CH boiler - gas or diesel?

[Nigel S]

We have a diesel bubble stove with back boiler and a circulating pump connected to three radiators and one of the coils of our twin-coil calorifier. This works pretty well and can get the boat very warm but it is not very controllable and if it is left running at night, the saloon gets rather too hot for anyone to sleep near it. It's also a bit of a performance to light it if you just want some hot water.

 

I am thinking of adding a CH boiler such as an Alde Compact (gas - as we already have gas on board for cooking) or a Webasto Thermo Top (diesel - as it would be more convenient to connect up to the main diesel tank and not to keep changing gas cylinders!) We would probably disconnect the bubble stove from the heating circuit and use it independently when required (I know you have to drain it first!) to avoid the systems fighting each other.

 

I understand that the new Aldes are pretty efficient so I'm not too worried about running costs, but it looks as though the Alde has to go somewhere inside the boat (e.g. in a cupboard or under a dinette) and needs a "chimney" so would take up useful space and generally be complicated to install in an existing layout. However it is supposed to be very quiet in operation.

 

The Webasto, on the other hand, could fit in the engine compartment but I am a bit concerned that it is supposedly more noisy - e.g. if it was set to come on early in the morning would it wake me up (I'm very sensitive to unexpected noises on board)? I know it also uses more power from the batteries but I recently installed some Varta AGM batteries which I think are pretty robust and I would usually expect to run it for just a couple of hours at a time as required.

 

Any comments anyone?

 

Thanks - Nigel

[GUMPY]

I had an Alde, an old one admittedly and it used huge ammonts of gas.......

After much research I changed for a Mikuni in the engine room and used the Alde space as a wine rack.

 

Our Mikuni is set to come on at 4am and run till 7am it heats the water and one heat leak radiator in the bathroom. All the other rads are off at the moment.

I dont hear it, however there is some slight ticking from the fuel pump down the fuel line to the old dutch which can be heard in the guest room.

If it re-piped it to a seperate fuel line from the stove that would go.

 

There are people that have had no luck with Mikunis / webastos etc but I will say that installtion is the key get that right and all will be OK.

One thing to remember is NOT to have a thermostst on the system just an on off timer and TRV on the rads. If mine runs for more than 3.5 hours with just the water and bathroom rad on it shuts down until the system temp has dropped then restarts. The system should be designed so that it doesnt shut down and restart in normal use.

Mine has run for 5 years now with only one major problem and that was an O ring giving way.

 

As for electricity usage, acording to Smartgauge, mine takes 6% of the battery bank for a 3 hour run thats about 12Ah, its run off its own bank as the rest of the boat is 24v

 

Julian

Edited September 21, 2007 by idleness

[chris w]

I have a Webasto Thermo Top C (5KW). It runs a 60L calorifier plus 3 radiators.

 

It comes on at full power for about 20 minutes when the system first starts up from cold. This uses 0.5 L of diesel per hour (ie: say 0.2L actual) and draws about 3.5Amps.

 

It then switches to half power for the remainder of the time and uses 0.25L of diesel/hour and draws 2.5A of current.

 

Assuming one has it ON for say 3 hours, the total consumption over that period will be:

 

Diesel: 1 litre max

 

Electricity: 8AH max

 

This is pretty economical on both diesel and electricity consumption.

 

Chris

[GUMPY]

Chris

 

Did you allow for the 20amps or so it draws for the first minute or so as it fires up?

 

I so much prefer measured results than calculated ones

 

Julian

[chris w]

My Webasto definitely does not draw 20A at start up for the first minute or so. I have ammeters on the battery banks and its start up current is around 3.5 amps (and, being geeky sometimes, I do monitor this kind of thing!)

 

Chris

 

BTW, even if it DID draw 20 amps for the first minute (which mine DEFINITELY does NOT) it would still only add 1/3 of an AH to the battery consumption so would be of no consequence anyway.

Edited September 21, 2007 by chris w

[GUMPY]

My Webasto definitely does not draw 20A at start up for the first minute or so. I have ammeters on all the batteries and its start up current is around 3.5 amps.

 

Chris

 

Interesting, it must work in a different way to the rest or they have developed a low current glow plug/pin. Can't find anything on how it works on their website.

 

Julian

[chris w]

From where do you get the 20A figure anyway?

 

I found the following on a Webasto dealer's site:

 

Integrated Thermostatically Controlled Variable Heat Facility

Ceramic Glow pin (Low current start up) Technology (my emphasis)

Maintenance Free Combustion Reliability

Further Reductions in Power Draw

 

Dims. 214 x 106 x 159 mm

 

The site URL is http://www.narrowboatbrassware.co.uk/page6.html

Edited September 21, 2007 by chris w

[GUMPY]

From where do you get the 20A figure anyway?

 

I found the following on a Webasto dealer's site:

 

Integrated Thermostatically Controlled Variable Heat Facility

Ceramic Glow pin (Low current start up) Technology (my emphasis)

Maintenance Free Combustion Reliability

Further Reductions in Power Draw

 

Dims. 214 x 106 x 159 mm

 

The site URL is http://www.narrowboatbrassware.co.uk/page6.html

I was just basing it on all the other heaters of the same type ie Mikuni etc.

