Trumatic Safety/drainage valves?

[Jackal]

Just got back from a weekend away in Norfolk and had problems getting any hot water from our new Truma 6000 boiler.

 

Of course the problem I think was the temperature not being sufficient to keep the valve closed. But unlike our previous van where the valve physically wouldn't stay in the "up" position (Truma 3000?) the valve stays up as if it should be closed but alas the water gushed out the bottom.

 

Has anyone else experienced this?

[Vernon B]

Check your instruction manual - valve up and water out doesn't sound right to me.

 

V

[Mr. Grumpy]

Quite right VB, up is closed and I stick a peg on mine to keep it closed. If the valve opens it not only drains the boiler but eventually the main water tank as well! As I understand things once the boiler is working it should not dump its water but as we only use it for blown hot air in winter I have not yet confirmed this.

[michele]

I'm sorry I was reading and I replied by mistake I wish I had the answer for you .

[Jackal]

Yep, the valve did drain the whole water tank, twice.

 

Having read the instruction manual, it may have had something to do with the fact that I'd opened both drain cocks thinking that they fed the boiler!

 

What I really wanted to know was whether the valve physically moves down like it did on my previous van?

 

This one seems to stays up regardless, but no hot water comes out!

[Brian Kirby]

Are you sure you've got all the air out of the system?  You have to pump 10/12 litres of water into the water heater before anything will come out of the taps.  All drain valves and the thermal dump valve must be closed, and all the taps/shower open on hot, to do this.  Before you attack the hot, make sure you've bled all air from the cold circuits, including, if its flush water comes from the main tank, the toilet flush. 

The thermal valve will go down when below the temperature threshold, or if you push it down.

[Derek Uzzell]

According to Truma's Operating Instructions, if a Trumatic C-Series heater is not switched on then its electrical safety/drain valve will open if the air-temperature at the valve's location falls below 4C. To permit the valve to be closed, either the air-temperature at the valve must be above 8C, or the heater needs to be switched on. As the valve is held shut by an electrical coil, if the leisure battery's charge is allowed to drop too low this can also cause the valve to open. (I don't think this is mentioned in the Instructions). Like Mr Grumpy, many motorcaravanners (including me) choose to jam the valve in the closed position to avoid the thing opening spontaneously.

 

When the safety/drain valve opens, whether just the heater's water contents are emptied, or the contents of the heater AND the motorhome's fresh-water tank, will depend on the particular water system involved. If a system uses a submerged water pump (I believe this is generally the case with Hymer), there's every chance the fresh-water tank will be drained via syphonic action. If a system employs a pressure-sensitive water pump, the fresh-water tank may be drained, but only if the water pump is switched on at the vehicle's control-panel. With a mongrel system like my Hobby's (pressure-sensitive pump/tap micro-switches), even if the control-panel's water-pump switch is in the ON position, only the heater will drain.

 

If an electrical safety/drain valve continues to let water through after the actuating button has been pulled upwards to the fully closed position, then there's something amiss with the valve. As Brian advises, the valve's actuating button will move downwards to the OPEN position if low temperature (or low battery charge) triggers it, or if it is deliberately pushed down.

 

The design of Trumatic C-Series heaters has been relatively unchanged for some 10 years and the electrical safety/drain valve's design has also remained static. Because C-Series appliances combine air and water heating, they have come to be known by the (unofficial) name "Combi". However, in 2007, Truma has introduced a replacement for the ageing C-Series.

 

The new range of heaters is officially called "Combi" by Truma (which will inevitably lead to confusion on motorhome forums!) and its design is radically different to that of the outgoing C-Series. The Truma website (www.truma.com) has details and Photo 17 on page 149 of MMM Dec 2007 shows the latest heater fitted to a Swift Voyager. (Note how Swift has carefully installed the appliance so that anything large and heavy - like a folding bike - stored beneath the bed has maximum opportunity to smash into the heater's unprotected end. Good thinking, guys!) The design of the safety/drain valve is also revised and its operation is no longer electrical. I have only seen photos of the new valve and haven't got Operating Instructions for it, so I can't comment on how it functions.

