Hot Water from Engine Calorifier vs Diesel Heater? - Canal World

My hot water currently comes from the engine which heats water in the immersion tank, but the boat also has a Mikuni diesel heater with radiators which according the manual can also be used to heat the hot water. So, just wondered if it's better while moored to run the engine to heat the water and also charge the batteries or if I just want hot water to plumb the diesel heater into the immersion?

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In at typical narrowboat the Mikuni should be baled to do both at the same time, heat the hot water and heat the radiators. There may be valves that allow you to turn the radiators off in the summer and/ or select rads, hot water, both.

If you have a shoreline to keep the batteries charged, then not running the engine would be best in most people's eyes because it reduces the wear on an expensive item.  With no shoreline, we are in or approaching the time of year when solar is unlikely to provide enough charge, especially as the Mikuni uses electricity all the time it is running, so the chances are that you will have to run the engine.

11 hours ago, GUMPY said:

If you have an immersion heater that's the cheapest, easiest, quickest way to het the water when on shore power.

Unless you wake up in the mornings and want to quickly heat up the boat with the diesel heater for an hour or two, in which case hot water can be obtained as a free byproduct.

It depends on the time of year, the boat and other forms of heating available, but for the last few weeks I've been letting my stove die down overnight and don't get it going in the morning because it will be too hot in the boat during the day, but I still need to heat the boat up first thing so I use the Webasto and also get what's effectively free hot water.

18 minutes ago, Paul C said:

I don't think its a "free" byproduct in that case. 

Why not? If I'm primarily using the Webasto to heat the boat for a couple of hours on a nippy morning then the hot water comes as a free byproduct as far as I'm concerned.

It's the same as people saying they get free hot water while cruising. If you're primarily using the diesel for propulsion and you get a tank of hot water then that's also a free byproduct. What's the difference between that and what I'm saying?

Edited October 12, by blackrose

13 minutes ago, David Mack said:

Webasto will use more fuel if it is heating the calorifier and the radiators, compared to heating the radiators alone. For the engine it will make no difference. Without the calorifier you will just shed more heat through the skin tank.

Really? I really don't think there's much in it and I'm sure any difference is cheaper than using the immersion to heat the calorifier from cold, which is the point I originally responded to. My Webasto Thermotop 5kW uses about 0.35 litres/hour (with the calorifier). I wonder how much less it would use without?

What about a stove with a backboiler connected to a calorifier? Would you say that's not free hot water as a byproduct of using the stove for heating, or are we saying it will use more coal so it's not free? I'm sure some people on the forum have been claiming it's free and nobody has ever challenged them.

Edited October 12, by blackrose

22 minutes ago, blackrose said:

What about a stove with a backboiler connected to a calorifier? Would you say that's not free hot water as a byproduct of using the stove for heating, or are we saying it will use more coal so it's not free? I'm sure some people on the forum have been claiming it's free and nobody has ever challenged them.

1st Law of Thermodynamics - energy cannot be created or destroyed - would suggest not. In the case of the stove, unless the backboiler is up to the same temperature as the rest of the stove (which will never happen), it will act as a heatsink and x units of coal will produce slightly less temperature rise. You could put more coal on to get the boat to comfy temperature (in a similar time to a stove with no backboiler), or you could put the same amount of coal on and it would take longer (and there would be less coal remaining unburnt).

Similarly, the fact that the calorifier is in the circuit will act as a heatsink and the diesel boiler would either work harder, or go for longer. 

Contrast with the example of turning the engine on only to charge batteries vs charging batteries AND heating water. An engine is effectively a miniature CHP plant (combined heat and power) and because the heat which would be otherwise wasted (to the environment, via the skin tank warming some canal water) is also being used in a useful way, the overall efficiency will go up significantly if both tasks are accounted for.

25 minutes ago, blackrose said:

Really? I really don't think there's much in it and I'm sure any difference is cheaper than using the immersion to heat the calorifier from cold, which is the point I originally responded to. My Webasto Thermotop 5kW uses about 0.35 litres/hour (with the calorifier). I wonder how much less it would use without?

What about a stove with a backboiler connected to a calorifier? Would you say that's not free hot water as a byproduct of using the stove for heating, or are we saying it will use more coal so it's not free? I'm sure some people on the forum have been claiming it's free and nobody has ever challenged them.

