Accumulators for calorifiers

[Strettonman]

I’m about to sort the water system and I’ve had different advice for accumulators. Do I need one soon after the water pump AND another on the hot feed from the calorifier ? 

 

Seems overkill but I gather the calorifier is only guaranteed if you have one on the hot feed but would be over 40ft away from the pump with a mixer valve in between. 

 

If two are needed I presume it is important for them to be the same rating. 

[alan_fincher]

They may look like, or even actually be the same thing, but an accumulator on the cold supply is not the same as an expansion vessel (EV) protecting the calorifier.  Each will be pressurised to completely different pressures, and whilst an accumulator can be any size, and only affects how regularly the pump cycles, an EV needs to be big enough for the volume of water in the calorifier it is there to protect.

 

If there is a non return valve (NRV) in the feed to the calorifier, (and there is on pre-plumbed SureCal/SureJust ones), then the accumulator can not in any way act as a substitute for not having an EV.  That is why SurejJust say their guarantee is voided if one is not fitted.

Edited June 16, 2019 by alan_fincher

[BEngo]

Yes you do need two. An accumulator adjacent to the pump is to prevent short cycling (unless you have one of the clever pumps with built-in anti cycling controls) and an expansion vessel on the hot water supply pipe near the calorifier.  This absorbs the extra volume in the hot water side as the water expands on heatting.  Size depemnds on the volume of your calorifier, and the storage temperature of your hot water.

Set the accumulator bladder to the pump cut in pressure and the EV bladder to the pump cut out pressure, using a tyre pump and pressure gauge on the Schrader valve in the end of the accumulator/ expansion vessel. If you don't know these pressures they can be measured  at the accumulator with a bit of switching on and off of the pump-  search for my post on how to set up an accumulator.

 

N

[Pie Eater]

Our boat is 20 years old and has never had either of the above so my question is are they really essential?

[Tony Brooks]

My take is that in times past the calorifiers seemed to be absolutely fine without an expansion vessel, just relying the the hot water PRV, so I suspect Surecal are covering their back, possibly because of insubstantial build quality etc.

 

Myown boat has no expansion vessel as such but the NRV is between the tank and accumulator and the pump pressure is set to about 20PSI, so the accumulator is pressurised to 10psi. As far as I can see there is plenty of volume for the accumulator to act as the expansion vessel as well.

 

If you do not want a disturbed night or t switch your water pump off at night I would say an accumulator is all but essential. If you are fitting a modern calorifier I think the build quality is likely to be such that an expansion vessel is also all but essential.

[Jen-in-Wellies]

24 minutes ago, Pie Eater said:

Our boat is 20 years old and has never had either of the above so my question is are they really essential?

Without an expansion vessel on the hot water side, you are relying on the pressure relief valve to prevent your calorifier from going over pressure and potentially bursting as the water inside warms up and expands. If the PRV sticks you could have a flood of scaldingly hot water. The prv is a single point of failure, rather than a backup to the expansion vessel. Beside which, cauliflowers are expensive and the continuous extra expansion and contraction from going up to PRV opening pressure and down to pump pressure is perhaps shortening its life. Your choice. My first calorifier didn't have an expansion vessel in the system and the PRV was acting like this. It sprang a leak and had to be replaced. The new one was fitted at the same time as an expansion vessel and has survived so far. Coincidence? Maybe.

 

The accumulator by the water pump isn't so important and only prevents the pump short cycling.

 

Jen

[peterboat]

3 minutes ago, Jen-in-Wellies said:

Without an expansion vessel on the hot water side, you are relying on the pressure relief valve to prevent your calorifier from going over pressure and potentially bursting as the water inside warms up and expands. If the PRV sticks you could have a flood of scaldingly hot water. The prv is a single point of failure, rather than a backup to the expansion vessel. Beside which, cauliflowers are expensive and the continuous extra expansion and contraction from going up to PRV opening pressure and down to pump pressure is perhaps shortening its life. Your choice. My first calorifier didn't have an expansion vessel in the system and the PRV was acting like this. It sprang a leak and had to be replaced. The new one was fitted at the same time as an expansion vessel and has survived so far. Coincidence? Maybe.

