Tourer water heater help

[adc14]

Hi,
My parents have asked me to take a look at their caravan, which has a couple of niggles. I've managed to sort most of them, but really having trouble with the water heater.
Thought it might be worth mentioning before I go into the purpose of my being here, that they were having problems with their water pump emptying their aquaroll water source. When they turned on a tap, the water pump just kept on going! Turns out, there was an adjustable valve under the offside bench seat, which when adjusted, resolved that problem and stopped pumping water once the tap was turned off. (not sure if this is linked to my problem...)

They have a 1997 Carver Cascade 2, which hasn't worked for a while. The remote, wall mounted switch, wasn't working - no lights illuminated at all. Turns out the two fuse carriers were a bit sloppy as once I tightened them, the lights illuminate when you flick the vertical switch.
I've scoured the internet and followed the correct procedure to fill the water heater/boiler with water, but when you flick the remote switch on, a few things happen except for providing hot water!
When you flick the switch, the green light illuminates, you can hear the pilot light clearly igniting, but then after about 5 seconds the red light then illuminates too (so both green and red are illuminated at the same time) and it all goes quiet. Some research tells me that the light combination indicates the flame hasn't sparked up properly, which could be caused by a number of factors.

How do I pin point what exactly the cause is? I've had a look on ebay to see what replacement parts are available, but before I start spending money on parts I don't need, I'd like to narrow it down first.

I've removed the outside cowl and removed the heater module. There's nothing I can see that's glaring obvious to indicate what's causing the issue. The PCB looks dry and undamaged. The onboard fuse is intact...I'm stumped!!

Can anyone help please?

 

[Sproket]

You need to get in touch with Gary @ arcsystems for advice on the Carver systems.

 

[Gozza]

I think from what you've said that you've done this, but I'll offer it in case I've misunderstood you...

The external air intake has a cover - have you removed this and kept it off while the ehater is running? I think you have, I think that's what you mean by taking the cowl off, but I may be wrong!. I have a Truma and whenever I've had a problem like you are describing, that's been the reason.

Failing that, have a look inside the air intake, as much as you can, and see if there are any blockages.

 

[Damian]

The cascade does not have a removable cover like the Truma unit.
The symptoms clearly indicate that the burner module is faulty and you need a new one.
Beware of buying from EBay as many offerings are NOT carver units but Henry ones and do not fit.

Gary at Arc Systems is the best person to contact for a replacement.

 

[adc14]

That's one thing I haven't done Gozza. I wasn't sure how safe that would be to do.
Assuming it works ok once I've taken the outter cover off, how can this be rectified? Clearly I don't have to keep taking it off everytime it needs to be used

Thank you for your advice

 

[NigelHutson]

Gozza is talking of the Truma water heater which has a cover on, and is totally different. As Damian has said, the Carver Cascade doesn't. Years ago I had the same problem, and it needed a new control unit. Someone has kindly posted the details of where to contact regarding the Carver system.

 

[adc14]

I've sent Gary an email - hopefully have a reply soon.

Thanks for all your advice!

 

[gary]

Thanks for the recommendations guys :cheer: I've now answered this directly, but, from what's said and briefly, first, it's got the wrong much older switch fitted which straight away begs the question why?
As for a 1997 module displaying this problem, if indeed this has not also been replaced?, it could just be damp but electronically speaking it's typical of many years production and probably more so in 97 for whatever reason?

General solution then is fix it and that's what I do of course

I will add my tuppence worth seeing as ebay has already been mentioned, that is, there is currently a plethora of 'tested and working' carver modules for sale on there, can't speak for all sellers of course but I've had several ending up here this year, and being polite, are simply not fit for purpose

 

[adc14]

Hi Gary,

Thanks for your reply.
So by the sounds of it, the incorrect main switch has been installed??
I've later found out that my Dad replaced the heater module a few years ago. Whether he bought a duff one, which is the explanation of why it's gone again, im not sure. They don't use their 'van *that* frequently, so it's not like it's been used to death.
How do I go about getting a recon module from you and at what cost?
Many thanks!

 

[gary]

Hi Adam, It is not the done thing to give details on forums, so you have my number on my email, please give me a ring

 

[Woody3]

Any gas appliance has to have a flame failure device, usually a thermocouple which looks like a thin finger and is mounted so that the upper part of it sits in the flame. If you have any knob operated gas unit it is usually to have to hold the supply knob pressed for 5-10 seconds after the flame has lit so that gas by-passes the main valve. When the thermocouple is up to temp it allows the main gas feed through and you can let go of the knob.

If this unit is electrically switched there must be some sort of timer which lets gas through for that start-up period, and from the OP says it seems that this is working, viz the unit lights and then goes out after about 10 seconds. I would look for a thermocouple and if you find it see if it is difficult to replace. I would guess that a standard unit will have been used and a replacement can easily be sourced from the likes of Screwfix or Toolstation for a fiver or so.

