Hi folks, my better half has a Halstead Ace combi boiler. The unit was fitted along with a totally new heating system about three years ago. Since that time the thing has been less than reliable. It works fine for central heating but gives intermittent forms of hot water service. The most common form of this problem is hot water for a few minutes and then a cut out of the burner, with a possible cut in or maybe not. If you wait a while the hot water comes back and is hot but for a limited period as before, and so on. This is not great when bathing or showering.
The original plumber has changed the diverter diaphragm three times. This has resulted in further bouts of good service each of about 3 – 6 months at a time before reverting to the state in paragraph 1. When I took a look at the problem I checked the resistance in the two thermistors and they were 10k ohms at room temperature, which is supposed to be correct. I can visually see that the plunger moves on the diverter valve to trip the micro switch when hot water is called for and this micro switch is fully depressed. This leads me to believe that the problem is not the diverter diaphragm.
I am not sure why changing the diaphragm has cured the issue before – but that’s why I am posting. My shot at fixing this was to remove the DHW exchanger and dunk it in acid for a couple of hours, clean it and re-fit it. This gave excellent results for two more months. But now the old symptoms have returned. I want opinions on what the root cause of this problem could be. So far as I can tell if the micro switch is getting depressed, the diaphragm is ok. If the DHW exchanger is clean then we should be able to shift the heat in the system into the mains water and not be hitting overheat in the primary circuit. This was possibly the problem we were hitting before, perhaps we are hitting it again, who knows
At the moment it is possible to get hot water at a reduced flow from the boiler in a constant delivery. Meaning turn the tap on low and it won’t cut out. This does again point back to the DHW exchanger being unable to shift the heat into the mains water quickly enough to avoid an overheat in the primary circuit. But sufficiently modulating to avoid this when under reduced load. The system does seem to be loosing pressure, and I suspect that this might be due to someone draining it through the pressure relief valve, which I have read in another post on this forum ruins the seals in the PRV, introducing air. These boilers do not like air, I have also read. Finally i shut off all the rads except one today, to just heat one room (the towel rads were also on as always), and I noticed the CH runs for about 5 minutes, then the pump stops momentairly and then resumes after about 2 seconds. Which is odd, I could hear this in the flow through the pipework. Plently of constant heat there though Might not be related but I thought I'd mention it.
So I am thinking do I get an new PRV, diverter diaphragm, clean the DWH exchanger again and fit a magnaflow, or scrap it and get another combi? I would rather get root cause and be done with it for a few years
Lots in there I know, but I want to provide all the data.
What say you?
The original plumber has changed the diverter diaphragm three times. This has resulted in further bouts of good service each of about 3 – 6 months at a time before reverting to the state in paragraph 1. When I took a look at the problem I checked the resistance in the two thermistors and they were 10k ohms at room temperature, which is supposed to be correct. I can visually see that the plunger moves on the diverter valve to trip the micro switch when hot water is called for and this micro switch is fully depressed. This leads me to believe that the problem is not the diverter diaphragm.
I am not sure why changing the diaphragm has cured the issue before – but that’s why I am posting. My shot at fixing this was to remove the DHW exchanger and dunk it in acid for a couple of hours, clean it and re-fit it. This gave excellent results for two more months. But now the old symptoms have returned. I want opinions on what the root cause of this problem could be. So far as I can tell if the micro switch is getting depressed, the diaphragm is ok. If the DHW exchanger is clean then we should be able to shift the heat in the system into the mains water and not be hitting overheat in the primary circuit. This was possibly the problem we were hitting before, perhaps we are hitting it again, who knows
At the moment it is possible to get hot water at a reduced flow from the boiler in a constant delivery. Meaning turn the tap on low and it won’t cut out. This does again point back to the DHW exchanger being unable to shift the heat into the mains water quickly enough to avoid an overheat in the primary circuit. But sufficiently modulating to avoid this when under reduced load. The system does seem to be loosing pressure, and I suspect that this might be due to someone draining it through the pressure relief valve, which I have read in another post on this forum ruins the seals in the PRV, introducing air. These boilers do not like air, I have also read. Finally i shut off all the rads except one today, to just heat one room (the towel rads were also on as always), and I noticed the CH runs for about 5 minutes, then the pump stops momentairly and then resumes after about 2 seconds. Which is odd, I could hear this in the flow through the pipework. Plently of constant heat there though Might not be related but I thought I'd mention it.
So I am thinking do I get an new PRV, diverter diaphragm, clean the DWH exchanger again and fit a magnaflow, or scrap it and get another combi? I would rather get root cause and be done with it for a few years
Lots in there I know, but I want to provide all the data.
What say you?
) and didn't bring any plumbing tools with me. (Thinking I would not be doing any plumbing for a change! ) Checked the diaphram, of course it's fine. So it's going to be flush and magnaflow time very soon!