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magictime

Electric heater - advice please!

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11 minutes ago, magictime said:

No offence was taken Sam, don't worry. And yes, I understand that no electric heater is really going to be adequate to heat a 55ft boat. But if I can spend maybe £20 on a piece of kit that keeps us slightly more comfortable in the evenings for a couple of weeks, that's surely worth considering.

 

I reckon my Refleks stove on one-third power - 1.2kW? - keeps the saloon about 10C warmer than it is outdoors. Is it that far-fetched that an 800W electric heater could keep it 5C warmer?

Oh and yes, if I could click my fingers and swap the Refleks for a solid fuel option, maybe I would - maybe. (The Refleks is expensive to run, but not without its upsides!) But we've got maybe £7000 of work booked in already this year and are on the point of adding double-glazing to that list, so paying for a new stove is not really on the cards.

But that 800 Watts wont be on in the evening. If the boat is a modern Trad with the engine inside the back doors then you would probably do as well to take the covers off and sit round that.

23 hours ago, bizzard said:

Years ago almost everyone had the gas bottle inside the boat, next to the cooker connected with a short length of rubber tube, only two connections to leak. BUT everyone religiousely turned the bottle off after every use of the cooker or heater. Those were the days when most folk were more practical with more inituitive. I never heard of anyone blowing thereselves up. Stupid Hazardous folkl are likely blow themselves up whatever they've got.  Nor did the cookers have all the fail safe devices.

That is why I said do his own risk assessment and balance that against the comfort. I know what I would do.

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2 minutes ago, ditchcrawler said:

But that 800 Watts wont be on in the evening. If the boat is a modern Trad with the engine inside the back doors then you would probably do as well to take the covers off and sit round that.

Alas it's not! And yes you're right of course about any heater not being on in the evening, but then sitting around for five hours as the temperature drops from maybe 15C to 8C sounds a bit more tolerable than sitting around as it drops from 10C to 3C.

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13 minutes ago, magictime said:

No offence was taken Sam, don't worry. And yes, I understand that no electric heater is really going to be adequate to heat a 55ft boat. But if I can spend maybe £20 on a piece of kit that keeps us slightly more comfortable in the evenings for a couple of weeks, that's surely worth considering.

 

 

Sorry but you still don't get it.

Never mind " Adequate "-----  read    "Nothing".

 

Your 110Ah single cabin battery feeding the inverter will not power a 500w heater for more than a few seconds before the inverter cuts out due to low voltage and by then the battery will be severely damaged. Running the alternator at the same time will cook that as well in short order. Never mind 800w, its just not going to work.

800w plus 10% inverter losses = 880w.   880w / 12v = 73.34 Amps, your cabin battery is 110Ah TOTAL NEW capacity, you will be lucky at that discharge rate to get 10% of that for a very short time.

Your alternator even if a 90A job will not give more than 60A and when it gets warm even less and when it gets really hot and burns out, damn all.

 

FORGET ALL ABOUT ELECTRIC HEATING. Seek an alternative.

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17 minutes ago, Boater Sam said:

Sorry but you still don't get it.

Never mind " Adequate "-----  read    "Nothing".

 

Your 110Ah single cabin battery feeding the inverter will not power a 500w heater for more than a few seconds before the inverter cuts out due to low voltage and by then the battery will be severely damaged. Running the alternator at the same time will cook that as well in short order. Never mind 800w, its just not going to work.

800w plus 10% inverter losses = 880w.   880w / 12v = 73.34 Amps, your cabin battery is 110Ah TOTAL NEW capacity, you will be lucky at that discharge rate to get 10% of that for a very short time.

Your alternator even if a 90A job will not give more than 60A and when it gets warm even less and when it gets really hot and burns out, damn all.

 

FORGET ALL ABOUT ELECTRIC HEATING. Seek an alternative.

Echo that.

I put an 800W oil filled radiator in the boat - on a shore line - some years ago, just to stop the cauliflower freezing.

The airing cupboard and tank are on one side of the boat with the second loo on the other and a door to the engine bay behind. Thus the heater was contained in a box as it were. The radiator failed to heat that space to any degree of comfort, i.e. - not even warm.

If it failed to heat that small partially enclosed  space - how would it fare in a larger space??

 

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46 minutes ago, Boater Sam said:

Sorry but you still don't get it.

Never mind " Adequate "-----  read    "Nothing".

 

Your 110Ah single cabin battery feeding the inverter will not power a 500w heater for more than a few seconds before the inverter cuts out due to low voltage and by then the battery will be severely damaged. Running the alternator at the same time will cook that as well in short order. Never mind 800w, its just not going to work.

800w plus 10% inverter losses = 880w.   880w / 12v = 73.34 Amps, your cabin battery is 110Ah TOTAL NEW capacity, you will be lucky at that discharge rate to get 10% of that for a very short time.

