Efficient Diesel Heating

[geem]

Agree that ducted warm air systems are quick to deliver heat, a lot quicker that the waste heat from a generator started from cold.

The other benefit of the hot air eberspacher type heaters is that the hot air is from outside the cabin which forces out the moisture laden air and so reduces the condensation in the cabin. A wet system with radiators would heat the existing moist air in the cabin so you may get more condensation on cold surfaces.

Colin. Www.solocoastalsailing.co.uk

The secret of moisture removal in a boat is the introduction of outside air heated up to room condition. Air at zero degC can be 100% saturated but heat it to 20degC and its RH drops to 26%.. It then has the ability to absorb moisture. It may be counter intuitive but you need outside air on a cold wet day. Whether you choose to heat the boat by drip feed oil heater, radiators or ducted air you probably need more ventilation than you think. The advantage of a radiant heat source like a drip feed heater is they are hot and you get lots of radiation that heats up the surfaces of the cabin. This creates warm surfaces. Combined with an open hatch a crack they work well. The air can be a little cooler as the surfaces are warm. This is not so good with warm air heating as the surfaces stay a little cooler any your warm air escapes when you open the hatch. I like drip feed heaters as you use so little power.

 

[ianj99]

Most people get their eberbastos to work reliably.
The downside of generators is that they are noisy on a small boat.

The talk of optimally loading the generator doesn't wash, the heater matrices or rads will only take the heat they need, so your engine will either be running light or short cycling.
Once the heating is up to temp, you may only want 1 kW or so.
I think this scheme only makes sense on a big boat with effective soundproofing.
Unless you can create a small truly quiet engine to run on red diesel.
Wispergen stirling engines never seemed to sell?

All the blown air diesel heaters are noisy unless fitted with a silencer, and I find them extremely annoying if I happen to be berthed next to one. Some of them are so loud you can hear well before you spot the offender.

Canal liveaboards usually have radiators and a wood burning stove. The circulating pump could be run off batteries via an inverter.

 

[Trundlebug]

All the blown air diesel heaters are noisy unless fitted with a silencer,...

No, not all.
Wallas are extremely quiet

 

[ianj99]

No, not all.
Wallas are extremely quiet

Thank the lord there's one! I know which to fit when my Force 10 Cosy cabin gas heater packs up.

 

[Steve_N]

No, not all.
Wallas are extremely quiet

Our Volvo Ardic was also near silent with silencers for both the exhaust and blown air. Perhaps it's a Scandinavian thing.

 

[geem]

Our Volvo Ardic was also near silent with silencers for both the exhaust and blown air. Perhaps it's a Scandinavian thing.

All the air blown types are quiet if you fit the correct silencers.

 

[pmagowan]

The secret of moisture removal in a boat is the introduction of outside air heated up to room condition. Air at zero degC can be 100% saturated but heat it to 20degC and its RH drops to 26%.. It then has the ability to absorb moisture. It may be counter intuitive but you need outside air on a cold wet day. Whether you choose to heat the boat by drip feed oil heater, radiators or ducted air you probably need more ventilation than you think. The advantage of a radiant heat source like a drip feed heater is they are hot and you get lots of radiation that heats up the surfaces of the cabin. This creates warm surfaces. Combined with an open hatch a crack they work well. The air can be a little cooler as the surfaces are warm. This is not so good with warm air heating as the surfaces stay a little cooler any your warm air escapes when you open the hatch. I like drip feed heaters as you use so little power.

Yes. I am considering working on a system of MVHR (mechanical ventilation with heat recovery) for my boat. Essentially instead of simply controlling the ventilation in a crude way it allows you to control it along with the heat. On a normal boat ventialtion is through uncontrolled leaks and through minimally controlled hatches and vents. This lets the cold air in and the hot air out. You then have to spend a lot of energy bringing the cold air up to temperature again. With MVHR the cold air is drawn in in much the same way as through a Eberspacher, with a low energy fan, but it passes by the warm air that is being extracted. The heat from the warm air passes to the cold air and so you recover most of it. It also works as a dehumidifier because, as you point out, the cold air when heated up has a low relative humidity. The warm wet air that is being extracted loses its moisture as it is cooled down and so generates some fresh water. I will do some experiments but it would allow you to duct warm wet air from drying lockers, toilets and showers, galley etc while replacing it with warm dry air.

 

[Trundlebug]

All the air blown types are quiet if you fit the correct silencers.

Anything's quiet when you fit a silencer to it!

The Wallas doesn't need a silencer to be quiet. It's quiet without one.

 

[rotrax]

I've always liked the idea of a Refleks type heater on a smallish boat. Silent, no elec consumption, reliable. Ideal at anchor but can't be used underway so no good for serious passage making.

Not so-a Refleks or the Canadian one-cant remember what they are called-are fine up to 15 degrees of heel.

Check the websites...............................

 

[NornaBiron]

I've always liked the idea of a Refleks type heater on a smallish boat. Silent, no elec consumption, reliable. Ideal at anchor but can't be used underway so no good for serious passage making.

We have a Refleks 61MFS fitted on our 49' monohull that can be used with no problems underway. It has a coil inside to heat the hot water tank which, in turn, feeds radiators throughout the boat - lovely and toasty and dry, at anchor or underway!

My husband has used various Refleks heaters on commercial fishing vessels within (cold) UK waters with no difficulties.

