Cylinder Jacket

[mayalld]

You are saying that an inadequate skin tank is inadequate. I agree. Two completely different things. Simples

 

Richard

 

Not quite.

 

I am saying that even with an inadequate skin tank, a boat can be used for a finite period of time before it boils.

 

That period of time will be greater if the stat is 70 degrees than if the stat is 80 degrees, and it may well be that with a 70 degree stat it is actually a longer time period than the time the engine is run for.

 

Less Simples!

[Yoda]

Not quite.

 

I am saying that even with an inadequate skin tank, a boat can be used for a finite period of time before it boils.

 

That period of time will be greater if the stat is 70 degrees than if the stat is 80 degrees, and it may well be that with a 70 degree stat it is actually a longer time period than the time the engine is run for.

Less Simples!

 

No, it will make no difference. The volume of the coolant will make a difference.

 

Internal combustion engines should be run as near to the coolant boiling point as possible.

[Ray]

Ray, would it be possible to post some photographs of your installation?

 

Richard

 

Will try to take some over the weekend if I remember the camera. It won't be a pretty site

[denboy]

A Pressure Reducing Valve like this?

 

I must admit that I thought of trying this idea as well. How did you settle on 1.3 bar?

 

We haven't got an expansion tank on the outlet, nor non return valve on the cold water input. We suspect that the accumulator is doubling as the expansion tank. I wonder if this makes any difference?

 

We don't think that the calorifier has an inbuilt NRV as the PRV (Pressure Release Valve) only trips when we test it.

yes thats the valve,and i have a tower shower fitted and still works fine on the reduced pressure,and water tank lasts longer

[nb Innisfree]

Seems to me that a hotter engine needs to dump less heat into ST, a cooler engine needs to dump more into ST

[alan_fincher]

Not quite.

 

I am saying that even with an inadequate skin tank, a boat can be used for a finite period of time before it boils.

 

That period of time will be greater if the stat is 70 degrees than if the stat is 80 degrees, and it may well be that with a 70 degree stat it is actually a longer time period than the time the engine is run for.

Less Simples!

 

Oh for heaven's sake Dave...............

 

All you say is of course true, but an inadequate skin tank is an inadequate skin tank, whether you run the engine with a 70 degree stat or an 80 degree stat.

 

The difference in time before trouble occurs will be highly marginal, and the bit I have highlighted in red is highly unlikely to apply in my view.

 

Running the engine less hard will make a big difference, but the choice of stat is highly unlikely to make a difference between boil, or not boil, unless you do very short travelling days, (which Ray has already made clear he generally does not...).

 

If he is not boiling his engine now, I am prepared to bet for absolute definite he will not do so with a hotter stat.

[Ray]

I managed to take the pictures last night but the connection speed is too slow so doubt I'll get them uploaded until after the weekend. I did manage to "feel" the pipework around the calorifierafter the Alde had been on for a while. The pipes beteen boiler and calorifier were as hot as expected, but everything else felt cool (and the overflow bottle was still empty). All I can assume is that there isn't an NRV on the inlet to the cylinder and the cold water is being pushed back out of the bottom of the cylinder as the hot water at the top is expanding.

 

I didn't get the Pressure Reducing Valve installed either today - the joys of a trip boat skipper and the boss asking you to work an extra trip when you planned to do things on your own boat. However, I hope to be able to fit the valve tomorrow.

 

Finally, our (short) cruise this weekend has been cancelled - the joys of a . . . . etc., etc., so we haven't been able to test whether the valve (which we didn't get round to installing) had helped to keep the water warmer. There's a chance we might get an hour or two of cruising tomorrow but we'll have to be back early afternoon (for another trip boat duty) so we won't get a fair chance to check the water after cruising (if we do get away) as it'll be either well under or well over the equivalent of our normal 12-14 hours overnight period when we can check the temperature.

 

Update to follow, when we've made some progress (with something).

[smileypete]

I managed to take the pictures last night but the connection speed is too slow so doubt I'll get them uploaded until after the weekend. I did manage to "feel" the pipework around the calorifierafter the Alde had been on for a while. The pipes beteen boiler and calorifier were as hot as expected, but everything else felt cool (and the overflow bottle was still empty). All I can assume is that there isn't an NRV on the inlet to the cylinder and the cold water is being pushed back out of the bottom of the cylinder as the hot water at the top is expanding.

