ve got a blockage (or multiple) in the microbore that I can’t get to. I tried rodding it with the system drained by inserting nylon strimmer line from the radiator end but no joy. Did a week with Fernox cleanser in back in the spring, no joy either. Short of lifting all the floors to locate the manifold I’m running out of ideas basically.
Header has its lid on and is wrapped in a jacket so hopefully nothing much other than the odd bit of dust or insect getting in via the steam vent pipe aperture.
Magnetic filter is fitted next to the boiler and was cleaned when the radiators were cleaned in the spring.
I’m not aware of any leaks but the plumbing in the house (1999 built) is awful, so anything is possible.
The fundamental issue seems to be that I’ve got a blockage (or multiple) in the microbore that I can’t get to. I tried rodding it with the system drained by inserting nylon strimmer line from the radiator end but no joy. Did a week with Fernox cleanser in back in the spring, no joy either. Short of lifting all the floors to locate the manifold I’m running out of ideas basically.
WrekinCrew said:
I believe professional installers must have a G3 qualification to install unvented systems. Does that apply to D-I-Yers too?
I think you have to have them tested annually by someone with the qualifications.I would assume that worst case, if you installed it yourself, you would be okay if you got your annual inspection done on day 1.
No ideas for a name said:
I think you have to have them tested annually by someone with the qualifications.
I would assume that worst case, if you installed it yourself, you would be okay if you got your annual inspection done on day 1.
Indeed, the plumber who replaced our cylinder recently said this. None of the (supposedly reputable) people who serviced the system over the past ahem 16 years have ever done so 😬I would assume that worst case, if you installed it yourself, you would be okay if you got your annual inspection done on day 1.
G3 is for unvented cylinders, not the actual system. Get the pressure relief wrong and you can potentially blow the side of your house out with an unvented cylinder, hence the qualification requirement.
Converting the flow and return system to pressurised makes sense for cleanliness and efficiency but it will, as said, potentially expose any leaks as you could be running at a higher pressure.
Note not all boilers are suitable for pressurised conversions iirc.
I’m not a plumber. Or a heating engineer.
Converting the flow and return system to pressurised makes sense for cleanliness and efficiency but it will, as said, potentially expose any leaks as you could be running at a higher pressure.
Note not all boilers are suitable for pressurised conversions iirc.
I’m not a plumber. Or a heating engineer.
alangla said:
gmaz said:
We changed from header tank to pressurised and it exposed that we had a small leak which meant that the pressurised system lost pressure every week or so. The pipes were buried in concrete (1970's bungalow) so difficult to find where the leak was. So we spent about £2,500 running new pipes in the loft which come down from the ceiling (unsightly)
Was that a full switch to a combi or just the heating circuit? How was it done?Remove heating feed and expansion tank.
Add a correctly sized expansion vessel, pressure gauge relief valve and filling loop to fill the system
Run out a new pressure relief valve pipe.
Boiler must have an overheat cut out
Hot water will stay as is
CH system will now be running at about 1.5 to 2 bar from what was previously.25 of a bar depending on f&e tank height
Add a correctly sized expansion vessel, pressure gauge relief valve and filling loop to fill the system
Run out a new pressure relief valve pipe.
Boiler must have an overheat cut out
Hot water will stay as is
CH system will now be running at about 1.5 to 2 bar from what was previously.25 of a bar depending on f&e tank height
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