Hi All,
We inherited an HRM Wallstar 12/14 "half moon" boiler when we bought our house 12 or so years ago. It's been reliable and based on advice from previous posts on here, we're aiming to keep it as long as we can. It's in an open vented Y plan config.
It's always run well, I've drained down and refilled the system numerous times over the years without any problems.
A couple of years back we had issues with flow. Balancing the system appeared to help (despite valves been wide open all the years prior). A few months later, issues reappeared and I suspected the circulation pump as it was noisy, so I replaced it. This made no difference. Took all the usual steps bleeding rads and running one at a time to push through any air, no difference. I noticed with ear pressed against boiler that I could hear air in the system/pump. Stopping and restarting the pump helped pull it through. Then on one particular restart there was one almighty gush of air and she ran lovely again.
I refit the bathroom during lockdown 1 last year, and drained down for a new towel rad. Exactly the same issues as the year before, could hear air and after many many pump restarts the big surge of air came through and she ran fine.
In November, we noticed some rads were cold. I rebalanced the radiators, which helped them to heat evenly, but they took forever to heat up. Boiler was getting up to full temp and thermostat cutting in, yet radiators and the return pipe to boiler cool. They did get red hot but took several hours. The hot water cylinder was only reaching 40 degrees at the thermostat when heated for an hour overnight, when it normally gets to 60 with ease. Ear pressed to the boiler, it sounded like the pump was intermittently passing air, then sounding normal, then air again etc. Its a UPS3 pump so no bleed screw.
I had a good look in the loft, pulled all the lagging off the pipes and noticed there was a non-return valve on the vent pipe! Sure enough I removed it and it was a bit caked up. I had no compression fitting to replace it, so pulled the innards out and refitted it. This made a big difference to the sound of the pump, after running on speed 3 for a bit the air was clear and it was running quiet.
However, the flow is still poor and the issue of very slow radiator heat up persists.
The system has always been run with inhibitor, however I decided to drain down at the weekend. I refilled and drained several times to rinse, and have added X400 for a couple of weeks. One thing I did which I haven't done before is remove the drain plug from the boiler itself to drain that. The initial water was black coloured (but not thick and sludgey), 3 or 4 rinses and it was clear again. However there was some bits of scale, metal fragments etc in it.
The system refilled really well, I was able to push all the air through with ease and bleed the rads. However, still issues with flow. I can get every radiator in the system red hot independently. I've checked all the TRVs and none are stuck, and the issue is present even with just the hot water circuit running.
I've spoken to a couple of plumbers however none are really interested in having a look. I had one booked in who didn't turn up!
Any ideas?
My thoughts in terms of what is left....
- pump? It's definitely running, sounds fine, relatively new. Can pumps run slowly or is it just a case of working or bust?
- blockage in the heat exchanger. Replacement online is circa £800!
- head pipework. I know the config isn't best practice, the feed tank is into the return line of the boiler, and the vent pipe is on the boiler side of the pump on the flow. BUT! It ran fine like this for many years?
Apologies for the long post, obviously there's a lot of history there. I really want to get this boiler going again, but the temptation to get someone in to fit a new combi is growing
Thanks for taking the time to read my essay!
We inherited an HRM Wallstar 12/14 "half moon" boiler when we bought our house 12 or so years ago. It's been reliable and based on advice from previous posts on here, we're aiming to keep it as long as we can. It's in an open vented Y plan config.
It's always run well, I've drained down and refilled the system numerous times over the years without any problems.
A couple of years back we had issues with flow. Balancing the system appeared to help (despite valves been wide open all the years prior). A few months later, issues reappeared and I suspected the circulation pump as it was noisy, so I replaced it. This made no difference. Took all the usual steps bleeding rads and running one at a time to push through any air, no difference. I noticed with ear pressed against boiler that I could hear air in the system/pump. Stopping and restarting the pump helped pull it through. Then on one particular restart there was one almighty gush of air and she ran lovely again.
I refit the bathroom during lockdown 1 last year, and drained down for a new towel rad. Exactly the same issues as the year before, could hear air and after many many pump restarts the big surge of air came through and she ran fine.
In November, we noticed some rads were cold. I rebalanced the radiators, which helped them to heat evenly, but they took forever to heat up. Boiler was getting up to full temp and thermostat cutting in, yet radiators and the return pipe to boiler cool. They did get red hot but took several hours. The hot water cylinder was only reaching 40 degrees at the thermostat when heated for an hour overnight, when it normally gets to 60 with ease. Ear pressed to the boiler, it sounded like the pump was intermittently passing air, then sounding normal, then air again etc. Its a UPS3 pump so no bleed screw.
I had a good look in the loft, pulled all the lagging off the pipes and noticed there was a non-return valve on the vent pipe! Sure enough I removed it and it was a bit caked up. I had no compression fitting to replace it, so pulled the innards out and refitted it. This made a big difference to the sound of the pump, after running on speed 3 for a bit the air was clear and it was running quiet.
However, the flow is still poor and the issue of very slow radiator heat up persists.
The system has always been run with inhibitor, however I decided to drain down at the weekend. I refilled and drained several times to rinse, and have added X400 for a couple of weeks. One thing I did which I haven't done before is remove the drain plug from the boiler itself to drain that. The initial water was black coloured (but not thick and sludgey), 3 or 4 rinses and it was clear again. However there was some bits of scale, metal fragments etc in it.
The system refilled really well, I was able to push all the air through with ease and bleed the rads. However, still issues with flow. I can get every radiator in the system red hot independently. I've checked all the TRVs and none are stuck, and the issue is present even with just the hot water circuit running.
I've spoken to a couple of plumbers however none are really interested in having a look. I had one booked in who didn't turn up!
Any ideas?
My thoughts in terms of what is left....
- pump? It's definitely running, sounds fine, relatively new. Can pumps run slowly or is it just a case of working or bust?
- blockage in the heat exchanger. Replacement online is circa £800!
- head pipework. I know the config isn't best practice, the feed tank is into the return line of the boiler, and the vent pipe is on the boiler side of the pump on the flow. BUT! It ran fine like this for many years?
Apologies for the long post, obviously there's a lot of history there. I really want to get this boiler going again, but the temptation to get someone in to fit a new combi is growing
Thanks for taking the time to read my essay!
Last edited:
