Glow worm hx24 f22 after draining down

[sotal]

I was dreading draining the CH down as the last few times I've done it, it has been an absolute pig to get going again after.

I drain it down, then when I refill, I bleed all the rads, bleed the grundfos pump, open the bleed valve next to the pump.

When I turn the boiler on, it kicks in but then gives the f22 error and shuts down. It won't then kick in again for a while even after a reset.

As I say it has done this for a few years now, only when draining down. After much messing it has got going again each time and been fine after.

I read about the fact that sometimes the f22 error can be from the pump being too fast, so I tried it on setting 1 instead of 2. No change.

Above the boiler on the flow and return pipes there are a couple of drain points. I've tried attaching a house to these and letting the water come through into a bucket. The flow did splutter a bit, but still no change. Both are now flowing well.

Spent a few hours trying to get it to start back up again. Think this might be the longest yet!

Any ideas?

It has been running fine since the last drain down perhaps 2 years ago.

Thanks

 

[sotal]

I've been lay thinking about what it could be. My only thought is that when it drains down it empties the header tank in the loft, this might pull sludge etc down from the header tank. I did note before that there was a build up of sludge stuff in the header tank. Could this make its way to the boiler and cause low pressure?

Undoing the drain valve above the boiler gives higher pressure on the return pipe than the flow.

 

[kidgreen61]

Why must you keep draining your CH system?
I hope you're adding inhibitor to it every time you refill?

F22 on Glow Worms is usually system pressure related, however as yours isn't a pressurised system, I assume it's a circulation issue.

 

[sotal]

Why must you keep draining your CH system?
I hope you're adding inhibitor to it every time you refill?

F22 on Glow Worms is usually system pressure related, however as yours isn't a pressurised system, I assume it's a circulation issue.

Well it is pretty hard to join into the main flow and return pipes to add the extension radiator without draining it down.

As I say the last time was circa 2 years ago. The time before was probably similar. Each time that we've had work done on the house and required a drain down to complete the work.

I'm not just draining down for fun!

Yes inhibitor goes in each time.

 

[sotal]

Also, just so that I can get it straight in my head. If I just have the hot water on then where does the water flow to if it is restricted in not flowing fast enough through the boiler? Is there some kind of bypass? If so can this bypass be adjusted to make sure more flows through the boiler?

 

[Gasguru]

It sounds like it doesn't like the flow and return temperature gradient...is the flow much hotter than the return above the boiler?
Turn the gas off at the meter or the valve under the boiler, stick the pump on max and put the heating on.
Keep reseting it when it fails to light. Give it several goes and see if that can shift the air in the heat exchanger.

The Hxi must have an auto bypass valve after the pump to ensure a minimum flowrate at all times through the boiler.

 

[sotal]

It sounds like it doesn't like the flow and return temperature gradient...is the flow much hotter than the return above the boiler?
Turn the gas off at the meter or the valve under the boiler, stick the pump on max and put the heating on.
Keep reseting it when it fails to light. Give it several goes and see if that can shift the air in the heat exchanger.

The Hxi must have an auto bypass valve after the pump to ensure a minimum flowrate at all times through the boiler.

When you say stick the pump on max, I take it that is the grundfos pump in the airing cupboard?

 

[Gasguru]

Indeed.

 

[sotal]

Indeed.

The pump, stat and controls are in a different location and have a different power supply.

If I tell the heating to turn on with the boiler isolated from the mains then it all runs, would this still run through the boiler and do what you were suggesting without the need to turn the gas off etc?

 

[ianmcd]

The pump, stat and controls are in a different location and have a different power supply.

Tthe pump should be wired to the boiler for the pump over run function to work

 

[sotal]

Tthe pump should be wired to the boiler for the pump over run function to work

Like many things in this house it is an oddity. The pump overrun I believe is disabled and there is a pipe stat on one of the pipes in the airing cupboard that keeps it running until the water cold to a certain point.

 

[Gasguru]

ALL the controls AND the boiler MUST be run from a single supply...anything otherwise is dangerous for anyone working on it and not compliant.
The pump MUST be connected to the boiler for the pump over-run timer to operate.
We're all assuming you have an ancient HXi model...

I'm suggesting you run the pump flat out to dislodge any trapped air in the heat exchanger (again assuming it's the old Hxi model), without the gas on there is no risk of damage to heat exchanger (from over heating under poor flow conditions). Run it in heating mode initially as there's a better chance of getting air free water from the radiator circuit.

 

[sotal]

It isn't that ancient. The boiler it replaced was from 1979, so I presume that is why. The boiler was replaced approx 12 years ago. So is only 12 years old. Obviously there is some connection between the two because the hive unit tells the boiler to turn on. The engineer who installed the give unit commented on it being on two supplies. Each has its own isolation switch next to it.

 

[Gasguru]

These boilers were never great with multiple design faults and few survive today.
Get the wiring sorted before it fries the next rgi that works on it, I would not have installed the Hive without rectifying the wiring issue.

 

[sotal]

I'm suggesting you run the pump flat out to dislodge any trapped air in the heat exchanger (again assuming it's the old Hxi model), without the gas on there is no risk of damage to heat exchanger (from over heating under poor flow conditions). Run it in heating mode initially as there's a better chance of getting air free water from the radiator circuit.

It doesn't have an i on the end of the model number.

I tried with the gas off resetting about 10 times. I can't hear any trapped air. After about a minute each time, I got F1 ignition fault.

I also tried running the drain valve on the flow pipe for about half an hour whilst letting it fill the system at the same time.

But I am still getting F22 - Low water pressure or ignition temperature rise too slow