Posiflow 3000 151 2201 problem

[Paul H]

Hi all

I have a problem with water pump in my Romahome R25. When I switch off the tap, the pump keeps on switching on and off every 3 seconds or so. Because it is connected to my webasto, it is pumping water out of the safety valve. Any ideas.? Thanks

[Keithl]

It sounds as though your pump is switched on/off by a pressure switch and the leaking safety valve is allowing the pressure to drop and the pump then turns on. You need to fix the safety valve to fix the pump. Try opening and closing the valve a couple of times while the pump is turned on to possible clear any debris holding the valve open.

[Derek Uzzell]

There's a 2010 MMM Magazine review of a Romahome R25 motorhome here

https://www.outandaboutlive.co.uk/userfiles/file/MMM historic road tests/live-in Romahome R25.pdf

The heating system was said to involve a Webasto Thermo Top C300 and there are 2016 operating and installation notes for it here

https://www.butlertechnik.com/downloads/Webasto_Heater_TTC300_Hot_Water_Heating_Operating_guide_with_Plate_Heat_Exchanger_USE.pdf

https://www.butlertechnik.com/downloads/Webasto_Heater_TTC300_Hot_Water_Heating_installation_guidelines_USE.pdf

 I'm not sure where in the Webasto system the "safety valve" is through which water is being expelled (or what the valve's purpose is) but - as Keith has advised - if that valve is 'downstream' of the Posiflo pump and fresh-water water is leaking through it, the pump will repeatedly cycle On and Off to try to maintain pressure within the motorhome's water system.

The Posiflo pump was discussed here in 2019

https://forums.outandaboutlive.co.uk/topic/47719-posiflo-3000-pump-issue/

As Posiflo pumps ceased being marketed in 2012, if Paul's pump's behaviour were due to unfixable problems with the pump itself, replacement would involve fitting a different make of pump. A SHURflo Trail King 2095-204-412 pump (readily available on-line for around £65) would be the logical choice.

However, although pressure-sensitive diaphragm pumps like the Posiflo and SHURflo products can 'cycle' On and Off spontaneously due to internal faults, usual cause for 'cycling' is a water leak downstream of the pump, often through a safety/drain valve that is not fully closed.

[Paul H]

Thanks for your replies. The safety valve is more of an outlet (sorry, my poor description!) just a small tank which has a tube that then goes outside the van. I can’t find any leaks either internally or externally. Clearly the water tap is on a micro switch and for the fact that he pump switches on and off clearly shows that here isn’t a problem there. I’m guessing now that it may be a problem with the pump itself. Not sure whether this information adds any more light? 🤔

[Derek Uzzell]

It's rare (though not unheard of) for a pressure-sensitive water pump like the Posiflo to be controlled by micro-switches on taps.

Normally (with this type of pump) when a tap is turned on and water begins to flow from it and the pressure within the motorhome's water system reduces, the pump 'senses' the pressure-reduction and switches itself on. When the tap is eventually turned off, the pump continues to run for a while to restore the pressure within the water system to its previous level, at which point the pump should switch itself off.

If a relatively small flow of water is leaking from the outlet of the "small tank" when the pump is running (and all the taps are closed) the pump will be able to repressurise the system temporarily and then switch itself off, switching itself back on when the leakage from the outlet has caused the pressure to drop again.
 

The problem you've described has all the hallmarks of the culprit being at the small-tank's outlet not with the pump, but it's difficult to offer a firm diagnosis without actually seeing what's happening and knowing how Romahome built R25s.

[colin]

As Derek has posted, it's very unlikely you have micro switches on the taps, you can check by looking to see if any wires go to the taps.

[Derek Uzzell]

When the water-pump is the pressure-sensitive type (eg. Posiflo and SHURflo products) if the pump is switched on WITH ALL THE TAPS FULLY CLOSED and the pump starts to 'cycle' rapidly - as is happening with Paul's Posiflo pump - either the pump itself is the culprit or (as in Paul's case) water is leaking 'downstream' of the pump and resulting in a pressure-drop in the water system.

A motorhome's water system could comprise taps fitted with micro-switches and a pressure-sensitive water-pump, and the system could operate perfectly well with the micro-switch wiring not connected to the pump. However, it's much more common to have one of the following system combinations

1:  Pressure-sensitive water-pump + taps without micro-switches.

2:  Submersible water-pump + taps with micro-switches.

3:  Submersible water-pump + taps without micro-switches + in-line pressure-switch.

My 2005 Hobby motorhome had a water system comprising a pressure-sensitive SHURflo water-pump operated by taps with micro-switches. The pump was turned on and off via the taps, but (while running) the pump also switched itself on and off according to the pressure in the water system. There were advantages to this combination, but whether these justified the significant extra electrical complexity is questionable. I never understood why Hobby had chosen this arrangement, but Hobby has always been a bit 'odd' where their motorhomes are concerned.