Calorifier flow cooling Hot Water Tank?

[Sea Dog]

Hi All,

 

Because the very hot water at the end of a day's cruising is only warm in the morning, I've long suspected that I may have the issue where flow in the calorifier circuits is cooling the domestic hot water tank.

 

This has been discussed here before so I've done a fair bit of reading about it and seen that the solution might be a non-return valve (NRV) or high points in the lines. I've also tried in the past to identify a suitable NRV for 5/8 inch internal diameter rubber hose without success.

 

Being alongside and on shore supply at the moment has offered the ideal opportunity of a fuller investigation whilst I have a tank of piping hot water via the immersion heater at the same time as both the engine and eberspacher circuits are stone cold.

 

At the vertical hot water tank located amidships, both of my calorifiers (upper eberpacher and lower engine fed) have cold bottom hoses and hot top hoses. If there was no flow at all I would expect all of these connection points to be roughly similar temperatures, right? The temperature differentials are stark. Both sets of pipes rise from the tank connections, the engine ones by about 2 feet to a duct at about 3/4 the height of the top of the tank, the eberspacher about 18 inches due to its calorifier being higher.

 

Going aft (20 feet-ish) to the engine space, neither small bore plastic eberspacher pipe is noticeably warmer than the other, but at the engine (Beta 43) the rubber 5/8 inch calorifier upper (supply) hose is warm (not hot) whilst the calorifier lower (return) hose is stone cold.

 

Do the panel think these symptoms are typical of the circulation issue? Would they agree that the eberspacher circuit losses are small enough to be ignored? If a non-return valve is the solution, where would it be best positioned and can anyone recommend a source for a suitable one which would fit into a 5/8 inch internal diameter rubber hose circuit?

 

Many thanks in advance.

[BargeeSpud]

Air lock? I've found that when my hot water temperature drops off, it usually means my coolant needs topping up & air is probably restricting the flow through the calorifier. For your Eberspacher to have the same problem could mean you have air in both supplies to your calorifier.

 

First, ensure the Eberspacher header tank has water in it, then run it, bleed your radiators & top up the tank as you go. That should sort the Eberspacher if it does have an air lock. For the engine, try running the engine from cold with the filler cap located on or near the thermostat housing off (not the expansion tank cap, if you have one), if you have air in the system, the water level will drop, so keep topping up the water as the level drops until it stops dropping.

 

Something safe & simple for you to try, so see if it makes a difference, if it is air, then the difference should be marked & your pipes should run hotter.

[Paul C]

In our boat, the calorifier IS the hot water tank - ie they're one and the same, its just a different name for the same thing. This makes reading your post confusing.

 

What do you mean by calorifier?

Hi All,

 

Because the very hot water at the end of a day's cruising is only warm in the morning, I've long suspected that I may have the issue where flow in the calorifier circuits is cooling the domestic hot water tank.

 

Being alongside and on shore supply at the moment has offered the ideal opportunity of a fuller investigation whilst I have a tank of piping hot water via the immersion heater at the same time as both the engine and eberspacher circuits are stone cold.

 

 

If the immersion is able to heat the tank and the 'circuits' are stone cold, then its not thermosyphoning which is removing the heat.

 

Maybe its just that the hot water tank isn't very well insulated?

[Keeping Up]

Is there any possibility that the flow and return pipes from the engine to the calorifier have been swapped over? When mine got accidentally swapped over, the engine would always cool the calorifier overnight.

[BargeeSpud]

Is there any possibility that the flow and return pipes from the engine to the calorifier have been swapped over? When mine got accidentally swapped over, the engine would always cool the calorifier overnight.

 

That's an interesting point, I don't understand how that would work mind, so I'd be interested if someone can explain that a bit more.

[NMEA]

Simply buy a standard 1/2" BSPF NRV and a couple of 1/2" BSPM to 5/8" hosetails.

 

where would it be best positioned and can anyone recommend a source for a suitable one which would fit into a 5/8 inch internal diameter rubber hose circuit?

[Sea Dog]

Thanks for the responses so far everyone.

 

To clarify some of the points raised above:

 

The Eberspacher and the engine both heat the water perfectly well. What I meant by them being 'stone cold' was that they've not been in use so any heat in those circuits is not residual from their recent use.

 

Header tanks and engine levels are fine. Because there's no issue heating up the hot water tank by any method, I don't suspect there are airlock issues.

 

I'm using the convention 'Calorifier' for the two wet heating elements themselver and the term 'Hot Water Tank' rather than use the same name there.

 

The Hot Water Tank is modern and very well insulated - blue plasticised finish which you can't feel the tank's warmth through, but the water in there is properly hot as you can feel it at the connections and in delivery at the taps.