 

[Damian]

Any gas appliance has to have a flame failure device, usually a thermocouple which looks like a thin finger and is mounted so that the upper part of it sits in the flame. If you have any knob operated gas unit it is usually to have to hold the supply knob pressed for 5-10 seconds after the flame has lit so that gas by-passes the main valve. When the thermocouple is up to temp it allows the main gas feed through and you can let go of the knob.

If this unit is electrically switched there must be some sort of timer which lets gas through for that start-up period, and from the OP says it seems that this is working, viz the unit lights and then goes out after about 10 seconds. I would look for a thermocouple and if you find it see if it is difficult to replace. I would guess that a standard unit will have been used and a replacement can easily be sourced from the likes of Screwfix or Toolstation for a fiver or so.

As far as Carver Cascade burner modules are concerned you are totally wrong about being able to source parts from Screwfix or any local place.
The unit utilises a flame recognition probe which is dual igniter and thermocouple, not something used in normal domestic type applications.
With Carver units it is best to leave repairs to someone who knows exactly what they are doing, and the best person is Gary at Arc Systems who knows everything there is to know about Carver items.

 

[ProfJohnL]

For your information

Thermocouples can only be used the appliance has a continuous flame burning such as a pilot light to keep the thermocoulple heated and producing a current to hold the solenoid element in the gas valve open. If the solenoid looses current from the thermocouple, it closes. It has to be manually reopened when you press the control vale in, to allow the heater to work again

Products like the Cascade, (all models) Caravelle 4, Truma boilers and combi boilers, and blown combustion heaters like the Truma E series and Carver P4, all use an electronic method of detecting the presence of a flame. There are three common methods, Flame conductivity, Flame rectification, and flame ionization.

Flame conductivity is easily fooled so its use is restricted to secondary devices and not primary safety systems. The re-ignitor fitted to the Truma SL series of heaters uses this, as the heaters do have a thermocouple as the primary safety system.

Flame rectification is the most robust system, a low powered ac signal is fed to the flame electrode, when there is no flame, the sum of the ac signal is 0v, But when a flame is present it completes a circuit between the electrode and the burner bar, and uniquely the flame has diodic characteristics, which rectifies the AC signal and produces a small negative voltage on the electrode. The control circuit will only respond to a negative voltage, which cannot be naturally produced by any other function of the heater. This is a robust system and is used by most manufacturers, including your modern home heating boilers

Flame ionisation utilises the chemical reaction that takes place within a flame, a high impedance electrode immersed in a flame over a metal burner bar will attract free electrons within the flame and the electrode will tend to develop a negative potential. As with the rectification process, it virtually impossible to fake this signal so is a reliable flame detection process. This is one of the systems is used in mines to detect fire or explosions remotely.However the signal is not as robust as the rectification system, and situations where you get flame lift of from the burner will destroy the signal. Poorly maintained appliances can produce flame lift off, which often used to occur when Propane was used The higher 37mb pressure resulting in a more vigorous gas air mixture in venturi tubes and emerging through the burner. It was also more prevalent when the propane contained more Propene, also known as Propylene mixed with the natural propane that some suppliers added to their commercial propane gas.

There are other flame recognition systems but these are generally highly specialised and reserved for commercial or scientific systems.

 

[Gafferbill]

With Carver units it is best to leave repairs to someone who knows exactly what they are doing, and the best person is Gary at Arc Systems who knows everything there is to know about Carver items.

.......I could not agree more.

I for one think it is irresponsible to post wrong advice on a public forum of a technical nature that has safety implications.
Even I know enough about Carver water heaters to know that such advice has been given in this thread!

The OP is being advised by Gary ............IMO all other advice can safely be ignored.

 

[gary]

trebilbly embarrassed now!

As it happens this question has been leading me a bit of a dance over the last couple of days, only because Adam the OP and a guy called Mark have similar problems... and phone numbers!, half the time then I was not sure who I was talking too!
Anyway, Adam is now better informed and should quickly find out his next move, probably the same as Mark who's module is on it's way this morning.

On the subject of thermocouples and as said is not the problem here, the hot end of a good one of these produces around 50 millivolts of electricity, the cold end screwed into the bottom of the gas valve connects this voltage to an electro magnet.
When you press down, you are manually opening the gas safety valve which is part and parcel of the magnet assembly, this valve is sprung loaded and the other end of the spring is held by a disc of iron which when the valve is manually opened is pressed in contact with the magnet.
When then the flame lights it energises the magnet, magnet then grabs the iron and the valve stays open when you let go. Once you switch off, the thermocouple cools and voltage reduces until the magnet lets go and safety valve shuts.
This letting go must happen within one minute, most often it's 40 seconds and it's that dull 'clunk' sound this makes you've perhaps wondered the cause of?

I say all that because if you listen to some plumbers it would seem to work by black magic!, while many must believe that themselves?.... perhaps it does also help to justify the prices some of them charge to change one!! :woohoo: