Pressure alarm sounding

[Jennifer McM]

The Izuzu 35 engine was running quite hard against a river flow for 2-3 hours on a hot day. Engine cooling system did not over heat (no smell of hot oil), but an alarm was sounding, though no warning lights.

 

We switched on the central heating circulation pump, and after 30 seconds the alarm stopped. This is the second occasion this has happened, the other time was last year.

 

We think this was due to excessive temperature in the hot water system as the hot tap water was scalding. 

 

The swim tank has been vented to remove airlocks, and we're pretty certain the engine cooling system is working normally.

 

Questions:

 

1. Is there an alarm system fitted to the hot water tank.... where is it? (we checked the boat's owners manual, and there's no indication)

 

2. Is there a vent fitted to the hot water tank to release excess pressure, as in domestic hot water systems?

 

Our boat's a 58ft semi trad Liverpool boat.

 

Appreciate any ideas - thanks

 

 

Edited August 5, 2018 by Jennifer McM

[Stilllearning]

Not sure about alarms on a hot water tank, but there will be a pressure release valve (PRV) fitted to the top of the tank. It will have a red knurled knob on it. Twist it briefly and a bit of hot water should shoot out (not much though).

This might solve the problem, as sometimes the PRV gets blocked with a bit of crud.

[Alan de Enfield]

19 minutes ago, Jennifer McM said:

The Izuzu 35 engine was running quite hard against a river flow for 2-3 hours on a hot day. Engine cooling system did not over heat (no smell of hot oil), but an alarm was sounding, though no warning lights.

 

We switched on the central heating circulation pump, and after 30 seconds the alarm stopped. This is the second occasion this has happened, the other time was last year.

 

We think this was due to excessive temperature in the hot water system as the hot tap water was scalding. 

A 'overheating' buzzer should sound well before you get to smelling boiling oil - if it gets to that stage then you have little or no lubrication in the engine and it is likely to seize up, so I would suggest that the alarm is working correctly.

The alarm goes off when you run some hot water off into either radiators or the taps, replacing some of the hot water in the calorifier with cold water which will help to slightly bring down the engine water temperature.

 

If this only happens when working hard on Rivers then it would suggest to me that your cooling 'skin tanks' are insufficient size - perfectly fine for use on canals where you are only using 4 or 5hp, but when you open it up and use 10 / 20 / 30hp the water cannot cool quick enough.

 

The recommendation for cooling tank size is a minimum of 1 square foot per 4hp. measure your tanks and see what size they are - ideally you should be looking for around 8-10 square feet of surface area.

Edited August 5, 2018 by Alan de Enfield

[nb Innisfree]

Could be the size of skin tank is borderline, big enough to just about cope, enough to keep engine happy but not quite enough for the alarm. Do you have an engine coolant temperature gauge? 

[Alan de Enfield]

Re-reading it - why do you think it is a 'pressure alarm' rather than a 'temperature alarm' ?

 

Generally the only likely 'pressure alarm' is for oil pressure, and that would normally be for LOW oil pressure, it would be rare to actually have an audible alarm, & most would simply have a dial-gauge showing Psi (or whatever foreign units they now use)

 

Confused.

[MtB]

26 minutes ago, Jennifer McM said:

 

1. Is there an alarm system fitted to the hot water tank.... where is it? (we checked the boat's owners manual, and there's no indication)

 

No.

 

26 minutes ago, Jennifer McM said:

2. Is there a vent fitted to the hot water tank to release excess pressure, as in domestic hot water systems?

 

Yes, but I'm not sure why you are asking this. Unsuitably high pressure in the hot water tank could only ever be a trivial side-effect of the overheating engine symptoms you describe.

 

I'd say almost certainly your engine is overheating and easing off the throttle would have made the buzzer stop too after a few minutes.

 

 

26 minutes ago, Jennifer McM said:

The swim tank has been vented to remove airlocks, and we're pretty certain the engine cooling system is working normally.

 

I'm curious as to what made you write this. Skin tanks don't normally air-lock. What made you 'vent' yours? Did you get air out, or just water? I think the evidence suggests your cooling system is NOT working properly.

 

One of my boats had a slight head gasket leak and combustion gases are leaking into the cooling system which accumulate in the skin tank. I'm wondering if you boat has the same problem. My 'workaround' was to fit an automatic air vent as it was only a temporary engine.

Edited August 5, 2018 by Mike the Boilerman

[Boater Sam]

Could the alarm not be the normal control panel sounder but the pressure release valve on the calorifier blowing off?

[MtB]

2 minutes ago, Boater Sam said:

Could the alarm not be the normal control panel sounder but the pressure release valve on the calorifier blowing off?