 One only has to think about the energy the stove or Webasto is passing into the system and the amount of energy that therefore needs to come from the fuel. Stove or Webasto will have to provide the energy to heat the water in the calorifier so if they do not provide more energy the time needed to get the boat and calorifier up to temperature will be longer so although, under those circumstances, the appliance will burn the same amount of fuel per minute, but it will do it for longer so more fuel is burned. That is all nice in theory and confirms Paul's assertion, but as the time taken to heat the calorifier is fairly short as long as no hot water is drawn off then The amount of extra fuel used may not be that great, and as in the majority of cases the calorifier is always heated that extra fuel burn would be considered normal, so in that respect it looks like a by product of heating the boat, but it is still not free heat.

1 hour ago, David Mack said:

Webasto will use more fuel if it is heating the calorifier and the radiators, compared to heating the radiators alone.

I was looking at a Webasto plumbing diagram recently and it showed the calorifier heating coil from the diesel heater connected like an extra radiator on the main radiator circuit. If that is normal then I assume people install a valve to exclude the calorifier at times?

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Does anyone know the emitter wattage of a calorifier coil? It would be interesting to know what proportion of the diesel heater output goes to heating water.

1 minute ago, Gybe Ho said:

Does anyone know the emitter wattage of a calorifier coil? It would be interesting to know what proportion of the diesel heater output goes to heating water.

It depends on the difference in temperature of the heating and the heated water.  But 500w or w has been mentioned here in the past for typical circumstances.

Back to Blackrose point, as has been said, engine heat is a waste product that would otherwise be dumped in the canal whereas calling for hot water from the Webasto is increasing its demand.  However, it is quite possible (depending on size of boiler and number of rad and other things) the Webasto will run more efficiently when made to work harder - so, at a guess, the increase in diesel burned could well be quite small.

6 minutes ago, blackrose said:

Ok so I stand corrected. It's not free but it is a byproduct and given the difference between diesel consumption of 0.35 litres/hour with the calorifier and whatever marginal difference in diesel consumption heating 4 rads without the calorifier, it's also a cheap byproduct.

Not really. There are 10kWh of raw energy in a litre of diesel but it is difficult to extract more than 3kWh in anything fitted on your narrowboat. With regard to cost this likely works out near to the kWh price a marina will charge for shore power.

Those 4 rads on your boat are unlikely to consume more than 2Kw even when the cabin temp is freezing. It takes 3 kWh to raise 55 litres of water from cold to 60 (c). If a calorifier coil is designed to heat the tank is a useful time period we can conclude more than 30% of your diesel heater output is taken by the calorifier.

25 minutes ago, Gybe Ho said:

was looking at a Webasto plumbing diagram recently and it showed the calorifier heating coil from the diesel heater connected like an extra radiator on the main radiator circuit. If that is normal then I assume people install a valve to exclude the calorifier at times?

That is perfectly normal, but any single port fitted is usually to allow balancing, like the lock shield valves on radiators. Some use a three port valve to allow the heat to be directed to rads only, calorifier only, or both. This would usually be used to allow the calorifier can be heated in the summer without having the radiators emitting heat and without messing with all the radiator valves. Arguably more important now a lot of solar is in use, so engines do not have to be run frequently for battery charging..

5 minutes ago, Tacet said:

It depends on the difference in temperature of the heating and the heated water.  But 500w or w has been mentioned here in the past for typical circumstances.

Thanks. I inferred a similar figure by working backwards from a reasonable expectation of heat up duration.

Is HW a nearly free incidental by product of diesel central heating? Scientifically definitely not.

In the case of a narrowboat operating in holiday mode where the cabin and calorifier is never cold and then the HW "byproduct" cost is less than the end of meal gratuity at a waterside pub.

In the case of a CCer narrowboat offgrid for the winter and where the calorifier is bought up to 60(c) twice a week then yes the cost is noticeable, say £10 to £20 a month however the hardcore offgridder will have a back boiler and the stove will run on scavenged wood.

You're well adrift  with your additional monthly  cost of heating a calorifier when the CH is operating anyway.

£20 will buy 20 litres of diesel at the domestic split.  Blackrose says his Webasto uses about 1/3 litre per hour - and that is for both space heating and domestic hot water; let's say (again generously) that the hot water consumes one third.  

So, he can have the Webasto heating the calorifier for about 180 hours per month for £20 of diesel.   Which is more than enough to heat a cylinder twice a week!

