Hot water problem

[ts3man]

I have a Burstner T680, with a Truma heating system. The pump to the cold tap is working, the heating is working, but the hot water is not. I have no leaks anywhere, but I cannot get hot water to the taps or shower. Can anyone help? I have spoken to a Reich pump dealer who feels that I do not need a new pump, but couldn't explain what's wrong. (?)

[Derek Uzzell]

As cold water is being pumped to your taps and shower (presumably at a reasonable pressure) it's plain that your water-pump is working OK.

 

I'm assuming that, when you turn on a hot-tap (or the shower's hot-water control) you can hear your water-pump start to operate (a Reich-branded pump will normally indicate a water-system with a 'submerged' pump in the fresh-water tank switched on/off by micro-switches on the taps) but no water comes out of the tap/shower.

 

If that's the case, then the logical cause would be a blockage of some sort in the water-system close-ish to the hot-water heater. This could be on the inlet or outlet side of the heater and might be due to a failed non-return valve, a failed/blocked heater vent-valve, or a pinched/kinked water hose.

 

If cold water isn't reaching the heater's inlet then (even if the heater is working OK) hot water won't come out of the heater's outlet. Conversely, even if there's no blockage in the water-hose leading to the heater's inlet, if there's blockage on the heater's outlet-side hot water won't be able to reach the taps.

 

As long as there's good access to the heater and the water hoses leading to or from it, it should be easy enough to diagnose the fault.

[Brian Kirby]

First, I assume you mean no water comes from the hot taps, rather than that water comes from the taps, but is not hot?

 

Second, does anything happen at all when you open a hot tap. For example, does the tap hiss, or splutter?

 

Working from Derek's assumption, that your van has a submerged pump actuated by micro-switch at the taps, which, given Burstner van and Reich pump seems highly probable, I wonder if the non-return valve on the Reich pump may have failed? This would allow water from the water heater to drain back into the fresh water tank, requiring the water heater to be partially re-filled each time a hot tap is opened. Depending on the installation, this may not have the same affect on the cold water side.

 

The answers to the above two questions may clarify if this is likely.

 

Each tap has one micro-switch, and the pump that delivers hot water is the same as delivers cold water, so if the pump runs for cold, it must, logically, run for hot. Besides which, you have clearly tried all taps, so a partial/intermittent failure in one tap seems to have been eliminated.

 

If a failed NR valve is not the answer, the only remaining logical answers are, as Derek suggests, a blockage - possibly a trapped hot system pipe somewhere - or there is a leak you have not yet spotted. On which note, I just wonder if that leak may be that the low temperature dump valve on the water heater is open, so as fast as the pump tries to fill the heater, the water just runs onto the ground?

[Derek Uzzell]

Brian Kirby - 2011-08-18 4:17 PM

 

...Working from Derek's assumption, that your van has a submerged pump actuated by micro-switch at the taps, which, given Burstner van and Reich pump seems highly probable, I wonder if the non-return valve on the Reich pump may have failed? This would allow water from the water heater to drain back into the fresh water tank, requiring the water heater to be partially re-filled each time a hot tap is opened. Depending on the installation, this may not have the same affect on the cold water side....

 

This raises the question as to whether the water heater (presumably a Truma C-Series using educated guesswork based on earlier postings) isn't actually empty. If there's a blockage on the inlet or outlet side of the heater, then it won't fill. While its certainly the case that, if a non-return valve in the water-feed to the heater (either on the Reich pump or separate) failed 'open', water could (and probably would) run back into the motorhome's fresh-water tank and empty the heater, as soon as a hot tap were opened the heater would begin to refill. As a Truma C-Series appliance produces characteristic noises when being filled, I think it's likely that ts3man would be aware that was happening.

 

...I just wonder if that leak may be that the low temperature dump valve on the water heater is open, so as fast as the pump tries to fill the heater, the water just runs onto the ground?

 

An open drain-valve would normally cause water to be lost irrespective of whether a hot or cold tap were opened. It is possible to envisage a water-system design with a drain-valve dedicated to the heater and a non-return valve 'upstream' of that valve, plus another drain-valve that just drains the system's cold-water side. But, if there's only one drain-valve and that's open, water will pour through that valve whenever the water-pump is operating. I'd also expect the water-pressure at cold-water outlets (taps, shower) to be way down if that (single) drain-valve were open.