 

A PRV passing steam doesn't sound anything like a warning buzzer!

 

But the possibility exists that the calorifier could have been boiling. A seriously overheating engine with a pressurised cooling system can run at over 100C, and heat the calorifier up to +100C too. 

[Boater Sam]

The OP said " ALARM" , he did not say it was the normal "buzzer" which made me think it is maybe an odd noise he is hearing, like a chattering PRV.

[alan_fincher]

34 minutes ago, Jennifer McM said:

Our boat's a 58ft semi trad Liverpool boat.

 

Liverpool Boats are one of the builders known on occasions to have built narrow boats, (and indeed wide beams) with inadequately sized skin tanks.

As has been said, a boat that is fine on canals may overheat when pushing hard on a river.

Even additional layers of blacking on an undersized skin tank can tip the balance between an overheat situation or not.

Do you know, or can you measure the area of your skin tank that actually presents to the canal?

Also how "thick" is it?

[Alan de Enfield]

3 minutes ago, alan_fincher said:

Liverpool Boats are one of the builders known on occasions to have built narrow boats, (and indeed wide beams) with inadequately sized skin tanks.

But wasn't that only during the 'great hub-cap' famine of the late 90's / early 00's ?

Edited August 5, 2018 by Alan de Enfield

[OldGoat]

FWIW; IME most narrow boats' skin tanks are too small. There's just not enough room to put a decent sized tank along the swim. Mine is 4ft and inadequate for river cruising (Just as well that my engine is heat exchanger cooled anyway).

Some years ago we hired from "the  Squadron Leader's fleet" and took it up the Thames tideway. As we approached Hammersmith the tide turned and we had to apply more 'wellie' and the overheat alarm came on... On our return we pointed that out to which the response was "we've never had that" (predictable, perhaps)

The point is that skin tanks work fine for normal canal cruising, but just don't cut it if you work the engine hard. 

[Alan de Enfield]

4 minutes ago, OldGoat said:

FWIW; IME most narrow boats' skin tanks are too small. There's just not enough room to put a decent sized tank along the swim. Mine is 4ft and inadequate for river cruising (Just as well that my engine is heat exchanger cooled anyway).

Some years ago we hired from "the  Squadron Leader's fleet" and took it up the Thames tideway. As we approached Hammersmith the tide turned and we had to apply more 'wellie' and the overheat alarm came on... On our return we pointed that out to which the response was "we've never had that" (predictable, perhaps)

The point is that skin tanks work fine for normal canal cruising, but just don't cut it if you work the engine hard. 

I'll probably get jumped on by the hard core NBers, but, are NBs REALLY designed, built & powered to work on Rivers with variable flows*, and in some cases Tidal effects ?

Personally, I think not, they are working on the edge of their abilities and it only takes a very small change to push them over that edge.

 

Is it a little like taking your saloon car and trying off-roading with it - yes it will be fine in 'good conditions', but as conditions worsen its just not made to do it.

 

Everything is good when used as intended.

 

* I know Rivers come in all shapes and sizes from a 'meandering stream (upper-Thames), to the 6-foot high Aegir on the River Trent

[David Mack]

45 minutes ago, OldGoat said:

FWIW; IME most narrow boats' skin tanks are too small. There's just not enough room to put a decent sized tank along the swim.

 

There's always plenty of room. No reason why a skin tank can't extend forward of the swim into the cabin area, or put two tanks on opposite sides of the swim, plumbed in series. It's just that too many boatbuilders can't be bothered, or just don't realise that by not providing a large enough skin tank they are handicapping the oversized engine that many seem to fit these days.

[nb Innisfree]

1 hour ago, OldGoat said:

FWIW; IME most narrow boats' skin tanks are too small. There's just not enough room to put a decent sized tank along the swim. Mine is 4ft and inadequate for river cruising (Just as well that my engine is heat exchanger cooled anyway).

Some years ago we hired from "the  Squadron Leader's fleet" and took it up the Thames tideway. As we approached Hammersmith the tide turned and we had to apply more 'wellie' and the overheat alarm came on... On our return we pointed that out to which the response was "we've never had that" (predictable, perhaps)

The point is that skin tanks work fine for normal canal cruising, but just don't cut it if you work the engine hard. 

I think shell builders are slow to react, sticking to 'tried and tested for years' approach, reluctant to recalculate design and rejig production. 

[OldGoat]

54 minutes ago, Alan de Enfield said:

I'll probably get jumped on by the hard core NBers, but, are NBs REALLY designed, built & powered to work on Rivers with variable flows*, and in some cases Tidal effects ?

