Calorifier raw water feed pump location DV20

[westerlylad]

Hi All. Cox engineering suggests installing a Johnson CM10 pump into the calorifier return line to the DV20 engine block, however I'm having trouble establishing a flow between the engine and my calorifier, which is about half a meter above my engine, despite having several attempts at backfilling the calorifier as suggested by Vyv.

Would it not be possible to install the pump in the line feeding engine water to the calorifier so that the pump would be pumping water up to the calorifier inlet?

I know that the water flowing to the pump would initially be hotter than in the return line position, but would that really be a problem?

Alternatively, could I install a tee piece with an isolation valve at the top of my calorifier feed line into which I could connect a hose to feed mains pressure water to my calorifier heating circuit, in case my problem is due to an air lock? Thanks in anticipation.

 

[vyv_cox]

I guess it would not be a problem with a more modern magnetic drive membrane pump, as is used for automotive applications. These run at far higher temperatures than a raw water cooled marine engine. Sadler placed the pump in the return line, using the old pump that was not rated for seawater (although they lasted fairly well)

However, having done this myself many times I emphasize that it can be very difficult to eliminate airlocks. I backfilled both hoses using funnels into the open ends

 

[westerlylad]

Thanks Vyv. I think I'll try moving the pump to the feed side and inserting a couple of T-pieces with isolation valves into the feed and return hoses near the entry points to the calorifier, so that I can fill the whole system using a mains pressure hose.

I wonder if that would cause any problems!

 

[wingcommander]

Any problems with the calorifier coil scaling up , ime considering doing this to a Bukh 24 raw water cooled. Also what temperature do you achieve at the tap.

Cheers

 

[westerlylad]

Just reporting back to say that my problem turned out to be a hard (salt?) buildup at my engine block return point. I poked this free with a screwdriver, following which I got the flow through the calorifer to establish okay. This is with the CM10 pump in the hot feed side, rather than the cooler return side. I'd say that the water temperature I'm getting from the calorifer is warm, rather than hot, but I'm happy enough with that.
Cheers.

 

[vyv_cox]

Hot water from our calorifier with a DV20 was far too hot to put a hand in after about 20 minutes of motoring. It sounds that you may still have a restriction or partial airlock.

 

[westerlylad]

Thanks Vyv. I'll have another poke around. It may be in the calorifiers own pipework, in which case I'm not sure how I would clear it.