Air flow of a vent ?

[W+T]

Hi all

 

How do i work out the air flow of one of these vents, i need to know for the BSS as i have a Voyager 4500 cooker and it needs 8500sqmm of ventilation.

 

 

https://www.midlandchandlers.co.uk/products/vent-mc-tannoy-9-s-s-13509-av-112

 

 

Captain Faffer

[Alan de Enfield]

2 minutes ago, W+T said:

Hi all

 

How do i work out the air flow of one of these vents, i need to know for the BSS as i have a Voyager 4500 cooker and it needs 8500sqmm of ventilation.

 

 

https://www.midlandchandlers.co.uk/products/vent-mc-tannoy-9-s-s-13509-av-112

 

 

Captain Faffer

Its not the 'flow' you need it is the "square mm's"

 

It is length x width and subtract 50% if it is a louvered (bars across it) vent.

 

So for example a  100mm x 100mm (4" x 4") would be 10,000  square mm.

Deduct 50% would give a vent of 5,000 sq mm's.

 

So you would need a vent 130 x 130mm x 50% = 8450mm squared.

[hider]

Its simply the area of hole.

You have to allow for any grill or louvre, most are marked with the free area.

8500 mm2  is a bit over a 9cm square hole, not a lot really.

[Alan de Enfield]

Just now, hider said:

Its simply the area of hole.

You have to allow for any grill or louvre, most are marked with the free area.

8500 mm2  is a bit over a 9cm square hole, not a lot really.

That would be about half of what you need.

 

90 x 90 = 8100 mm squared which even without the 50% deduction for the louvres is insufficient.

 

Have a word with your mate Sam - he may have some more accurate numbers.

[hider]

Sorry, I don't need to talk to anyone, i said a bit over a 9cm square hole, not a 9 cm square grill. Suggest specsavers and a manners course.

[W+T]

That maybe how its worked out but that does not add up to me. if you have a 6x6 louvre vent then 50 percent is not open. 

 

[Alan de Enfield]

On 07/06/2019 at 20:01, W+T said:

[Deleted because of obscene language - original post also removed].

Maybe this will help.

 

FACTORS AFFECTING TOTAL EFFECTIVE AREA OF FIXED VENTILATION
The total effective area of fixed ventilation’ is: the total area of fixed ventilation provision, as
measured.
Each ventilator, door, window, hatch and any other openings should be measured carefully to
determine their individual effective area of fixed ventilation.
Careful examination must be made of each ventilator to determine the presence of any device which
would reduce the clear air opening e.g. filter, insect screen, fan blades.
Where filters or screens are fitted, they must also be in a clean and serviceable condition as partial or
complete blockage of the clear air openings could make the ventilator totally ineffective.
Louvered doors are a common form of providing fixed ventilation and the effective area needs to be
carefully measured.
The total effective area of fixed ventilation is designed to provide:
• combustion air for appliances that are not room‐sealed;
• for the evacuation of combustion products from appliances that are not room sealed;
• renewal of fresh air for habitation and comfort.
CALCULATION OF FIXED VENTILATION REQUIREMENTS
The formula used to calculate the fixed ventilation requirement is derived from BS 5482‐3 Annex B
(Code of practice for domestic butane and propane gas‐burning installations — Part 3: Installations
in boats, yachts and other vessels), but as extended by BS8511 Annex A (Code of practice for the
installation of solid fuel heating and cooking appliances in small craft) to address solid fuel stoves and
other appliances.

Edited June 12, 2019 by Athy

[Ex Brummie]

Visit your local heating merchant. Most ventilators will have the free air stamped on them. You will need a fixed louvre; a sliding grille is non compliant.

The vent for an appliance would normally be low level, so one in the bottom of your door would be better than a mushroom. Remember for BSS, the specification is for high and low ventilation, and is based on cabin volume and occupancy potential. Also, IIRC, noncompliance is not a fail on a private boat, just advisory.

Edited June 7, 2019 by Ex Brummie
Fat finger hit end instead of shift

[PaulD]

I used Vetus vents which comes with a mesh grill for the interior. The area of 49.69 cm2 is reduced to an effective 31.80 cm2 with the grill fitted.