 

The accumulator by the water pump isn't so important and only prevents the pump short cycling.

 

Jen

Virtual Greenie Jen, I have had my cauliflower burst, the EV failed, and my PRV because it was in a bad position wasnt rotated as often as it should be [never] Anyway I installed a new EV close to the cauliflower with the PRV on top and check the pressure rgularly along with rotating the PRV!! Once scalded never happens again

[cuthound]

Just before we bought DQ she had a new Surecal calorifier fitted at a cost of over £700.

 

Fitting an expansion vessel at under £150 seemed like a good insurance policy.

[blackrose]

£150? I bought mine for about £40. That was about 10 years ago but still, have they increased in price that much?

 

Mine is stainless. This 8 litre one is epoxied but only £29.

 

https://www.toolstation.com/expansion-vessel/p29704?store=GL&utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&gclid=CjwKCAjw0ZfoBRB4EiwASUMdYT13h0Ti17Vbr-edvppGxp62rfMsZ2mRoaDaoqokqCrIQcgZ63mWshoCwO4QAvD_BwE

 

Is this one ok for fresh water or should it be stainless inside?

 

 

Edited June 16, 2019 by blackrose

[alan_fincher]

I'm guessing that the £150 is to have something fitted professionally, not to do it yourself?

 

Otherwise yes, maybe £30 to £40 for a suitable vessel, and maybe another tenner for the plumbing bits required.

 

It's not always entirely obvious, but a flexible tap connector is often the best way of joining to the parallel threaded brass connector that many are fitted with.

[MtB]

16 hours ago, Jen-in-Wellies said:

 

The accumulator by the water pump isn't so important and only prevents the pump short cycling.

 

 

I'm inclined to disagree. The trickle of split calorifiers (boo-hoo) posted about on here seem to mainly happen on installations with no water pump accumulator.

 

My tentative explanation for this happening is the resultant rapid hunting on and off of the water pump cycles the pressure in the calorifier up and down hundreds of times more frequently than on installations with one, which causes metal fatigue in the copper of the calorifier, and consequent splitting.

 

 

 

In other words, I suspect fitting a water pump accumulator when the calorifier has no NRV, vastly extends the life of the calorifier.

 

 

[Jen-in-Wellies]

1 minute ago, Mike the Boilerman said:

 

I'm inclined to disagree. The trickle of split calorifiers (boo-hoo) posted about on here seem to mainly happen on installations with no water pump accumulator.

 

My tentative explanation for this happening is the resultant rapid hunting on and off of the water pump cycles the pressure in the calorifier up and down hundreds of times more frequently than on installations with one, which causes metal fatigue in the copper of the calorifier, and consequent splitting.

 

 

 

Good point. Increased fatigue cycles could well be a risk to the cauliflowers wellbeing. (Thought I'd put CaRT's latest buzzword in there!).

 

Jen

[MtB]

22 minutes ago, Jen-in-Wellies said:

Good point. Increased fatigue cycles could well be a risk to the cauliflowers wellbeing. (Thought I'd put CaRT's latest buzzword in there!).

 

Jen

 

Greenie for that!

 

It's hard to tell because the number of failures is so small, but when I encounter one I always ask about whether the system has accumulator(s) fitted and the answer has always been 'no' so far.

 

Cue a string of about ten boaters in 20 mins now saying theirs failed with two accumulators fitted.... ?

 

[Jen-in-Wellies]

16 minutes ago, Mike the Boilerman said:

Cue a string of about ten boaters in 20 mins now saying theirs failed with two accumulators fitted...

And another ten boaters saying "I've had my boat for 40 years. Never had one of these new fangled cucumber things and it still has its original cauliflower." It wouldn't be CWDF otherwise!