Your alternator even if a 90A job will not give more than 60A and when it gets warm even less and when it gets really hot and burns out, damn all.

 

FORGET ALL ABOUT ELECTRIC HEATING. Seek an alternative.

I don't have a '110Ah single cabin battery'. Maybe you're thinking of my 110A alternator? The nominal capacity of my domestic battery bank is 870Ah (4 x 435Ah 6V Trojans), although the batteries are about 5 years old and I suspect the actual capacity is quite a bit lower than that. In any case, we can run a washing machine (with engine running) with no ill effects. So there's no question that an 800W heater will run OK for a while; my original concern was that the batteries might not get a full charge over the course of a day's cruising if such a heater was running for hours on end.

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My bad, sorry misread your post, 70 and 110A alternators

 

Ok, so you could reckon on putting back  maybe 120A into the batteries running the engine over tickover of course. That's 1440 W.

 So if you took your batteries down say 25% assuming they are in top form and you don't want to damage them, that's an optimistic 430 Ah.

Drawing off 74A, you could maybe run for 3 hours, at that rate of discharge you cannot expect much more as the rate of discharge affects the capacity greatly.

But then it is going to take 3 times that time at best to replace that charge in the batteries.

 

Would someone else check my figures please, its late here and there have been a few beers?

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3 minutes ago, Boater Sam said:

Ok, so you could reckon on putting back  maybe 120A into the batteries running the engine over tickover of course. That's 1440 W.

 So if you took your batteries down say 25% assuming they are in top form and you don't want to damage them, that's an optimistic 430 Ah.

I'm not sure you read the original question - he said the heater would only be 'on' when the engine was running.

 

Using your own figures - running the engine would produce 1440w so even with Inverter and other losses he could happily run the 800w heater without taking anything from the batteries.

 

The question remains - would there be enough power 'left' after running the heater to put some charge into the batteries to see him over the rest of the day & nights 'normal' consumption without unduly discharging the batteries ?

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3 hours ago, Boater Sam said:

FORGET ALL ABOUT ELECTRIC HEATING. Seek an alternative.

Or, alternatively, temporarily seek a landline (pull into a marina perhaps?) and get the diesel heating repair done there?  

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2 hours ago, Alan de Enfield said:

I'm not sure you read the original question - he said the heater would only be 'on' when the engine was running.

 

Using your own figures - running the engine would produce 1440w so even with Inverter and other losses he could happily run the 800w heater without taking anything from the batteries.

 

The question remains - would there be enough power 'left' after running the heater to put some charge into the batteries to see him over the rest of the day & nights 'normal' consumption without unduly discharging the batteries ?

I suppose one option would moor up at 6pm-ish, turn off engine and heater, check battery monitor an hour later, run engine for another hour if less than 12.4V; plus maybe only switch the heater on in the afternoon, after a good four hours plus of cruising/battery charging in the morning.

 

10 minutes ago, Sea Dog said:

Or, alternatively, temporarily seek a landline (pull into a marina perhaps?) and get the diesel heating repair done there?  

Tempting! But we're wanting to head south asap anyway so it just feels a bit ridiculous to fork out for somebody's travel now when we're going to be practically on the doorstep of Ed at Four Counties Marine Services in a couple of weeks' time, and he's happy to look at both systems.

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12 hours ago, TheBiscuits said:

Yeah, but you are paranoid!

 

You have a spare inverter, two spare propellers and probably a spare engine.  I sometimes wonder if you have a whole 57ft boat inside your 72ft boat as an emergency spare.  :icecream:

:P

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7 hours ago, Alan de Enfield said:

On my 'Sea Boats' I do keep 'small' spares on board

Yes, but not everyone has a spare hull and a spare engine on one boat 😁

 

I do agree that carrying basic spares onboard makes sense, even for those who don't know what to do with them.  It makes it much easier for someone to help you if you have the bits!

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Excuse me but Reflex stoves are very simple devices with no moving parts or electronics, what is so broken that it can be simply fixed?

I used to have an Old Dutch and the only thing that stopped that working was the mica glass disintegrated one Easter Sunday, couldn get a spare for 2 days.

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7 minutes ago, Loddon said:

Excuse me but Reflex stoves are very simple devices with no moving parts or electronics, what is so broken that it can be simply fixed?

I used to have an Old Dutch and the only thing that stopped that working was the mica glass disintegrated one Easter Sunday, couldn get a spare for 2 days.

Or a mucky filter

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3 hours ago, Loddon said:

Excuse me but Reflex stoves are very simple devices with no moving parts or electronics, what is so broken that it can be simply fixed?

I used to have an Old Dutch and the only thing that stopped that working was the mica glass disintegrated one Easter Sunday, couldn get a spare for 2 days.

