My second thread here, the first having been about numerous concerns over a new system install with non working underfloor, and possibly undersized pipes etc...
The issues have now mostly been resolved, however one still remains, the boiler going into overheat as I dont think there is an adequate escape route for heat during the pump overrun.
There is currently no bypass installed (miscommunication between boiler and his employee doing different bits of the job on different days, it got missed) - there is a bypass to be installed shortly.
My questionis that rather than waste this heat, can it be routed so as to bypass the valve to the HW cylinder?
i.e. when the system stops calling for heat, the last remaining bit of heat from pupm overrun is then diverted through the HW just to take the last bit of heat out of the heat exchanger.
Current system layout is as below:
At present boiler 1 is switched off and lock valves isolated to prevent reverse flow
under floor heating zone valve is locked open, being controlled by its own pump and individual valves at the manifold.
When the system shuts off at present, the zone valves to HW and CH are closed, so I would assume the pump overrun then would flow through the open underfloor circuit, but if this has also been running, then it would appear that either the pump at the manifold is too restrictive and doesnt allow this route to be used as an overrun bypass, or the return is already up to temperature and thus not an effective overrun loop.
What I propose is installing a bypass that would just allow heat from pump overrun into the HW cylinder.
However, thinking it through, this may not be the best of ideas as it does allow for the possibility of heat flowing uncontrolled into the cylinder in the event of a failure of the bypass valve. Effectively making a great big pressure cooker.
There is no seperate run to a towel radiator that could be used, so is the alternative running several metres of pipework round the garage and back to provide enough for a bypass? As there is pottentially the need to accomodate the heat from two boilers wanting to run pump overrun, then does this increase the length/capacity of any bypass required.
I will eventually be having the system changed to a low loss header setup, which should see the problem removed I hope.
While waiting for the bypass to be installed (plumber on hols at present and not back for a fortnight), another possible solution may be to open the taps slightly to the 1st boiler which is currently switched off and allow this run to be used as an escape route, hoping that it doesnt bring with it a reverse flow issue and cause early shut off of the running boiler..
Open to comments advice
The issues have now mostly been resolved, however one still remains, the boiler going into overheat as I dont think there is an adequate escape route for heat during the pump overrun.
There is currently no bypass installed (miscommunication between boiler and his employee doing different bits of the job on different days, it got missed) - there is a bypass to be installed shortly.
My questionis that rather than waste this heat, can it be routed so as to bypass the valve to the HW cylinder?
i.e. when the system stops calling for heat, the last remaining bit of heat from pupm overrun is then diverted through the HW just to take the last bit of heat out of the heat exchanger.
Current system layout is as below:
At present boiler 1 is switched off and lock valves isolated to prevent reverse flow
under floor heating zone valve is locked open, being controlled by its own pump and individual valves at the manifold.
When the system shuts off at present, the zone valves to HW and CH are closed, so I would assume the pump overrun then would flow through the open underfloor circuit, but if this has also been running, then it would appear that either the pump at the manifold is too restrictive and doesnt allow this route to be used as an overrun bypass, or the return is already up to temperature and thus not an effective overrun loop.
What I propose is installing a bypass that would just allow heat from pump overrun into the HW cylinder.
However, thinking it through, this may not be the best of ideas as it does allow for the possibility of heat flowing uncontrolled into the cylinder in the event of a failure of the bypass valve. Effectively making a great big pressure cooker.
There is no seperate run to a towel radiator that could be used, so is the alternative running several metres of pipework round the garage and back to provide enough for a bypass? As there is pottentially the need to accomodate the heat from two boilers wanting to run pump overrun, then does this increase the length/capacity of any bypass required.
I will eventually be having the system changed to a low loss header setup, which should see the problem removed I hope.
While waiting for the bypass to be installed (plumber on hols at present and not back for a fortnight), another possible solution may be to open the taps slightly to the 1st boiler which is currently switched off and allow this run to be used as an escape route, hoping that it doesnt bring with it a reverse flow issue and cause early shut off of the running boiler..
Open to comments advice