 

Jen ?

[MtB]

1 hour ago, Jen-in-Wellies said:

And another ten boaters saying "I've had my boat for 40 years. Never had one of these new fangled cucumber things and it still has its original cauliflower." It wouldn't be CWDF otherwise!

 

Jen ?

 

We've already had one of them - in Post 4...!!!!

 

 

[Captain Fizz]

I replaced my colorifier last year after the original split.

I installed a stainless steel unvented storage cylinder.

Much better insulated, stays hot for days, and has a 25 year guarantee.

[Guest]

3 hours ago, Mike the Boilerman said:

 

I'm inclined to disagree. The trickle of split calorifiers (boo-hoo) posted about on here seem to mainly happen on installations with no water pump accumulator.

 

My tentative explanation for this happening is the resultant rapid hunting on and off of the water pump cycles the pressure in the calorifier up and down hundreds of times more frequently than on installations with one, which causes metal fatigue in the copper of the calorifier, and consequent splitting.

 

 

 

In other words, I suspect fitting a water pump accumulator when the calorifier has no NRV, vastly extends the life of the calorifier.

 

 

Interesting thoughts.

[peterboat]

Mine was my own fault, my old cauliflower was on the stern swim along with the EV and the PRV, when I moved the new cauliflower to the cupboard I didnt move the EV and PRV because it was to big and Idintgetaroundtuit!!! so my cauliflower split after about 5 years of abuse! It was repairable by Newark copper cylinders for £50 so it wasnt the disaster it could have been and now in the cupboard is all the gear to stop a repeat performance

[TheBiscuits]

3 hours ago, Jen-in-Wellies said:

And another ten boaters saying "I've had my boat for 40 years. Never had one of these new fangled cucumber things and it still has its original cauliflower." It wouldn't be CWDF otherwise! 

I'm just waiting for the first one to tell us they have installed a series of pressure sensors linked to an armadillo or a raspberry that cuts out the pump to avoid water hammer instead of just using a cucumber on their cauliflower.

 

My money is on @Jen-in-Wellies !

[Jen-in-Wellies]

4 minutes ago, TheBiscuits said:

I'm just waiting for the first one to tell us they have installed a series of pressure sensors linked to an armadillo or a raspberry that cuts out the pump to avoid water hammer instead of just using a cucumber on their cauliflower.

 

My money is on @Jen-in-Wellies ! 

Already on it. Down the greengrocers right now. Exotic pet store next.

Jen ?

[cuthound]

7 hours ago, alan_fincher said:

I'm guessing that the £150 is to have something fitted professionally, not to do it yourself?

 

Otherwise yes, maybe £30 to £40 for a suitable vessel, and maybe another tenner for the plumbing bits required.

 

It's not always entirely obvious, but a flexible tap connector is often the best way of joining to the parallel threaded brass connector that many are fitted with.

 

Yes to gain access to the calorifier and pipework required the airing cupboard/wardrobe to be dismantled.

[MtB]

1 minute ago, cuthound said:

 

Yes to gain access to the calorifier and pipework required the airing cupboard/wardrobe to be dismantled.

 

In which case whoever fitted it there needs to be made to service it annually!

 

 

[Strettonman]

Thanks everyone - sorry for radio silence but phone threw a woddler and only just got it back. 

 

I will I’ll go for a EV downstream of the calorifier. I gather it should be 10% of volume so I need a 5ltr EV. Surecal website come up at over £60 but on eBay you can get EVs for central heating systems for less than £20. Is there something special about boat EVs ? Also, is there any real benefit in including a pressure gauge ?

the calorifier in going to be on the swim next to the engine so if I can fit it in is there any reason why the EV shouldn’t also be out there - same me storage space in the cabin. 

[hider]

Central heating EVs are for sealed systems, yours will be using fresh water, big difference. Hence the price.

[Iain_S]

As above; get one that's rated for potable water.