I started a thread a couple of weeks ago looking for advice on how to fix it. Long story short we've tried everything obvious, it's still not working, and now we seem to have a slow leak of diesel where we must have failed to re-attach a pipe quite right (don't worry, the valve in the supply line is closed so nothing presently leaking). In any case we are in a hole and have decided to stop digging.

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On 08/03/2019 at 18:03, Sea Dog said:

Hot water bottles are 'free' heat when you're cruising and will take the chill off the bed - early nights may be in order?

I'm thinking that to some extent the answer is right there - the best solution is to find some way to harvest the heat generated by the engine and if you have a calorifier heated by the engine then you're part way there. Quick back of the envelope calc, 50 litres of water heated to 80 degrees C has 12MJ of energy to give out (assuming cooling to 20 degrees C). That's the equivalent of running a 1KW heater for over 3 hours if you can harvest all of that. If it's situated under the bed then take the insulation off the top once you stop (and maybe move the mattress) and at least that space should get a certain amount of heat into it. If you're running the engine for hours after the water has heated up then draw some off into other containers (and insulate as necessary if you want the heat for later).

 

That may be a slightly mad idea, but I don't think it's the maddest idea on this thread!

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8 hours ago, aracer said:

If it's situated under the bed then take the insulation off the top once

Have you actually seen a calorifier ?

How would you propose removing the insulation ?

How would you replace the insulation when the other means of heating were 'fixed' ?

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Yeah, the one under my bed which has loose bits of foam insulation over the top of it...

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8 hours ago, aracer said:

I'm thinking that to some extent the answer is right there - the best solution is... cruise 'til dusk and go straight to bed with a hot water bottle!

Fixed that for you!  :D

 

(He'll get to his repairer sooner too) 

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Given the cost of buying electric heaters and then probably new batteries it would prove cheaper to pay for Ed Shores to travel to the boat and fix the heating NOW 😊

  • Greenie 1

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1 hour ago, Alan de Enfield said:

That is not normal.

Nothing, but absolutely normal on a narrowboat.

Each one is carefully hand crafted and designed for its purpose (not...)

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10 hours ago, aracer said:

I'm thinking that to some extent the answer is right there - the best solution is to find some way to harvest the heat generated by the engine and if you have a calorifier heated by the engine then you're part way there. Quick back of the envelope calc, 50 litres of water heated to 80 degrees C has 12MJ of energy to give out (assuming cooling to 20 degrees C). That's the equivalent of running a 1KW heater for over 3 hours if you can harvest all of that. If it's situated under the bed then take the insulation off the top once you stop (and maybe move the mattress) and at least that space should get a certain amount of heat into it. If you're running the engine for hours after the water has heated up then draw some off into other containers (and insulate as necessary if you want the heat for later).

 

That may be a slightly mad idea, but I don't think it's the maddest idea on this thread!

In theory there's a nice easy way to harvest the heat you're talking about: the Mikuni control panel has a 'Water Pump' setting that is supposed to send hot water from the calorifier round the radiators. Ed (Four Counties) made this suggestion. Trouble is, I'm pretty sure the previous owner of the boat, when doing his run-through of the systems for us upon purchase, said he'd never got this to work. (I wasn't quite clear on what he was trying to tell me at the time, but this fits.) It's the first thing I'll be trying when I get back to the boat but I'm not holding out too much hope.

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12 minutes ago, magictime said:

In theory there's a nice easy way to harvest the heat you're talking about: the Mikuni control panel has a 'Water Pump' setting that is supposed to send hot water from the calorifier round the radiators. Ed (Four Counties) made this suggestion. Trouble is, I'm pretty sure the previous owner of the boat, when doing his run-through of the systems for us upon purchase, said he'd never got this to work. (I wasn't quite clear on what he was trying to tell me at the time, but this fits.) It's the first thing I'll be trying when I get back to the boat but I'm not holding out too much hope.

That's very interesting - my system (one of the originals) doesn't have it and there's no mention of the facility in the latest offering from MV heating?

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1 hour ago, magictime said:

In theory there's a nice easy way to harvest the heat you're talking about: the Mikuni control panel has a 'Water Pump' setting that is supposed to send hot water from the calorifier round the radiators. Ed (Four Counties) made this suggestion. Trouble is, I'm pretty sure the previous owner of the boat, when doing his run-through of the systems for us upon purchase, said he'd never got this to work. (I wasn't quite clear on what he was trying to tell me at the time, but this fits.) It's the first thing I'll be trying when I get back to the boat but I'm not holding out too much hope.

 

I had a 12 volt pump fitted to my Webasto to do this, as it allows the calorifier to be used as a crude heat exchanger to heat the radiators when under way.

 

However it only gets the radiators tepid, rather than hot when the engine is running.

 

It is OK for keeping the inside of the  boat a few degrees above ambient whilst underway but wouldnt be any good as a form of heating after you have stopped and would leave you without hot water the next morning.

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