Why does my blown air heater go MOO-ooo-moo-OOO-

May 9, 2018
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Our Trumatic E2400 Space Heater... to you and me that's a gas powered blown air heater... well it makes an odd noise. Like some kind of ghostly pregnant cow making little short mooing sounds. It resonates inside the van, but unfortunately it can also be heard outside.
Just worth mentioning... this is a campervan/motorhome, not a caravan. I hope I don't get kicked off the forum for admitting this.
The noise is coming from the flue outlet/exhaust which is situated underneath the van, pointing down.
The heater has a high and low setting, and the noise is there on both settings, but worse... a bit louder and more regular... when on high. It improves slightly once the heater has warmed up, but it's still bloody annoying.
I thought at first that it might have been just a unique combination of external breeze and van position playing tunes over the mouth of the open flue tube... just like you'd get if you blew across the neck of a wide tube with a sealed bottom end; but I checked and there wasn't a breath of wind.
I've not had this van long, but before we came away on our 5 month Italian tour... we're in week three now, in the Dolomites... we re-tested everything on a short trip to the Scottish Solway coast. Everything seemed fine then.

So what's causing this, is it a regular and known occurence on this model of heater, what can I do to stop or minimize it?

A few decades back we had a LWB Transit camper that had a Propex blown Air Heater. That was a little noisy, but it was just a slight and very acceptable roar. We were woken early one morning by an irate camper complaining how we'de kept him awake half the night with our loud music. I thought he was nuts... but just assured him we did no such thing. The next night, I realized what he'd heard was the gentle roar of our propex exhaust bouncing between the stone wall, only 3 foot away, and the rows of other vans against this wall. The magnified reverberating result was like Rolf Harris' Didgeridoo.
Now, we all know that no-one wants bothering with any Rolf related incidences, but I also don't want to disturb fellow campers. So I need to either find a solution, hope for warm weather, or camp on our own.
 
Apr 19, 2017
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Sorry, can't help with your particular problem.

However, the diesel blown-air heater on my boat can also create a beautiful 'MOOOOOO' lasting several minutes if for some reason it has become flooded with excess diesel!

Also, my home condensing boiler often creates a very pure 400Hz note for several seconds when it starts up...particularly from cold. That one is just an unfortunate length of flue pipe which just happens to resonate :(
 

Damian

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Mar 14, 2005
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It could be one of a number of things.
First is the flue length and its position under the van, or it may be a damaged burner gauze.

I would suggest that it is the latter and that will need replacing, but a word of caution, it is not usually a straight forward case of swap new for old, there are several other problems that can unearthed whilst doing the job.
 
Nov 11, 2009
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My caravan Truma room heater makes a slightly different noise when on gas with the fan running compared to when it’s on electric. On gas there’s a rhythmic sound that slowly pulsates but I put this down to variation in gas burning as the thermostat controls it. But it goes once up to temperature. But of course the caravan flue goes vertically upwards out to the roof.
 
Nov 16, 2015
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This is interesting as My Coachman when we are in winter and the outside temps are in the low to minus temps, when the heating kicks in from say 10 c going upto 20c for the night to day heat gives out a sound like a tube train coming into a station. But only for qbout 5 to 10 minutes , it's a Truma Combi unit. No Speed control on the fan , automatic. It doesnt happen in the summer when the outside temps are 10 c at night going up to the balmy 16c.
 
Jul 15, 2008
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Damian-Moderator said:
....... it may be a damaged burner gauze.
I would suggest that it is the latter and that will need replacing.

I agree.........almost certainly a rusted burner gauze allowing the flame to travel down to the jet.
You will need new parts......best left for when you are back in the UK as you will have to remove heater.
 
Nov 16, 2015
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Well Pilchard, If you get back to the Uk by September 15th And get to the Woosie fest, your travels would make interesting listening to. I wonder what your next interesting hickup might be. ? :p
Hutch.
 

Parksy

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Nov 12, 2009
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EH52ARH said:
Well Pilchard, If you get back to the Uk by September 15th And get to the Woosie fest, your travels would make interesting listening to. I wonder what your next interesting hickup might be. ? :p
Hutch.
Please say on topic Hutch, I'm not sure if you missed my previous intervention in this vein but once again I'll tell you that there's a long running thread on the Chit Chat message board that you should add your little diversions to.
 
Mar 14, 2005
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Fuel burning closed combustion heaters humming is actually quite common. Principally becasue they have all the attributes of an organ pipe. it just needs the gasses in the exchanger and exhaust pipe to be agitated at exactly the right frequency, to cause the entire combustion tract to sympathetically oscillate. Generally such issues are short lived and the heater will pass through the phase as it warms up. With most convection heaters the volume level of the noise or its frequency is quite low,and often goes unnoticed.

