Free Heat?

[cobaltcodd]

If I put the heater on in my car on full, with the fan on "4", after about 2 minutes it's almost too hot in there to continue.

 

This had me thinking - why not put a car heater matrix and blower motor into my engine bay? To do this I'd cut into the hose that goes to the skin tank and run the hot water feed through the radiator, and then onto the tank, for more cooling. After all, they are designed for the pressure and flow rate an engine typically puts out.

 

If you don't want heat, then don't put on the fan (and so all is normal), but if you did then have a small piece of ducting to direct the air through the bulkhead and into the cabin (that happens to be a bedroom for me). As long as the fan can suck in fresh air to be heated then all should be OK.

 

Quite often I've run the engine to charge the batteries, and have succeeded in doing that, but also raising the canal water temp ever so slightly, instead of benefiting from the waste heat that I could have benefited from.

 

I've poked around on ebay for a second hand car one, and there are loads, but you can also get custom made ones as well, such as

 

http://www.carbuildersolutions.com/uk/compact-car-heater

 

and

 

http://www.carbuildersolutions.com/uk/52kw-car-heater-kit

 

These look quite good as one outlet could go straight into a cabin, and another could be directed into an airing cupboard or equivalent

 

If your boat is slightly under-cooled for a run against the tide on the Trent this would also help.

 

Thoughts? Ideas? am I mad?

 

 

[Guest]

You are not mad, or I am. I did something similar but used a fan assisted house type radiator (it was in a skip.) This is teed off the hot water feeds from engine to the calorifier. It warms the whole cabin in minutes when the engine is running. Used it this afternoon when we moored up cold and wet. Chucks out about 4kW IIRC. Downside is the fan is 240V so inverter needs to be on.

No reason why similar can't be done with car unit, or perhaps one from a larger type vehicle. Had I used such a unit, I would have put it in the rear steps, just to below and right of fire extinguisher in pic

This is easily the best improvement we made after fitting out the boat initially. I would highly recommend same to anybody.

Never had to use it to dump heat in emergency, but imagine it would work well.

Edited August 31, 2015 by Guest

[Top cat]

One possible downside is you will be making an extra noise path from the engine bay.

 

Top Cat

[nicknorman]

There's no reason not to do this.

 

We have two heat recovery systems, a 1kw matrix and blower that is fed from the calorifier loop and blows warm air into the legs of the steerer (trad stern) plus a heat exchanger on the loop to the skin tank that, with a small pump, circulates hot water around the cabin central heating radiators (that are also fed from a mikuni). It is nice to have "free" heat!

 

The only thing to be careful of is to not restrict the flow through the skin tank. I Td the connections off either side of a 28mm gate valve so with the valve open there is no restriction and the flow mostly bypasses the heat exchanger, with it partially or fully closed hot water is encouraged around the heat exchanger.

One possible downside is you will be making an extra noise path from the engine bay.

Top Cat

Yes this is a good point, take the water pipes into the cabin and use the blower to recirculate cabin air. Edited August 31, 2015 by nicknorman

[Arthur Brown]

I once found some fan and matrix heaters specifically designed for fitting under a kitchen unit behind the kick space, so the fittings are on the market (usually ebay!) for whatever you want.

 

However consider what proportion of time you will want the heat on when the engine is running.

 

Also I'd consider piping hot water along the boat and being very sure that the air to be heated is clean air away from engine and exhaust and stove fumes.

 

Once you fit pipes that could be used for central heating then heating a calorifier and radiators are options, and heating the circulating water with the engine, the stove and maybe a kerosene burning heater all become options, from which you can chose. As the system gets more complex you need to control it well to ensure that heat goes where you want.

[Paul C]

Definitely not mad, many boat have radiators fed by engine coolant. Basically, of course its not "free" heat because you're burning the fuel to generate it, but its increasing the overall efficiency and using the heat which would otherwise be wasted. Its possible to overcool the engine, or greatly prolong its warm up time, though.

[Arthur Brown]

An internal combustion engine loses energy as heat, mechanical output power and lost reciprocating machinery losses. You might as well recover the thermal waste rather than push it into the canal. Be sure that you get some heat from the exhaust gasses too.

Edited August 31, 2015 by Arthur Brown

[RLWP]

To do this I'd cut into the hose that goes to the skin tank and run the hot water feed through the radiator, and then onto the tank, for more cooling.

 

This is the correct way to do the job.

 

I would be wary of adding a lot of cooling into the calorifier circuit as it isn't thermostatically controlled - there's no guarantee that your engine would run hot enough

 

Richard

[Mike Jordan]

Been there and got the Tee shirt! there was an article showing how to do it complete with pipe diagram etc in the December 2011 edition of Waterways World. You can still download it from the WW website for a few pounds.

