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nbtarragon...
nbtarragon...

Posted: Sat Dec 15, 2012 1:18am

Post Subject: Calorifier heating circuit

Dear Experts, I have just obtained a new calorifier (75 litre horizontal Surecal) to replace my existing small domestic unit. As part of the installation, the location of the calorifier is moving into the main cabin (previously within the engine room) where it will hopefully gently warm a wardrobe. As I am going to run new pipe-work, I wondered if it was a realistic idea to try to extend the pipe-run, and include some radiators (possibly fin-rads) under the bed, to help get more of the waste-heat from the engine to be made good use of in the colder months. The engine is a beta marine 38 (1503) and currently has a 15mm hot water take-off on the air intake side of the engine block, which returns to a 15mm tee of the 28mm cold return hose from the bottom of the skin tank. It struck me that it would be possible to enlarge the take-off to the calorifier (inter alia) circuit, for example, to use a 28mm equal tee. My questions are: Is this sensible? If it is, should the system be run such that there is a 28mm 'trunk' feed pipe which feeds the calorifer, and any other circuits in parallel, with an associated 28mm return 'trunk'. Is there a sensible limit to the size/length of the total pipe run before the engine's water circulation pump will struggle? Yours faithfully, Patrick Vale

Tony-B...
Tony-B...

Posted: Sat Dec 15, 2012 7:54am

Post Subject: Calorifier heating circuit

First of all not all the heat the engine produces is actually waste heat. The engine has been designed to operate within a specific range of temperatures for maximum efficiency and life. If you draw excessive heat from the engine it will never reach the required temperature. I am sure the Beta takes the calorifier feed from the engine side of the coolant thermostat rather than the skin tank side. This means the thermostats can not control the loss of heat from the engine. This is fine for just a calorifier because many years experience shows the longer warm up time is not a problem. (NOTE - Some engines use two thermostats so one controls the calorifier take off, while a few take the coolant from the skin tank side of the thermostat but I do not think yours is one of them). Once a calorifier is hot it does not take any heat from the coolant but on the other hand the calorifier take off is usually the cabin heater take off when the engine is used in other equipment and we know how much heat a car heater an produce without affecting the engine temperature so what you want to do is possible BUT I do not like the implications of your plans for 28mm pipes feeding "any other circuits". It sounds as if you might be contemplating heating the whole boat at some stage. The heater take off was originally designed for 15mm or 5/8" or so pipe or hose of a meter or so length between engine and cab heater so apart from extra coolant capacity 28mm piping would produce I suspect the only way to find out just how far you can push the system is to try it. Yes larger bore pipes should allow circulation over longer distances. However my advice is to keep any extra pipe runs and heat take off modest. Use the 15mm pipes as now, feed the hot water to the calorifier and then on to the finrad or whatever. In this way the cold calorifier will take all the heat it needs for a fast warm up and as it warms the water flowing on the the finrad will gradually get hotter. One other point. I fear that the longer and more complex you make this circuit the greater the difficulty you will have in bleeding all the air from it so think about this and how it may be helpful to install bleed vents when you do the work. Tony Brooks

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