 

As far as filling a Trumatic C's boiler with water and venting air from the water system are concerned, I follow this routine:

 

1. Ensure all water drain valves are closed.

2. Fill fresh-water tank.

3. Make sure all taps are closed.

4. Place shower hand-set in deep bucket.

5. Open shower hot tap fully and switch on water-pump.

6. When water emerges smoothly from shower hand-set the boiler will be full.

7. Close shower hot tap and vent air from the other taps one by one, using bucket to avoid water splashing.

[Thai Bry]

When the safety/drain valve opens, whether just the heater's water contents are emptied, or the contents of the heater AND the motorhome's fresh-water tank, will depend on the particular water system involved. If a system uses a submerged water pump (I believe this is generally the case with Hymer), there's every chance the fresh-water tank will be drained via syphonic action. If a system employs a pressure-sensitive water pump, the fresh-water tank may be drained, but only if the water pump is switched on at the vehicle's control-panel. With a mongrel system like my Hobby's (pressure-sensitive pump/tap micro-switches), even if the control-panel's water-pump switch is in the ON position, only the heater will drain

Derek

Many thanks for this, you've in one little paragraph have answered something that's been bugging me for the last 4 days.

I went to check the heater in our van to make sure that it was empty of water, and to also make sure that the main fresh water tank was also properly drained of water. I was not surprised that the hot water tank was empty as the drain valve was open, but I was totally surprised that the fresh water tank was totally empty as well.

Yes it is a Hymer.

I've looked high & low in ALL the instruction books that came with our new van & could NOT see anything like you've mentioned.

Thank you once again.

An enlightened Thai

Thai

[Jackal]

Thanks for you'r replies.

 

I will try again at the weekend. Of course, not having the weighty tome that is the Hymer Instruction Manual with us at the weekend didn't help, d'oh!

 

But I'm still a bit worried that the valve doesn't automatically open like my old one did.

 

Either that or the 8C minimum wasn't breached which I find hard to believe!

[Derek Uzzell]

Jackal:

 

I suggest you re-read my previous posting.

 

Truma's safety/drain valve does NOT automatically open at 8C, it opens at 4C (which is pretty damn cold for the interior of a motorhome). Once it has opened, unless the valve 'senses' that the temperature in its vicinity is above 8C, raising the actuating button to the valve-closed position will be ineffective - the button will just drop back down to the open position. Alternatively, one can turn on the heater which will override the 8C temperature inhibition.

 

IAEFRTFM

[Jackal]

Sorry Derek, I was under the impression that it opened at 8C not 4C.

 

My old one was a bugger and seemed to open at will.

 

The new one hasn't budged and I really can't believe that the temperature hasn't dropped below 4C in the last few days.

 

I know they're controlled by a coil but the Truma manual mentions a fuse and that's what I was suspecting had gone wrong.

[Derek Uzzell]

Jackal:

 

A Truma C-series appliance carries a fuse (or fuses) in the electronic control-unit(s) attached to the outer surface of the heater, but this protection applies to the heater itself not the safety/drain valve.

 

As the valve is held in the closed position electrically, it needs to be provided with a 12V power supply that operates continuously, but how motorhome manufacturers arrange this will vary. My Hobby has a distribution-box carrying 10 fuse-ways. A 10A fuse protects the 12V power supply to the C-6002EH heater and this supply is switched on or off via the main switch on the motorhome's control panel, while a 3A fuse protects a 'permanently live' 12V supply feeding the safety/drain valve and the Dometic fridge's electronics. The latter supply will continue to provide power unless the 3A fuse fails or the leisure battery is disconnected or its charge is heavily depleted and, in such cases, a closed safety/drain valve will open. Your Hymer's valve will almost certainly have its power supply fuse-protected and (if you are lucky!) your motorhome's documentation will identify the fuse involved. Removing the fuse would allow you to confirm that your valve will open if it loses its 12V supply, though it wouldn't confirm that it is sensing temperature correctly.

 

The important thing to remember with this valve is that it senses the air temperature immediately next to itself and not the weather. With the UK's fluctuating November climate, even if the air temperature outside a well-insulated motorhome falls to 4C, there's every chance that the temperature at the valve within the vehicle (even if it's unheated) will remain above that figure.

 

Clearly your valve works as far as draining the boiler and remaining shut when the actuating button is raised to the closed position are concerned. If you are becoming fearful that your valve won't open automatically to provide frost protection, then you could perhaps check this by packing some bags of ice round it, or spraying some plumbing pipe-freezing gas near it.

[Jackal]

Thanks again Derek.

 

I will try out a few permutations to test it fully at the weekend.