The E 2400 and its siblings are rather different beasts. and it is a far more technically advanced product that requires an in depth knowledge of how to service and repair them.

They use blown combustion, which automatically means the combustion tract is being agitated more and is more likely to make a louder audible noise.

There can be many reasons why a particular heater is noisy, but the first thing to check is the route of the concentric flue and air intake pipe. Some times a small change to its route can relieve the problem but you usually have limited options to make any significant changes.

The E series heaters are far more technical than Truma's convection heaters , and not every caravan workshop will have the knowledge to deal with them. But some other known issues that can make a heater noisy are fans getting clogged with dust and debris. These are difficult to clean, and care must be used to avoid upsetting the balancing clips. motor bearings wearing out, Motor brushes.(which are replaceable),

These products are used in motorhomes, lorry cabs, Ambulances, mobile libraries/incident rooms, boats, and some building site huts. Where they are used almost daily they definitely require an annual service.
 
May 9, 2018
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Christ you lot... it must have been a bad TV night! ;)
That's a hell of a lot of really good replies. And there's me thinking you'd all say... "no mate. they don't fit them to caravans, don't know anything about them."
But some of it makes depressing reading with the distinct possibility it might need a professional overhaul when we get back to the UK. It's not sounding like a job I'd want to get involved with.
Of course, it could also be temperature related. I don't have an external max/min thermometer but we are in a high mountain region and the valley we are in at the moment is at 1320m. Winter has hung on late here this year and there is still a fair amount of snow in the gulleys and shaded ledges. So I'm guessing nightime temps are circa 10 degrees c.
My main concern is safety though.

My better half... she who must be obeyed... has a nose that functions as a highly sensitive universal detector for all things untowards... even BS. She will reject glassware, cutlery, plates in a restaurant because they smell, several times over, 'till I wish the ground would open up and swallow me.
For days before I repaired that fridge she'd been complaining about the smell of gas. I poo-poo'd it, but just to prove her wrong I started soaping every gas joint in sight... starting with the 4 tap isolating manifold in a cupboard. I couldn't believe what I found. The tiniest leak you could imagine! From the fine froth laid on that particular gas union a solitary bubble grew... taking 10 minutes to grow to the size of a tiny petit pois. How could she smell that?!!! She's a pain! I nipped it, and job done.
But the Fire Angel CO detector went off the other evening. It's fixed at head height on opposite side from the cooker and I'm glad I took it out of the boiler cbd at home and brought it with. But there had been a fair bit of gas cooking going on, both oven and hob, fridge deep chilling those beers, and sitting down pogged with the heater running... it went off. It could be the heater; could be the blower stirring up CO from the only just finished cooking: could have been some rogue CO coming in through a window from the heater. But it had never occured before, and two further evenings of blown air use has not triggered a single bleep. I'll be checking the Fire Angel out online... and treat it with a new battery, just in case. The weather will be getting warmer at night soon so shouldn't need the heat, but will deffo keep an eye on any CO situation, and deffo get the heater overhauled when we get home.
Any recommends for a good value for money service agent? Pref. in Cumbria... but even from Dover to Bristol to Cumbria... on our way back.

I checked out "Woosie fest"... "amusing tales of caravan related woe, incompetence, clumsiness or sheer stupidity"... Is that me he's referring to?
 
Nov 16, 2015
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Pilchard, not at all. Good oh on your wife noticing the gas, we had a similar incident, couldn't find the leak , when we moved on found we were pitched above a rats nest and the gas smell came from that.
 
Mar 14, 2005
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Could be a variety of things as already stated. We had similar problems with previous van which had Whale underfloor heater with long inlet and exhaust pipes of fairly small diameter. These were quite sensitive to ambient wind conditions as although technically a balanced flue situation the outlets were quite a long way apart and thus not subject to exactly equal pressure and flow conditions. One was tucked up behind the chassis member and a simple bend down cured the problem.
The current van has a truma Combi system and you can hear the exhaust note changing frequently in conditions of variable winds but not loud enough to be annoying.
As I'm sure Prof will agree fluid flow and particularly gas flow can be quite a mysterious matter.
 
