I posted a thread a while ago about strange boiler temperature behaviour in my S-plan heating and hot water tank system, and I concluded that water was flowing through my boiler backwards. This was definitely the case, however I wasn't sure if the pump was simply backwards or the boiler pipes were switched. I've tried changing both and got some weird results.
I initially had delta T at the boiler of about 8-10C, along with strange behaviour (not relevant for this thread), however after flipping the pump I saw 18-24C depending on load which I thought was more in line with what I was seeing. But then I was collecting lots of bubbles from somewhere when the hot water was on, so I started to wonder if the pump was now pushing water through the system the wrong way round and maybe the air vents weren't doing their job. So I put the pump back the original way and swapped the boiler connections. However that has led to the boiler delta T going back down to 8-10C. In all cases the pump was on low or medium - the difference between the two settings is slight. So the question is - which way round should the water be flowing?
I've sketched out my airing cupboard below as it is now, which is how it was originally installed. There are four pipes going into the floor, and I cannot work out what they all are or why there are four of them.
Since the boiler was able to generate a dT of 20C or more when the flow was reversed through the pipes, I don't know why it wouldn't be able to now. The water is flowing the correct way through the boiler in both cases. The only thing I can think of is that hot water is somehow being diverted to the return of the boiler without going through any radiators or the cylinder heating coil. Pipes C and D always get warm, but I don't know if this is conduction or not. The return from the hot water cylinder does get warm though even when the HW is off and the CH is on. I thought this must be because the HW motorized valve is leaking but now I'm not so sure. I have replaced the ABV just in case that was the problem - it wasn't.
- Why does the pipe after the ABV split into two? Where do they go?
- Which pipe is connected to the boiler and which to the rads - A or B?
- Is that picture correct, or should it be pumping the other way round?
I initially had delta T at the boiler of about 8-10C, along with strange behaviour (not relevant for this thread), however after flipping the pump I saw 18-24C depending on load which I thought was more in line with what I was seeing. But then I was collecting lots of bubbles from somewhere when the hot water was on, so I started to wonder if the pump was now pushing water through the system the wrong way round and maybe the air vents weren't doing their job. So I put the pump back the original way and swapped the boiler connections. However that has led to the boiler delta T going back down to 8-10C. In all cases the pump was on low or medium - the difference between the two settings is slight. So the question is - which way round should the water be flowing?
I've sketched out my airing cupboard below as it is now, which is how it was originally installed. There are four pipes going into the floor, and I cannot work out what they all are or why there are four of them.
Since the boiler was able to generate a dT of 20C or more when the flow was reversed through the pipes, I don't know why it wouldn't be able to now. The water is flowing the correct way through the boiler in both cases. The only thing I can think of is that hot water is somehow being diverted to the return of the boiler without going through any radiators or the cylinder heating coil. Pipes C and D always get warm, but I don't know if this is conduction or not. The return from the hot water cylinder does get warm though even when the HW is off and the CH is on. I thought this must be because the HW motorized valve is leaking but now I'm not so sure. I have replaced the ABV just in case that was the problem - it wasn't.
- Why does the pipe after the ABV split into two? Where do they go?
- Which pipe is connected to the boiler and which to the rads - A or B?
- Is that picture correct, or should it be pumping the other way round?