 

The routes of the pipe runs themselves match the hose lengths and suggest that they're unchanged since it left the builder (Simon Piper) 6 years ago. The prevoius owner put 12 hours on the boat from new in 5 years, so I don't think he'll have noticed anything to go messing about. However, the pipe getting warm on the engine is the upper one on the Beta 43, labelled as 'calorifier supply' in the Beta 43 engine manual and the top one of the pair from the engine at the Hot Water Tank / Calorifier - is that the right way round?

 

Hope that clears up any confusion and thanks again.

[ditchcrawler]

If the thermosiphon is very inefficient then the water will be moving very slowly so you may not detect the engine getting warm but your observation of the cold connections coming in seem to point to it. with no flow as you say they should all be the same temperature due to conduction.

[Loafer]

If your clarifier is below your engine, the hot water can self-circulate around your engine water jacket and keep your engine nice and warm, at the cost of your hot water reservoir.

 

We put a '90 degree' water-cock in the circuit, to be closed in passing when we stop the engine. That made a BIG difference and our water stayed decently hot til the morning. That could be replaced by an automatic solenoid valve, controlled by alternator D+ terminal. Thats wot I'm going to do one day.

 

 

ETA missed the post above whilst typing.

Edited January 2, 2015 by Loafer

[smileypete]

As Keeping up says, try swapping the hoses over if you can so top (engine) goes to bottom (calorifer), not top to top. The hose to the top of the coil should ideally go down to baseplate level at some point too.

 

cheers, Pete.

~smpt~

[Detling]

As Keeping up says, try swapping the hoses over if you can so top (engine) goes to bottom (calorifer), not top to top. The hose to the top of the coil should ideally go down to baseplate level at some point too.

 

cheers, Pete.

~smpt~

seconded.

 

Swapping the top and bottom (at the calofifier (hot tank)) engine connections will stop the thermo cycle. As the engine water is pumped around it will happily flow uphill when the engine is running.

[Sea Dog]

Thanks again fellas. So the 'Calorifier Supply' (from the top of the engine) should be feeding the bottom of the two connections on the side of the vertically mounted Hot Water Tank? Certainly it seems to be to the top one right now as those are the pipes that are warm each end.

[Keeping Up]

Yes in theory your existing setup is correct and my newly installed Beta 43 works fine that way (but then it uses a different takeoff point for the upper hose, it uses the one that the original manufacturer Kubota intended), but it is very likely that it will work better when reversed as I had to do on my old Perkins engine.

[Loafer]

I'm having a bit of a senior moment. I'm not understanding how you can stop the hot water in a hot tank from rising to the cold engine, if the engine is above the tank. Whichever way you wire up the input and output. Surely the hot water will still rise up from the top of the hot tank, to the engine, and the cold water in the engine jacket will replace it?

 

Can someone nice and patient please explain how you can stop that without a stop cock?

[adrianh]

You need to add resistance to flow in the pipework between the engine flow and the calorifier.

The water pump on my Kubota (Beta) is quite happy pushing water through a standard 1/2" bsp threaded non return valve - similar to this http://www.amazon.co.uk/BRASS-CHECK-VALVES-NON-RETURN-FEMALE/dp/B007JX2NY2.

As this is a bsp thread you can purchase hose tails with a male thread and stem in every 1/8" increment diameter to match the ID of your hose as well as a range of mm dia's.

This type of NRV has a very low cracking pressure, or you can dismantle and reduce the number of turns on the spring until it just closes.

I use the same set up on my Mikuni.

Another alternative is to use a 1/2 bsp 12/24 volt valve - spring closed type - from the solar water heating suppliers ( can't find the detail at present but mentioned in other posts).

Wire this from the ignition switch so that it opens when the engine runs, this will present little flow resistance but cost more to fit.

I would fit any of these options as close as possible to the tank.

[MtB]

I'm having a bit of a senior moment. I'm not understanding how you can stop the hot water in a hot tank from rising to the cold engine, if the engine is above the tank. Whichever way you wire up the input and output. Surely the hot water will still rise up from the top of the hot tank, to the engine, and the cold water in the engine jacket will replace it?

 

Can someone nice and patient please explain how you can stop that without a stop cock?

 

 

The motive force circulating hot water back around the engine and cooling the HWC is microscopic, and relies on the fact that water in a system tends to stratify, i.e warm water percolates higher and cool water sinks to the bottom.

 

When the hot pipe from the engine is connected at the top of engine and then to the top of the calorifier, (and vice versa for the cooler return pipe), stratification in the calorifier gets mirrored in the engine block, but if the hot flow pipe from the top of the engine is connected to the bottom of the calorlifier, and vice versa, this mirroring effect is likely to be disrupted as hot water from the top connection on the calorifier is less likely to flow downhill to the bottom connection on the engine.