As its a ceramic pin rather than a glow plug that explains the difference

I went to

http://www.webasto-marine.com/index2_en.php

as the logical place to get info!

Julian

[Nigel S]

As an update to my original message, this project may turn out to be over-ambitious - I have just heard from Harworth Heating (the people who make the Bubble stove) that the "wet" version of the stove cannot be used dry at all, even if you drain it down (whereas I had been assured by one installer that this would be no problem).

 

So unless anyone's got any ingenious ideas, it looks as though it wouldn't be possible to install an independent boiler as well.

 

Nigel

[Mr Leigh]

Gas V's Diesel Central Heating

 

Alde 3010 Boiler - LPG @ 17.49 per 13kg bottle = £0.54 per hour giving 5.5kW - 0.4amp draw

 

Eberspacer Hydronic 5 - Diesel @ £1.00 per litre = £0.62 per hour giving 5kW - 4.6amp draw

 

Eberspacer hydronic 10 - Diesel @ £1.00 per litre = £0.90 per hour giving 7.5kW - 6.08amp draw

 

I think £1 per litre is optimistic, most people I have spoken to estimate the price at the pump to be closer to £1.10.

 

The Alde can also be run on 230V electric if you have a shoreline giving 2.1kW power. It also has no servicing requirement

[carlt]

£1 per litre? You can still run your diesel boiler on red, even after Nov 2008.

[Ernie]

Bought two 13kg gas bottles yesterday - now £20.17 per bottle. My Alde won't be on too much at that price.

[bristol & argo]

As an update to my original message, this project may turn out to be over-ambitious - I have just heard from Harworth Heating (the people who make the Bubble stove) that the "wet" version of the stove cannot be used dry at all, even if you drain it down (whereas I had been assured by one installer that this would be no problem).

 

So unless anyone's got any ingenious ideas, it looks as though it wouldn't be possible to install an independent boiler as well.

 

Nigel

 

OK, so leave the Bubble setup alone, I assume the other heating coil in the tank is connected to your engine, so the pipes are allready running past where you want to put the new/alternative heat source anyway.

 

I think there was discussion recently about how to effectively combine the plumbing, but two non return valves seems the easiest.

 

 

Simon.

[CampinGazz]

Chris

 

Did you allow for the 20amps or so it draws for the first minute or so as it fires up?

 

I so much prefer measured results than calculated ones

 

Julian

 

i know this was answered last year,

 

but a little of what i know about these heaters and current consumption...

 

the old eberspachers/webasto's did use a glow plug, and the 12 volt versions did indeed use 20 amps on startup for the glow plug,

 

however the latest versions of these heaters use glow pins, and also they apeer to not power it fully anymore, i noticed this on my motorhomes battery monitor, when the eberspacher D5W is starting up, the current draw fluctuates, from about 3 amps to 7 amps, it's at 7 amps most when it's first starting up, but when it's nearing the end of the start up cycle, it's pulling very little current, the plug is being given power in bursts to keep it at the temp needed to sustain combustion till it's self sustaining,

 

i also notice this when the batteries are low, the lights will flicker in tune with the glow pin power consumption, rapid flickers at first, then they space out, till they stop alltogether as the heater is fully started,

 

There's also the afterburn when the heater shuts down, but that's about 4 amps atthe most, and again pulsed.

 

Now my 12 volt fridge on the other hand... bought it on the understanding that it'd pull 3.5 amps an hour, (shoreline, the 2 door fridge freezer) i measure a max of 9.5 amps when the compressor is at full speed (compressor starts up slowly, pulls 4.3 amps, then goes up as it speeds up) and the thing runs 12.5 minutes on, 19 minutes off, this is in 22 degree ambient temps, no reduction at night as the interior of the van is heated to 22 degrees, worked out we'd need at least 80 amp hours per day to keep it going, and even with 335 watts of solar panels, and 465 ah of batteries, we can't last more than 2 days outside summer time... and of course the heater is on day and night then too.

[wotnot]

I considered the Alde 3010 which I believe is the latest model. However, after reading the manual I decided against for the following reason:-

 

NB! Copper pipes, joints or water

storage tanks should not be used in

the system. Aluminium pipes alone

are best. Do not mix different metals

as this can give rise to seriuous corrosion

damage.

 

PAGE 15 ALDE INSTRUCTION PDF

This is a bit of nuisance with a new build but a retro-fit as NigelS is intending might need a fair bit of stripping out.

Edited January 10, 2008 by wotnot

[wotnot]

Just noticed this has been covered earlier:-

 

http://www.canalworld.net/forums/index.php?showtopic=10810

[Phoenix_V]

If you join a scheme such as the rboa scheme gas can be bought at much cheaper than calor prices

[bridgit]

Bought two 13kg gas bottles yesterday - now £20.17 per bottle. My Alde won't be on too much at that price.

I pay £16 for a 19kg.