Calorifier Expansion Vessel

[kalanka]

I am fitting a new Quick 25L B3 calorifier to be heated by coolant from a 28HP VP 2003 in a 34 foot sloop. The domestic water circuit is pressurised by a Jabsco PAR pump.

The B3 installation diagram shows an expansion tank in the hot water circuit. The calorifier it is to replace does not have any obvious expansion tank and has worked well for a long time. Could anyone explain the purpose of the expansion tank? Is it a necessary addition or could it be omitted?

Thanks

 

[pvb]

I am fitting a new Quick 25L B3 calorifier to be heated by coolant from a 28HP VP 2003 in a 34 foot sloop. The domestic water circuit is pressurised by a Jabsco PAR pump.

The B3 installation diagram shows an expansion tank in the hot water circuit. The calorifier it is to replace does not have any obvious expansion tank and has worked well for a long time. Could anyone explain the purpose of the expansion tank? Is it a necessary addition or could it be omitted?

The Quick instructions actually show an expansion tank in the cold water circuit. An expansion tank will allow the slightly increased volume of water as the tank heats up to be absorbed without triggering the relief valve and letting water into the bilges. As long as there are no non-return valves, the expansion tank could be in either the hot or cold pipes.

It's well worth getting the thermostatic mixing valve kit too.

 

[VicS]

But with no NRV you may some warm water from the cold water taps as the hot water system heats up

There is a good explanation of accumulator tanks here:
https://www.jabscoshop.com/files/Accumulator and Expansion Tank Instructions ZPWL4 doc595.pdf

 

[neilf39]

I's normal to have an NRV between hot and cold so the hot water can't get to mix a bit with the cold when coming out the cold tap. If you have one then you should have an expansion tank. If you don't then you will likely get water coming out of the calorifier pressure relief valve (PRV) and going into the bilge when it heats up which you may not have noticed on your old setup. I assume you have a PRV.

 

[Plum]

I am fitting a new Quick 25L B3 calorifier to be heated by coolant from a 28HP VP 2003 in a 34 foot sloop. The domestic water circuit is pressurised by a Jabsco PAR pump.

The B3 installation diagram shows an expansion tank in the hot water circuit. The calorifier it is to replace does not have any obvious expansion tank and has worked well for a long time. Could anyone explain the purpose of the expansion tank? Is it a necessary addition or could it be omitted?

Thanks

Assuming your calorifier has a non return valve in the domestic water inlet so as the water expands as it is heated it is not forced back into the cold watet system, then you have two choices: fit an expansion tank in the hot outlet to absorb the increased pressure, or, let the pressure releif valve releive the pressure and put a hose from the prv into a 1/2 litre container which you empty once in a while. My boat has the latter and has worked perfectly well for 20 years.

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