 

Nothing can be guaranteed but swapping the connections over won't make the problem worse, might well reduce it, and will probably completely eliminate it. All with no messing about with valves.

 

And by the way, the calorifer doesn't care which way around the connections are to it's coil. It will work equally well either way around when there is a pump running.

 

MtB

[David Mack]

And by the way, the calorifer doesn't care which way around the connections are to it's coil. It will work equally well either way around when there is a pump running.

 

But if you want gravity circulation from a stove to a calorifier coil you do need to connect top to top and bottom to bottom.

[Sea Dog]

Useful to hear from someone who's had the issue and solved it Adrian, thanks, particularly since you accounted for NRV cracking pressure which was a concern. Also a concern is the rating to 100 degrees which seems marginal but if it works in your system I guess it's ok.

 

I'm a bit surprised that, given that it seems to be a fairly commom issue, there hasn't been a bunch of 'here's what I've done and it works' replies which would've put this thing to bed.

 

I did a bit of research into previous offerings that the connections were reversed, but Surecal's own diagrams don't differentiate between the flow and return connections and neither did any other circuit diagram I could find - it's as if it doesn't matter. However, reading through Tony Brooks' website here, I found "connect the HOT (away from the engine) pipe to the higher calorifier "coil" connection and the return to the lower one" which is how mine is connected.

 

The tails connecting my coil go directly upwards about 2 feet to join the pipework going aft to the engine, and I'm wondering whether longer tails to allow them to fall first may prevent the hot water rising so easily and break the thermosyphon?

 

While I've been typing this I've also had replies from Mike and Dave, for which I'm grateful. Mike's point about avoiding valves if possible chimes with my own inclination, and is the basis for the question about tails above.

 

Thanks again all.

[MtB]

Useful to hear from someone who's had the issue and solved it Adrian, thanks, particularly since you accounted for NRV cracking pressure which was a concern. Also a concern is the rating to 100 degrees which seems marginal but if it works in your system I guess it's ok.

 

I'm a bit surprised that, given that it seems to be a fairly commom issue, there hasn't been a bunch of 'here's what I've done and it works' replies which would've put this thing to bed.

 

I did a bit of research into previous offerings that the connections were reversed, but Surecal's own diagrams don't differentiate between the flow and return connections and neither did any other circuit diagram I could find - it's as if it doesn't matter. However, reading through Tony Brooks' website here, I found "connect the HOT (away from the engine) pipe to the higher calorifier "coil" connection and the return to the lower one" which is how mine is connected.

 

The tails connecting my coil go directly upwards about 2 feet to join the pipework going aft to the engine, and I'm wondering whether longer tails to allow them to fall first may prevent the hot water rising so easily and break the thermosyphon?

 

While I've been typing this I've also had replies from Mike and Dave, for which I'm grateful. Mike's point about avoiding valves if possible chimes with my own inclination, and is the basis for the question about tails above.

 

Thanks again all.

 

This is an overhang from when cylinders were heated by natural convection. A case of "that's how we've always done it so that's what goes on the tank labels". I'm sure Tony would agree, if asked, that it doesn't really matter with a pumped circuit.

 

 

But if you want gravity circulation from a stove to a calorifier coil you do need to connect top to top and bottom to bottom.

 

Agreed, but I did specify a pumped circuit in the post to which you are replying. Good to clarify the point in case someone reading this is installing a natural convection (gravity circulation) system.

 

 

MtB

 

 

Edit to add, there IS a circumstance where it can matter. Connecting the flow from the engine to the bottom connection can, when initially filling up, lead to difficulties filling it with water and air-locking of the circuit. Manual air vents may be needed, in particular on the top connection from the cylinder.

Edited January 3, 2015 by Mike the Boilerman

[Loafer]

 

 

The motive force circulating hot water back around the engine and cooling the HWC is microscopic, and relies on the fact that water in a system tends to stratify, i.e warm water percolates higher and cool water sinks to the bottom.

 

When the hot pipe from the engine is connected at the top of engine and then to the top of the calorifier, (and vice versa for the cooler return pipe), stratification in the calorifier gets mirrored in the engine block, but if the hot flow pipe from the top of the engine is connected to the bottom of the calorlifier, and vice versa, this mirroring effect is likely to be disrupted as hot water from the top connection on the calorifier is less likely to flow downhill to the bottom connection on the engine.

 

Nothing can be guaranteed but swapping the connections over won't make the problem worse, might well reduce it, and will probably completely eliminate it. All with no messing about with valves.

 

And by the way, the calorifer doesn't care which way around the connections are to it's coil. It will work equally well either way around when there is a pump running.

 

MtB

 

Ta MtB.

 

Whilst I see that the stratification in both the hot tank and the engine water jacket could be almost self-cancelling, in terms of motive force, that state of affairs doesn't last long though, does it?

