Open vented system, No HW or CH, BAXI 80HE boiler shows Ignition Lockout after tried to start a few times

[Johntheo5]

Check around there with your magnet and obviously check that that gate valve is fully opened by shutting it ( ~ 3 full turns) and then reopening it fully.

What make/model of HW cylinder.
I have a 150L twin coil (oil fired coil and solar coil) the oil fired coil is 0.62m2 and I carried out tests a good few years ago, the coil absorbs ~ 8kw with a dead cold cylinder and falls to ~ 2.5kw (flowrate is 10.0LPM) when the cylinder is approaching its SP temp of 60C, boiler flowtemp is ~ 70C (65C/75C, oil fired cut in/out) this is no problem as oil fired boilers spend their whole life cycling but could present poblems wit a gas fired boiler which fire up at about 60% of their max output and if they can't/don't modulate down rapidly enough then will trip the burner at their SP+5C and won't refire until the anticycle time has elapsed, this may be your problem? especially when the cylinder is getting up in temperature.

 

[Johntheo5]

Looking at your system again, it looks like you may have had the conventional VCP but at some stage was converted to the combined vent & cold feed because you have the 15mm cold feed with isol valve connected to a 22mm cold feed pipe from the cistern, I often wonder if the two pipes are better off being the same diameter, ie like my 52 year old system where I have a very short piece of 22mm cold feed teed into the 22mm vent.
You might ensure that your vent pipe isn't dipping into the water in the F&E cistern, also strange that you seem to be getting air ingress with that system.
Also check the condition of the F&E cistern.

 

[fandyman]

I see you have a OV. system, how is the vent and cold feed done, are they on the boiler flow where from the boiler you gave vent then cold feed then pump?

Can you get someone to sart the boiler on HW only and see if you get some vent pump over and check it again when boiler is switched off, you may have to wait for 3 mins or so before the circ pump stops.

I've done this test and did not get any vent pump over both with boiler starting and boiler switched off. Waited good 5 mins.

 

[Johntheo5]

Thats good, combined seems to be working OK, vent is above the cistern water level?, maybe install that AAV next?, you could change the pump mode to cp2, that will increase the pump head from 3.0M to 4.5M which should give ~ 23% more flow so HW flow from 10.0LPM to maybe 12.2LPM, might help?.

What is your HW cylinder capacity & make/model?.

 

[fandyman]

Thats good, combined seems to be working OK, vent is above the cistern water level?, maybe install that AAV next?, you could change the pump mode to cp2, that will increase the pump head from 3.0M to 4.5M which should give ~ 23% more flow so HW flow from 10.0LPM to maybe 12.2LPM, might help?.

What is your HW cylinder capacity & make/model?.

See a photo of the HW cylinder.

 

[fandyman]

One of the main places where a blockage may occur is where the cold feed is teed into the system, if you follow the pipe back from the pump inlet (towards the cistern) you should come to the cold feed and no more than 150mm further back, the vent pipe, test around these two pipe tees etc with the magnet.

Re this if I checked and have the magnet attaching to this section around where it tees off in many places how does it related to the fact the pump is pumping at the right speeds on the CC2 settings in different HW, HW&CH, CH modes? Maybe the blockage is just partial and the flow is about right even though the magnet attached. Would that be possible?

 

[fandyman]

Check around there with your magnet and obviously check that that gate valve is fully opened by shutting it ( ~ 3 full turns) and then reopening it fully.

What make/model of HW cylinder.
I have a 150L twin coil (oil fired coil and solar coil) the oil fired coil is 0.62m2 and I carried out tests a good few years ago, the coil absorbs ~ 8kw with a dead cold cylinder and falls to ~ 2.5kw (flowrate is 10.0LPM) when the cylinder is approaching its SP temp of 60C, boiler flowtemp is ~ 70C (65C/75C, oil fired cut in/out) this is no problem as oil fired boilers spend their whole life cycling but could present poblems wit a gas fired boiler which fire up at about 60% of their max output and if they can't/don't modulate down rapidly enough then will trip the burner at their SP+5C and won't refire until the anticycle time has elapsed, this may be your problem? especially when the cylinder is getting up in temperature.

Checked the gate valve by closing it fully and opening and all fine.

 

[fandyman]

Re the slackening the compression nut that attaches the cylinder coil top pipe to the coil inlet see the photo attached.

Is this the right one?

Other than that I did buy a infrared thermometer to test the reading of the A & B (I could not verify them by hand as they were too hot) and I did notice that if I put HW only the B was about 45C while the A was about 20C. Would that make sense?

What I mean here is the A does not go complete cold but a fair bit colder (which is hard to register by hand) and whether this is expected or indeed a problem.

 

[fandyman]

I think the only thing that remains to be checked is the slackening of the compression nut right? Not sure I can diagnose more unless I missed sth from previous posts. What I mean is I cannot make the system work any better without my physical interference.

 

[Johntheo5]

See a photo of the HW cylinder.
View attachment 360248

Can you post a close up photo of the label as I can't read the data.

 

[Johntheo5]

Re the slackening the compression nut that attaches the cylinder coil top pipe to the coil inlet see the photo attached.

Is this the right one?

View attachment 360249

Other than that I did buy a infrared thermometer to test the reading of the A & B (I could not verify them by hand as they were too hot) and I did notice that if I put HW only the B was about 45C while the A was about 20C. Would that make sense?

What I mean here is the A does not go complete cold but a fair bit colder (which is hard to register by hand) and whether this is expected or indeed a problem.

Yes, thats the one to slacken, say 3/4 to 1 turn, use a pair of gloves and then give the pipe a good shake and you should break the seal easily enough.

20C reading at port A would be correct but 45C on port B seems very low if the boiler was firing with a flow temperature of say 65/70C?.
Can you get the boiler firing continuously even if you have to run both HW&CH and take a reading on that top pipe (that you are going to break the seal on) and take another reading on the coil outlet where it exits near the bottom of the cylinder, that will give some idea of the coil dT.

I would have expected a greater flow through that coil even on CC2 at 3M but you could have fouling of the boiler HEX (heat exchanger) etc or the pump impeller vanes might be partially blocked and still give seemingly correct power readings, you could isolate the pump by shutting the isolating valves on either side, removing the 4 stud bolts holding the pump head to the body and remove it to inspect the impeller and pump ports for obstruction.

 

[fandyman]

See cylinder from close up.

 

[Johntheo5]

That's a fairly substantial coil area at 0.96m2 (mine is only 0.62m2), it gives a pressure loss of 0.1bar or 1.0M, not of much use though since they don't specify the coil flowrate.

Anyhow take those coil flow/return readings, and try and vent any air from it.

How long does it take to reheat the cylinder, even roughly??.

Have you looked into the F&E cistern to see the condition of it?.

 

[Johntheo5]

Re the coil.
Query asked below.

 

[fandyman]

That's a fairly substantial coil area at 0.96m2 (mine is only 0.62m2), it gives a pressure loss of 0.1bar or 1.0M, not of much use though since they don't specify the coil flowrate.

Anyhow take those coil flow/return readings, and try and vent any air from it.

How long does it take to reheat the cylinder, even roughly??.

Have you looked into the F&E cistern to see the condition of it?.

Yes I did look into F&E cistern and it is fine - no sludge build up (I drained the system down in June and cleared all the sludge that was there and there was a fair bit of that).

I am not sure how long it takes to reheat the cylinder as I did not have to use HW for a while after it went cold last time.

I will take the flow/return readings next time I am up there.

With venting air from it am I risking anything (obviously with the boiler etc turned off)? I just do not want to create any more problems for myself