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Calorifiers and hot water


Guest plesbit

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So, who’s going to have £50 with me then?

Cooling is a simple matter of physics and mathematics, heat produced is carried away by the coolant, if the heat produced is too little for the always over engineered systems on a marine engine it will not get up to temperature, it was never designed to pootle about producing no heat. Bear in mind that your engine will be producing something like a 10th of the output using the 20 or so HP required to drift along at 5mph whereas a BMC 1500 or Perkins will be running at 50 to 75 % of it’s rated capacity.

Have you asked many KA owners the question Simon? I suspect most of them stay tied up to shorepower 90% of the time and rarely overnight on the broads anyway from what I have oberved.

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So, who’s going to have £50 with me then?

Cooling is a simple matter of physics and mathematics, heat produced is carried away by the coolant, if the heat produced is too little for the always over engineered systems on a marine engine it will not get up to temperature, it was never designed to pootle about producing no heat. Bear in mind that your engine will be producing something like a 10th of the output using the 20 or so HP required to drift along at 5mph whereas a BMC 1500 or Perkins will be running at 50 to 75 % of it’s rated capacity.

Have you asked many KA owners the question Simon? I suspect most of them stay tied up to shorepower 90% of the time and rarely overnight on the broads anyway from what I have oberved.

I'm tempted David :naughty:

If I leave my 300hp Subaru ticking over in the street it will still reach it's designed operating temp' That if some little bugger doesn't jump into it and dissapear two guns

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I see your point Rod, but what will happen is that as some of the cold water that has been sat in the Calorifiers pipework enters the engine block, it does indeed lower the coolant temp, thus closing the thermostat again until the 80 C is re achieved again then re opens. This Ballet will go on until the water in the Calorifier has reached a similar temp to that of the coolants designed running temp. Usually 30 mins or so... cheersbar

Exactly - the whole point of a thermostat, ANY thermostat (be it the one in your engine your fridge) is to regulate temperature. Temperature goes higher it opens, temperature goes lower it closes, thus the overall situation remains roughly at the same temperature.

Believe it or not, I can see everybody's point. I hear David, and to be honest he's saying exactly what I thought 3 years ago with Silver Dream. She took longer to heat up than any hireboat I'd ever used and I put that down to exactly what David says here.

Bear in mind that your engine will be producing something like a 10th of the output using the 20 or so HP required to drift along at 5mph whereas a BMC 1500 or Perkins will be running at 50 to 75 % of it’s rated capacity.

The port AQD32 in Silver Dream was more than double the power of any broads cruiser I've come across and worked in tandem with another identical starboard engine. Consequently it used bugger all power to attain river speeds, plus it was a 6 cylinder mass of cast iron which sucked up a lot of heat. However, eventually (normally about an hour) it had managed to generate a tank full of piping hot water. So it doesn't take much logic to extend that the AD41P, which is twice as powerful, is doing even less work and generating even less heat. Add in that some cooling is done directly by raw water, such as the oil cooler, and it is perfectly logical that the engine would never get warm enough to open the thermostats at all because it will be losing heat as fast as it is generating it. Even so, it seems to be just a bit too cool. David hasn't said whether he had the same problem with Kingfisher when she was on the Broads - similar sized boat, similar powered engine, slightly different technology but same laws of physics.

I haven't asked any AD / KAD owners the question - I don't know who has any but it's a fair bet that Jupiter's Mist and Crackerjack are running these engines. I have, however, managed to consult the engineers at the Volvo dealer in Brundall and they immediately said that sounds wrong and the engine should still heat up to temperature, albeit slowly. If I get a chance I'll pull the thermostats out at the weekend and test them. In fact the engineer thinks I might even find they're not in there at all. I hope he's right and David's wrong but, in my experience when it comes to technical things David is very rarely wrong which doesn't bode well for my hopes of getting some decent hot water. And jimbo, you're very brave for taking him on! ;)

Perry, that also crossed my mind, but the luke warm water out of the hot water system appears to back up results from the temperature sender - unless, that is, it simply needed more time. From Brundall to Surlingham Ferry and back - that was how long we gave it. Not sure how much that is in real time but in Silver Dream it generated enough hot water for a nice shower.

