Engine Bay Tube Heater

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Ian_Rob

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I thought I would put a tube heater in my engine bay this winter. Measured to the face of the acoustic insulation it is about 600mm x 750mm x 1000mm high, too small for a 120watt/600mm long tube heater that I have. The engine gets in the way. A 60w/300mm long heater would fit but would one serve any useful purpose in below zero conditions or would I need two? The bay would be closed so not a huge volume to heat.
 
Not a real answer I know but when I overwintered in England and ( up a mountain ) in France I used an electric green house heater which could be set to come on at low power below freezing point.
It was 500 watts but cycled and did not consume a lot of power.
 
Presumably you are wanting to prevent frost damage and avoid damp. I would guess that a 60w heater in such a small volume would be more than sufficient to do that. I have used 2 x 1000mm ones for an entire 33" boat (one in the aft berth and one in the forepeak) for several years with no problem with the engine and hot/cold water systems. You need to be sure that the heater will switch off of it gets too warm and nothing closeby can melt or get overhot
I highly recommend a plug type thermostat set to come on at 5 degrees and positioned lower than the heater. This will avoid wasting electricity and keep costs down.
 
Ian_Rob said:
I thought I would put a tube heater in my engine bay this winter. Measured to the face of the acoustic insulation it is about 600mm x 750mm x 1000mm high, too small for a 120watt/600mm long tube heater that I have. The engine gets in the way. A 60w/300mm long heater would fit but would one serve any useful purpose in below zero conditions or would I need two? The bay would be closed so not a huge volume to heat.
Click to expand...

1. Specific heat capacity of air is 1.006 kJ/kgC
2. mass of air:
density of air is 1.225 kg/cu.m
volume = 0.6 x 0.75 x 1 = 0.45cu.m
mass = density x volume = 1.225 x 0.45 = 0.55 KG
3. Lets assume you want to heat it from -5C to 5C - Temperature differential = 10C

energy needed = 1.006 x 0.55 x 10 = 5.533KJ

A 60W heater releases 60J per second.

So if you engine space was perfectly insulated and had nothing in it but air, it would take about 92 seconds to heat that space by 10 C! Now of course its not perfectly insulated. And its not empty - it has a great hulking metal heat sink in it!

Specific Heat of Steel (engine) is ~ 0.5kJ/kgC, and the engine will weigh something between 100 and 400kg. So could need something like 2000kJ to heat it by 10C. You don't really need to heat the engine but as its not insulated it will be being heated by the air so you have no choice. That will take 33333seconds, or about 9 hours. Now the engine is in the air so its not loosing heat back to the air that you don't know about. But it will loose heat through the prop and anything else...

But if the compartment is well insulated, I think a 60W might just do the job - but it does depend what the job is! If its -20C outside I don't think it will... if its -2 I think it will be fine...
 
Ian_Rob said:
I thought I would put a tube heater in my engine bay this winter. Measured to the face of the acoustic insulation it is about 600mm x 750mm x 1000mm high, too small for a 120watt/600mm long tube heater that I have. The engine gets in the way. A 60w/300mm long heater would fit but would one serve any useful purpose in below zero conditions or would I need two? The bay would be closed so not a huge volume to heat.
Click to expand...

Consider one of these
http://www.ebay.co.uk/itm/200w-Fros...868952?hash=item2cb509a418:g:rFUAAOxy69JTBey7
 
Thanks for the continuing replies which are really helpful and to ShinyShoe for putting some bones on the issue.

I am winterising the boat this weekend and running the heating to keep warm. The Webasto ducting passes through the engine bay and got me thinking whether one could fit a frost thermostat and an additional outlet and use the boats existing heating system to take the chill off with the added benefit of good air movement throughout? What I don't like (and my insurers might have a similar view) is running it unattended. That being said, I am not entirely happy even with tube heaters.
 
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MartynG said:
Consider one of these
http://www.ebay.co.uk/itm/200w-Fros...868952?hash=item2cb509a418:g:rFUAAOxy69JTBey7
Click to expand...

I like the look of this and it is the right size but I am not sure I would put it below the engine ( as I was hoping to do with a tube heater) for fear that oil my drip onto the open element.

The electric tapes/ropes are interesting but difficult to see where one could safely apply them on a Volvo D1-30B?
The 230/430 degrees C operating temps are 2x/4x the operating temp of the engine and could presumably damage hoses and wiring?
 
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The 100W tape is 1/2 inch wide and 4 feet long.

If you wrap that round the block of the engine , possibly attaching it with a heat resistant adhesive tape such as Silicaflex, and control it by a contact thermostat set for +(Whateveryou decide)C, then the metal mass of the engine block will take all the heat from the tape and spread it through the whole engine.

To make it more effective, undo a galley fire blanket (glassfibre weave) and drape that over the engine to reduce heat loss.


For a more elegant solution, consider an engine pre-heater such as the Kenlowe

http://www.kenlowe.com/Heating.php

and

http://www.ebay.co.uk/itm/CAR-ENGIN...220-240V-2KW-65-C-FITS-ALL-CARS-/222130407497

Again a thermostat will bring the engine up to n degrees. You really don't need much heat from any system as has been pointed out. I am trying to suggest a safer and more effective system of heating the engine water than circulating wasteful hot air round it.

And if the boat is on the hard standing, why not drain the coolant and save it for next year, and just leave lots of venitlation in the boat. She won't come to harm and will stay dry - much more than closing everything up.


The more I think about a pre-heater plumbed into the coolant side, the more I like the idea for its effectiveness and efficieny in keeping the engine warm. And there's also the advantage that in the boating season you can arrive on board, switch on the pre-heater, and 30 mins later the engine is warmed up with none of that nasty cold period where 80% wear takes place.

Have a word with VolvoPaul and see what he says.

These pre-heaters are used on all the Devon and Somerset Fire engines to ensure the vehicles can be driven away without delay and can use the window and crew cab heating. The pre-heaters are left switched on the whole time when in the garage.
 
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Ian_Rob said:
I like the look of this and it is the right size but I am not sure I would put it below the engine ( as I was hoping to do with a tube heater) for fear that oil my drip onto the open element.
Click to expand...
I do have one and bought it from B&Q a few years ago. Unfortunately it seems no longer to be available at B&Q. I have never placed the heater below the engine . But I do stand it horizontally it is small enough to be fitted in its intended vertical orientation if you have space
 
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I am glad shinyshoe has confirmed the science. A small mains bulb in an inspection lamp under the engine works fine for most UK situations. I have one timed to come on for ten hours overnight, power consumption is very small. It keeps frost at bay and more importantly, for me, it keeps condensation off the engine

The heat is never wasted as it helps promote a flow of air through the boat for those of us that do not trust dehumidifiers.
 
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