The above system boiler heats a hot water cylinder and heating for 3 bed house. Heating and water are separately controlled by means of Danfoss 24hr controller and 3 port valve. The boiler has failed to fire recently when timed, it switches itself on, does not try to fire and after about 15 seconds cuts out (with a fast flashing green light showing on the panel). If the hot water is switched off, and heating only activated, the boiler will usually fire, and if hot water is turned back on about 2mins later, the system will continue to work perfectly. The 3 post valve and controller in my opinion appear to work as they should. The boiler pressure will run a little above what is desirable when it first fires (about 3.5bar) then settles down to 3 bar. Any thoughts?
Ideal Mini S24
- Thread starter rysogillo
- Start date
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I assume this is a true system boiler and not a combi being used as a system or hybrid?
Firstly the pressure should be 1.5 Bar. Have you left the filling loop open?
Your problem is most likely to be caused by flow restrictions in your system. To confirm this, the boiler's flow switch would have to be viewed while the problem is about to occur.
A flow rate of 20-30 li/min would be typical.
A temperature survey would identify if the system is properly designed and set up for suitable flows.
Tony Glazier
Firstly the pressure should be 1.5 Bar. Have you left the filling loop open?
Your problem is most likely to be caused by flow restrictions in your system. To confirm this, the boiler's flow switch would have to be viewed while the problem is about to occur.
A flow rate of 20-30 li/min would be typical.
A temperature survey would identify if the system is properly designed and set up for suitable flows.
Tony Glazier
Thanks for that Tony
Its a true system boiler, Ideal Standard Mini S24, on a sealed system.
I think i've sorted the pressure problem, the fill loop was connected and appeared to be off, but was actually slightly open. The valve is faulty and will need to be replaced, but i've disconnected it and capped it for now.
I've checked for any obvious restrictions in the system, and have largely ruled out air as being the cause. All rads heat up fine, with no delay, they have all been bled also. The cylinder and DHW system have had air bottle valves fitted also, i've loosened the upper connection at the cylinder coil just to be sure, but there is definetly no air.
The CH flow switch on the boiler does work differently at start up in CH and DHW modes. When DHW is selected only, the boiler goes through its start up procedure (ie starting the circulation pump), and generally will not fire. In this instance, the CH flow switch only opens about half as much as it does when CH is selected only (and it then in turn fires.)
I cannot comment at present on the flow and return temperatures, and will get this checked. The only other comment is that the sytem has workede fine for well over a year, and decided to malfunction. My understanding is that there would either appear to be a restriction (either in the cylinder coil or possibly the motorised valve, although i've disconnected this and checked it), or that the flow switch or another boiler component may be faulty, due to prolonged operation at high pressure.
I'm happy to get someone in to have a look at the system, but i'd rather have a fair idea of the problem first. A chap called in last week and wanted to rip out the motorised valve, thermostat and timer (and boiler if i'd let him) and replace with a lever valve, and had only given the system a glance. I have to say, I had to ask him to leave!
Any advice would be welcome
Its a true system boiler, Ideal Standard Mini S24, on a sealed system.
I think i've sorted the pressure problem, the fill loop was connected and appeared to be off, but was actually slightly open. The valve is faulty and will need to be replaced, but i've disconnected it and capped it for now.
I've checked for any obvious restrictions in the system, and have largely ruled out air as being the cause. All rads heat up fine, with no delay, they have all been bled also. The cylinder and DHW system have had air bottle valves fitted also, i've loosened the upper connection at the cylinder coil just to be sure, but there is definetly no air.
The CH flow switch on the boiler does work differently at start up in CH and DHW modes. When DHW is selected only, the boiler goes through its start up procedure (ie starting the circulation pump), and generally will not fire. In this instance, the CH flow switch only opens about half as much as it does when CH is selected only (and it then in turn fires.)
I cannot comment at present on the flow and return temperatures, and will get this checked. The only other comment is that the sytem has workede fine for well over a year, and decided to malfunction. My understanding is that there would either appear to be a restriction (either in the cylinder coil or possibly the motorised valve, although i've disconnected this and checked it), or that the flow switch or another boiler component may be faulty, due to prolonged operation at high pressure.
I'm happy to get someone in to have a look at the system, but i'd rather have a fair idea of the problem first. A chap called in last week and wanted to rip out the motorised valve, thermostat and timer (and boiler if i'd let him) and replace with a lever valve, and had only given the system a glance. I have to say, I had to ask him to leave!
Any advice would be welcome
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Its unlikely the boiler has been damaged. Since it works OK on heating then its working fine.
If the water has been leaking from the PRV then the system may have become quite dirty and clogged parts of the system. Whats the colour of the water?
Its still most likely to be a blockage on the HW only circuit. Thats could be anywhere!
Tony
If the water has been leaking from the PRV then the system may have become quite dirty and clogged parts of the system. Whats the colour of the water?
Its still most likely to be a blockage on the HW only circuit. Thats could be anywhere!
Tony
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