Calorifier

[chris w]

8 litres is the perfect size expansion vessel for a 65 litre calorifier. The expansion of the water could be as much as 4% but expansion tanks have a rubber membrane in them which means that only half the volume is available to hold water. So one actually needs an expansion vessel of 8% to accomodate the water expansion. This tends to get translated into a rule-of-thumb of 10% which, in your case, would equate to 6.5 litres and the nearest available "standard" size is 8 litres.

 

I would suspect that very few people, if any, have an 8 litre accumulator on their water pump (2 litres being more normal)and so the accumulator will, in the vast majority of cases, not handle the calorifier expansion, with the result that the PRV will still lift. In answer to a query above too, the PRV won't suddenly lift and dump a litre over the side. As the calorifier heats up, the PRV will open gently and will continuously weep water over the side. Of course if one has a NRV fitted the accumulator is isolated from the calorifier anyway and so can do nothing for calorifier expansion.

 

It's always a good idea to manually turn the PRV a few times, and let it spring back on to its seating, say on a bi-monthly basis to ensure that there is no build-up of chalky deposits under the seating due to its having been weeping.

 

Chris

Edited November 4, 2008 by chris w

[Keeping Up]

I suspect many systems do not have a NRV, so the cold system accumulator also acts as an expansion vessel. which helps ........ or not!

Or they have a system like mine where the NRV is in the hot water pipe between the calorifier and the first hot tap.

[mikevye]

Or they have a system like mine where the NRV is in the hot water pipe between the calorifier and the first hot tap.

 

I was advised to fit the NRV on the cold inlet prior to the calorifier to resolve the problem of hot water out of the cold tap when the tap was first opened but I don't understand the need for one on the hot outlet.

[Guest TerryL]

I was advised to fit the NRV on the cold inlet prior to the calorifier to resolve the problem of hot water out of the cold tap when the tap was first opened but I don't understand the need for one on the hot outlet.

If you actually had this problem then this solution on it's own can only create further problems. The answer is a properly thought out installation to start with.

[chris w]

If you actually had this problem then this solution on it's own can only create further problems. The answer is a properly thought out installation to start with.

 

Mike is correct........ let's assume there is no NRV and that the boater has a typical accumulator on the water pump. The pressure in the hot calorifier will be much greater than this (regardless of whether an expansion tank is fitted or not), maybe as much as 40psi, so when a cold tap is opened, hot water will flow from the cold tap for the time it takes for the calorifier pressure to drop to the pump's cut-in pressure of around 20psi . I fixed this exact issue for someone in my marina by simply fitting an NRV for them in the cold feed just before the calorifier.

 

In my opinion, a "properly thought out installation" includes an NRV. What's the disadvantage of fitting one? I would always advocate the fitting of an expansion vessel on the calorifier too.

 

Chris

[mikevye]

If you actually had this problem then this solution on it's own can only create further problems. The answer is a properly thought out installation to start with.

 

To make a critical sweeping statement like this and with no details of my system leaves me in no doubt as to why forum members fall out with you. I will however tell you that surecal advised me to put the NRV in as the retail unit (as opposed to bare shell) has one fitted in the factory!

[Guest TerryL]

To make a critical sweeping statement like this and with no details of my system leaves me in no doubt as to why forum members fall out with you. I will however tell you that surecal advised me to put the NRV in as the retail unit (as opposed to bare shell) has one fitted in the factory!

I'm a heating engineer and I have a license to install these things so I know about them very well and that makes me able to make critical sweeping statements. Surecal are not necessarily giving you the best or complete info, compare it with domestic setup. If you are offended by me trying to help to improve the knowledge and to see a better and simpler way of doing these things that won't cause any problems then struggle on and don't read, this is still an open forum. Fitting the expansion vessel at the calorifier cold inlet will avoid the need for a NRV.

[carlt]

I'm a heating engineer and I have a license to install these things so I know about them very well and that makes me able to make critical sweeping statements. Surecal are not necessarily giving you the best or complete info

Do Surecal not employ heating engineers?

[mikevye]

I'm a heating engineer and I have a license to install these things so I know about them very well and that makes me able to make critical sweeping statements. Surecal are not necessarily giving you the best or complete info, compare it with domestic setup. If you are offended by me trying to help to improve the knowledge and to see a better and simpler way of doing these things that won't cause any problems then struggle on and don't read, this is still an open forum. Fitting the expansion vessel at the calorifier cold inlet will avoid the need for a NRV.

 

Thats cool TerryL, your last sentence makes sense and I can relate to that thankyou. Trouble is the lack of space for the expansion vessl against the size of the NRV which is why it was fitted.

[Guest TerryL]

Do Surecal not employ heating engineers?

Why ask me? The systems you get on boats where people often live as their main home would not be permitted in other domestic premises so without any regulation they are usually substandard toy copies. That's a fact borne out by the frequent problems that are experienced. It seems that people are more inclined to just talk about their problems in depth and struggling on with complicated calculations and theories than to fix them properly and get on with their boating, very odd. You don't have to buy expensive substandard marine equipment and suffer poor living conditions because you live on a boat. You do have to take into account space considerations on some things of course but that can often be overcome with a bit of thought and fitting parts remotely in spare spaces.

