Mini S24 - Persevere or replace

P

pricey34

Guest
Hi,

I'm at my wits end with my Ideal Mini S24 boiler. For the last 3 years I have had problems. Its on a sealed system. Every now and then the CH Flow microswitch doesn't make when CH called for ( ususally OK on Hotwater), because the hydraulic flow sensor pin isn't driven out far enough to make the switch contact.

The system pressure has always had to be at about 1.5 bar for it to work ( any more and as the system heats up - it approaches the 3 bar and dumps out the tundish.)

I've had the CH Flow switch hydraulic assembly out numerous times, cleaned it, replaced the diaphragm and cleaned the plastic venturi ( embedded in the body ). This has ususaly done the trick.... for a while until it all happens again. Every year is the same and I can't take it anymore.

Yesterday, I had the same issues but worse - No flow switch make on hot water or CH. I did the ususal thing ( all pretty balck inside ) but still no joy.

My thoughts are that theres muck in the system ( even though the system was installed 5 years ago ) and the ideal mini design just can't tolerate it. As we speak I'm sitting here freezing - looking at my miserably cold wife and thinking what to do next. I'm thinkiing about getting british gas to install a new ( different ) boiler to the tune of £2K.
Is the ideal mini s24 a lost cause? If I got a new boiler would I have the same issues? Is the ideal mini just too sensitive a boiler and a lost cause?

Any help very gratefully recieved.
 
100% heatexchanger blockage, scale and or sludge, get system cleansed and flushed and inhibited then replace heatexchanger, problem solved

As for the pressure, the expansion vessel sounds as if it needs recharging, or maybe too small for the house and a second may need to be installed (in the hotpress?) cold fill pressure should be 1/1;5 bar and shouldn't really get over 2.5 on full load, the fact that when it dumps you are most likely topping up with fresh water is where the heatexchanger is being killed!
 
Hi DGOBS,
Thanks very much for your quick and informative response.

OK, if I get the system cleansed and flushed and inhibited then replace heatexchanger, will I then eventually have to clean the flow switch in a year or two time?

I'm trying to work out if my system is excecessively crudded up or that the ideal mini is ultra sensitive to this issue? i.e would it be best to get the system cleansed and flushed and inhibitedand then replace the boiler for a more tolerant model?

Is there any additional measures I can take ( water softener?) to ensure minimal crudding up after its been flushed?

Many Thanks DGOBS for giving me your time on this cold Saturday evening!
 
the flow switch is not the issue, its the heatexchanger restricting the flow thats the problem (always on this boiler)

I must add, you are NOT entitled to open the boiler and do this yourself, it constitutes 'gas works' to open the appliance, and this can be met with an up to 15,000euro fine or max 3 years in clink, I kid you not!

No additional measures, flush, cleanse, and dose with 'lots' of a good quality inhibtor (and a bottle of boiler silencer never goes amiss) but do ensure your system is sound and does not require 'topping up' more than once or twice a year
 
Going for it

Ok -

Short Term
we're gonna get the system cleansed flushed and re-inhibited and get the heat exchanger replaced and boiler serviced at the same time ( al done by professionals) This should sort out the issue for now

Long term
Enusre the boiler is serviced yearly which should include a clean out of any muck in the boiler components? This should negate the need to increase system pressure ( through introducing fresh water) to temporarily "get round any muck related flow issues". This in turn should preserve the life of heat exchanger and ....my wife will smile again!

Sound like a plan DGOBS? Wish I could buy you a pint somehow, you've been most helpful.
 
Lol, no bother

Make sure the expansion vessel gets recharged (to 1 bar) and fill system to the same
once it is cleansed and inhibited then there should not be any muck (sludge/scale) building
up to begin with (as it can't be removed from the heatexchanger)
 
DGOBS
I can't believe I didn't update you on what we did. Sincere apologies that was ignorant of me ( In my defence, we've had kids and its been.... hectic to say the least). Hopefully you are still willing to help as everything you posted appears to 100 % correct

So, as per your recommendation we got the system powerflushed and heat exchanger replaced and all good!.....until recently......

I looked back on this post and one thing I missed was the epansion vessel issue you mentioned. So heres what I'm seeing now....which I think confirms your thinking about the expansion vessel cpacity.

Here goes:
We recently had a new rad fitted and since the rad was fitted, in order for the CH flow switch to make when the heating only is called for, the cold pressure needs to be at about 1.3 bar, as shown on the boiler pressure gauge. The issue is that as the house heats up, the pressure gauge on the boiler shows about 3 bar and water starts dripping into the tundish ( as designed to do ) - just like before. So when the heating shuts off, the cold pressure goes down below 1.3 bar ( bout 0.75 bar ) which is not enough to bring the CH flow switch in when CH is called for. I am relucatant to keep topping up the pressure from the filling loop as this will sludge up the system eventually ( I think this is what may have clogged the heatexchanger a couple of years ago - as you mentioned! )

I have checked the components of the system and found we do have a 12 litre external expansion vessel which is appears to be connected to the hot water cylinder cold inlet, so I think that this caters for increased pressure in the hot water tank only.

