Trying to help a friend remotely with this symptom of an Ariston boiler:
"Is displaying a fault which my handbook says could be due to low water pressure, and to increase the water inlet coming in to it... where might this inlet be? The boiler is coming on, getting to a certain temp (varies) then closing down."
think it needs repressurisating - here's a pic below the unit:
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tap(s) need to be turned (slowly i think) - I'm thinking its the ones for the flexible hose...
I've never quite understood why all boilers seem to require manual intervention to repressurise them. No system is perfect - they'll all lose some water by some means or other. Back in the good old days all hot water came from a cylinder and all heating water was circulated in a loop that was constantly fed at gravity pressure by a header tank that rather nicely took care of everything.
Now you have to turn two stupid little taps after you discover, on a cold winter's morning, that the central heating never came on two hours ago as it was supposed to and that the bath the children had the night before means that there's no hot water for your morning shower...
Why is a safe and reasonably fool-proof automatic pressurising not possible at a sufficiently marginal expense to the average boiler?
I guess it helps you to pick up faults before they get worse, things like leaky PRVs, pinhole leaks, failing expansion vessels etc. FWIW though, I only have to increase the pressure slightly every year on my system.
I have seen commercial systems with automatic re-pressurising though...
But if the system is losing pressure, there's an underlying problem which needs to be fixed. Re-pressurising it may work in the short term, but the symptoms will return.
Once a properly installed system has been bled a few times to get all the air out, it should run for years on end without needing to be re-pressurised. As you are doubtless aware, topping up is a discrete operation, and you're supposed to disconnect the filling loop once you've done it (although many people don't!)
I'm sure that automatic top-up is *possible* - but it's not *desirable*. You would need a permanently connected filling loop (which is bad) plus an electrically operated valve to let water in when required. If that valve failed, you could potentially get the system pressurised to mains pressure - resulting in constant water loss through the PRV. Even if an auto top-up system worked properly, it would mask common problems like expansion vessel failure, resulting in the constant replacement of the system water - with loss of inhibitor, and introduction of air.
Apart from that, it's a good idea!
Incidentally, the F&E tank on a vented system doesn't *always* take care of everything. Usually, so little water is lost that the ball-valve doesn't have to open for a very long time. If a leak does then occur, so that a top-up is needed, chances are that the ball-valve will stuck firmly shut!
Some have a pressure pre-set, do they? But *not* also a top-up management system? That sounds like the worst of both worlds!
Our Baxi just has two taps and a pressure guage, and topping up relies solely on hand-eye co-ordination.
Well, quite. But any system which is capable of an automatic top-up should be able to give an indication (however rough) of the number of times it's had to top itself up. And maybe give a visual warning that someone passing by the boiler can spot, such as a highly visible red light that latches on once a top-up has occurred, until somoene cancels the warning thus absolving the boiler of further responsibility.
Once you have automatic repressurisation hardware (electronically-controlled water valves) the complexity of the management system is a trivial expense. I assume there's a microcontroller of some sort in the boiler, as our Baxi gives various coded error messages and temperature display on a 2-digit 7-segment display. Therefore having a few lines of extra code which allows a repressurisation to be activated, but only for a limited time (in order not to continue spewing water somewhere in the house!) is a virtually zero marginal cost to the entire development event for the boiler. Having an even cleverer system which knows not to initiate a top-up within an hour of a previous top-up again is also a fairly trivial software solution which doesn't require additional hardware: microcontrollers have clock systems and I think you can extend them to be able to count a period of any arbitrary length, seconds hours or millennia, possibly!
Put it this way: it took several goes for me eventually to find out where the small leak in an insufficiently-tightened fitting in our (2yr old) replacement heating system was. Only on the third occasion did it leak a sufficient quantity of water such that rather than just dampen the loft insulation wool it dripped through the ceiling and left a small puddle of water in the hallway.
For us there was absolutely no benefit in having a shut-down scenario and an enforced manual top-up. How many hours and/or hundreds of pounds of labour would it have taken to find the tiny leak after the first shut-down occurred? It might never have been found either visually or through a pressure test, since the leak clearly only got triggered once in a blue moon through whatever combination of events and environmental conditions! The loft insulation could have dried before we found it, too. We might as well have had a system which allowed the leak to show itself *properly* and be done with it.
