Combi Boiler

kev2009

Hi,
I noticed that my combi Ideal logic 24 boiler pressure was down to 0.2 today, no error codes showing, boiler still works as normal so as I'm aware pressure should be between 1 and 1.5 bar, I've filled it up to just over 1 bar.  I then than some hot water and noticed the pressure go up to 1.5bar.  Once I turned the water off, it went back to just over 1 bar.  is this normal?  The pressure gauge is in a awkward position (underneath boiler on left hand side) so not easily visible so I've not paid any real attention to it in general so I'm not sure if the gauge used to go up when hot water was turned on or not.  I noticed just before xmas last year, it dropped to 0.5bar but today was lower.
I don't see any signs of water leaking out anywhere (tiled floor below boiler so not as if water is being soaked up by carpet and no signs of water on tiles) so not sure if this is something to be concerned about or not.  Boiler is approx. 5.5 years old so I was expecting it to go for around 10 years before I started to have any potential problems, especially as its a small place so not requiring to heat a large house or anything.  Also don't see any water leaks anywhere else in property.
Up until now, I've done nothing but have the boiler serviced each year and I've never noticed the pressure gauge showing below 1 until just before xmas last year (after it was serviced), until then its always sat a little over 1 bar on the rare occasions I checked it.
Thanks
Kevin

jefaz07

The pressure difference between hot water heating is fine. Nothing to worry about. 

As for the pressure drop it could be the heat exchanger. I know of a good few Logics where they leak internally and drain away via the condensate. So you’d not know unless it was stripped down. 

Perhaps get a GSR in. 

kev2009

Hi, Many thanks, I've topped it up to just over 1bar so I'm going to monitor it and see if it drops again and also get a time line of how long it takes to drop.
Funny thing is, no error codes on boiler at all, which I was expecting to see.
Any idea as to a tough guide on prices for a heat exchanger, if that is indeed it?
GSR I presume is Gas Safe Registered engineer?
Thanks
Kev

Jeepers_Creepers

When we next get a chilly evening and you turn the CH back on, monitor the pressure then. Starting point from cold, and what happens over the next half hour or so as it heats up fully.

I'm surprised, too, that the boiler didn't shut down - I guess some are more sensitive than others. Most, tho', will shut right off at around 0.5bar.

Is your pressure gauge an analogue type? Bear in mind that this gauge is just for your info, whereas the one that would shut the boiler off with an error code is an internal electronic sensor.

kev2009

Hi,

The pressure gauge looks very similar to this:-

jefaz07

kev2009 said:

Hi, Many thanks, I've topped it up to just over 1bar so I'm going to monitor it and see if it drops again and also get a time line of how long it takes to drop.
Funny thing is, no error codes on boiler at all, which I was expecting to see.
Any idea as to a tough guide on prices for a heat exchanger, if that is indeed it?
GSR I presume is Gas Safe Registered engineer?
Thanks
Kev

If it’s the heat exchanger then get a fixed price repair from Ideal. The only way to go really. 

That’s what I and many others do. Cheaper for you. I had some videos and I can’t find them...but it’s just a constant internal drip into the collector. 

Yea, GSR is gas safe engineer. 

kev2009

From what I read online, it seems my boiler would stop working at below 0.3 bar so I guess my boiler could of been at 0.3, difficult to read underneath it but it was between the the 2 black bar lines at the bottom on left hand side so it's feasible it was at 0.3 (minimum required to operate) according to what I read online.  After topping it up to just just above 1 bar but not as high as 1.2 bar, when I turned on hot water, it went up to probably 1.4 - 1.5 bar and then back to just above 1 bar when I turned water off.
Will monitor it and see if it drops any more.  As I said, I've had it 5.5 years and very very rarely checked it as its been around 1 bar since it was put in and it's never caused a issue so never really check it as its serviced every year so I leave to them, just happened to notice it by chance. So unsure over what period of time it has been slowly dropping pressure.  All I know is from around mid December last year until now (so roughly 3.5 months), it's dropped from approx. 0.5bar to 0.3bar, did seem to take a fair bit of water to top it back up to just above 1 bar though.  First time I've ever topped it up or in fact topped up any boiler so maybe it was normal
Kev