1 hour ago, Gybe Ho said:

Not really. There are 10kWh of raw energy in a litre of diesel but it is difficult to extract more than 3kWh in anything fitted on your narrowboat. With regard to cost this likely works out near to the kWh price a marina will charge for shore power.

Those 4 rads on your boat are unlikely to consume more than 2Kw even when the cabin temp is freezing. It takes 3 kWh to raise 55 litres of water from cold to 60 (c). If a calorifier coil is designed to heat the tank is a useful time period we can conclude more than 30% of your diesel heater output is taken by the calorifier.

Well there seems to be some difference between your view and Tacet's who like me thinks the difference could be marginal. 

I was talking diesel consumption rather than heater output, but assuming they correlate then you're saying that if I isolate the calorifier coil my Webasto would only be burning 0.25 litres/hour (30% less than my current consumption). Sorry but that just doesn't stack up with the consumption figures I've got because once the calorifier is heated (30mins) it's no longer drawing heater output and I'm running the heater for often much longer than that.

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Edited October 12, by blackrose

You can be sure the internals are identical. The 4 vs 1 hot air vents is simply a different end piece molding. Focus on the peripherals. Focus on the controller. Does it have the features you want. Try to find out if it uses the universal motherboard. If it does replacing the controller is easy.

I see these have the soft green fuel line. Likely to cause problems. Plan on replacing with the nylon kind.

You're probably going to need longer exhaust tubing.

Understand it is not likely to produce 8 KW heat output. These are Espar D4 knockoffs. A D4 produces 4 KW heat.

I just bought an Hcalory 8 KW heater. No complaints so far but it's output is nowhere near the output of the 8 KW Espar in the boat.

Years ago I lived abroad in Seattle. During the relative to your location cold snaps the D4 knockoff I installed could heat one cabin at a time. i guess it's still better than having only space heaters that have to stay on low

You can be sure the internals are identical. The 4 vs 1 hot air vents is simply a different end piece molding. Focus on the peripherals. Focus on the controller. Does it have the features you want. Try to find out if it uses the universal motherboard. If it does replacing the controller is easy.

I see these have the soft green fuel line. Likely to cause problems. Plan on replacing with the nylon kind.

You're probably going to need longer exhaust tubing.

Understand it is not likely to produce 8 KW heat output. These are Espar D4 knockoffs. A D4 produces 4 KW heat.

I just bought an Hcalory 8 KW heater. No complaints so far but it's output is nowhere near the output of the 8 KW Espar in the boat.

Years ago I lived aoard in Seattle. During the relative to your location cold snaps the D4 knockoff I installed could heat one cabin at a time.

could you give any reasons?
from previous posts, the lcd switch panel tend to break down, so the knob style may last longer?

I had one several years ago on a prior boat and the control panel backlight failed. It still worked but it was very difficult to see the numbers. It's default setting was 20C or 68F which was about where I'd set it anyway so I just left it there. It didn't have Bluetooth or anything but it did have a key fob remote to turn out on and off. No temp control on it. We hung the remote on a hook in the vee berth and turned it on and off from there.
For fuel I put another pick up tube in the main tank and cut it a couple inches shorter than the engine pickup so the heater couldn't use up all my fuel.

I had one several years ago on a prior boat and the control panel backlight failed. It still worked but it was very difficult to see the numbers. It's default setting was 20C or 68F which was about where I'd set it anyway so I just left it there. It didn't have Bluetooth or anything but it did have a key fob remote to turn out on and off. No temp control on it. We hung the remote on a hook in the vee berth and turned it on and off from there.
For fuel I put another pick up tube in the main tank and cut it a couple inches shorter than the engine pickup so the heater couldn't use up all my fuel.

yes, I remember the number 68F. so I was reading your post. The UK has just banned the importation of Vevor brand of diesel heaters and Vevor has started a recall (January 11, ). The reason? "potential for passengers to inhale dangerous levels of poisonous gases should the product not be installed correctly." Okay. Same could be said for my Ford Lehman diesel engine (actually made in the UK).

Apparently, the distinguishing fault of the Vevor diesel heater is that the installation instructions aren't clear. Same could be said of the majority of items from China, including other diesel heaters.

Interesting about Vevor agreeing to a recall. I would have thought remediation would be simple and less costly. Send out a notification with clear installation guidelines and a free CO monitor. Not only would the diesel heater be safer, but also boats with diesel engines (or any engine). Hard to understand why poor installation is a fault. Poor instructions? Yes. It's what we all expect from cheap Chinese goods. Buy as you say, why not issue better instructions as opposed to a recall?