 

Diagnostically, one of the more useful things to be told is whether a problem has suddenly occurred or has developed over time. In this instance, if the lack of hot water has suddenly happened, then it's reasonable to assume an 'event' has taken place - like a hose being squashed or a valve failing. On the other hand, if the flow of hot water at the taps/shower has previously showed signs of dimimishing, then there's the possibility of the heater's water-vessel being internally 'scaled'. I've no idea what the likelihood is of this happening but, if a heater's water-vessel becomes progressively lime-scaled inside, a blockage must ultimately occur. See the following on 'de-scaling':

 

http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=13476&posts=8

[Brian Kirby]

Until the OP clarifies a bit, we can't know. I agree the dump valve scenario is not logically strong, and would almost certainly result in run off via the valve in the event either hot or cold taps were opened. However, when drowning, floating straws offer small comfort! :-D

 

From his post, on further reflection, I wonder if he means there is cold water instead of hot water coming from his hot taps. It isn't entirely clear.

 

He refers to the heater working, but does not refer specifically to the water heater. So, might he not have realised that with heating selected, in summer, the water will not heat because the space heating 'stat will kill the heating long before the water gains any heat? I also wonder if he may think the heater is an instantaneous type, rather than a storage system that takes about half an hour to heat the stored water when the water heating function is selected?

[Randonneur]

The other thing to think about is the state of the gas bottle. We have had a similar experience, the hob was working and also the fridge/freezer on gas but the heating failed each time until we realised that the gas level detector was on red and not green, we thought there was plenty of gas in the bottle but obviously not.

[Derek Uzzell]

When I'm having difficulty trying to diagnose a forum member's technical problem because the details provided are sparse or apparently ambiguous, my initial reaction is to look through the person's previous forum postings.

 

In ts3man's case there are only three postings to work with, but it's evident from these that he (Real Name=John Cecil) is an experienced motorcaravanner with foreign-touring experience.

 

Despite being gently prompted back in 2009, John has never revealed the age of his Mercedes-based Burstner T-680. My files indicate that Burstner marketed the T-680 from at least 2004, but dropped the model (and all other Mercedes-based designs) for the 2007 model-year. So we are probably talking about a vehicle 5 to 7 years old fitted with (assuming that John's T-680's heating system is the original) a Truma C-Series combination air/water heater, probably a C-6002.

 

Now, while over 10 years as a motorhome-forum Agony Aunt has taught me that assuming anything is a dangerous practice, I must assume in this instance that, after owning his T-680 since at least 2009 and using it abroad on aires, John will have learnt how his heater normally functions. So, when John explains that "The pump to the cold tap is working, the heating is working, but the hot water is not", I conclude we are being told that something peculiar is happening.

 

The only setting for a Truma C-Series appliance to do what Brian describes is ""Winter operation - air heating without hot water requirement". This setting would normally be chosen only when the heater is empty of water or when there's no requirement for hot water. Clearly neither of these factors should apply here. If (as Randonneur suggests) there were an inadequate gas supply, then the heater would recognise this and shut down (red 'fault light' illuminated on heater's control panel). There's no indication this happens with John's heater.

 

Taking John's original posting at face value, he apparently has cold water emerging as normal from the cold taps, he has confirmed that the heater appears to be heating water as he would normally expect (ie. the heater is in water-heating mode, starts and runs without going into 'fault state' and - the obvious check to make - the heater gets physically warm), but no water emerges from the taps/shower when the taps/shower outlets are turned to their hot-water positions. If that scenario is right, then there's really got to be a blockage somewhere.

 

(Come on John, let's have some feedback from you, please. I'm sure you don't want Brian and me to think we've been wearing out our diminishing number of brain cells to no useful purpose. :-S :-S :-S)

[Brian Kirby]

Then, Mr Spock, I have to say I agree your conclusion is logical. :-) Either heavy scale is blocking the hot water outlet, or a water line must have become pinched, or simply have flattened out at a bend. I can't really see why pipe (if it is anything like our 2005 Burstner it will in fact be reinforced, transparent, food grade hose) that was previously happily curving around inside his van, should suddenly decide the bend is too acute and flatten, so I'm inclined to suspect scale or a pinch due to something that has been carried, either in the heater enclosure (assuming there is one), or in a locker that the pipes pass through. Seems we shall never know! Fun, ain't it? :-D

[XRN]

