Good morning peeps.
Bear with me.............this is a 2 parter !!!!
Nearly 2 years to the day my newly installed Viessman 100W boiler has started kettling and will not behave.
Bit of background on the system. I installed it on an open vent system, changing from Y-plan to S-plan, added a small UFH system to it, fitted a maganclean, fitted an ABV, autmoatic vent, TRV's (not to all rads) and flushed the system out prior to commisioning. The system and boiler has been working great in its 2 years.....................
Then just before Xmas was woken by the sound of trickling water when the boiler fired from up from cold early in the morning (boiler is directly below the bedroom). Quick check over and nowt leaking. Spoke to plumber mate of mine who said check the header tank as it might be dry/frozen/full of crap. All ok there.
Anyway few more weeks of this and the diagnosis appears to kettling. Even had the Viessmann engineer check it out and his conclusion was the same. Just cannot bottom out how this is occuring???
Have been fiddling with various aspects of the system, pump speeds (set at 2, normally), UFH settings (separate recic-pump), ABV settings (was set at 2), draining, bleeded, dosing with X200, even 5 hrs powerflushing last weekend (water was fairly clean, not too dirty), cleaned header tank out (bit of debris in this), but still the problem persists...
The boiler is at its worst from cold, no matter what part of the system is calling for heat? Usually more noticeable in the morning as the UFH is first out of the blocks and I'm in bed!!!!. During the day it settles down and is quite happy and purrs along like a kitten. I have taken to turning the boiler stat down a notch or two which does help with the noise. All indications are it is a flow problem, as the flow/return at the boiler is quite obvioulsy greater than 8-10deg??
So..........any suggestions??
My next plan of action is to tee into the pipework driectly at the boiler and try and flush it at source?? I'm thinking it may have some debris / air lodged at the heatexchanger. The design has a spiral wound horizontal heat exchanger which I've googled and could possibly be air trapped in the top of the coils???
I also have a new recirc pump ready to go into the system (got a 15/50 at present with an Alpha 2 15/60 to swap over in its place) How can you tell if a pump is on its way out??? Its been in there for 15years and sounds as good as the day it was put in. The rads warm up fine and theres' plenty of hot water
My plumber mate has also suggested re-postioning the Magnaclean as at present it is in the CH circuit (where I would assume most of the magnetic particles would be generated???) He's suggested postioning it directly on the return??
As I said when its all warmed up and running, all is well and the system is smooth.
Righto, fast forward a few weeks and now I'm here...............
Righto I'm back......update on the kettling !!!
I have since, completely flushed the system again. Cut into the flow/return direct at the boiler and flushed it there. Flushed the entire CH system, then flushed every radiator induvidually, then the entire CH system again for good measure. Flushed the floor circuit, flushed the DHW circuit.
All in all the floor and DHW was fairly clean, the CH circuit was a bit cloudy, but nothing too bad.
I've changed the pump to a Alpha 2, taken the Honeywell ABV apart and checked it, and its all ok. Repositioned the Magnaclean to protect the whole system.
Stripped the old 15/50 pump down for curiosity and its looked fine.
At the moment the kettling still persists. I've been fiddling with various settings on the ABV, and the Alpha pump but am chasing my tail.
I've been looking at the setting procedure for the ABV and the Alpha 2 and the various charts are great if you are working in a laboratory, but how you calculate the various flow rates, pump heads etc etc on a live system is beyond me !!!!
The boiler itself is working great and will behave all day long when the firing is low, it will tick along at 70-75deg without a whisper, soon as the thing ramps up from 1-5bars (especially from cold) on the burner scale she's kettling again. 200L/H is the min flowrate required, but how you test that at the boiler just using temp is a new one on me !!!!
My next port of call is the return and flow temp sensors in the boiler. I might even ditch the ABV as I cannot rememeber why I put it in there in the first place ?????...........The boiler has pump over run, there are a few rads in the CH system without TRV's, the UFH has TRV on the blender but I've got an additional rad on that circuit which should get rid of the heat..........
Input greatly appreciated
Bear with me.............this is a 2 parter !!!!
