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Posted: 17 February 2007 8:17 PM Subject: Truma c6002
Location: Cumbria. Elddis Xplore 540
I have a Burstner t-615 motorhome on a Fiat chassis. The vehicle is fitted with a Truma C 6002 gas powered water boiler with blown air heating. Following the Truma instructions the system is primed but as soon as the water taps are closed water siphons out of the boiler back into the cold water tank. I assume there should be a non return valve somewhere in the system to prevent this happening but I do not know where it is. The system functioned perfectly until the van was laid up for the Christmas period. There is no information in either the Burstner hand book nor in the Truma instruction book on solving this problem or any mention of any valves in the system. Other than fitting a new non return valve into the system does anyone out there have any suggestions?
Posted: 17 February 2007 8:39 PM Subject: RE: Truma c6002
Location: Swindon, Bailey Pegasus 462
Hi Mr Grumpy,
Your post was answered by a forum subscriber, but must have got lost before you read it !
The gist was there is a dump valve (Electrical safety/drain valve) fitted to your system somewhere between the fresh water/pump and boiler. The valve is soleniod operated and may be stuck or being called into this position. Aparently the fix is to force the valve to a closed position with a cloths peg or safety pin.
I am sure someone will give you a better answer soon.
Posted: 17 February 2007 9:07 PM Subject: RE: Truma c6002
Location: Cumbria. Elddis Xplore 540
Thanks for trying to help but the dump valve is operating OK. The problem arose duing the habitation check but I could not leave the van long enough for the mechanic to solve the problem. The boiler is filling but as soon as the taps are closed the water appears to siphon back into the cold water tank. I have concluded that either there is a non return valve fitted but it is not working correctly OR air is entering the system through a faulty tap or joint and causing the water in the boiler to become pressurised and pushed back into the tank. All and any ideas welcome.
Posted: 17 February 2007 9:17 PM Subject: RE: Truma c6002
It was me Terry!
Mr Grumpy- Have you closed your boilers automatic water dump valve? If not it will dump your boilers water as you fill it. This valve is a safety feature to protect the boiler in cold weather and automatically dumps the boiler contents if the temperature drops to around 8C - and remains open. It cannot be closed again and left to its own devices without the temperature rising above 8C again near where the valve is positioned. However, many, or most, owners overide the valve by holding it shut in various ways. I have found that a LARGE safety pin engages with the groove in the device perfectly and cannot slip off when fastened.
Converters place the valve in some weird and wonderful places but your motorhomes manual should indicate where it is.
Posted: 17 February 2007 9:25 PM Subject: RE: Truma c6002
I should have added that if you do keep the valve closed manually then you no longer have a safety device to automatically protect your boiler from freezing up. Either drain the boiler or keep your eye on the weather when the van is stood up - or use the vehicle with the temperature around the boiler above freezing.
Posted: 18 February 2007 9:09 AM Subject: RE: Truma c6002
The potential requirement for a non-return valve is stated in the "Water Connection" section of the Truma Combi Installation Instructions:
"With submergible pumps install the Truma non-return valve (35) between the pump and the first branch (arrow indicates flow direction). This is not necessary with pressure pumps which already have a non-return valve installed."
It used to be that Installation and Operating Instructions for the Combi range of heaters were combined in a single leaflet. Nowadays they are in separate leaflets and only the Operating Instructions leaflet for the particular Combi-model installed is likely to reach the motorhome buyer. If you want a C6002 Installation Instructions leaflet, then contact Truma(UK) (www.trumauk.com) and they'll be happy to send you a copy.
Anyway, your problem has all the hallmarks of an inoperative non-return valve, as I touched on in the earlier thread to which Terry gave a link. Such valves may a) be integrated into the submergible-pump itself, or b) be separate but attached to the pump, or c) be completely independent of the pump and installed in the cold-water supply-hose somewhere between the pump and the heater. The first 2 options are the most likely, but a Burstner dealer should be able to confirm the exact arrangement in your particular motorhome. At worst you'll have to replace the complete pump; more probably you'll just need a new non-return valve.
Worth adding perhaps that, if the Truma electric safety drain-valve opens on a water system fitted with a submergible-pump, then there's a good chance that, as well as the Combi boiler, the complete contents of the fresh water tank will be drained by siphon action. This differs from the scenario where the valve opens on a system fitted with a pressure-sensitive diaphragm pump and the tank is emptied due to the pump being left ON. In the latter case water-tank draining can be stopped, or prevented, by switching OFF the pump; in the former case, siphonic draining can commence and continue irrespective of the submergible pump being switched ON or OFF.
(Water systems with submergible pumps and Truma Ultrastore boilers also require a non-return valve to be fitted 'upstream' of the boiler.)
Posted: 18 February 2007 1:39 PM Subject: RE: Truma c6002
I can vouch for that. Our Burstner siphon fed water system has the complete caboodle dumped when the auto valve operates. Also, the valve, being yards away from the warm boiler enclosure, dumps the water irrespective of whether the boiler contain hot (and therefore safe from freezing) or cold water. Or it did do until I locked it closed.