Personally, I think not, they are working on the edge of their abilities and it only takes a very small change to push them over that edge.

 

Is it a little like taking your saloon car and trying off-roading with it - yes it will be fine in 'good conditions', but as conditions worsen its just not made to do it.

 

Everything is good when used as intended.

 

* I know Rivers come in all shapes and sizes from a 'meandering stream (upper-Thames), to the 6-foot high Aegir on the River Trent

No, I for one won't jump on you, (Duckie)..

I designed / specified  mine  as best I could (traditional boatbuilders don't line their customers mucking around with 'their' specifications) but got pretty well what I wanted, long swims, elliptical stern and so on. Larger engine for punching the flow on the Thames. We've been out in it when Red Boards appeared, but I wouldn't deliberately set out in those sorts of conditions. It managed well, but (as in all good boating) you have to understand what you can and can't do.

 

As it happens I do have an estate car than can and does do limited off road (soft roading) and again OK as long as you understand its limitations 4WD OK, but rotten grould clearance.   

 

1 hour ago, Alan de Enfield said:

I'll probably get jumped on by the hard core NBers, but, are NBs REALLY designed, built & powered to work on Rivers with variable flows*, and in some cases Tidal effects ?

Personally, I think not, they are working on the edge of their abilities and it only takes a very small change to push them over that edge.

 

Is it a little like taking your saloon car and trying off-roading with it - yes it will be fine in 'good conditions', but as conditions worsen its just not made to do it.

 

Everything is good when used as intended.

 

* I know Rivers come in all shapes and sizes from a 'meandering stream (upper-Thames), to the 6-foot high Aegir on the River Trent

 

31 minutes ago, David Mack said:

 

There's always plenty of room. No reason why a skin tank can't extend forward of the swim into the cabin area, or put two tanks on opposite sides of the swim, plumbed in series. It's just that too many boatbuilders can't be bothered, or just don't realise that by not providing a large enough skin tank they are handicapping the oversized engine that many seem to fit these days.

Agreed. It's no goo treating a hull as a standard commodity and expect your whatever-it-is major extra to fit in without some compromise.

[Detling]

Question for the OP does his engine control panel have Oil pressure and Temperature gauges or is it the basic one without such vital information.

 

By his comments I suspect he does not have these, the alarm on mine is linked to Oil pressure not temperature so I think his engine is getting hot and the oil pressure is dropping too far, thus triggering the alarm, running hot water will reduce the engine temperature as suggested and then the cooler oil thickens enough to raise the pressure and turn the alarm off. It is not a good idea to ignore it, bigger/additional skin tank, check correct oil level and ensure correct oil type is used, modern car engine oil is not ideal for our old fashioned engines.

[Chewbacka]

My control panel has a single sounder fed by 2 diodes from the coolant overtemp switch and the oil low pressure switch, so either fault will cause it to beep.

[Cyan]

Thank you boaters for your interest in our Alarming river cruise. Jenny's other half replying, the engine driver in this case.

1. Swimtank size:  The engine coolant alarm did not sound and there was no sniff of hot engine oil, with only an engine overheat alarm, no dial gauge, it is reasonable to assume that engine coolant temp was within normal operating range.

2. The alarm sound came from the area where the Caly Tank is located and I surmised that the domestic hot water temp. was causing the 'Sound'

3. Confirmed by reducing the tank temperature by running the circulating  C.H. water pump.

4. Our domestic hot water is always very hot after engine running for 2/3 hours.

q. Is there a valve that restrict water flow to the domestic hot water coil? Bit like a radiator thermo valve? This would help to control the domestic hot water temperature.

 

I will investigate the PRV fitted to the top of the H.W.Tank and check all is well.

The swim tank had not been bled for more than 2 years, quite a lot of air was released until water flowed out of the vent. I topped up the coolant system with approx 75cl of water after venting the tank. Since then no coolant loss and a further venting resulted in only water flow, no air was released. Hopefully there is no issues with head gasket and the like. Engine starts clean with no visible smoke, black or white, on startup.

 

Once more, thanks for your interest and suggestions

[nb Innisfree]

9 minutes ago, Cyan said:

Thank you boaters for your interest in our Alarming river cruise. Jenny's other half replying, the engine driver in this case.

1. Swimtank size:  The engine coolant alarm did not sound and there was no sniff of hot engine oil, with only an engine overheat alarm, no dial gauge, it is reasonable to assume that engine coolant temp was within normal operating range.

