Lukewarm central heating on Intergas Rapid 32

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I have an Intergas Rapid 32 boiler which was installed less than 10 months ago, all new pipework installed at the same time. I have 2 zones, both controlled by Google Nest thermostats.

The CH worked fine during the last winter, I stopped using it around May. However I just started re-using it to find out that all the radiators are lukewarm, even after leaving the boiler running for several hours.

As you can see from the photo below, the boiler is correctly calling for central heating (code 5) and water pressure is 1.5 bar, however the flow CH pipe is not that hot, only around 26 degrees (note that the central heating water is set to 80 degrees in the boiler's settings).

I noticed 2 things:
1) The boiler does not make much noise when calling for CH
2) If I slightly unscrew the syphon cup, water drops constantly -> is this normal for water to discharge constantly when the boiler is calling for CH?

Things useful to know:
- The DHW always worked fine.
- The condensate hose is not blocked (I made it drained into a bucket temporarily)
- I think a blockage is very unlikely since I have 2 different zones and also have a bypass valve (I would expect the return CH pipe to be much hotter)
- Sometimes the boiler makes a "click" noise, like when something goes too hot and dilate

As the boiler is under warranty, I will call Intergas once they re-open after the bank holiday weekend. In the mean time I was wondering if anyone could give me some tips on how to troubleshoot the issue.

I followed the troubleshooting steps from section 10.2.6 of the manual and increased the pump speed to 90 and the "Starting speed CH" setting to 70, it seems to have helped a bit but the boiler goes quiet again after a minute.

1663530149073.png


I am leaning towards a pump or condensation issue, what do you think?

Thanks!

PS: the boiler manual is available from https://www.intergasheating.co.uk/a...stallation-manual-Intergas-Rapid-88923805.pdf

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Hold the 'radiator' button down, you'll get a number, what is the temperature of your heating, perhaps it's been set too low. (just read again, I think 80° is possibly a bit hot, think I've got mine on 55°)

Water will drip out of the syphon malarkey, the cup should be full of water.

Are you sure the programmers are allowing it to come on??

The pump comes on daily for a few seconds to stop it seizing, you might have noticed this, mine it at around 7am, if you still have hot water, then I think this suggests the pump is good.
 
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Just thought... You could turn the programmers off, and turn the boiler to T-ON, this uses the boilers own timer, you might have to set the times, when you want it on/off etc, but it will test to see if the programmers are causing the issues, if still no heating, then it will need investigating.
 

CBW

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I don’t think the pump runs on hot water for these, but tbh I don’t think you’d have lukewarm heating either. If the boiler temperature was set too low you’d get a number 1 in the small window, indicating that the temperature is satisfied.

What I would check first is trapped air, so vent the boiler (bleed vent is on top) and vent upstairs radiators, being careful as very hot water will want to expel.
 
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the nest stats have opentherm controls don't they?

the 80 degrees in the settings might be the maximum allowable temperature not the actual temp it should produce.

the opentherm will adjust the radiator water temps based on the learning of the nest stats to reduce gas usage. it may be simply seeing that to get to the target temperature a low temperature flow is all that's required.

theres not a lot in these boilers (if anything) that otherwise can affect the heating so it's most likely an external signal provided thats the culprit.
 
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Just thought... You could turn the programmers off, and turn the boiler to T-ON, this uses the boilers own timer, you might have to set the times, when you want it on/off etc, but it will test to see if the programmers are causing the issues, if still no heating, then it will need investigating.
Same issue using T-ON and the internal boiler programmer. I have 2 Google Nest thermostats wired as such https://www.diynot.com/diy/threads/2-google-nest-thermostats-for-2-zones-connected-to-intergas-rapid-32kw.579295/#post-5091543, I think it would have been odd for both to exhibit the same issue all of sudden...

the nest stats have opentherm controls don't they?
Both Nest stats are set-up as ON-OFF switches, not Opentherm, the reason being is that those stats do not support Opentherm in a multizone environment, it can only be done with a single zone.

What I would check first is trapped air, so vent the boiler (bleed vent is on top) and vent upstairs radiators, being careful as very hot water will want to expel.
I already bled the whole system, including the bleeding valve on the top of the boiler.

If the issue is not boiler related, the only thing I can thing off is an airlock somewhere in the pipework, I am now going to drain the whole system (avoided doing so for now due the inhibitor, and sometimes can make airlocks worse).
 
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No luck after draining the whole system :(, lukewarm water to all the radiators (from both zones) with the boiler being suspiciously quiet.

Is there a way I can definitely rule out the pump being the issue?
 
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Sorry can't really help.


I've just put mine on to test, it's currently running, 5 on display, I'd forgotten how quiet it is, there's hardly any noise, it's getting hot, not scorching but my boiler is set low.

Previous comment is correct, the pump is not used for Hot water.

Have you heard if your pump has been doing the anti-seizure cycle? if the pump was shot, surely this wouldn't operate.

I like the idea of the clip in thermometers, did you fit these or plumber?
 
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Take the case off. Set the programmer to off then set parameter 2 to 1

Flick it between 1 and 0 a few times and you should hear the pump start and stop

That will run the pump on its own without the boiler firing and you will be able to see and hear if the pumps working (big oblong plastic thingy at the bottom right) without fan noise
 

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I would double check the heating temperature setting and then look at the zone valves next, make sure they’re fully engaged.
 
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Sorry can't really help.
You actually helping me, thanks a lot for your time.

Have you heard if your pump has been doing the anti-seizure cycle? if the pump was shot, surely this wouldn't operate.

The manual says the following:

"In addition, the pump runs automatically for 10 seconds once every 24 hours in order to prevent seizing. This automatic switching on of the pump occurs at the time of the last call for heat."
Hence I will have to wait until tomorrow 9pm (been doing some tests), but I just found this setting:

1663618104505.png


which seems to activate the pump, I can hear an additional noise (though as you said, this boiler is very quiet). When I revert the setting to 0, the light noise stops.

On that basis I think I can rule out the pump.

To summarise the current and relevant situation; when I call for heat, the boiler starts and I can feel the temperature of the flow CH pipe increasing (getting decently hot), but after around 30 seconds the temperature of the flow CH pipe decreases and remains lukewarm.

I like the idea of the clip in thermometers, did you fit these or plumber?
I bought those when living in a different property because it was difficult to balance the radiators (never been an issue in my current place, I did most of the pipework myself, 22mm pipe going to most radiators or converting to 15mm very close to those). I got cheap ones from Aliexpress, search for "thermometer pipe".
 

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Take the case off. Set the programmer to off then set parameter 2 to 1
Well spotted, I just came across that setting earlier, it would seem my pump is working (those are pretty quiet by the way). PS: didn't remove the case off though.
 
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