May 9, 2018
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From the general trend of advice being given so far, I think the best course of action is to do nothing and stop stressing. In fact, the same evening I started this thread, we used the heater again and it seemed a little improved. Maybe, like me, it'd got a little out of condition from lack of use and just needs a week or so of putting through it's paces.
But the main thing, as I've already mentioned, is safety. Now I've read up on our Fire Angel CO-9D Alarm, it seems that it gets triggered by fairly low levels measured over varied periods of time... depending on severity of CO levels. It seems quite possible that it had been measuring CO from hob and oven which had been in use immediately prior to switching on the heater. I think the only way we can do a definitive check on any potential CO emmissions into the van is to put the CO detector outside while cooking in the evening, then bring it back inside when the heating goes on. The weather is warming up quite nicely at the moment, so maybe not many more cool evenings to test things out.
 

Damian

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Re reading your original posting, you say you are in the Dolomites, is that at any significant altitude?

The reason I ask is that I had a very similar situation on a customer van which only became really noticeable at altitude, at sea level or close to sea level the heater worked quietly.
On that occasion it was a split in the burner gauze, which after being replaced solved the problem.

Your heater is a different type of heater and is a pig to work on so I would leave it to a Truma qualified engineer, or even better send it back to Truma for fault finding and repair where it will come back as good as new.

Just to comment on the CO readings, it will be using the hob and oven that triggers the detector, not the heater as that is room sealed, which would beg the question as to when the cooker was serviced and output checked.

And finally to correct an earlier comment about the flame going back to the jet, that cannot happen as the gas mixture is too rich to support flame at that point.

What you have is "Lift Off", where the flame lifts away from the burner then back tracks to where it should be.
 
Apr 19, 2017
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Does your CO detector have a digital display of the peak level detected since it was last reset? I find this very informative. The best one for this I have found is the KIDDE. I also have a FireAngel, but find this a real pain as it insists on making a horrendous BEEP if you simply want to check the peak level .....and has a long-winded process to reset to zero. (However with things like this, the next model from the same brand may function totally differently ..... and you never get the opportunity to try them out before you buy :( )
 
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Damian-Moderator said:
Re reading your original posting, you say you are in the Dolomites, is that at any significant altitude?

Damian,
The peaks of the Dolomites go above 3000m ....but I think pilchard has stated in another thread that he is at about 1300m. That is still enough to significantly reduce the oxygen level (as my wife who suffers in that way can confirm!). I am trying to get my head around whether the altitude will also affect the (regulated) gas pressure, but that will have to wait for the morning.
 
Nov 16, 2015
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It would effect the system but as it it doesnt have a fuel control unit for it as in the aircraft using similar systems.. . The Mooooo wooof is the delayed light off as Damien states, with the flame catching back to the "holding " gauze. A new Ignition plug might help. . But if it works , an extra blanket works as well.
 
Mar 14, 2005
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VicMallows said:
.... I am trying to get my head around whether the altitude will also affect the (regulated) gas pressure, but that will have to wait for the morning.
....

Gas regulators utilise a diagram against which the atmosphere presses on one side and the gas pressure on the other, a spring is used to bias the diaphragm and sets the differential pressure that gas will be supplied at, consequently the gas will always be supplied at teh same pressure above ambient.

At extreme elevations, the rarefied atmosphere may cause some appliances to burn a little rich. Most of the time this is not a major issue for caravanners, as such elevations are relatively short lived, But it is a factor that permanent installation appliances have to take into account and they will supply differently sized jets or burners for furnaces.
 
May 9, 2018
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I'm just loving this thread!
Where do you get so many techno-buffs in one place all chipping in?
I feel I'm learning more than my little brain can absorb!

Anyway, we are at altitude. Today at M1300+. But we have been, and will be again, staying at M2400. Having said that, the evenings just happened to be warmer when we were at M2400.

I wonder if the altitude/oxygen levels could be having a slight effect on our Boxer 2.8 HDI engine, as I've sensed a very slight degree of "hunting" on occasions?
It's cetainly having an effect on us two, as it's been 13 years since we were at these elevations. Then, we hardly noticed it and after 4 months were as fit as butchers dogs. This time our age is telling a little.

So apart from agreeing that a flame could never be sustained at the fridge jet... I either agree with everything said so far, am not qualified to comment, or have no experience.
Keep it coming... it's all interesting and, you can never be too well informed.
 
Jul 15, 2008
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.......worth noting that a CO detector can give an alarm if you have an on charge lead acid battery that is giving off hydrogen gas.
I don't know if gasses from your leisure battery can enter the habitation area of your motor home.
 

Damian

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Quote " I don't know if gasses from your leisure battery can enter the habitation area of your motor home."

Quite a lot of motorhomes have the leisure batteries under the front seats, so it is possible for gases to be in the habitation area, however, there would be a rotten egg smell as well if it were the battery.
 

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