 

See https://www.vetus.com/en/ventilation/deck-ventilators/aireador-de-cubierta-tipo-ufo-8164.html

 

A proper CE marked vent should give this information in the data sheet which you need for the RCD. Maybe the data sheet comes inside the box with the Midland Chandlers vent.

 

 

[David Mack]

Try asking Midland Chandlers. - There's an "Ask a Question" tab on the MC webpage.

[BilgePump]

On the type of vent you've linked to, without being able to see exactly how they're constructed and the sizes of the holes / gaps, it may be nigh impossible to get anything other than a pretty wild guess on the airspace they will give. Surely MC should have a tech sheet for them somewhere, given their safety function. Like said in the preceding post, it's prob a case of asking them to have a look on/in the box. They're described as a Taiwanese copy of another so poss not properly certed but maybe MC could at least give you an 'unofficial' idea of the size of the originals. They do look smart if they will be big enough for your mm2 requirement.

 

With all the talk of louvre vents in  this thread (despite not being the type the OP is wanting to fit) I realised just before the BSS test that I had to have fixed ventilation on the boat even without gas so just got some louvvres for £1.50 each from toolstation.  After having tried and failed to work out their bloomin' airspace beforehand, when I got them, it was stamped on the packet! The ones that cover up to a max of 9"x3" openings give over 3000mm2 iirc.  The bigger ones, for a 9"x6" opening, provide 8500mm2 airspace. That should give an idea of the size of  louvre vent needed to give that kind of airspace, although these ones are only thin and cheap aluminium, don't have any CE markings and say not suitable for venting gas appliances.

[Grebe]

Interesting stuff, thanks for that.

 

Supplementary Question - If you have a louvre type cover on each side of the opening are you down to 25% area?

[WotEver]

1 minute ago, Grebe said:

Supplementary Question - If you have a louvre type cover on each side of the opening are you down to 25% area?

Good question. I suspect no, but I’ll be interested to hear the answer from someone that actually knows. 

[BilgePump]

Can't answer that but I too would be interested to know if someone else can provide one. I'd already got the plywood door in place and my boat in the water before realising that as the opening vents in the side of the hull weren't 'fixed' they couldn't be counted. Consequently, I had to cut the hole in a rush with a pad-saw and it's not the prettiest job on the inside so I thought about tidying it up with another louvre sandwiching the ply. Didn't do it though because I didn't know how an examiner would calculate the airspace with one on each side and didn't want to necessitate a re-test which would have meant more time and money wasted on another short term licence (boat had never been on CaRT waters before and never had a BSS cert so couldn't get a long term licence until I had the BSS pass).

[WotEver]

56 minutes ago, BilgePump said:

Can't answer that but I too would be interested to know if someone else can provide one. I'd already got the plywood door in place and my boat in the water before realising that as the opening vents in the side of the hull weren't 'fixed' they couldn't be counted. Consequently, I had to cut the hole in a rush with a pad-saw and it's not the prettiest job on the inside so I thought about tidying it up with another louvre sandwiching the ply. Didn't do it though because I didn't know how an examiner would calculate the airspace with one on each side and didn't want to necessitate a re-test which would have meant more time and money wasted on another short term licence (boat had never been on CaRT waters before and never had a BSS cert so couldn't get a long term licence until I had the BSS pass).

In the mean time why not tidy the hole up with some quadrant (or other) moulding? They can hide a multitude of sins

 

[dor]

1 hour ago, BilgePump said:

Can't answer that but I too would be interested to know if someone else can provide one. I'd already got the plywood door in place and my boat in the water before realising that as the opening vents in the side of the hull weren't 'fixed' they couldn't be counted. Consequently, I had to cut the hole in a rush with a pad-saw and it's not the prettiest job on the inside so I thought about tidying it up with another louvre sandwiching the ply. Didn't do it though because I didn't know how an examiner would calculate the airspace with one on each side and didn't want to necessitate a re-test which would have meant more time and money wasted on another short term licence (boat had never been on CaRT waters before and never had a BSS cert so couldn't get a long term licence until I had the BSS pass).

Ventilation is advisory on private boats so even if you did get it wrong it wouldn’t be a fail.