I read the boiler manual and it says it has an integrated 6 litre expansion vessel. We don't have an external expasnion vessel on the CH Hot Water circuit.I have bled all air from the system completely. So, I am thinking that we now have increased volume in the CH Circuit (due to new rad) and the increase in pressure due to expansion is too much for the boilers internal expansion vessel. So the question is "Do I need to get a sperate expansion vessel installed on the CH circuit?

Hopefully you can help.

Many Thanks
 
Have you checked the air pressure of the expansion vessel, sounds like it may just need recharging
 
DGOBS ....you cracked it!

Hi DGOBS,

Thanks for getting back to me!

The issue is fixed!...So heres what I did after revisisting your post(Its quite a long reply as I hope someone else may benefit )

With the boiler system charged to 1.3 bar cold starting pressure, I located the Expansion Vessel (EV) in the boiler ( at the back of the boiler ) I pressed the Schrader valve pin on the EV ( at top ) and and heard air escaping, so I presumed diaphragm in vessel had not split as there was no water coming out out of the valve.

I then went to a well known car/bike shop and bought a mini digital type gauge from the car dept for eight quid.

Back at home, I isolated the CH flow and return pipes, opened the boiler drain cock ( white fitting just behind wilo pump) and drained the boiler. I then re measured the EV air pressure and it was almost nothing. So, at this point I presumed that the EV had lost its 10psi charge over time - this would explain the observed large ( >2 bar ) pressure difference from cold startup pressure (1.3 bar) to when the heating was working- the increase in volume of water (due to expansion as it was hetaed) was not being mitigated by the volume of air air in the EV!

So, With boiler drain cock still open, I pumped air ( with a Bike Pump ) into the EV Schrader valve until I had 10 psi in there ( as measured with the digital gauge ) I then opened the CH and flow and returns, charged the system to 1 bar and fired up the boiler.

So with a cold starting pressure of 1 bar and the boiler temperature stat to max, I cranked up the room stat to 25 and the hot water tank to 60 to see what the pressure differential when system was maxed out. It floated at around 2 bar...... so happy days!. At the same time I cleaned out the magna clean, topped up with inhibitor and bled the air from the rads.

Interestingly, before charging the EV, the cold starting pressure used to have to be 1.3 bar (at least) to get the Flow switch in -and I also had to stagger the hot water and Ch startup times otherwise the flow switch would not come in with both CH and HW valves open.

The situation now is, both DHW and CH valves can open at the same time with only 1 bar cold starting pressure and the flow switch makes and boiler fires up!....I think the reduction the volume of water in the boiler (as a result of pumping up the EV ) means that more flow is achieved at the flow switch when the pump starts....result!

Thanks for you steer DGOBS, as soon as I started having problems agagin I referred back to your original post which mentioned the EV....I guess in the heat of getting the heat exchanger replaced, system cleaned, magna clean fitted and having kids..the EV dropped off the radar....looks like it was a major contributory factor all along....just like your original post said...Happy wife = Happy Days.

Cheers DGOBS..... heres to a warm XMAS!

​
 
Good to hear you have sorted it, however, a little word of caution:

Unless you are a Registered Gas Installer with RGII, you cannot work within the gas boiler, even if you are not touching the gas side. Even an electrician is breaking the law and committing a criminal offence if they even wire into the boiler.

If the expansion vessel and circulating pump is external to the boiler, you can of course work on these but if they are incorporated within the boiler as you have described, then it is classed as within the remit of gas works.

Apologies for putting a damper on it! But it is always better to be safe than sorry, as if you are not a RGI, you may not recognise a potential issue you may unknowingly cause within the boiler whilst working within it.
 
Shane007 thanks for your word of caution? I'll get a boiler safety check done so I can tiick that safety box. I think it's about £75.
Although,this qualification does not appear to to be a measure of competency...... as three different gas registered installers have been round ( including an ideal boiler engineer ) and they failed to spot the issue!

Thanks for the heads up though.

Cheers
 
It is a measure of competency but it does not give experience. That is only obtained over time.
I am surprised so many did not cop the issue as this would be a typical symptom of that problem. It should also have been picked up on your annual service as part of the service, is draining the boiler and checking the vessel pressure and re-charging as required.
 
hey can anyone help me i have an ideal mini s24 gas boiler and it cut out on me 2 days ago.. it was frosty weather and it just stopped.. when i press the reset button the fan comes on and its getting gas but its not making any attempt to light a constant red light comes on after lockout.. also the valve letting in the water was leaking so it went to 3bar. i let it back to 2 but i dont think thats the problem please help
 
Sounds like faulty NTC. Also there could well be gas to the boiler but the gas valve may not be opening.
Either way, you need to call an RGI.
 
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