Sorry to highjack an old thread but I thought this was a good place to raise a similar problem I have with my new (to me) 2001 Hymer 680 Starline. I topped up the fresh water tank and after closing the heater solenoid drain valve, bled through hot and cold water systems to all taps. Whilst trying everything out with 240v hooked up at home the Truma C6002 heater was put into winter setting, thermostat at 20 deg which should give heating and hot water. It fired up ok and the yellow lamp on the controller lit up indicating the water was heating. After a few minutes the fan came on and hot air was nicely being pumped around the cab. After about 30 minutes and the temperature inside toasty warm I ran the hot taps but only got cold water out, not even luke warm!! The yellow lamp was still on and the exhaust outside was blowing hot which suggested the heater flame was still on but even after an hour no hot water. Each time I ran the taps I got air and spluttering coming out first which suggested that the previous posts referring to the pump non return valve passing are correct but once cleared plenty of pressure so I believe no system blockage. Firstly, does this suggest there a problem with the heater and secondly, where is the pump non return valve fitted and what would it look like? Think it is a Reich? pump. Thanks

Rob

[Derek Uzzell]

I’m not Hymer-literate, but my understanding is that the water-pump normally used is the submersible type (ie. it’s located within the fresh-water tank itself) and (as you say) is usually a Reich product.

 

I can’t confirm where the non-return valve will be in your case, but it will normally be close to the pump and quite likely attached to the pump itself. There are examples of Reich submersible pumps here

 

http://www.reich-web.com/en/sanitary/water-pumps/submersible-pumps/results,11-10.html

 

one of which is marketed with a non-return valve pre-fitted to its outlet.

 

This is an example of a Reich separate valve that would be installed in the water hose rather than on the pump.

 

http://www.outdoorvalue.co.uk/products/556-reich-caravanmotorhome-water-supply-non-return-valve.html

 

The basic Truma C-6002 heater was gas-only, though there was a C-6002(EL) version that had a low-power 240V water-heating (but NOT air-heating) capability.

 

When the heater is in blown-air mode much of its heat output will be transferred to the air passing through it and water-heating will be much slower than if the heater were in water-only-heating mode. But, after an hour, you ought to get at least warm water. Have you tried running the heater (on gas) in “Summer Operation” (ie. water-heating-only) to see what happens? A C-6002 ought (in Summer Operation) be able to heat water from cold to 40 degrees C within 30 minutes, and to 60 degrees C within 45 minutes.

 

It’s possible that a lot of the water in the heater is being lost during the heating process, either through a leak somewhere between the pump and the heater (which you’d almost certainly notice as water would be coming out from beneath the motorhome) or the water is siphoning back into the fresh-water tank because the non-return valve is not functioning. In both cases I would have expected a LOT of air to come spluttering out of the taps when you open them, as it would take some while for the water-pump to refill the heater.

 

I doubt there’s anything much wrong with the heater. It has been known for the ‘breather valve elbow’ fitted to the heater’s hot-water outlet to fail, but you’d find water emerging from under the motorhome if that happened. The heater’s safety/drain ‘solenoid’ valve might be leaking but (again) water would be dripping under the vehicle.

 

If - after topping up the fresh-water tank - you were able to bleed the water system successfully so that water flowed cleanly and splutter-free from all hot and cold water-outlets, but spluttering occurs later, air is entering the water system from somewhere.

 

I’m minded to go along with your diagnosis that the non-return valve is the culprit. You might be able to test that theory if you put enough water in the fresh-water tank to allow you to fill the heater and fully bleed the system, and then emptied the water remaining in the tank and checked if water was draining back through the pump. To do that you’d need to be able to see into the tank, but I don’t know if that’s practicable with your motorhome.

[XRN]

Thanks for the advice Derek, the link to a non return valve is good and gives me an idea what to look for. My thoughts are that the non return would be the obvious starting point as no water is draining out of the bottom of the motorhome and everywhere is dry inside. I can check if the system is flowing back to the tank by lifting the pump out after shutting off the taps but may be a week or two before I can do that. I know there is no NR valve fitted to the pump so I will have to trace the visible pipework outside the tank. Thanks again,

Rob

[Derek Uzzell]

This 2012 MHFacts discussion may be helpful

 

http://forums.motorhomefacts.com/60-hymer-motorhomes/102697-hymer-truma-non-return-valve.html

 

When a submersible water-pump is used a non-return valve (NRV) is essential and, for maximum effect, it really needs to be as close to the pump’s water-inlet as practicable. This means either integrated into the pump itself, attached directly to the pump, or (if the NRV is separate) not far from the pump.

 

NRVs vary in design and examples are shown here

 

http://www.leisureshopdirect.com/caravan/water/water_supply_fittings/non_return_valves.aspx

 

 

[XRN]

Result, non return valve fitted after the pump has sorted the hot water problem and also improved the speed of flow in taps and in the loo.