Ideal isar HE35 diagnosis

18 month old isar HE35 broke down this morning. No hot water, no heating, it's not firing, no error codes and no lights. Checked power to unit, all seems ok and water is pressure normal. Only sign of life seems to be the "ticking" sound from diverter valve head actuator (red honeywell head, CP waterset) when switching on.

Having read others problems I thought it might be the PCB (the older black version, not orange) but opened it up and it looks clean with no blown components.

Any ideas appreciated!

If you have 240v to PCB without anything on the display, then unfortunately it will need replacing.

the boiler may still be under guarentee if it was installed under one of the boiler schemes. You would need to ask your installer. All of these schemes automatically give 2 years parts cover not the one year that ideal normally give. The symptons that you have do suggest the pcb failure.

If pcb fuse is ok then it is the pcb gone.

Hi guys, got a new PCB (the new orange one) and that has fixed the problem of the completely dead boiler. I now have another couple of problems though.

Firstly, having ignited the boiler and then switching off the programmer (no longer demand for CH) the boiler display continues to display c and supply CH. Turning on the DHW tap the display changes to d as it should and resets to 0 when not in use. This is currently the only way to turn off the CH.

When the CH is turned on at the programmer and/or the boiler displays c and it's supplying CH when it shouldn't there's also a god awful noise coming from the diverter valve/head and the pressure gauge needle vibrates/jumps.

Also, when the boiler supplies DHW it also supplies CH (even though no demand for CH). Same also happens when it's pre-heating the plate.

What do you think? Buggered valve? Or could it be the jumper settings on the PCB?

I originally set the jumpers according to the paperwork that came with the new PCB which is pairs 2&3 on the PCB and 2 on the user control panel. But speaking to Ideal tech "help"line they said the jumpers should be set the same as the original black PCB, 2&5 with the PCB in situ and no jumpers on the user control. Can anyone confirm this?

I should also add that the diverter head is operating (taken it off and watched it do it's thing) and the valve can be operated manually which is why I'm thinking jumper settings.

The jumpers should be replaced as they were on the old PCB.

Never set any jumpers on the user control

Go with the old jumper positions, but don't forget there is a pump over run of approx 6 minutes.

Thanks gasman and gas4you, that clears up the jumper settings for me. Had no idea the pump over run was that long though, just checked it again and the CH does indeed turn off after 6 mins.

I've also noticed the water pressure is rather high. Currently at approx 2.5 bar rising to 3.2 when in use and the PRV isn't opening automatically. Could this excess pressure be causing the loud vibrating/whining noise and jumping needle when the CH is on (noise not there with DHW or pre heating)? I guess it could also be stopping the diverter valve from closing causing the rads to get hot when the DHW or pre heat is running?

If so what's the best way of getting that pressure back down to normal levels assuming the PRV is stuck? Apologies for that basic question, I'm more of an electrical girl than the plumbing type usually!

Underneath the boiler, you will see some valves. On the far right, there is the return pipe isolating valve. Attatch a small bore hose to the drain off point and slowly open the drain valve anti-clockwise to release the pressure. The pressure should be approx 1.5 bar when the system is cold. Remember to switch off the boiler system before attempting this proceedure.

Depending on which way the filling loop is fitted (i.e. non return on cold fill side) you can release it from the filling loop. Or any drain off.

Cheers guys, I'll drain some water off when I get back home and see if that makes any difference. Was talking to hubby and he confessed "yeah I thought I better re-pressurise it", when asked why if the pressure wasn't low he said "because it's the only way I know how to fix boilers"!

The diverter valve cartridge sounds as if it may be sticking partially between heating and hw or some debris stuck behind it preventing it from closing. This will cause rads to heat up on pre heat and also water to be cooler.
The vibration through the gauge is normally a sign of poor circulation and overheating.
If the noise is only on heating then its the div valve or a system problem (check lockshileds on rads and a bypass must be fitted (rad or auto)).
This is due to the boiler running 35 kw on hw but only 24kw for heating so pump fault tends to show up on both but especially water.