Nearly 2 years to the day my newly installed Viessman 100W boiler has started kettling and will not behave.
Bit of background on the system. I installed it on an open vent system, changing from Y-plan to S-plan, added a small UFH system to it, fitted a maganclean, fitted an ABV, autmoatic vent, TRV's (not to all rads) and flushed the system out prior to commisioning. The system and boiler has been working great in its 2 years.....................
Then just before Xmas was woken by the sound of trickling water when the boiler fired from up from cold early in the morning (boiler is directly below the bedroom). Quick check over and nowt leaking. Spoke to plumber mate of mine who said check the header tank as it might be dry/frozen/full of crap. All ok there.
Anyway few more weeks of this and the diagnosis appears to kettling. Even had the Viessmann engineer check it out and his conclusion was the same. Just cannot bottom out how this is occuring???
Have been fiddling with various aspects of the system, pump speeds (set at 2, normally), UFH settings (separate recic-pump), ABV settings (was set at 2), draining, bleeded, dosing with X200, even 5 hrs powerflushing last weekend (water was fairly clean, not too dirty), cleaned header tank out (bit of debris in this), but still the problem persists...
The boiler is at its worst from cold, no matter what part of the system is calling for heat? Usually more noticeable in the morning as the UFH is first out of the blocks and I'm in bed!!!!. During the day it settles down and is quite happy and purrs along like a kitten. I have taken to turning the boiler stat down a notch or two which does help with the noise. All indications are it is a flow problem, as the flow/return at the boiler is quite obvioulsy greater than 8-10deg??
So..........any suggestions??
My next plan of action is to tee into the pipework driectly at the boiler and try and flush it at source?? I'm thinking it may have some debris / air lodged at the heatexchanger. The design has a spiral wound horizontal heat exchanger which I've googled and could possibly be air trapped in the top of the coils???
I also have a new recirc pump ready to go into the system (got a 15/50 at present with an Alpha 2 15/60 to swap over in its place) How can you tell if a pump is on its way out??? Its been in there for 15years and sounds as good as the day it was put in. The rads warm up fine and theres' plenty of hot water
My plumber mate has also suggested re-postioning the Magnaclean as at present it is in the CH circuit (where I would assume most of the magnetic particles would be generated???) He's suggested postioning it directly on the return??
As I said when its all warmed up and running, all is well and the system is smooth.
Righto, fast forward a few weeks and now I'm here...............
Righto I'm back......update on the kettling !!!
I have since, completely flushed the system again. Cut into the flow/return direct at the boiler and flushed it there. Flushed the entire CH system, then flushed every radiator induvidually, then the entire CH system again for good measure. Flushed the floor circuit, flushed the DHW circuit.
All in all the floor and DHW was fairly clean, the CH circuit was a bit cloudy, but nothing too bad.
I've changed the pump to a Alpha 2, taken the Honeywell ABV apart and checked it, and its all ok. Repositioned the Magnaclean to protect the whole system.
Stripped the old 15/50 pump down for curiosity and its looked fine.
At the moment the kettling still persists. I've been fiddling with various settings on the ABV, and the Alpha pump but am chasing my tail.
I've been looking at the setting procedure for the ABV and the Alpha 2 and the various charts are great if you are working in a laboratory, but how you calculate the various flow rates, pump heads etc etc on a live system is beyond me !!!!
The boiler itself is working great and will behave all day long when the firing is low, it will tick along at 70-75deg without a whisper, soon as the thing ramps up from 1-5bars (especially from cold) on the burner scale she's kettling again. 200L/H is the min flowrate required, but how you test that at the boiler just using temp is a new one on me !!!!
My next port of call is the return and flow temp sensors in the boiler. I might even ditch the ABV as I cannot rememeber why I put it in there in the first place ?????...........The boiler has pump over run, there are a few rads in the CH system without TRV's, the UFH has TRV on the blender but I've got an additional rad on that circuit which should get rid of the heat..........
Input greatly appreciated
That image from a viesmann manual by Chris is typical of Viessmanns totally chaotic and disastrous entry into the Uk, fair enough they don't do vented in Germany, but they could of asked a 1st year apprentice for a diagram of F&V connections. 