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I reckon it's about 40 mins (there and back) which should be getting close to enough time. Plus we were punching on the way there, the revs getting up to around 1500rpm for that. On the way back they were about 1200rpm and the engine temperature actually dropped!

But you may be right - not enough time. Still, for the sake of a bit of time on Saturday to whip the stats out and test them it's probably worth doing. Sunday we may take her a bit further, say Brammerton.

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Firstly Simon welcome back to the "Wet ones " I am not in a position to comment on all the informed previous posters.Several observations for me would be that if one engine was not reaching temperature then the second engine would? or do the pipes to the colorfier join and go through one coil? Could be as you say no thermostats fitted but then the temperature would increases gradually ? Our system is providing the opposite effect .within half an hour the gauge reads 80c and the water is to hot to touch .We are going to fit a temperature mixer (between hot and cold )which will only send water to the taps at the selected temperature.A long shot but you may have something like this connected to the system but set low?

cheersbar:party2:

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Guest chriscraft

hi the simple answer is change the stats,they are probably the originals,They could also have gunge on the seats alowing leaks,you could try a bottle of coolant treatment on the closed side but the open/freshwater side you would have to remove to check...i am woffling just change the stats :wave

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Yep, I'm going to take the stats out (assuming they are there) on Saturday. I won't have time before then due to something called work. I don't believe I can make any further observations until the stats have been examined and tested. I have to say in my years of owning old cars I have had many thermostat failures and every single one has ended up failing to close rather than failing to open. I don't know what the life expectancy is of these things - the engine is 8 years old.

The thing is David, you are saying that Kingfisher DID get up to temperature (85C) on the rivers, she just took a good 60 mins or so to do so because so little work was being done by the engine. Yet you also appear to be saying, unless I have misunderstood, that Grenick probably won't get up to temperature. Why the difference?

It's certainly true I'd love to see what a nice run across Breydon would give us - you could certainly tell the difference on Silver Dream if she'd been at sea or on Breydon.

Roy - there's only one engine in this one!

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No Simon, I'm saying it will take a long time to get there not that t never will. Oddly enough I get the same thing in my diesel car. If I go out straight into stop start London traffic it takes ages to warm up but if I go straight on to the M11 link road at 50mph it’s up there in no time.

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Guest chriscraft

If there not there that would explain the constant low temp,you could have a another problem if you put them back ie overheating which removal of the stat(s) is an easy cure keep us posted

chers trev

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No Simon, I'm saying it will take a long time to get there not that t never will. Oddly enough I get the same thing in my diesel car.

Right, thanks for clearing that up. Did you notice that I said on the return journey with the tide behind us and running at reduced revs the engine temperature actually reduced from that of the outbound at higher revs? But we won't really know the answer until we do a longer run and it may be some time before we get the opportunity to do that, whereas I will have the chance to check the stats are fitted and test them if they are.

Thanks for the suggestions everyone.

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Simon your 200hp engine will produce around 120kw of heat at full chat and still around 15kw at river speeds an average domestic boiler is 12kwh. Your calorifier will accept around 3kw. Your stat is there to regulate the temperature by controlling the flow to the heat exchanger. It sounds like your stats have been removed or stuck (unlikely) If you replace the stat why not replace/upgrade the impeller at the same time and why not try water wetter made by redline I have seen this used at santa pod to great effect for added cooling.

Jonathan

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If the stats have been removed though, my concern is why?? :?

Actually that would MY concern. ;)

No seriously though, this has already been discussed and it would not surprise me at all if they're not in there. If that turns out to be the case then clearly the first course of action is to order some up and get them put in. If the engine then threatens to overheat I'll likely take them out again until after our week out on the rivers at which point we can then investigate more closely.