 

[NUTMEG]

Might be an installation thing. My webasto AT3500 is NOT noisy and has no silencer fitted. Roars a bit on start up but quickly turns itself down to a whisper. My mate three or four boats down from me can not use his Eber at night as it intrudes audibly on his neighbour.

I offer no explanation but, honestly, you can not hear mine from the bows or the pontoon and only just hear it in the cockpit.

 

[Plum]

Yes. I am considering working on a system of MVHR (mechanical ventilation with heat recovery) for my boat. Essentially instead of simply controlling the ventilation in a crude way it allows you to control it along with the heat. On a normal boat ventialtion is through uncontrolled leaks and through minimally controlled hatches and vents. This lets the cold air in and the hot air out. You then have to spend a lot of energy bringing the cold air up to temperature again. With MVHR the cold air is drawn in in much the same way as through a Eberspacher, with a low energy fan, but it passes by the warm air that is being extracted. The heat from the warm air passes to the cold air and so you recover most of it. It also works as a dehumidifier because, as you point out, the cold air when heated up has a low relative humidity. The warm wet air that is being extracted loses its moisture as it is cooled down and so generates some fresh water. I will do some experiments but it would allow you to duct warm wet air from drying lockers, toilets and showers, galley etc while replacing it with warm dry air.

That's interesting. Seen it in houses but never a boat, yet. Do let us know how the experiment goes.

Colin. Www.solocoastalsailing.co.uk

 

[ip485]

I have found the Webasto totally reliable. I have had it de-cocked once. I always run it at full power. It has the advantage that it produces heat quickly, and is independent of pretty much every other system. It has the disadvantage that its a little noisy (the fan to force the air through 50 foot of ducts is quite noisy).

The Genset is a bit more noisy still, and it seems a luxury to run it just to produce hot air. With an 8KW Genset its not "pushing it" that hard. The Genset has proved a little less reliable than the Web. but still pretty good.

Reverse flow A/C has so far proved totally reliable and the smaller units can be run off the batteries but again the system is reasonably noisy.

If you want almost silent, really effective heat independent of pretty much everything other than its own sytem then the Web. hot water system is perhaps the best product on the market and if based anywhere cold and love aboard would be the system I would fit - room of course permitting. To do it properly it is a signifcant outlay.

 

[rob2]

... and if based anywhere cold and love aboard ...

If no heating, I can assure you there will be no love aboard! (Freudian slip?) Many years ago my then girlfriend and I went on the Broads to celebrate the end of her finals. Due to inclement weather, she wore her duffle coat in bed...

Rob.

 

[ghostlymoron]

I stand corrected. No substitute for real life experience. I thought the flue might be a problem.

We have a Refleks 61MFS fitted on our 49' monohull that can be used with no problems underway. It has a coil inside to heat the hot water tank which, in turn, feeds radiators throughout the boat - lovely and toasty and dry, at anchor or underway!

My husband has used various Refleks heaters on commercial fishing vessels within (cold) UK waters with no difficulties.

 

[GHA]

I stand corrected. No substitute for real life experience. I thought the flue might be a problem.

I use a little computer fan blowing into the air intake (round the back) of a refleks so it works without the flue extension, fine on passage though it doesn't like the dinghy on deck with winds from nearly dead ahead. Seems to work fine, running for weeks at a time the smoke alarm or CO alarm never go off, and a gas soldering iron or just charging the batteries can set off the CO alarm. Great heater, toasty boat with a little pot of stew on top on a wild winters night just makes you feel good

 

[rotrax]

I use a little computer fan blowing into the air intake (round the back) of a refleks so it works without the flue extension, fine on passage though it doesn't like the dinghy on deck with winds from nearly dead ahead. Seems to work fine, running for weeks at a time the smoke alarm or CO alarm never go off, and a gas soldering iron or just charging the batteries can set off the CO alarm. Great heater, toasty boat with a little pot of stew on top on a wild winters night just makes you feel good

Wow GHA-what are you charging the batteries with?

A charging lead acid battery produces hydrogen, not CO.

A new CO meter might be worth a punt-it might be detecting Hydrogen and not CO!

 

[GHA]

Wow GHA-what are you charging the batteries with?

A charging lead acid battery produces hydrogen, not CO.

A new CO meter might be worth a punt-it might be detecting Hydrogen and not CO!

Or before assuming you know what's what and throwing out a functioning alarm you could try Google to find out more ,,,,,,,,,

Lead-acid batteries produce Hydrogen when charging. Carbon Monoxide detectors use something called a "Metal Oxide Semiconductor (MOS)" sensor, which detects a variety of gases including Hydrogen.

A MOS sensor calibrated for CO will give a false positive in the presence of Hydrogen gas at ~10% of the actual value. So, that ~85ppm reported of CO was in reality ~850ppm of Hydrogen gas.

Hydrogen's LEL is ~4% or ~40,000ppm, so no danger there.

It turns out, Carbon Monoxide detectors will provide false positives many substances, including (but I don't think limited to) the following:
- hydrogen
- acetylene
- dimethyl sulfide
- ethyl alcohol (drinking alcohol)
- ethylene
- hydrogen cyanide
- hydrogen sulfide
- isopropyl alcohol (rubbing alcohol)
- mercaptan (odorant in natural gas/propane)
- methyl alcohol/methanol
- propane
- nitrogen dioxide
- sulfur dioxide

 

[AHoy2]

Same experience with the CO alarm when charging a 400Ah battery bank (which is in a vented area). Interesting to see the figures from GHA above though.

 

[rotrax]

Good info-thanks.