Volvo water temps - gauge readings

[mjf]

After the exchanges last week when we were milling around off Cowes before the RYS salute I was able to watch the water gauges more carefully than when blasting about 'at sea'.

Both rise together to 150 then the stbd carries on to 175 before settling out at that.

The port one stays at 150 for a while then lifts to 175 - then drops back occasssionally to 150ish before rising to 175.

Very clearly there is drain off of waste heat to the domestic water system and the saloon demister ring, quite surprised at the number of cycles the 150/175 readings made in 2.0 hrs with no load on the engines to speak off.

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[Moose]

Yep, thats what mine do but they only reach about 160.

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[adarcy]

I'm glad everyone is now agreeing generally.

But I've just thought - the calorifier water doesn't get hotter and hotter on a long run to reach anything near freshwater coolant temperature so there is probably a separate thermost allowing coolant into the calorifier. Not seen an obvious one on ours but it makes sense. If so, there are 2 thermostats engine and calorifier so perhaps it is not unreasonable that they cycle a bit if you're trolling about. You're unlikely to notice any fluctutation if the engine revs and heat production is up

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[Wiggo]

Not sure about that. While prodding around at the weekend, I found the immersion heater thermostat on the tank set at 75*C, which seemed high at first. A little reflection says that the engines run to about the same temp, and there is no reason (other than lagging losses) that the tank shouldn't reach the same temp as the engines. So it makes sense to have the immersion at the same temp, otherwise, you'd get used to setting the temperature on the mixer taps while on shorepower, then scald yourself while at sea.

The tank does have a pressure relief valve, so it's possible that it periodically vents hot water under way, and refills with cold, so allowing the tank to soak up more heat from the engine.

But if Mike was only idling, then the main/only engine thermostat may have been genuinely cycling. The other engine may just have a slightly different thermostat (10% variation was mentioned).

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[adarcy]

Makes sense (as usual Wiggo)

only..........
We've recently had our oil coolers + heat exchangers cleaned out and we now run at a steady 80 Centigrade previously ran 85 ish and the hot water whilst hot doesn't feel THAT hot and no cooler since our engines run cooler maybe it just goes to show how innacurate/insensitive human beings are

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[Wiggo]

or you have a more sophisticated calorifier than we do. Water at 75*C is bloody dangerous, but it does mean that you can get away with a smaller hot water cylinder (as you mix a little very hot water with a lot of cold). Could be Sealine being a bit cheapskate (perish the thought!)...

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[adarcy]

<<more sophisticated calorifier>>

doubt it - old + crock like it's owner

<<75*C is bloody dangerous>>

that's what I meant, yes it IS hot and far too hot to have your hand in so use lots of cold but somehow doesn't feel anywhere near scalding or maybe I've just learned to be v wary of it in the past !

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