Trianco Aztec 4kw boiler question

[Jethrosax]

Good morning, the boiler had tripped this morning with low pressure and the gauge shows 0.6 bar. I’ve turned the boiler and the underfloor heating pipe valves off but, I’m beginning to be concerned that there might be a leak of water from the system so after re-pressuring the vessel, assuming that I can do that with a tyre pump and the pressure can be checked using a tyre gauge. I’ll re-fill with water to 1.0 bar and with the isolation valves off leave it for a couple of hours. If no leak then open the isolation valves and do the same thing. Hopefully there are no leaks.

Certainly do not want to contemplate ripping up the floor to get to the John Guest couplers.

Jethro

 

[Madrab]

you MUST leave this drain point open and remove the dust cap at the top of that vessel, and pump it up to 1.0 Bar

Dead important for you to be able to check and adjust the pressure in the Expansion Vessel (EV) properly. Yes a tyre pressure gauge can be used to check the pre-charge and then even a bicycle pump will get it to 1 bar. . Re-pressurise the whole system to 1 bar and then isolate the unit. If the pressure drops over time then you want to check the pressure relief valve (PRV) outlet for water dripping from it. If the EV has lost it's pre-charge pressure then the system pressure can rise to the point where the PRV opens. If the valve is older then sometimes it won't seat itself back down again properly and can slowly release the pressure.

If the pressure holds and then drops when you open the valves then the leak is out on the system somewhere.

 

[Jethrosax]

Thanks Rob really helpful. The boiler was installed in 2011 so the PRV might be leaking, I will check that if the water pressure falls over time. It’s a pity that there were no service instructions when it was installed, just a fault-finding guide.

Jethro

 

[snb1]

drop system pressure to zero and leave valve open.
pump up expansion vessel to 1.0 bar and check that shraeder valve isn't leaking when you unplug air pump
close valve. raise system pressure 1.0 bar only. turn system back on.

locate PRV(pressure release valve) pipe. ( should be an open end of pipe outside)
there shouldbe any water coming out of it.
place a small bag over it and sucure with an elastic band.
if system all ok tomorrow then it was just the expansion vessel
if system has leaked in to bag then prv needs changing
most likley on 12yr old system it needs a new expansion vessel and a prv

 

[Jethrosax]

Thanks, I’ll try that. The bag idea very useful. I’ve asked Trianco if they know if an equivalent expansion vessel, as I understand that the Aztec range were obsoleted in 2012, the PRV is still available. So maybe it would be wise to get spares. Just hoping it’s only an expansion vessel problem.

Jethro

 

[snb1]

if it is the expansion vessel failed you can always fit another one elsewhere. Often if you calculated the size with underfloor it needs a bigger expansion vessel

 

[Jethrosax]

Just a quick update. The expansion vessel was re-pressurise to 1 bar. Confirmed with a known gauge and the schraeder valve checked for leaks. (I had to remove the pump body to access the valve). As the unit was re-filled to 1.2 bar on the inbuilt pressure gauge, (briefly) touching 3bar the PVR that had had a plastic bag secured around it all night was checked and found free of water. After about an hour the underfloor isolation valves were opened and there was a slight increase in pressure of about 0.25 bar. The pressure remained steady at that for over a hour. The heating was then put on and the water pressure rose to 1.4 bar where it has sat during the testing.

Since the expansion vessel definitely had zero pressure probably at the time I started this post chain and had never been filled since its installation in 2011 is it now best to check it annually or given the history, the parts availability situation and the valve accessibility just leave it and look to changing the boiler in a few years? Parts are definitively more difficult to come by?

Thanks to everyone for their advice, I have learnt a lot and am really grateful.

Jethro

 

[Madrab]

the parts availability situation and the valve accessibility just leave it and look to changing the boiler in a few years? Parts are definitively more difficult to come by?

Glad that has sorted it, was obviously overpressurising due to no expansion and the PRV was releasing the pressure. Parts not being available would certainly be a driver to look at replacing but no point until it starts to cause issues.

The Pressure Relief valve will be easily sourced and an external EV and PRV could be added, it would more be if the heat engine was showing problem signs that it would be time to replace would be my take, unless you can afford to upgrade and wish the re-assurance of a new warrantied unit.

 

[Jethrosax]

It only gets used from October to April and not constantly so I’ll live with it.

Thanks again
Jethro

 

[Jethrosax]

It seems that I may have been too optimistic, the boiler was on for fIve or so hours and the water pressure was consistently at 1.5 bar. It turned off about two hours ago when the room thermostat reached the set temperature and the water pressure is now showing 0.8 bar, ie. 0.4 bar lower than when it was at cold rest, so if the boiler runs tomorrow I’ll put the plastic bag over the PRV outlet and if there’s no sign of leaking, I guess it’ll be back to check the EV and if the air pressure has fallen attempt to source a similar replacement as the space inside the cabinet is limited. A bit disappointing.

Jethro

 

[snb1]

you can fit an external expansion vessel anywhere as long as it is connected to the heating pipework. the one inside is a 2lt expansion vessel. just not sure of what size connection. if you know that then you will be able to get one that will fit, but as long as its not leaking just fit an additional expansion vessel elsewhere

 

[Madrab]

Looking at the MI the PRV is a standard 3bar, so if the system pressure is only every getting to 1.5 bar max then either the gauge is faulty, the PRV is passing (check the outlet) or if no water then the system water is being lost somwehere else.

 

[snb1]

Looking at the MI the PRV is a standard 3bar, so if the system pressure is only every getting to 1.5 bar max then either the gauge is faulty, the PRV is passing (check the outlet) or if no water then the system water is being lost somwehere else.

if the diapragm has gone in the expansion vessel then the air would get released through the auto air vent. basically if you find the charge pressure in the expansion vessel has dropped when you recheck it ( make sure you have dropped the system water pressure to zero first) then that is the problem

 

[Jethrosax]

Thanks snb1, when I checked it previousl, I drained down the whole system which meant removing the pump body to gain access to the EV inlet valve. Going on what Madrab has said, I may have a faulty pressure gauge, previously when I checked the PRV drain there was nothing coming out of there. So if I get the same happening today and the EV pressure is good then a faulty gauge may be likely. I think that I have eliminated the under floor pipework and John Guest couplers in the floor since on turning the isolation valves to flow thru position prev the pressure rose ever so lightly implying that the pipes and joints had retained integrit. Looks like a gradual process of elimination, so it bit time consuming.

Thanks
Jethro

 

[Jethrosax]

Just checked the boiler this morning and the under pressure failure light is lit. The pressure gauge shows 0.8 bar as before, so that part including the PRV seems to be working correctly. Will isolate the under floor piping again and drain the system to check EV pressure, since the EV is at the moment no. 1 suspect. Got some other stuff to do today, so not Ideal.

Thanks
Jethro