Connecting calorifier/waterheater to engine

[ed80]

Hi all,

I have a calorifier on board which is currently only heated by the mains heating coil. I would like to connect this to my engine (a Yanmar 4JH3E) to provide hot water away from the dock. I know exactly where to connect on the engine, but I have a question about hot to prime everything and make sure there is sufficient coolant.

The calorifier is mounted about 5 feet from the engine, slightly above it. Looking at how it should be connected, there seems no logical place to fill this loop with coolant, and remove all air from the system. Can anyone help suggest the best way to do this?

Many thanks,
Edward

[hjohnson]

Ideally you would have an expansion tank higher than your domestic hot water tank connected in as well. The expansion tank becomes the high point in your coolant system, and makes it easy to top off.

Failing that, you’ll need to fill it up as best as possible, then keep an eye on your coolant levels for a while and top off as necessary.

[capt jgw]

I had the same problem on my boat. I bought a small header tank made for hot rod cars on eBay and mounted it slightly above the heater and filled the system from there. It worked fine. I had tried it first without the tank but the circulating pump would not pump uphill to the heater.

[stormalong]

Engine coolant is run with some pressure. The heat exchanger cap (radiator cap) is rated in PSI - about 10 to 15. Coolant overflow tanks are connected so that the pressure cap has to open for coolant to flow into them. Just putting an unpressurized overflow tank at the highpoint of the coolant loop defeats the pressure that the engine is designed for.

Once the coolant loop is primed there is no need for a high point overflow. A "T" fitting with a cap on it should be used to get all the air out of the system. An automotive flushing kit has this fitting included in it. Just cut the hose to your calorifier (us yanks call it a water heater) at the high point fit the fitting with coolant fill at the "T" fitting until it overflows. Cap it and run the engine a few minutes and top off again. After a good engine run check for air at this point again. This is to prevent vapor lock. If air surrounds your engine coolant pump it will not circulate the coolant and the engine will overheat.


https://www.dkhardware.com/prestone-...BoCrPgQAvD_BwE

[capt jgw]

The header tank I used had a pressure cap and maintained pressure.

[ed80]

Thanks everyone for your advice. I will check the engine compartment to see if a header tank will fit neatly, I found a couple of small tanks which have pressure caps which should work, otherwise I will look at adding a tee at the highest point and filling from there.

[wrwakefield]

The easy way to contend with bleeding air from a pressurized liquid loop is to install automatic bleeders at high point(s) in the loop. This is very common in home hydronic heating circuits, and I have been installing them on my boats for decades.



Appended is a photo of one installed on the top (outlet) of a 'bus' heater plumbed into the engine coolant loop (about 3 feet above the engine.). There is also one on the highest water heater coolant outlet.

To purge air and fill the coolant system to capacity, just run the engine up to temp with the coolant reservior cap removed ["radiator cap"] so you can view and continue topping coolant as it circulates. Reinstall the cap when it won't take any more coolant. (e.g., After maybe 10 mins at normal engine operating temperature.) These will make your next engine coolant change much easier.

Those with hydronic heating systems should also take note; replace the manual bleaders with these.

I use and recommend the purpose designed Watts FV-4M1 units that have a silicone valve rather than a Schrader valve. They are cheap at under US$15 each.

In case any of this is useful.

Cheers, Bill