Central heating flow issue: Boiler lockout

[robjs]

We had an extension last year which involved adding new rooms (2) and obviously radiators. We had a new boiler fitted at same time - ideal logic+ H30.

All was ok for few months but then boiler started to lock out at end of short heating cycles with L1 code. It only does this when the room thermostat calls for heat for say 10 mins to top up heating. A reset on boiler resolves it but it's a pain because you can't just leave the heating on to maintain a temperature.

The error code relates to lack of flow. It's clear that on those short cycles the water hasn't circulated fully and the boiler doesn't like it. If the house is heating from cold (i.e. heating runs for 25+ mins, it's fine).

We've changed the pump. All the rads work fine.

A pump overrun has been suggested but as it errors straight away when the room thermostat clicks off I don't see how the pump continuing will help. The pump always running would solve this but surely that isn't the solution!

The system did have the necessary additives put in.

My hunch is something in pipework restricting flow. If it is, what are options? Of course, pulling up floorboards etc wouldn't be ideal!

 

[ianmcd]

Your boiler already has a Fan over run inbuilt, do you have TRVs on all radiators? if you do your system needs an external by-pass, if you have an S plan you will need a system by-pass if you fit a pump over run, the pump over run is wired via a relay that can be temp controlled or time controlled the pump doesnt run constantly

 

[Only me]

The boiler might have a pump over run built into the electronics. Is there a an automatic bypass on the external pipework to facilitate a pump over run?

I had wee look at the instructions after reading Ian’s post and as he states,there’s only a fan over run. It does state in the instruction thou if you have two ports or trvs on all rads you do need a by pass.

 

[robjs]

Thanks. (note, I’m just a homeowner trying to work this all out so looking for advice on next steps – I have limited understanding)

Yes, have TRVs on all rads (except one nearest room stat)

We do have a bypass fitted.

The boiler doesn’t have a pump overrun apparently. I can’t see how an overrun will help as the error code comes on as soon as the call for heat ends so the pump running on for a short period surely won’t make a difference?

 

[ianmcd]

Thanks. (note, I’m just a homeowner trying to work this all out so looking for advice on next steps – I have limited understanding)

Yes, have TRVs on all rads (except one nearest room stat)

We do have a bypass fitted.

The boiler doesn’t have a pump overrun apparently. I can’t see how an overrun will help as the error code comes on as soon as the call for heat ends so the pump running on for a short period surely won’t make a difference?

can you hear the fan continuing to run when the boiler demand stops ?

 

[robjs]

Yes. When the boiler goes into standby it sounds like a fan running for a few mins afterwards. This is a brand new boiler.

 

[ianmcd]

@shambolic might be able to offer more informed help as he knows the boiler inside out, the boiler is still under warranty as long as it was registered, but there may be a call out charge if it turns out to be an installation fault, is it on an open vented system or a sealed system ?

 

[robjs]

Thanks. It's an open vented system. I did contact Ideal who said check thermistors (which was done) and pump (now replaced). They suggested blockages as a possible option too and suggested it was "system related". Note it did work for a few weeks before this behaviour started.

 

[ianmcd]

Go to the highest radiator and open the bleed screw and see if there is much flow in the water coming out, it could be that when the system was drained to add the new radiators that some sludge has been drawn into the system and blocked at the cold feed .

 

[robjs]

Do I open this rad valve when the heating is on or off? It’s a standard house ground/first floor so assume any rad will do? I don’t know how much flow to expect from this so not sure what I’ll learn (as I said, I’m a novice here). How would I check the cold feed?

 

[ianmcd]

The cold feed should be a 15mm pipe that comes from the small F&E tank and connects to the heating system it is what fills the system with water, best tried with heating and HW both off, if water comes out of the bleed valve on an upstairs radiator and doesnt stop then the cold feed is OK if it doesnt or it stops the Cold feed is blocked, if you can see where the cold feed joins the system pipework see if a strong magnet is attracted to the copper pipe, if it does that is where the blockage is

 

[robjs]

Thanks, I'll see how I get on. Again, through my lack of knowledge, how much 'topping up' would a central heating system get on an ongoing basis? My, presumably incorrect thought was that once it's filled up it's filled up. If the feed pipe is blocked are you thinking there is a lack of water in circulation?

 

[shambolic]

What size are the pipes coming out the boiler? Do they come off the top and go straight down?
Is it a modulating pump.
Is the bypass a white Honeywell one?
Do you have weather compensation stat outside.
Pipes should be 28mm as boiler over 18kw.
Modulating pumps modulate down and don’t open bypass screw it right out to 2.
What you are getting is the boiler overheating as it’s shutting down while still on high rate this means 30kw of heat can’t get away quick enough.
Also need to get installer to check wiring. If weather comp fitted as a hw off must be fitted to SL 2 or boiler will stay on 24hrs a day with pump off leading to FD and L1 faults.
Ps the boiler doesn’t have a pump overrun as it’s was deemed overkill and installers hated having to wire pump back to boiler like the original.
So it was removed.

 

[robjs]

What size are the pipes coming out the boiler? Do they come off the top and go straight down?

Not sure. Recent install by Gas Safe engineer

Is it a modulating pump.

Grundfos UPS3

Is the bypass a white Honeywell one?

Not sure (not home).

Do you have weather compensation stat outside.

No idea. Installer did not mention this,

Pipes should be 28mm as boiler over 18kw.

I assume they are the right diameter.

Modulating pumps modulate down and don’t open bypass screw it right out to 2.

Don't understand this!

What you are getting is the boiler overheating as it’s shutting down while still on high rate this means 30kw of heat can’t get away quick enough.

Yes. If the heating runs for a long time it's fine as it's been long enough for heat in/out to balance.

Also need to get installer to check wiring. If weather comp fitted as a hw off must be fitted to SL 2 or boiler will stay on 24hrs a day with pump off leading to FD and L1 faults.

Boiler goes to "00" when on standby (and if hasn't gone to L1)

Ps the boiler doesn’t have a pump overrun as it’s was deemed overkill and installers hated having to wire pump back to boiler like the original. So it was removed.

So would making the pump continue be a potential solution (even though it errors straight away)? Or is a blockage more likely? It did work OK for the first few weeks.

 

[ianmcd]

as said @shambolic is the expert on this one, just because your installer was GSR doesnt mean that the install is correct, as Shambo correctly says a boiler shutting down at 30KW is a very hot potato and needs to get that heat away somehow, hope he manages to sort it out for you