I have made a number of the units down the years using car parts. Its a very effective heating method, the heat losses from a car at 70mph must be huge, a well insulated boat at 4mph is a different matter. Strangely enough plenty of people are keen to heat water with a calorifier to make a saving but don't seem to think of space heating. Go for it!

Mike.

[Guest]

Been there and got the Tee shirt! there was an article showing how to do it complete with pipe diagram etc in the December 2011 edition of Waterways World. You can still download it from the WW website for a few pounds.

I have made a number of the units down the years using car parts. Its a very effective heating method, the heat losses from a car at 70mph must be huge, a well insulated boat at 4mph is a different matter. Strangely enough plenty of people are keen to heat water with a calorifier to make a saving but don't seem to think of space heating. Go for it!

Mike.

My thoughts too.

[NMEA]

Absolutely no reason not to, I have done it in the past for fishing boat wheelhouses and there are commercially available matrix with from one to several duct outlets to the job quite nicely, one point worth noting is to incorporate a thermal relay to prevent fan operation until the coolant is at operating temperature for best results. Many Scandinavian boat builders have incorporated a similar system for windscreen demisting for many years.

[Scholar Gypsy]

I'd support your mad idea too - I added two radiators running off the heat exchanger that came with my engine, but was not used. (Photos)

 

In addition to the point about not adding too much to the bypass circuit, as that can make the engine run too cool, the advantage of using heat exchangers is that it minimizes the size and complexity of the primary circuit.

 

That matters to me, as a leak or burst or other failing in the primary circuit is mission critical ie your engine will overheat and then stop. A leak in a secondary circuit just results in a less toasty boat and water (and antifreeze) all over the cabin floor - annoying but not mission critical.

[Guest]

I'd support your mad idea too - I added two radiators running off the heat exchanger that came with my engine, but was not used. (Photos)

 

In addition to the point about not adding too much to the bypass circuit, as that can make the engine run too cool, the advantage of using heat exchangers is that it minimizes the size and complexity of the primary circuit.

 

That matters to me, as a leak or burst or other failing in the primary circuit is mission critical ie your engine will overheat and then stop. A leak in a secondary circuit just results in a less toasty boat and water (and antifreeze) all over the cabin floor - annoying but not mission critical.

I do like the idea of using a heat exchanger, largely for the reasons you state. I connected into the calorifier feeds for evaluation purposes, but so good was the result, it is like that 11 years later. I have not been aware of any undercooling (Vetus 415 engine.) If using any extra rads I would definitely go the heat exchanger route thoguh.

Absolutely no reason not to, I have done it in the past for fishing boat wheelhouses and there are commercially available matrix with from one to several duct outlets to the job quite nicely, one point worth noting is to incorporate a thermal relay to prevent fan operation until the coolant is at operating temperature for best results. Many Scandinavian boat builders have incorporated a similar system for windscreen demisting for many years.

Agreed. The rad I fitted has a thermal relay.

[johnmck]

We have a heat exchanger, so whilst charging up, the boat was toasty with the radiators as hot as when the central heating is on. Comes in handy on days like today.

[RLWP]

I have not been aware of any undercooling

 

Have you got a temperature gauge?

 

Richard

[Top cat]

All very interesting, I have wondered about doing something similar myself, does any one have photos or a schematic they would like to share?

Alde make a heat exchanger designed to get heat from the engine cooling circuit into the cental heating circuit. Never used or even seen one but it might come in handy. http://www.alde.co.uk/itemdetails.php?itemId=58

 

Top Cat

[Guest]

 

Have you got a temperature gauge?

 

Richard

Aye. Never seemed to make any difference, but I suspect that is down to minimal extra pipe length over and above calorifier. I got lucky. The other thing is i am rarely a "tickover charger" usually using a genny if moored. I suspect if idling for hours that slow warmup might be an issue.

Edited to add we have valves in the pipework, so when the heater is idle (most of the time) the valves are closed.

Edited August 31, 2015 by Guest

[nicknorman]

All very interesting, I have wondered about doing something similar myself, does any one have photos or a schematic they would like to share?