In I purchased a Calaer heater from Fisheries. I think it was a re-marketed Chinese D4 knockoff. Came with excellent instructions. Don't install in the inhabited spaces, use high temp sealant on the exhaust joints.

It was on overpriced POS but the Chinese heaters had not hit the market big time yet.

The UK has just banned the importation of Vevor brand of diesel heaters and Vevor has started a recall (January 11, ). The reason? "potential for passengers to inhale dangerous levels of poisonous gases should the product not be installed correctly." Okay. Same could be said for my Ford Lehman diesel engine (actually made in the UK).

Apparently, the distinguishing fault of the Vevor diesel heater is that the installation instructions aren't clear. Same could be said of the majority of items from China, including other diesel heaters.

Interesting about Vevor agreeing to a recall. I would have thought remediation would be simple and less costly. Send out a notification with clear installation guidelines and a free CO monitor. Not only would the diesel heater be safer, but also boats with diesel engines (or any engine).

Is vevor is the only victim while other knockoffs continue to be allowed to sell in UK?

It couldn't be more popular than others, given all are derived or copied from the same technology

The UK has just banned the importation of Vevor brand of diesel heaters and Vevor has started a recall (January 11, ). The reason? "potential for passengers to inhale dangerous levels of poisonous gases should the product not be installed correctly." Okay. Same could be said for my Ford Lehman diesel engine (actually made in the UK).

Apparently, the distinguishing fault of the Vevor diesel heater is that the installation instructions aren't clear. Same could be said of the majority of items from China, including other diesel heaters.

Interesting about Vevor agreeing to a recall. I would have thought remediation would be simple and less costly. Send out a notification with clear installation guidelines and a free CO monitor. Not only would the diesel heater be safer, but also boats with diesel engines (or any engine).

Is vevor is the only victim while other knockoffs continue to be allowed to sell in UK?

It sounds like UK custom inspected a shipment of Vevor heaters and made the decision on Vevor. I don't know if they were aware of thousands of identical units coming in under other brand names. I'm sure they are now.

We also turn ours off at night and enjoy the toastiness of a down comforter. Since our unit came with a remote fob, we can simply turn on the heat for a few minutes before getting up to start the coffee. I haven't yet found a fob to start the coffee.

I was at the boat today and turned on the diesel heater. I just bought a little digital thermometer that shows the "inside" temperature and three remotes. I put one of the remotes in the engine room. I was surprised to see that the diesel heater raised the engine room temperature at the same rate as the cabin temp even though there are no registers in the ER. ER is smaller and the remote is near the ceiling, but still a lot of heat radiating off of just the exhaust in the ER and maybe the first couple of feet of ductwork before it enters the cabin. I'll have to think about whether there is a way to get more of that heat into the cabin. The heaters do "waste" a lot of heat out the exhaust. Youtube has numerous videos of hackers trying to recover exhaust heat. Some are clever and show promise, some as usual for Youtube are pretty stupid.

I see three challenges, I'm sure there are more but as "they" say, I don't know what I don't know.

• If I were to pass air over or adjacent to the exhaust pipe and the pipe leaks, even a tiny bit, I am introducing exhaust gasses to the living space.
• What happens when diesel exhaust is cooled? What by products are generated? How do those affect the exhaust tubing? A quick search turns up this paper Effect of cooling recirculated exhaust gases on diesel engine emissions. I haven't read it but it may help to understand the chemistry.
• These heaters don't like their exhaust restricted, enough restriction and they won't light.

One of the youtubers experimented with using a diesel EGR cooler. This would mean transferring the "waste" heat to water, then pumping that water to the living space to an air handler similar to what hydronic systems use. Yes, complicated, more parts, more power required. But if any exhaust leak in the system introduces the toxins to the water, I won't be breathing the water. It might be better to use the EGR cooler to heat domestic water?

You're a clever out of the box thinker. I will be interesting to see what you come up with if you decide to try it.

I was surprised to see that the diesel heater raised the engine room temperature at the same rate as the cabin temp even though there are no registers in the ER. ER is smaller and the remote is near the ceiling, but still a lot of heat radiating off of just the exhaust in the ER and maybe the first couple of feet of ductwork before it enters the cabin. I'll have to think about whether there is a way to get more of that heat into the cabin.