KevO
Well-Known Member
I know what they do but do you really need both? Space is a little limited so I could prob get away with a 2L one, maybe 2 of them at a real push but are they both absolutely necessary?
Calorifier - Expansion and Accumulator tanks
- Thread starter KevO
- Start date
paulajayne
Well-Known Member
One allows for expansion on heating side and the other provides residual pressure so that the pump is not forever cycling (storing pressure like a battery).
So doing different jobs.
So doing different jobs.
Old Bumbulum
Well-Known Member
In short, no, they're not both strictly necesary.
Plenty of info, guidance and diagrams available on a google search!
Plenty of info, guidance and diagrams available on a google search!
neilf39
Well-Known Member
You should have an expansion tank but you may not need an accumulator, it depends on your pump. I have one that has a bypass that stops it cycling.
vyv_cox
Well-Known Member
No, not essential at all. My Sadler is the SE version that comes with a calorifier but it had neither as-built. I added an accumulator immediately after the pump to cut down the continuous pump operation when the taps were open.
An expansion tank may be needed if there is a NRV at the cold water inlet to the calorifier but if not then expansion can occur backwards to the accumulator. But as my boat shows, there is usually sufficient elasticity in the hoses to take up the small water expansion on heating.
An expansion tank may be needed if there is a NRV at the cold water inlet to the calorifier but if not then expansion can occur backwards to the accumulator. But as my boat shows, there is usually sufficient elasticity in the hoses to take up the small water expansion on heating.
pvb
Well-Known Member
As Vyv says, they're not essential. I don't have either on my boat. If you have hot water piped to the heads, there'll probably be more than enough hose to cope with slight expansion.
KevO
Well-Known Member
I do have H+C to the head and galley so that sounds good.
rogerthebodger
Well-Known Member
As has been said an expansion is not essential but if you don't have an expansion tank I would recommend a pressure relief valve fitted to the Calorifier inlet after the NRV.
This is how my hot water Calorifier is setup.
This is how my hot water Calorifier is setup.
AndrewB
Well-Known Member
But with simple pumps it's the other way round. The accumulator will prevent it cycling, and will also serve as an expansion tank (takes up the extra when the water in the calorifier is heated and so expands. However the expanding hot water will get into the cold water pipes. If your system has a non-return valve to prevent this, you will also need a separate expansion tank.
Plum
Well-Known Member
I have neither and all works well. Without an expansion tank the PRV on the calorifier will open to let out and excess pressure. I have a 0.5l container to collect this and empty it occasionally.
(Edited: i said NRV when I meant to say PRV)
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lw395
Well-Known Member
I think you mean the pressure relief valve?
My view of this, having had to sort out some odd problems is that some odd things can happen sometimes, which an expansion vessel can help with.
Calorifier water can get dangerously hot.
If you have a thermostatic mixing valve or temperature limiting valve on the shower/heads taps, then it may not work properly or at all if the hot side is pressurised by expansion above the cold side.
It's plausible to get scalding water out of a cold tap which is seriously not clever.
In the limit, if you thrash the engine and boil the calorifier water, I'm not sure an accumulator actually prevents this though.
In practice, there is usually some air space in the calorifier which acts as an accumulator/expansion vessel.
A lot of people switch the water pump off at night, if you don't have an NRV on the calorifier inlet, then you can get hot out of the cold tap due to the air or EV pressure.
johnalison
Well-Known Member
I have to admit that I have never completely understood my system. It has an accumulator and a PRV with a non-return valve included, an odd item that was hard to source when it needed replacing. I have never had hot or even warm water coming from the cold taps, so it works for me. It will work with a failed accumulator but is better with one, and currently, touch wood, has no leaks and will not normally pump in the night.
Plum
Well-Known Member
AndrewB
Well-Known Member
Mine was exactly like this when I bought my boat. The result was that not only did the water system judder when the taps were turned on and the pump activated, but also there was a steady leak from the PRV.
The previous owner had tried to control this with a load of padding round the pump, plus an elaborate system for catching the leak! He wasn't very practical. It was a small matter to repressure the accumulator correctly and to remove the non-return valve. Now it all runs smoothly, though I do get a quick shot of warm water when I open the cold tap in the galley. Its not enough of a problem for me to bother with an expansion tank.
prv
Well-Known Member
Same here. Pump doesn't run except when first turned on and when a tap is opened, hot water works as expected (and never comes out of the cold taps), and the tank overflow bottle needs emptying of a litre or so of water maybe twice a season. I put a float switch in it connected to a flashing LED to remind me, since it's such an infrequent job.
Pete
vyv_cox
Well-Known Member
I have seen some installations in which the cold water Tee to tap/calorifier is on the calorifier itself. In this case warm water could flow back and then out of cold water tap. In our case the Tee is about a metre away so we never experience this particular problem.
