Gasfitter question - external heater vent

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gzt

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#279578 24-Oct-2020 11:38

I have a Rheem 20 external gas water heater with the standard vent. In summer with the windows open, the gas exhaust smell etc comes into the house. In winter with the windows closed not an issue. The prevailing wind may change in summer as well.

I measured the distances to the windows and all that is compliant as expected. Rheem has an exhaust attachment listed on the website - this moves the vent horizontally 400mm for compliance reasons and will not help in itself here.

Something like an exhaust at roof height is what I need. Are there any compliant custom options?

Froglotion

208 posts

Master Geek

#2591567 25-Oct-2020 08:05

Could you install a trellis wall to the side of the water heater (compliant distance)? Got a photo of the setup? Not that many options really, could move the water heater but that will increase wait times at the tap, but may not make too much difference. I try install them so that fumes won't blow in, but often you don't have many options. Other option could be to install a basic ventilation system, say positive pressure, into the house. If the window opening is for ventilation, it would not be required most likely. So would help with house ventilation and remove the fume problem.

Bung

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#2591569 25-Oct-2020 08:22

The internal version of the tankless heater has a sealed venting through the roof. Is there any provision for the external unit to be ducted? I'm thinking about a location under very wide eaves. Curiously none of the location maps showing distances from windows etc include any reference to overhang.

Froglotion

208 posts

Master Geek

#2591583 25-Oct-2020 09:34

Below an eave is 300mm minimum clearance for any fan assisted appliance with an input of 50MJ/h or higher. External water heaters don't have any allowance for fluing like an internal one. Best you can do is install a flue diverter which may exhaust the fumes to either the left or right. Have done this when a house had a shade sail installed nearby. Installed diverter so that hot exhaust couldn't get near the shade sail.

gzt

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#2592995 29-Oct-2020 08:30

It's between two windows. One metre clearance on one side. Two metres clearance on the other side. It's usually the two metre side with problems tho it does happen to both.

I noticed today the unit is mounted below a ventilation gap in the monolithic cladding. I'm not overjoyed about that either.

The model 20 does not have an internal equivalent. Model 27 does. My first hope was the flue kit from the 27 is compatible with the 20 - I don't think so. My second hope is using the 20 spreader/director attachment and modifying it to create a two metre or longer flue above roof height.

Froglotion

208 posts

Master Geek

#2595863 1-Nov-2020 11:41

Seal the gap if you want, I wouldn't worry about the hat at all though. Assuming it's a typical 10mm slot or similar.

That is some decent clearance from Windows, so there isn't much you can do really. Wind is going to blow the exhaust around as it wishes. I can't think of any way to eliminate some of the exhaust getting inside really.

gzt

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#2595880 1-Nov-2020 12:44

Looks like the solution is going to be the external/internal 27 with the flue, in an enclosure.

It's unfortunate there are no flue to roof options for the smaller externals. It would be a pain living next door to one of these in some of the tighter urban environments.

Froglotion

208 posts

Master Geek

#2595883 1-Nov-2020 13:05

Would need to have the gas pipework checked too to confirm it has the capacity for the larger water heater.

The flue system on internal units don't tend to be UV stabilised, so the enclosure would need to cover that too. The section that goes out the roof will be fine of course.

And yeah when they jam houses together all sorts of services become annoyances. Outdoor heatpump units are loud and would be more annoying to me.

I don't tend to open any windows as the ventilation in my place means it's not required. Otherwise I'd perhaps get some smell I side from my external water heater as mine is closer to a window than yours.