Rain entering chimney!

[bob b]

I went out to the motorhome to fit some carpet tiles earlier and found a very slight trickle of water running from out of the bottom of the heater surround. Upon investigation, the vent ducting leading up to the chimney is wet and coated in mildew (see photo). It is not leaking from the entry point into the roof, so it must be gale driven rain entering the chimney top.

I've cut a bit off an old motorbike  innertube and slipped it over the vent opening (see photo) to keep the rain out. I post it just to make others aware that the same could be happening to their motorhomes/caravans. Just got to remember to take it off on the rare occasion that I use the heater! 

[docted]

I hope it is not entering the van through the chimney as the chimney should be sealed from the inside of the van i.e. a sealed flue. If not sealed you may suffer from CO poisoning , at present with the flue blocked your heater will not work . The water as shown in your picture would I hope be condensation.

[pepe63xnotuse]

I just took it, that Bob meant that the rain had been entering down the inside of the flue stack..and from there had "moistened" the pipe/hose, from the inside, out.. ? :-S

[bob b]

pepe63 - 2014-01-03 1:01 PMI just took it, that Bob meant that the rain had been entering down the inside of the flue stack..and from there had "moistened" the pipe/hose, from the inside, out.. ? :-S

That's right. The water is running down the inside of the chimney. I'm going to isolate the gas from inside the cupboard and hang a label on the gas tap to remind me that the chimney top is obstructed.

[lennyhb]

That mildew is on the outside of the outer pipe and looks like it has been there for sometime. The flue pipes are normally two concentric pipes the main flue pipe is inside the brown pipe.

If like you think it is coming directly in the flue you would not see it on the outside of the outer pipe.

 

I think you may have a much more serious damp problem, with any luck may just be the flue roof seal.

[bob b]

That does make sense Lenny. The outer duct is to protect adjacent material from conducted heat coming from the actual flue pipe. It's blowing another gale here, so will add re-sealing the chimney to my rapidly lengthening list of jobs!

[lennyhb]

bob b - 2014-01-03 3:37 PM

 

That does make sense Lenny. The outer duct is to protect adjacent material from conducted heat coming from the actual flue pipe. It's blowing another gale here, so will add re-sealing the chimney to my rapidly lengthening list of jobs!

 

Horsham! you northerner's don't know what a gale is. I'm a couple of hundred yard from the beach in Lancing we got some real wind here. :D :D :D

[Mike B.]

lennyhb - 2014-01-03 4:27 PM

 

bob b - 2014-01-03 3:37 PM

 

That does make sense Lenny. The outer duct is to protect adjacent material from conducted heat coming from the actual flue pipe. It's blowing another gale here, so will add re-sealing the chimney to my rapidly lengthening list of jobs!

 

Horsham! you northerner's don't know what a gale is. I'm a couple of hundred yard from the beach in Lancing we got some real wind here. :D :D :D

 

if you want real wind-come up here on Emley Moor-horrendous over the last week-Especially after the mrs had extra sprouts at Christmas

Mike

[Mike B.]

However, I had a similar problem in France couple of years back after a bad storm water came in round the chimney for the oven/grill and I found the problem was the rubber seal round the tube where it entered the roof had cracked sealant. I lifted the seal, cleaned it and re-sealed it with silicone sealant and then pushed the rubber ring back down and left it to set- it's been fine since. Maybe this could be your problem too

Mike

[Derek Uzzell]

Truma's instructions for installing the roof-cowl for S-Series convector heaters are to use the rubber sealing ring (provided with the heater kit) WITHOUT further sealing materials. This is OK as long as the installation is carried out carefully in the first place and the rubber sealing ring doesn't degrade.

 

I had a roof-mounted exhaust for my Herald's heater and a leak developed at the chimney-to-roof rubber joint. (Pointed out to me by the Truma technicians when the Herald's Atwood heater was swapped from a Truma C-3402 unit.) Like Mike I just cleaned the joint and used sealant.

[PaulMarlin]

I have the same in my motorhome, wind driven rain at a shallow angle enters the flue and drips down between the inner flue (aluminium) and outer heat shield (looks Iike cardboard). The first 12 vertical inches are dry, then the pipe has a bend and the outer cover gets wet.

 

The roof seal is good. Does anyone know of an after market rain deflector that doesn't affect flue efficiency?

 

Otherwise, I feel an inventing session coming up.

[Derek Uzzell]

Welcome to the Out&About Live forums, Paul.

 

I’ve attached a photo of the Truma flue roof-cowl below for reference.

 

I notice that a similar ‘cover related’ question to yours was asked on the CaravanTalk forum in 2008

 

https://www.caravantalk.co.uk/community/topic/17213-truma-flue-covers-avante-505/

 

and the final posting there suggests that, if rainwater manages to get between the stainless steel inner ‘exhaust’ tube and the outer ‘cardboard’ tube, there’s a strong possibililty that this is because the two tubes have not been properly fitted to the roof-cowl. As I understand it, with Truma S-Series convector fires, rainwater may be driven into the inner stainless steel tube, but that water should then drain out at the fire end.

 

I’m 99.99% sure that no cover/deflector is marketed (or has ever been marketed) to guard against rainwater blowing into the inner stainless steel tube.

 

Might be useful to have details of your motorhome

 

https://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/IDENTIFYING-YOUR-MOTORHOME/54713/

 

and also what type of heater (convector fire or combination air/water heater) it has.

[Keithl]

Both Derek's photo and the OP's photo appear to have the top part of the cowl missing!

 

My 2004 AT has a separate, much larger diameter, cover clipped onto the top of the part shown. I'll try and find a picture to add.

 

Keith.

 

Edit: Looks like it could be either Truma part number 830702 or 830703.

[Derek Uzzell]

As shown on the drawing below, there are several possible ‘cowls’ for a Truma heater’s roof chimney.

 

1 = Truma part number 30700-01 - Cowl top T-1

 

2 = Truma part number 30700-02 - Cowl top T-2

 

3 = Truma part number 30700-03 - Cowl top T-3

 

6 = Truma part number 30010-20900 - Cowl roof

 

1, 2 and 3 seem to be alternatives to 6, but I don’t know off-hand what the purpose of each of the alternatives is.

[Keithl]

Mine looks very much like option 3.

 

Keith.

[Derek Uzzell]

Apparently the T1, T2 and T3 cowl tops are fitted when a Truma gas-fuelled heater is to be operated while the vehicle is being driven. (Page 8 of this link)

 

http://www.groveproducts.co.uk/medias/documents/grove/pub/BIZ1801%20Spares%20Truma.pdf

 

Logically, as it's to be expected that rain would often be blasting horizontally against the cowl top in such a case, these alternative tops MIGHT provide extra protection against water ingress - though I still favour the idea that, if the outer tube is getting wet, it's likely to be because the tubes have not been properly attached to the top of the flue.