 

Just because the pipes feel cool doesn't mean they're not losing heat.

 

I would certainly lag any pipes to, and fittings on, the calorifier with thick lagging.

 

Also I'd try the following:

• Run at least 10L hot water at full flow an hour before stopping engine.
  
• Draw off hot water in evening at a slow rate if possible.
  
• Switch off the pump overnight.
  

cheers,

Pete.

Edited August 21, 2009 by smileypete

[Ray]

Right. We fitted the Pressure Reduction Valve yesterday - must read the instructions first in future! I assumed that you screwed the adjuster in to reduce the pressure - no, you screw it out! Anyway, couldn't get the associated gauge to seat properly - it kept weeping, so we removed it as soon as we had the adjuster set so that water came out of the taps when they were opened and the shower also worked.

 

We went for a little cruise during yesterday afternoon - about 5 hours - and moored up around 5pm. We had two showers and did some washing up after eating (just after we moored). We used a little hot water around 11pm and it was still piping hot - we couldn't make the boiler fire up - that is driven by a cylinder thermostat set to a little under 60 degrees so water in the cylinder must still have been that hot.

 

We turned the boiler on this morning around 8am and it fired up (the cylinder stat wanted heat). We measured the water temperature at the tap at 38 degrees, almost acceptable for a shower, had we wanted one.

 

It wasn't a fair test as we wouldn't normally moor quite so early and definitely wouldn't have showers in the evening and expect the water to still be hot enough for more showers the following morning. We've no plans to go cruising for a while now (other than the odd short jolly around midday) so any further tests will have to wait for a while.

 

In the mean time I'm optimistic that we may have improved the situation. I'll try lagging the pipework as well in the mean time to see what happens.

 

I appreciate that we may be losing heat through the unlagged pipes but as each circuit is effectively blocked, either by an NRV or an electronic gate valve, I don't think that we have any complete circuits to facilitate convection so not sure how the water can move around to enable that loss to occur.

 

What purpose will running 10 litres of water off about an hour before stopping the engine serve?

 

We sleep light at night - in fact, I sleep so light that I'm often awake for much of the night! - and would hear the pump if it cut in, even if only briefly. I presume the idea of turning it off is to stop water being drawn into the cylinder.

 

I presume the slow draw off is intended to slow the refill rate. Hopefully, the pressure Reduction valve will now do that.

[Ray]

Here's the requested pictures. I said they weren't pretty

 

The right hand side of the Alde boiler is on the left of the top picture. The upper pipe, the one that disappears through the bulkhead, is the outlet from the PRV. The next one, going down the picture, a the cold water supply that is currently isolated from the calorifier's mixer via a (manual) valve that is hidden behind the Alde (in other words, this connection is currently doing nothing). Below that is the hot water supply from the calorifier, 15mm horizontally, and then 22mm for the rest of the run. The remaining pipe, partially hidden by the boiler's flue, is the hot water outlet from the Alde.

 

The light blue box towards the bottom of the picture is one of the two electrically driven 12v gate valves.

 

 

In the lower picture the 22mm pipe on the right is the hot water from the calorifier and the light blue boxes are the two electrically controlled gate valves which replaced the manual gate valve originall installed (and one of which can be seen in the picture - the other is off camera, in the run to the radiators). The left hand most vertical pipe is the return to the Alde.

 

The five horizontal pipes exiting behind the Alde are, from the top down, the hot feed (from the Alde, via the valve) to the calorifier's top coil. Next is the return from the calorifier top coil. This is followed by the calorifier's lower coil connections, disappearing through the bulkhead into the engine room. The fifth and final pipe is the cold supply into the bottom of the calorifier.

 

The lower electronic valve is in the feed supply from the Alde to the radiators.

 

We have a switch by the Alde that opens the upper valve (when the cylinder stat demands heat). We have the standard room stat and combined switch above the bed which we operate to open the lower valve when the stat says it is too cold (and we don't feel too warm) to heat the radiators.

 

There is an NRV between calorifier and engine, just the other side of the bulkhead.