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ChrisNelms
ChrisNelms

Posted: Mon Mar 04, 2019 6:55pm

Post Subject: Cruising with an empty calorifier

Each autumn I winterise my narrowboat by emptying the water tank and draining the calorifier. In spring I prepare for the new boating season by cruising for an hour to refill from a water point. The boat's calorifier is an upright cylinder with two indirect coils inside it, one connected to the Webasto boiler and the other to the Beta 50 engine's cooling system. I'm concerned that when I refill with cold water, the indirect coil connected to the engine will be very hot and the sudden addition of cold water might cause damage. Am I worrying unnecessarily, or should I try to isolate that coil from the engine while cruising with an empty calorifier?

Tony-B
Tony-B

Posted: Mon Mar 04, 2019 8:53pm

Post Subject: Cruising with an empty calorifier

I think there must be hundreds of boaters that do as you do without problem. In any case a copper coil is not a complex shape like a cylinder block and the copper is fairly ductile and that should avoid stress caused by sudden cooling. The coil shape is a good one to minimise stress cause by expansion and contraction because it will just slightly alter its diameter. I think this is probably a theoretical problem rather than a practical one.

ChrisNelms
ChrisNelms

Posted: Tue Mar 05, 2019 1:03pm

Post Subject: Cruising with an empty calorifier

Thank you for the speedy reply Tony; much appreciated. I've been worrying about this more than you would imagine. Experience in life has taught me that taking any metal at a temperature of, say, 85°C and suddenly cooling it to mains water temperature can cause problems. Thanks for putting my mind at rest.

Tony-B
Tony-B

Posted: Tue Mar 05, 2019 2:53pm

Post Subject: Cruising with an empty calorifier

For completeness: there MIGHT be a problem with running the engine with an empty calorifier but it relates to the lack of support for the coils and the lack of vibration damping by the water. This was particularly the case for certain horizontal calorfiers where the coil was in fact a sort of double walled cyinder, open at both ends and supported by half inch copper tube at each end. These did fail where the inner part joined the pipe. I have not seen any evidence of this on vertical calorifiers. Calorifiers have much thicker walls than domestic indirect cylinders so are far more able to support the coils with no water in the calorifier body. You also need to consider the temperature difference between the water being pumped into the calorifier and the water in the coil. The water in the coil will be at about 90C while the water flowing into the calorifier is unlikely to be much under 10C by the time it has travelled down the boat absorbing heat from the pipes a sit goes. Also it takes time to fill the calorifier so total submerging of the coil is likely to take several seconds so the water moving up the outside of the coil will be warmed by the coils below it.

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