Ridged pipe for hot air heater

[Ian_Edwards]

My boat has an Eber Hydronic, some of the hot air pipes run inside lockers and are vulnerable to crushing.

I assume I can use a ridge pipe 60mm OD (so it slides inside the flexible pipe) to prevent crushing.

The hot air never gets that hot, because it's heated from hot water, via a matrix heater.

I'm assuming that most "plastic" will withstand 80 deg C, my guess at the max temperature of the hot air, so just about any plastic pipe will do?

Is this correct?

Just checking before a make a potentially expensive mistake!

Thanks in advance.

 

[David2452]

The answer is nobody knows, and neither do you until you measure the temperature to be sure, you would almost certainly get more benefit from some decent insulation, I have tried all sorts and come back to thinsulate sleeve, available as an Eberspacher or Webasto part. If to use that and sleeve over it with something rigid that should prevent crushing.

 

[Pladdatoo]

Hi
I used rainwater down pipe, sliced lengthways (on one side) at it is too small especially when the ducting is sleeved with thinsulate or similar. It gave sufficient anticrush properties for me and with the decent insulation doesn't get anyway hot enough to melt, even at the sharp end of the installation.
Regards

 

[David2452]

Hi
I used rainwater down pipe, sliced lengthways (on one side) at it is too small especially when the ducting is sleeved with thinsulate or similar. It gave sufficient anticrush properties for me and with the decent insulation doesn't get anyway hot enough to melt, even at the sharp end of the installation.
Regards

Indeed, with Thermoduct the surface temperature never gets much above 60C even on a hot air unit.

 

[Ian_Edwards]

Hi, I'm not thinking of putting a sleeve over the duct, I'm thinking of using plastic pipe instead of the duct.

My guess that since drain pipes from kitchen sinks, may well see water temperatures approaching 100 deg C (someone pouring a boiling water down the sink), then a Hydronic system using hot water and matrix heater is unlikely to reach 100 deg C, probably more like 80 deg C?.

Running the system on the boat today ( I've been fitting insulation to the ducts), I could comfortably put my hand on the hot air duct, even at the outlet from the matrix heater.

I guess I'll give it a go tomorrow and see what happens.

 

[Ian_Edwards]

Update

I had a look around B&Q and found "FloPlast 2.5Mtr x 68mm Round Downpipe" at about £8.

The flexible ducting (about 60mm ID) used with the Eber Hydronic slides snugly into this pipe, you have to make sure that it is circular in cross section, to do this I cut a 100mm length of the down pipe and used it as a former. The flexible ducting is quite soft and can be formed with your fingers. Sliding 50mm of so of the flexible ducting into the drainpipe makes a more or less air tight joint. I used a wrap of duct tape to secure it.

I've used the drainpipe to duct air along the inside of lockers, where the standard ducting gets crushed. I've used the original ducting for the bendy bits.

I've also insulated all the ducting in the system with Therma Wrap, which is a bubble wrap with aluminium foil on both sides, I cut this into 300mm strips and formed it into tubes, taped along the long seam with aluminium foil tape. This was then slid over the ducting.

The modification have worked well so far, there is significant more hot air reaching the cabins and I haven't succeeded in melting the drain pipe, it ran for about 3 hours yesterday afternoon.

 

[Pinnacle]

I had a look around B&Q and found "FloPlast 2.5Mtr x 68mm Round Downpipe" at about £8.

The flexible ducting (about 60mm ID) used with the Eber Hydronic slides snugly into this pipe, you have to make sure that it is circular in cross section, to do this I cut a 100mm length of the down pipe and used it as a former. The flexible ducting is quite soft and can be formed with your fingers. Sliding 50mm of so of the flexible ducting into the drainpipe makes a more or less air tight joint. I used a wrap of duct tape to secure it.

I've used the drainpipe to duct air along the inside of lockers, where the standard ducting gets crushed. I've used the original ducting for the bendy bits.

I've also insulated all the ducting in the system with Therma Wrap, which is a bubble wrap with aluminium foil on both sides, I cut this into 300mm strips and formed it into tubes, taped along the long seam with aluminium foil tape. This was then slid over the ducting.

The modification have worked well so far, there is significant more hot air reaching the cabins and I haven't succeeded in melting the drain pipe, it ran for about 3 hours yesterday afternoon.

Sounds like a result!

We have found insulation improves the system greatly.