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Maudesmaster

Centrifugal pump 3 LW

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I am fitting out a new build 62' with a 3 LW 

The top of the Skin tanks are about 4" below the centrifuge pump After around 1/2 hour running 3/400 rpm the pipe work from pump around block and head up to Borman header tank are warm Skin tanks feed and draw are cold 

Any thoughts on this 

thanks in advance 

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Not quite sure if I understand what you are saying, but to me it sounds like you are concerned about the return water from the skin tanks being cold when the 3LW has been idling for 1/2 hour?  To me that is normal as my 3LW tends to run quite cool when just sitting there idling, you will need to work it for some time before that changes.

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What temperature is the top of the engine at? It may well still be warming up and recirculating via the short pie back to the pump. As PeterG has said, warming up at low revs will take a long time. Is the recirc line back to the pump warmer than the feed line to the skin tanks?

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My 3LW operates at 45 deg C in normal conditions (up to 50 deg after some river work).  This means that the thermostat never opens and therefore the skin tank feed and return remain cold.  The "short circuit" gets warm/hot so you should have two warm/hot and one cold pipe on the pump.  The consequence of this is that there is no ability to heat hot water from the engine, you might want to consider this when specifying your system.  We use either an Eberspacher Hydronic or a 1kW immersion powered by a 3.5kW Travel Pack.

After half an hour the top cover is only a few degrees above ambient.  Full operating temperature takes about 1-1.5 hours of cruising.

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We have a 2lw and had similar sort of problem, engine rarely getting to 60 deg and so no domestic hot water.  Fitted 1" 1/2 ball valve in the pipe from the thermostat to the floor skin tank.  Result loads of hot water, engine does not over heat and I only open the valve on rivers. Sorted!

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Hi folks

I have a 3LW fitted in my boat. It's been sitting idle for 8 months while the boat was built round it. Finally got the fuel supply, starter and coolant system completed yesterday. After some time on tick over, the top rail started to get warm and the temp was around 40C.

I applied a bit of load (3KW alternator). The temp then started to rise and was heading past the 70C mark - which I believe is a lot hotter than it should be.

My first thought was a sticking thermostat, so I took that out and restarted the engine. I was expecting the return side of the pump to be ice cold (skin tank temp is close to freezing), but it's luke warm, as if the coolant is moving around a bit by convection. The temp did drop away to 30-40C, but I am questioning whether the circulating pump is working properly. I have a gearbox oil cooler fitted in series with the return and that was quite warm too - again, I would expect it to be ice cold with a good flow from the skin tank.

Is there any way I can test the pump, without pumping all the coolant out and taking the pump cover off to physically inspect it?

 

Thanks in advance for your help.

 

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I would check both thermostats but perhaps nothing is wrong given current ambient conditions. Consider the following:-

 

A 3kW electrical load is still very low for this size of engine, approx 10% rated load?

 

Which thermostat do you have fitted? Gardner specified two types, a cooler one for constant high load and a higher setting for variable (traction) loads. Note that the lower temperature is for highy loaded engines and this probably does not apply to a 3LW in a narrowboat so the higher temp stat may be fitted? The higher one seems common on narrowboats looking at the following thread

 

I started our 3LW yesterday, with the boat internal temperature at approx 1C. After running on a reasonable fast speed for about 40 minutes (not tickover) the block and head of the engine was hot but the crankcase etc was still pretty cold. The mass of these engines is large, there will be some flow round the cooling circuit even if the thermostats are working ok, this may be enough under very cold external conditions to give the results that you have noted?

 

 

Extract of Gardner Directions handbook

 Water Circulation.-This is effected by a circulating pump, gear driven by the engine. It is recommended that the temperature of the outlet water from the engine be not allowed to exceed 175 F. (80 C.) and that, in most cases, the most satisfactory operating temperature is 140 F. to 160 F. 60C. to 71C.). Special cases, such as Rail Traction duty and heavy duty vehicles, should be submitted to the works for individual consideration.  Generally, the higher the duty which an engine is called upon to perform, the lower should be the temperature to which the water is controlled and arrangements made .to achieve this end. 

 

 

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Many thanks for the input! I've just got back from the boat... spent the whole day messing around with the cooling system. Thermostat checked out fine, so that went back in. Then a mate of mine suggested making sure there wasn't an airlock anywhere (bearing in mind this was a new refill). Well, after a lot of faffing around with various hoses, etc, having let the engine heat for an hour or more, I then gave the engine a few good blasts at higher revs. 

 

Before too long, very hot water started making its way round the system, through the skin tank and back, nice and cold.

 

A result! Happy that this problem has been sorted! :)

 

Now I just need to find out why it's running lumpier than school custard... the whole boat is shaking!

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4 hours ago, jonesthenuke said:

A 3kW electrical load is still very low for this size of engine, approx 10% rated load?

 

3KW is around 4HP, which is, as you say, about 10% of the rated output, but that's measured at 1,200rpm. At 420rpm, it's only about 10HP, so the load was about 40%, which did make it bark a bit!

 

 

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When diesels are run at low load/temp /high speed ,a condition known as bore glazing sets in...which will eventually result in very smoky exhaust , loss of compression  and hard starting...Very common in gensets used in houses ,where the only load is a few lights.

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