Jeepers_Creepers

Yes, that's an analogue display. It gives you a good indication of the system pressure, but is obviously not completely accurate, so if your boiler is reckoned to shut off at below 0.3 bar, then most likely the actual pressure was fractionally above that - so it was on the verge of shutting down! The pressure sensor for controlling the boiler is not that 'clock' but an internal electronic sensor. Quite likely everything 'sensorish' is working fine - it's just that your pressure didn't quite drop enough

From what you say, the pressure jumps a bit as soon as you turn it on - ie draw DHW - and drops again when you turn the hot tap off. I guess this is simply due to the action of the circulating pump - the gauge might be on the 'flow' side of this pump so is simply sensing the increased flow pressure.

What we really want to look out for is a more gradual increase in pressure when the boiler is running on CH. This would be down to the system water (ie everything in the boiler and the radiators) heating up and expanding. This is normal, and is catered for by an 'expansion vessel' inside the boiler. This vessel accommodates the expanding volume of hot water, so the pressure remains fairly constant. If, however, this vessel is faulty (pretty common), then the expanding water has nowhere to go, and the pressure goes up significantly, often well over 2 bar. If it gets close to 3 bar, then it forces open a discharge valve and dumps the excess water outside your house. If that happens, then when your system cools down again, it'll be lacking that water = a drop in pressure.

This would be the 'best' cause of system pressure loss - much better than a failed exchanger or a hidden leak in your pipework.

So, the next time you run your CH, please keep an eye on the pressure and let us know what it does.

kev2009

Sure, will do thanks.
I had a quick look, it looks as if a replacement heat exchange for my boiler (depending on exact model if needs) is between £60 - £80 plus then of course a fee for a engineer to come and install it.  Is the Expansion vessel much cheaper/easier fix out of interest?
Thanks
Kev

Jeepers_Creepers

kev2009 said:

Sure, will do thanks.
I had a quick look, it looks as if a replacement heat exchange for my boiler (depending on exact model if needs) is between £60 - £80 plus then of course a fee for a engineer to come and install it.  Is the Expansion vessel much cheaper/easier fix out of interest?
Thanks
Kev

Er, cough, er, lol, er not April 1st - are you sitting down?

The main exchanger for your boiler costs in excess of £400, and replacing it is probably the most involved job to do with the boiler - 2 or 3 hours worth?

You are definitely in 'fixed price repair' territory, but you'd need to ensure the MEx is covered in this.

I think you've looked up 'secondary exchanger' or 'plate-to-plate' type.

(You can', tho', get 2nd-hand or 'refurbished' exchangers for a lot less)

Let us know what happens with the system pressure as the boiler gets up to full working temp.

kev2009

oh wow, I had a look on a parts site and it shows a Heat engine kit at £350 but didn't say exchange so i thought that was something else
I seem to recall at the time looking up the price for the boiler (it came with property when i bought it) and it was around £800-900 for the boiler so *if* it works out it is that much i.e. £350 + engineers time, it may be more beneficial to replace the boiler as i see some are now 10 or 12 year warranty etc.
I didn't pay for any extra warranty on boiler after the initial warranty run out as they said once it gets to 7 years old, they wouldn't repair it at all and recommend replacing it.. So I thought well lots of boilers on market have warranty for 10 years and most people i know had had a boiler over 10 years so i figured 10 years should be minimum with no real issues so i decided extra warranty wasn't worth it and would be best to keep the money and pay as needed if at all in that time.
Will certainly update thread but maybe a while as coming into the warmer months.
Thanks for your help so far, much appreciated!
Kev