calorifier expansion bottle

[Sammy Lou]

Hi,
I've had a new engine fitted over the winter and as part of the engine install I've had a new hotpot 15l calorifier hooked up to the engine cooling circuit. The domestic plumbing has not been done and its for me to now modify the existing system to remove the old gas water heater and convert to the new calorifier system. Looking at the hotpot literature it recommends installing an expansion bottle after the calorifier on the hot water circuit (there is already an accumulator on the cold water supply) but does not specify the size. ASAP have hotpot 2l expansion bottles but this seems big for a 15l system. Does anyone have any experience? Jabasco do a 1l size that seems more appropriate & would fit better. Any help much appreciated.

 

[David2452]

If your new calorifier has an NRV on the cold input then you will need a separate expansion vessel unless you remove it, with such a very small calorifier if there is no NRV then I wouldn’t bother. Again with such a small calorifier I certainly would never fit an expansion vessel on the hot side as every time you use some hot you will have hot water in the (uninsulated) vessel which will cool and be wasted. I always install expansion vessels (of any size) on the cold feed but after an NRV, on Surejust products there is an NRV on the inlet which has no indication that it is there so I remove it and fit it on the upstream side of the vessel.

 

[VicS]

What David says of course.

For further info / interest see https://www.jabscoshop.com/files/Accumulator and Expansion Tank Instructions ZPWL4 doc595.pdf

 

[rogerthebodger]

Hi,
I've had a new engine fitted over the winter and as part of the engine install I've had a new hotpot 15l calorifier hooked up to the engine cooling circuit. The domestic plumbing has not been done and its for me to now modify the existing system to remove the old gas water heater and convert to the new calorifier system. Looking at the hotpot literature it recommends installing an expansion bottle after the calorifier on the hot water circuit (there is already an accumulator on the cold water supply) but does not specify the size. ASAP have hotpot 2l expansion bottles but this seems big for a 15l system. Does anyone have any experience? Jabasco do a 1l size that seems more appropriate & would fit better. Any help much appreciated.

On my system I have a NRV in the cold water inlet to the calorifier and a pressure release valve in the outlet of the calorifier set at a pressure just above the cold water pump pressure.

In this setup you do not need a expansion bottle after the calorifier.

 

[whiteoaks7]

So where does the water go when it expands? The only way it can reduce pressure (assuming the taps are not turned on) is through the pressure relief valve. On our boat this was the setup I inherited but I added a vessel when I got fed up with the wet cockpit locker bilge. I guess a plan might be to try it - you can always add a vessel later, you could also do the sums to see how much expansion you'll get over the temperature range (maybe 20C up to hot engine coolant temp say 70C? which gives about 0.15L expansion if I got the sums right). [or you can go here and play: http://www.engineeringtoolbox.com/vo...ion-d_315.html ]. Probably not as bad as that in practice because the calorifier will also expand and so will any local pipework.
Read more at http://www.ybw.com/forums/newreply.php?do=postreply&t=475303#qfhV50RODWAdptUS.99

 

[Sammy Lou]

Thank you all. Much appreciated. So, I think that, for now, I won't fit an expansion tank. I'll fit an NRV in the cold water inlet line and leave some room for retro-fitting an expansion tank at a later date if necessary, if the PSV is discharging to the bilges excessively.

 

[PaulRainbow]

Thank you all. Much appreciated. So, I think that, for now, I won't fit an expansion tank. I'll fit an NRV in the cold water inlet line and leave some room for retro-fitting an expansion tank at a later date if necessary, if the PSV is discharging to the bilges excessively.

You misread post #2

 

[PaulRainbow]

On my system I have a NRV in the cold water inlet to the calorifier and a pressure release valve in the outlet of the calorifier set at a pressure just above the cold water pump pressure.

In this setup you do not need a expansion bottle after the calorifier.

This is how mine is, it is also how my last boat was and neither drip water into the bilges. I presume that is because, as David says, the calorifiers are small.

 

[lw395]

This is how mine is, it is also how my last boat was and neither drip water into the bilges. I presume that is because, as David says, the calorifiers are small.

And very likely have an air space in them.

 

[prv]

The only way it can reduce pressure (assuming the taps are not turned on) is through the pressure relief valve. On our boat this was the setup I inherited but I added a vessel when I got fed up with the wet cockpit locker bilge.

I inherited a similar setup but with the pressure relief outlet drained to a plastic bottle of somewhere around 1.5 litres. I added a float switch 2/3rds of the way up, wired to a warning LED, and it comes on and needs emptying about once per year. An expansion tank would probably be better, but I'm satisfied with this. I believe the tank is a 20-litre one, I'm not sure if there's a non-return on the inlet.

Pete

 

[rogerthebodger]

This is the Vetus calorifier fitting kit that Consists of 4 x hose pillars 1/2"BSP for 16mm hose, tee piece, pressure relief valve (4bar) and non return valve with drain off point.

http://www.vetusdirect.com/calorifier-water-heater-5-sized-model-wh20c-wh75c/