 

Once the engine has cooled to ambient, with the hot water tank still containing hot water, I still can't see why the circulation doesn't begin.

 

My cauliflower is almost directly below my BD3, and the cauliflower circuit leaves, and arrives at, the upper part of the engine, near the water pump.

 

I certainly couldn't stop the hot water tank from warming the engine without a stop cock. If we close that, after heating the tank, it lasts for ages.

 

Is there summat wrong here?

Edited January 3, 2015 by Loafer

[MtB]

 

Ta MtB.

 

Whilst I see that the stratification in both the hot tank and the engine water jacket could be almost self-cancelling, in terms of motive force, that state of affairs doesn't last long though, does it?

 

Once the engine has cooled to ambient, with the hot water tank still containing hot water, I still can't see why the circulation doesn't begin.

 

My cauliflower is almost directly below my BD3, and the cauliflower circuit leaves, and arrives at, the upper part of the engine, near the water pump.

 

I certainly couldn't stop the hot water tank from warming the engine without a stop cock. If we close that, after heating the tank, it lasts for ages.

 

Is there summat wrong here?

 

 

With the hot and cold connections to the engine at approximately equal height, I suspect circulation WILL still begin...

 

With natural convection systems once they are convecting, they tend to continue even if the pipes go up hill and down dale. On the other hand if the pipes are not arranged to assist convection it can be very difficult to get it started, even though it continues easily once happening.

 

ISTR having the same problem with my BD3 too. But I hated it and got rid of it ASAP. Now the Kelvin fails to heat the cauliflower at all :-/

 

MtB

[Loafer]

 

 

With the hot and cold connections to the engine at approximately equal height, I suspect circulation WILL still begin...

 

With natural convection systems once they are convecting, they tend to continue even if the pipes go up hill and down dale. On the other hand if the pipes are not arranged to assist convection it can be very difficult to get it started, even though it continues easily once happening.

 

ISTR having the same problem with my BD3 too. But I hated it and got rid of it ASAP. Now the Kelvin fails to heat the cauliflower at all :-/

 

MtB

 

I'm constantly disheartened by how much you hated your BD3! I love mine! Yes I have a hankering for old and venerable, my favourite being a Kelvin J2 or 3, but it's totally out of the question for me to change it.

 

The BD3 is a stalwart among engines!

 

I

[MtB]

I have to say, they are wonderful, reliable, powerful engines and it's nothing more than personal prejudice born of the circumstances under which I acquired it. It was a compromise because Mrs MtB so wanted this particular boat after we'd looked at LOADS, when I really wanted a Gardner or a Kelvin. After the dull and boring Beta 35 it was a big step towards being a vintagey sort of engine and I hoped I would grow to like it, but I didn't. Nothing intrinsically wrong with it (other than the persistently unpleasant exhaust smoke), I just never grew to love it.

 

Would not stop be getting one again in the right circumstances though. A most excellent engine provided you understand it isn't going to cut it if you really want a proper vintage lump. I guess I fell for the Beta marketing describing it as a 'tug engine'. Which it isn't. (Whatever a tug engine IS, lol!)

 

 

MtB

[Loafer]

I have to say, they are wonderful, reliable, powerful engines and it's nothing more than personal prejudice born of the circumstances under which I acquired it. It was a compromise because Mrs MtB so wanted this particular boat after we'd looked at LOADS, when I really wanted a Gardner or a Kelvin. After the dull and boring Beta 35 it was a big step towards being a vintagey sort of engine and I hoped I would grow to like it, but I didn't. Nothing intrinsically wrong with it (other than the persistently unpleasant exhaust smoke), I just never grew to love it.

 

Would not stop be getting one again in the right circumstances though. A most excellent engine provided you understand it isn't going to cut it if you really want a proper vintage lump. I guess I fell for the Beta marketing describing it as a 'tug engine'. Which it isn't. (Whatever a tug engine IS, lol!)

 

 

MtB

 

Ah that's made me feel a bit better. Mind you, ours doesn't smoke, drink (oil) or have any other bad habits. And it's incredibly shiny. If I ever work out how to put a photo here, I'll post a picture one day!

[adrianh]

The limitation of 100 deg C on valves usually means they is unsuitable for steam use or even pressurized water systems working just above this temperature.

Your engine is hopefully only running at 80 deg C max - if not a lot of the nitrile rubber seals fitted in the gearbox and engine will have a very short life!

Items that run at higher temperatures are fitted with Viton rubber and/or PTFE seals.

As others have said, apart from the initial fill, the pumped flow direction will make little difference.

If you want details of the motorized valve, let me know and I will find it when I am next at the boat.

I have one on the radiator system, controlled via the Mikuni thermostat when on engine boat heating mode, as I was getting complaints about the boat getting too hot!