2. The alarm sound came from the area where the Caly Tank is located and I surmised that the domestic hot water temp. was causing the 'Sound'

3. Confirmed by reducing the tank temperature by running the circulating  C.H. water pump.

4. Our domestic hot water is always very hot after engine running for 2/3 hours.

q. Is there a valve that restrict water flow to the domestic hot water coil? Bit like a radiator thermo valve? This would help to control the domestic hot water temperature.

 

I will investigate the PRV fitted to the top of the H.W.Tank and check all is well.

The swim tank had not been bled for more than 2 years, quite a lot of air was released until water flowed out of the vent. I topped up the coolant system with approx 75cl of water after venting the tank. Since then no coolant loss and a further venting resulted in only water flow, no air was released. Hopefully there is no issues with head gasket and the like. Engine starts clean with no visible smoke, black or white, on startup.

 

Once more, thanks for your interest and suggestions

On Innisfree I installed a thermostatic mixing valve on the calorifier HW outlet, it mixed cold water from the supply pump with cal hot water to keep water at selected temp (providing tank was above selected temp of course) 

 

ETA: If swim tank is correctly plumbed in to the engine it should never need bleeding as any air should rise through the top hose and then into engine header tank. 

Edited August 5, 2018 by nb Innisfree

[Cyan]

38 minutes ago, Detling said:

Question for the OP does his engine control panel have Oil pressure and Temperature gauges or is it the basic one without such vital information.

 

By his comments I suspect he does not have these, the alarm on mine is linked to Oil pressure not temperature so I think his engine is getting hot and the oil pressure is dropping too far, thus triggering the alarm, running hot water will reduce the engine temperature as suggested and then the cooler oil thickens enough to raise the pressure and turn the alarm off. It is not a good idea to ignore it, bigger/additional skin tank, check correct oil level and ensure correct oil type is used, modern car engine oil is not ideal for our old fashioned engines.

Hi Detling, your thoughts on oil pressure and oil content and quality.

1. There is a oil pressure warning and coolant overheat warning on the instrument panel fed by different sensors.

2. Oil used is from Morris's of Shrewsbury, specifically for canal boat diesel engines. Changed religiously with new oil filter every 250 hrs. Oil is dark but not black and 'smells right'

3. Oil level is correct to the full mark and never requires topping up between changes.

 

Thanks for your input, I appreciate your thoughts on the matter.

The 'alarm sound was not from the instrument panel but much further forward, probably in the H.W. cylinder area.

[alan_fincher]

13 minutes ago, Cyan said:

 

1. Swimtank size:  The engine coolant alarm did not sound and there was no sniff of hot engine oil, with only an engine overheat alarm, no dial gauge, it is reasonable to assume that engine coolant temp was within normal operating range.

 

Without a reliable gauge, I don't think you can make that assumption.

Do you know what the thermostate opening temperature is supposed to be?
Do you know it is opening at design temperature?
At what temperature does the engine overheat alarm go off?
Has it ever?
If it hasn't gone off in recent times, can you be sure it actually works?

I think you are wrong to assume that the engine getting far hotter than the engine thermostat temperature will automatically start to produce hot engine oil smells.  In my experience you can get a pressurised cooling system well over 100 degrees, and still not produce oily smells.

If your domestic water is getting very hot, then by implication it is likely your skin tank is as well.  At the moment I don't think you have the evidence to say if "too hot".

I note you didn't actually answer questions about skin tank dimensions.

[Cyan]

3 hours ago, Alan de Enfield said:

Re-reading it - why do you think it is a 'pressure alarm' rather than a 'temperature alarm' ?

 

Generally the only likely 'pressure alarm' is for oil pressure, and that would normally be for LOW oil pressure, it would be rare to actually have an audible alarm, & most would simply have a dial-gauge showing Psi (or whatever foreign units they now use)

 

Confused.

Hi Alan,  The sound was similar to that made by our gas whistling kettle when near to boiling. Hence my reasoning it was related to domestic H.W. overheating. 

The alarm was not from the normal instrument panel alarm which sounds for low oil pressure, engine coolant overheat and alternator output failure.

Thanks for your input!

[Stilllearning]

A PRV can make all sorts of amusing/alarming noises ranging from farty to squealing.

[Alan de Enfield]

2 minutes ago, Cyan said:

Hi Alan,  The sound was similar to that made by our gas whistling kettle when near to boiling. Hence my reasoning it was related to domestic H.W. overheating. 

The alarm was not from the normal instrument panel alarm which sounds for low oil pressure, engine coolant overheat and alternator output failure.

Thanks for your input!

It sounds then like it's the PRV doing what it should do and 'blowing off'.

 

I'd still suggest that you look at the size of your skin-tanks as if the water is getting too hot you stand to damage your engine.