Thanks for that Jonathan. The engine was fully serviced (by the Volvo dealer) recently and replacement impellers are listed on the invoice. It is clear that the belts are all new so I see no reason why they would not have changed the impeller. I've got some spares left over from Silver Dream anyway - according to the boxes they came in they fit the AD41's too so I've got plenty if needed.

Jimbo, if we're crossing Breydon together for the NBN birthday bash you may end up having to rescue me if I overheat. :lol:

Of course, having said that, have you seen the tide times for that day? Yikes!

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Simon,

Ring ASAP supplies and explain your engine temperature problem and ask them about Hotpots.

Sorry if something similar has been posted but I'm off to work and only read pages 1 and 5 :norty:

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Alrighty then.

- Stats both present and correct.

- Port side stat jammed open by a stone causing a gap of around 3mm all the way around.

- Stats removed and tested. Didn't have a thermometer but as they got up to within touching distance of boiling they were both clearly wide open.

- Port stat does not fully close, the spring is probably bent from its previous problem, but the gap is down to around 1mm. In due course I'll get another one ordered up.

As with what David says it, I expect it will still take quite some time to warm the engine up as it doesn't generate much heat and there's a lot of cast iron there to heat up, but a 3mm gap around one of the stats certainly cannot have been helping.

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Hi Simon

A lot of valuable info in this thread, may I add my twopennith. are the calorifiers running of the port engine with the faulty thermostat? If so that is your problem. Marine engines, no mater what size (Well In our sector anyway) with sealed pressurised cooling systems are in effect no different to most car engines. the only difference is the radiator is replaced by a heat exchanger cooled by raw water. Providing the thermostats are operating correctly I would expect the engines to be up to full operating temperature 80-88 c within 10-15 mins maximum even at idle.

cheersbar

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Hi Col,

Well we're looking at heading out for a bit today. There is still a small gap around one of the thermostats so there'll still be some flow through the heat exchanger and calorifier but there's nothing I can do about that until I swap out the offending stat. I'll have a word with Keyparts on Monday. But the stat is only open by about a 1mm now so it will be relatively restricted flow. But, as David says, there is nearly half a ton of cast iron to heat up, which is going to take some time especially with only low power usage.

Something else to consider. You fry something, the pan becomes extremely hot. If you then blow on the pan to cool it down it will take a very, very long time before it cools enough that you can touch it. If you pour cold water on it, it will pretty much cool to touchable temperature instantly. Water is a far better substance for heat transfer. The AD41 has a huge great oil cooler which is raw water cooled, so not controlled by the thermostats. That will keep the oil temperature cool and will therefore retard what is going to be a very slow heating up process anyway.

I think there's a lot of learning to be done with this boat. Comparatively Silver Dream was quite a simple beast!

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Right, found out nothing useful during Sunday's jaunt.

It would have been nice on the longer run that is Brammerton, and with the thermostat, whilst not fully closing, having a much smaller gap than before but sadly some dimbo thought it would be a good idea to test the immersion on the Saturday afternoon - and then went home without either testing the water or switching it off. Anyway, next day, and £3 of shorepower later, I can testify that there was enough hot water to cook a lobster without the need for a kettle or pot. Five hours later when we left the boat the water was still just as hot but whether that was still from the shorepower or from the calorifier is anyone's guess. The engine did run hotter, but not by a huge amount and never even got close to fully warmed up - probably around 60C I'd say, if the gauge is accurate.... and if I am reading it right (the gauge appears to be logarithmic and the intervals are unclear until the 80C mark).

I doubt we'll get a decent shot at it before we head out on our proper holiday.

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Hi Simon

Is the engine with the good thermostat running at full temperature i.e. 80-88 c. Does the calorifier run of the port or starboard engine? With most thermostats they will be set to start opening at 80-88c. At river operations (low Speeds) the thermostat will probably only open 1-2mm max as that will be enough to regulate the temperature. As with a car it will only fully open when under heavy load. If it is open as you say, you will never reach operating temperature.

cheersbar

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