Of course. But all things fail. Even manually-operated taps. I'm assuming that's why the boiler has two taps in series, so that you have to open *both* to open the filler loop? Looking at my boiler, that's all they appear to be: two taps in series. You can just as well have two electrically-operated valves instead of one. You can also design valves with integral microswitches to offer feedback to the control system to indicate one or more possible fault conditions.
As I've just written in another post, you can make a clever control system that eliminates the need for a boiler shut-down at the first whiff of a problem, but which does alert the user. You could even have an annoying piezzo-electric buzzer if you liked. Boilers have microcontrollers in them. Once you've got an extra panel lamp, the electrically-operated valves and the warning buzzer, anything else is just a bit of software development that is a one-off marginal expense, so the cleverness of the system is not a problem, only the additional cost of the physical components.
For example, you could easily devise a system which doesn't top up more than once every 24hrs. Or one which doesn't allow a top-up state to persist for more than 20 seconds if the desired pressure is not reached, to avoid pouring water out of a hole somewhere. That's just noddy software, easy-peasy. Or one which will top-up once (with the 20-second rule applying) but will not top-up again a second time until the user resets the warning condition, thus handing responsibility to the user to investigate further. With or without an annoying warning buzzer!
As I said in my other message, the shut-down state was of no use to me, as it took several top-ups over 2 years to identify the mystery leak which may have dribbled very slowly, but only after the third (?) top-up did it spew out enough water in one go so as to be detectable by a puddle on the hall floor and ruined paint on the hall ceiling. I needed to know that something was wrong in the form of a slow or occasional leak - but I didn't benefit from having no heating one winter morning!
All those things are easy - it only requires the willingness of the home-owner to absorb the extra cost of the electrically-operated valves, because the marginal cost of the software development is a negligible one-off.
I built a simple auto-fill system here at Lowe Towers.
It's basically a 1-bar Pressure Reducing Valve, and an electrically operated solenoid in series.
The control system is trivial, it's a DIN-rail timer module.
When the heating comes on in the morning / afternoon, the switched live to the boiler is intercepted at the timer module, and it activates the solenoid for a 10-second fill-period. After 10 seconds, it times out and drops over to fire the boiler.
So the system operates for typically 20 seconds a day: once at each 'on' period from the CH timeclock, when thy system will be cold.
The timer / solenoid is there to prevent it feeding a major leak.
My belief is that the two taps are there so that the system remains sealed when the flexible filling loop pipe is removed - as it is supposed to be when not actively being used, in order to prevent accidental over-pressurisation.
My guess is that, even if it didn't feed a major leak, it would still mask a partial failure of the expansion vessel. You'd pressurise at start-up, the pressure would rise above 3.5bar when the system got hot, and expel water through the PRV. The pressure would fall below 1 bar when the system cooled - and be topped up by your automatic system at next start-up. Twenty seconds would be sufficient for this, but you'd soon lose all your inhibitor!
OK, but the system just blindly goes ahead and does it every morning if it needs to. You're still pumping 10 seconds of water every day and the user might be non the wiser as to what is going on. A slightly more complex system would, as I described, not force a shut-down the very second a pressure loss occurred, but neither would it blindly do a top-up every day: it take a more analytical approach and make more informed decisions, based on the number and frequency of the top-ups, as to whether shutting down would be the more sensible thing to do rather than just alerting the user and carrying on. That's why such analysis should (and could) be done by the microcontroller/microprocessor that already exists in the boiler.
Yes, it might mask that. I do monitor the system hot pressure from time to time to see if it's creeping over the usual 2.5 ish bar.
But the main reason I needed the auto-fill was that the system does have a trivial leak ( it drops below the boiler's threshold over about 1-2 weeks ). I'm not prepared to rip up the flooring to find that.
And I *need* to be sure the system will come on when I'm away for extended periods over the winter to avoid freezing.
That's the major driver here, and over-rides most other concerns. The system as-designed does what I need.
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