Just thought i would mention on this thread that i had a Baxi 630 installed in January and has been a brilliant combi boiler. It is quiet and and does a good job of supplying decent amounts of water through our thermostatic shower. Has a 7 year guarantee and the guy who installed says he always recommends Baxi (he has installed lots of Baxi duo tec's and platinum's with very few problems and Baxi are brilliant if their are any problems). He said that the 600 range was a new range but that they seem to be great quality.
Which combi boiler / radiators ?
- Thread starter GeX
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Given you seem to be in the trade. We've just bought a house with a Vaillant Ecotec Plus. We've found we keep losing hot water, and on checking the boiler we get the F.62 error which seems to point towards a gas valve failure.
Hitting the reset switch tends to fix it for a day or 2 before it needs reseting again.
Any idea how much it'd be to repair (i'm assuming it's around 7 years old).
Honestly I would not get a combi boiler. Your decision of course, but I get more people complaining about them not heating the house correctly in the winter. It explanation is complicated but believe me there are a lot of people out there saying that their house never seems to get as warm as it did in the winter, and they are correct. Not only that but combi boilers are a lot more complex than a standard boiler and later in life can become a maintenance nightmare. Standard boilers could not be more simple. Not to mention the fact that pressurising an existing radiator system may well cause major problems. Older systems tend to leak when they are suddenly pressurised.
Why would a combination boiler fail to heat a house, they tend to be oversized for central heating requirements. For instance we went from a 17kw standard boiler to a a combi with 28kw on the central heating.
For that very reason. They are too powerful.
I knew this would happen - that I would have to explain it, lol.
OK here goes!
When a boiler heats a radiator system the boiler is inputting heat and the radiators are radiating it. The boiler continues to input heat until the water reaches a specific temperature then it turns off. The boiler then waits a per-determined time until it repeats the process. The temperature in the room is determined by how quickly the radiators lose heat to the room offset by how quickly the room loses heat to the outside world.
Choosing the correct power boiler is not just a case of plonking in the largest boiler you can afford.
If you put in a boiler that is under-powered then the room is losing heat to the outside world faster than it is gaining heat from the radiators. The end effect is the boiler stays on all the time because it can't get the water temperature up to it's switch off point. That alone is not the end of the world but it's not fine if the boiler is constantly on and the room has not reached a comfortable temperature. That's a clear indication that the boiler is not powerful enough.
If the boiler is too powerful then what happens is that the radiators can't transfer the heat to the room fast enough and the water reaches maximum temperature too fast. The boiler switches off too fast, perhaps as little as a few minutes after it switched on. It then goes in to it's cycle time so there is a huge delay before it tries again. So what you get with a boiler that is too powerful is that it gives a very short burst of heat that does pretty much nothing.
Ideally what you want is the boiler power and the radiator power equally matched and the radiators power equal to more than the loss rate of the house. When you have that the boiler should come on, the heat transferred to the water is all lost by the radiators so the return temperature is low, and the boiler remains on for half an hour to and hour and heats the house to target in one or maybe two cycles.
So, anyway, the issue with combination boilers is they are way too powerful. The often don't stay on long enough to warm the house in one hit. Sometimes they never actually manage to get the house to decent temperatures.
The way to correct the problem is of course to fit radiators that emitt heat far faster than the radiators you already have. Often this is by changing them to doubles rather than singles. I mean nothing wrong with that but often installers don't do that to save money and the end result is a degraded system.
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Yeah that doesn't happen in my system. Need to do your research on modern systems.
Mine starts at full power and heats the water to 80c then as demand falls as room temperature increases the boiler instead of cycling on and off just reduces the temperature often down to 25c to maintain a 21c in my rooms. It will also reduce or increase the flow rate.
The only time the boiler ever cycles in mine is if only one room calls for heat which is very very rare the boiler pretty much runs the while time with no cycling.
My radiotors are also massively oversized to allow the boiler to use lower temperatures to maintain condensing.
You need a better combi boiler, one with opentherm and with a better modulation.
Exactly, but a lot of people don't have good boilers, ergo they end up with issues. My real point here is that there a lot of installers who just install something cheap and rubbish that actually degrades a houses heating rather than improving it.
I see your point, a lot of installers don't tend to do any calculations or care of your system is efficient.
You also raised a very important point that condensation boilers are hopeless for normal radiators, so oversized should be fitted anyway, and mostly they are not. Otherwise the entire point of a condensation boiler is lost. I mean they were designed for underfloor heating which of course runs at a much lower temperatures. Anyway....
what boiler do you have please?
Ideal Vogue gen 2
Yes
My eight year old Vaillant can be programmed to output whatever kW your radiators can handle within it's 10-25 kW range. So you get the boiler that suits your house and needs, and then tune it what your radiators can handle.
I'd suggest that if people are still having problems with this on combis, they just haven't set them up correctly. Certainly mine wasn't initially done correctly, and we did experience fast cycling as you describe, but five minutes with the manual and an online calculator sorted that out.
I would blame poor installations if it's not done properly, just like those guys that install condensate pipes on the level and where they will freeze.
I really don't think removing an existing combi boiler and installing a system boiler is a good idea. I've got one bathroom, the current combi is 'fine' and heats the house.
What you have said in a further post is not relevant as the boiler I'm having fitted (and controller) will allow the boiler to modulate the flow temperature. It won't go on/off/on/off/on/off.
Why is it not a good idea? Well, like I said, it's a personal choice, but I tend to dislike combi boilers. The more sophisticated ones are just more prone to problems. But I can understand people who want high tech solutions. More importantly, the problems I tend to encounter is that installers just don'e understand the system they are trying to install ~ very often they will not spend out on modifications to radiator system, which of course then causes problems. And retrospectively trying to get a more complex boiler repaired can be a bit of a nightmare. I remember one boiler that suddenly changed it's operation but absolutely no one could work out why. But I am probably just biased by weird experiences! if you are content in your choice of both boiler and installer then I am sure everything will be fine.
Thanks for this.
I spoke to a plumber round the corner who doesn't do repairs but he suggested the best option was to ring British Gas. Said they do a fixed fee repair for £199 including parts which is much lower than anyone else would be.
I looked and they do it based on time. Under 2 hours is £199 but over that it goes up to around £400
If it is the PCB or valve does it sound like it'd be a less than 2hr job?