Lost pressure control switch

The AS Service Centre moved mine outside of the vent and electrics box to make it accessible.

Flash.  I took it in last week for some warranty work which among other things required a new pressure switch.  When they fitted the new switch they moved it to its new location.  They quite rightly said that the pressure switch has to be accessible and where it was fitted was not accessible.  They said they had discussed it with Auto-Sleepers’ R&D which is across the road from the service centre.  There was no charge.

It switches the pump in the tank on when a tap is opened and off again when the tap is closed. I think the location of the switch is only an issue with the dinette layout?

Thanks Marconi.  The in-line pressure sensitive switch is also a non return valve (NRV) for the whole water system which should stop pressurised water from flowing back through the submersible pump into the fresh water tank.  I believe it should also stop non-pressurised water from doing the same i.e. under thecweight of gravity if the pump is switched off and there is a leak in the system or a tap is left open.  In my case the NRV holds the water under pressure but not when the pressure is released.  The NRV can become contaminated with debris and cause water to flow back through it in which case the pump will come on intermittently to restore the water pressure without a tap being opened.  The NRV can be dismantled for cleaning which is another reason for the switch to be accessible.

Marconi,

Yes on my photo you can see three white dollops (excluding the pressure switch).  The white dollop to the right of the Truma drop valve (inlet side) is a NRV.  This is the NRV recommended in the Truma Combi-E installation instruction to separate the hot water from the cold water which you have and Marquis moved not knowing what it was for.  A new NRV was fitted back in its place by Willersey last week. The white dollop to the right of the pressure switch (inlet side) is where Marquis moved the NRV to, not knowing that the pressure switch had a NRV let alone one that was spring assisted and could be cleaned.   Willersey decided to leave it where it was as it was doing no harm.  Excluding the pressure sensitive switch NRV, this gives me two NRVs where you only have one.  The white dollop to the left of the pressure switch (outlet side) is not a NRV.  It is a ‘T’ piece allowing the cold water to go directly to the three mixer taps and the toilet flush.

The NRV in the pressure switch assembly works fine when surrounded by water but is resistant to opening when the system has been drained and the pump is initially only pumping air - many people experience problems with priming the Whale system because of this. It seems logical to me that the additional NRV's are likely to make priming even more problematic?

Peter Brown - thanks.  If it becomes a problem I’ll take it out.

Marconi,

I think yours and mine are the same it’s just that the water is flowing in opposite directions.  On mine it flows from the the cold water junction (‘T’piece) through the NRV past the Truma drop valve into the Combi and then to the three hot water mixer taps.  The NRV is where it should be according to the Combi installation instruction.  If the NRV was the other wrong side of the Truma drop valve, opening the valve would only allow the cold water to drain.  The hot water would be trapped in the system as the NRV would not allow it to reach the drop valve.  With the NRV in the correct position opening the drop valve will allow both the cold water and hot water to drain through it.  The situation may be different if the taps are opened after turning the pump off as this will depressurise the system.  Water may then flow back through the NRV as it requires pressure on it’s outlet side to work, at least that is my understanding.  As you have discussed with me off-line, the pressure switch NRV should be different because it’s spring assisted.  It should prevent water flowing back through it regardless of the water pressure. As you know, this has been confirmed by Whale which concerns me because my pressure switch NRV, unlike yours, does not behave in this way.  Once the pressure is taken off the outlet side it allows water to flow back through it into the fresh water tank as of course does the redundant NRV, which isn’t spring assisted, that Marquis through their lack of understanding placed in series with the pressure switch NRV.

Marconi,

My arrow is as you suspect pointing away from the pressure switch towards the Truma drop valve.  If it was pointing the other way, no water would get to the Combi and hot water taps.  From what you have said about your installation, the NRV is the wrong side of the Truma drop valve.  This will mean that unless you open a hot water tap no water will drain from your hot water system when you open the drop valve.  The big concern here is that your hot water system is not being protected as it should be from frost.