Alde make a heat exchanger designed to get heat from the engine cooling circuit into the cental heating circuit. Never used or even seen one but it might come in handy. http://www.alde.co.uk/itemdetails.php?itemId=58

Top Cat

I used a plate heat exchanger from eBay, and a solarproject pump:

 

http://www.ebay.co.uk/itm/Stainless-steel-plates-PLATE-HEAT-EXCHANGER-brazed-NORDIC-TEC-25-65kW-insulation-/252059918827?var=&hash=item3aaff121eb

 

 

When choosing a heat exchanger, be sure to get one with connectors that are easy to connect to. And bear in mind that the thermal transfer rating (ie kW rating) is based on a big temperature difference which, since you want the rads as hot as the coolant, you won't achieve. I think I went for 25kw and it was barely enough to get about 3 or 4kw out. The rating doesn't mean that rate of heat transfer will be achieved since it is proportional to the temperature difference and therefore self-regulating. Ie you can't over-spec it.

 

Also, have the flow directions opposing ie the hot side of the inlet on the same side as the hot side of the outlet, in order to maximise the heat transfer.

Edited August 31, 2015 by nicknorman

[ROBDEN]

Definitely not mad, many boat have radiators fed by engine coolant. Basically, of course its not "free" heat because you're burning the fuel to generate it, but its increasing the overall efficiency and using the heat which would otherwise be wasted. Its possible to overcool the engine, or greatly prolong its warm up time, though.

Shouldn't the engine thermostat take care of that?

[Top cat]

Thanks

 

Thats a LOT cheaper than the Alde offering at £170, mind you everything they sell is overpriced.

How big is it , I dont see any dimensions on the e bay listing

 

Top Cat

Edited August 31, 2015 by Top cat

[nicknorman]

Thanks

Thats a LOT cheaper than the Alde offering at £170, mind you everything they sell is overpriced.

How big is it , I dont see any dimensions on the e bay listing

Top Cat

The one I got was a different make, but I think they are all much the same size (including the Alde one). The different power ratings are just thicker or thinner. You can perhaps get the general idea of size from the photo bearing in mind the 28mm gate valve.

[dor]

If you just want to get a bit of background heat you may already have a system installed. The calorifier can be used as a heat exchanger, you just need to fit a switch so you can turn on your CH pump without running the boiler. You may need to balance the flow; I have this by using two 22mm full flow lever ball valves, on in the rad circuit (except bathroom rad which is always on) and one on the calorifer circuit. These are there anyway so I can select HW, heating or both.

 

The rads won't get as hot as they would with the boiler, but they can provide a reasonable amount of heat.

[Scholar Gypsy]

Paul C, on 31 Aug 2015 - 6:57 PM, said:

Definitely not mad, many boat have radiators fed by engine coolant. Basically, of course its not "free" heat because you're burning the fuel to generate it, but its increasing the overall efficiency and using the heat which would otherwise be wasted. Its possible to overcool the engine, or greatly prolong its warm up time, though.

Shouldn't the engine thermostat take care of that?

 

It depends on how your system is set up. On my boat - and I think this is not unusual:

 

• the calorifier runs from the bypass circuit,
• the output for this is taken before the thermostat (so that the water has somewhere to go when the thermostat is shut)
• when the engine warms up, the thermostat opens and then the water can flow around the keel tank etc
• So if you put too many heat sinks into the calorifier circuit, then it can take longer for the engine to warm up, and indeed if you are running it gently (narrow canals etc) it may never get to its optimum temperature.
• With our engine the boatyard didn't want to put any radiators into the calorifier circuit
• The rads I mentioned above run from the main heat exchanger. That only gets hot once the thermostat has opened ie the engine has reached 82 degC.

[Chewbacka]

I don't think you could use a car heater unit as it is small bore hence low flow and if you put that in series with your skin tank I can see a real risk of engine over heat, especially on rivers etc. however you may be able to use a car radiator but again not too much extra pipe length or tight bends as it will impede the flow. You would also need to consider how to insulate the radiator as on a hot day when your fan is off the radiator will release heat into the engine space making the alternators etc run hotter. So though I think your idea is doable,you may have short term and long term problems if you don't fully consider the thermal management issues.

[PeterDHS]

You need a biscuit tin, two computer fans cut into the lid, a switch,and a bleed valve. Plus hoses in parralel to the calorifier feed, and whatever ductwork/wiring required. I took the electrical feed from the horn switch.

Ours is housed in the calorifier cupboard at rear of boat, ducted under the bed and exits in the central bathroom. It means on a wet day the bathroom is tropical for defrosting me and drying clothes without/before firing up the stove. With the bathroom door open the whole central portion of the boat is warmed.

Not noticed any drop in engine temp (70), or any downside at all. Go for it.

 

I fitted a bleed valve on a high t-off which means I can easily bleed the heater matrix (ex fiesta) and the calorifier.

 

Peter