[W+T]

4 hours ago, WotEver said:

Good question. I suspect no, but I’ll be interested to hear the answer from someone that actually knows. 

According to my BSS chap no it doesnt just 50%..

2 hours ago, dor said:

Ventilation is advisory on private boats so even if you did get it wrong it wouldn’t be a fail.

Afraid it is needed as mine has just failed on it.

[W+T]

19 hours ago, PaulD said:

I used Vetus vents which comes with a mesh grill for the interior. The area of 49.69 cm2 is reduced to an effective 31.80 cm2 with the grill fitted.

 

See https://www.vetus.com/en/ventilation/deck-ventilators/aireador-de-cubierta-tipo-ufo-8164.html

 

A proper CE marked vent should give this information in the data sheet which you need for the RCD. Maybe the data sheet comes inside the box with the Midland Chandlers vent.

 

 

Just home with one now and there is nothing in the MC UFO vents, just a copy of the Vetus though. but opening of the inner area is 92mm ID.

[Alan de Enfield]

15 minutes ago, W+T said:

According to my BSS chap no it doesnt just 50%..

Afraid it is needed as mine has just failed on it.

In which case complain to the BSS and point out the letter A in the section on Ventilation.

This indicates it is an 'advisory'

 

A Letter "R" indicates 'required'.

 

How much longer are we going to put up with untrained BSS examiner making up their own rules ?

 

8.9 Ventilation
8.9.1 Is the vessel provided with adequate fixed ventilation?               A

 

 

 

Edited June 8, 2019 by Alan de Enfield

[W+T]

3 hours ago, BilgePump said:

Can't answer that but I too would be interested to know if someone else can provide one. I'd already got the plywood door in place and my boat in the water before realising that as the opening vents in the side of the hull weren't 'fixed' they couldn't be counted. Consequently, I had to cut the hole in a rush with a pad-saw and it's not the prettiest job on the inside so I thought about tidying it up with another louvre sandwiching the ply. Didn't do it though because I didn't know how an examiner would calculate the airspace with one on each side and didn't want to necessitate a re-test which would have meant more time and money wasted on another short term licence (boat had never been on CaRT waters before and never had a BSS cert so couldn't get a long term licence until I had the BSS pass).

They work louvre vents out at 50% of the vent size.

[Alan de Enfield]

1 minute ago, W+T said:

They work louvre vents out at 50% of the vent size.

As I stated in Post #2

 

It is  all detailed (hidden) within the BSS website.

[W+T]

1 minute ago, Alan de Enfield said:

In which case complain to the BSS and point out the letter A in the section on Ventilation.

This indicates it is an 'advisory'

 

How much longer are we going to put up with untrained BSS examiner making up their own rules ?

 

8.9 Ventilation
8.9.1 Is the vessel provided with adequate fixed ventilation?               A

I agree, what this examiner has done is taken the oven as both hobs and  grill and oven on full wack and did his calculation after he left then said a dew days after i need min of the 8500sqmm for it. 

3 minutes ago, Alan de Enfield said:

As I stated in Post #2

 

It is  all detailed (hidden) within the BSS website.

I think Bigle pump missed it so just pointing it out again to him. 

[Richard10002]

The BSS guy for mine at both previous BSS exams said that he had to assess it as though it was Christmas Day with all 4 gas burners and oven on full, and someone having a shower before dinner, such that the gas heater would also be on full.

 

On this basis he said that my boat falls short by a few square cm of ventilation, but he he could only advise me, and he acknowledged that the chances of the worst case scenarios were slim.

[W+T]

Well i have

 

3 clam shells at 2500sqmm......7500sqmm   

 

Vetus copy UFO but with a larger hole and that come in at 6600sqmm so 50% ...... 3300sqmm

 

Solar vent hard to worork out but has a 70mm ID hole so 1500sqmm to any body with any sense.

 

If he isnt happy with that all high level and spread around the boat top then i will go else where and pay another BSS inspector.

 

I have to say it did pass on a few items that it should of failed as i missed them before the BSS was done and he said nothing about them, i didnt point hem out.

 

hey ho

[hider]

You  can take  any measurable gap around hatches, slides, windows etc and include them as ventilation. It all counts.

Most boats are over ventilated if you work it all out.