 

 

Thats cool TerryL, your last sentence makes sense and I can relate to that thankyou. Trouble is the lack of space for the expansion vessl against the size of the NRV which is why it was fitted.

But you've still got an expansion vessel, or you should also have if you are using a NRV, it's not an alternative. Fit the expansion vessel in a convenient space and run a pipe back to the calorifier cold inlet.

[RLWP]

I suspect many systems do not have a NRV, so the cold system accumulator also acts as an expansion vessel. which helps ........ or not!

 

What! Because we don't have an NRV (except the valves in the pump) our cold system accumulator acts as an expansion vessel! We haven't got a cold system accumulator.

 

Richard

 

Really, I wonder that we ever get any water at all...

[mikevye]

But you've still got an expansion vessel, or you should also have if you are using a NRV, it's not an alternative. Fit the expansion vessel in a convenient space and run a pipe back to the calorifier cold inlet.

 

But I've got 8 litres of accumalator/expansion tank on the hot side as previously stated does this not count?

[Guest TerryL]

But you've still got an expansion vessel, or you should also have if you are using a NRV, it's not an alternative. Fit the expansion vessel in a convenient space and run a pipe back to the calorifier cold inlet.

 

 

But I've got 8 litres of accumalator/expansion tank on the hot side as previously stated does this not count?

That's what I said, you need a NRV because otherwise the hot will backfeed with the expansion vessel on the hot. You only need sufficient expansion in the right place which should be on the cold. If you are getting hot water in the cold then it is because the vessel on the hot side is backfeeding like an accumulator through the calorifier when the cold tap is opening due to insufficient cold accumulator capacity or pre-charge pressure.

 

Fitted in the cold the expansion water will be cold and no hot water will get to the cold tap and it's simpler. Surecal haven't thought of that and is the only reason why you have to fit an NRV! The expansion vessel will also last longer in the cold and without a NRV will also act as an additional acummulator. Some domestic unvented cylinders have an airgap for expansion and it's only them that need a NRV which can backleak.

[chris w]

That's what I said, you need a NRV because otherwise the hot will backfeed with the expansion vessel on the hot......

 

As you are a "heating engineer with a license" (sic), at least make up your mind which side of the fence you are on.

 

You make the statement above saying one needs an NRV, to stop backfeed, which contradicts your statement from a few posts above, towit: "However you are unlikely to get hot water reversing out of a vertical or horizontal calorifier in practice because the bottom part is always unheated and cold due to stratification. This is another carefully thought out myth easily overcome by common sense and good plumbing practice............ "

 

Are you sure you're a heating engineer or just a heating mechanic? (with or without a licence?)

[Guest TerryL]

As you are a "heating engineer with a license" (sic), at least make up your mind which side of the fence you are on.

 

You make the statement above saying one needs an NRV, to stop backfeed, which contradicts your statement from a few posts above, towit: "However you are unlikely to get hot water reversing out of a vertical or horizontal calorifier in practice because the bottom part is always unheated and cold due to stratification. This is another carefully thought out myth easily overcome by common sense and good plumbing practice............ "

 

Are you sure you're a heating engineer or just a heating mechanic? (with or without a licence?)

You never were very good at reading and understanding technical posts but I thought you'd appreciate the spelling, gives you something to pick holes in, towit.

[chris w]

You never were very good at reading and understanding technical posts but I thought you'd appreciate the spelling, gives you something to pick holes in, towit.

So yet another query you haven't answered. Same old Mr Langridge.

 

(BTW There were other spelling mistakes in your post too, but I thought more than one at a time might be difficult for you to handle.)

[ChrisPy]

in India they call them PLUMPERS !!

[Guest TerryL]

Is there anyone genuinely interested who can't understand my posts and would like me to clarify?

[ChrisPy]

like not being able to scratch an itch in the middle of your back, innit?

[chris w]

Is there anyone genuinely interested who can't understand my posts and would like me to clarify?

 

Me me me me me me..........

[mikevye]

Is there anyone genuinely interested who can't understand my posts and would like me to clarify?

 

yes please, you give some waffle about stratification and cold water at the bottom of the cylinder which I find a bit difficult to accept but with additional heating from the CH coil AND the engine heating coil there is no way that the calorifier water temperature wont be uniform throughout. Also I had the problem of hot water back feed prior to fitting the accumulator as the factory fitted NRVv had failed.

Edited November 5, 2008 by mikevye

[chris w]

yes please, you give some waffle about stratification and cold water at the bottom of the cylinder which I find a bit difficult to accept but with additional heating from the CH coil AND the engine heating coil there is no way that the calorifier water temperature wont be uniform throughout. Also I had the problem of hot water back feed prior to fitting the accumulator as the factory fitted NRVv had failed.

I notice Mike that he never bothered coming back to you despite the fact that he said he would. This seems pretty typical as he has many questions from me unanswered as well.

 

At least when he doesn't come back and actually explain something, one knows that he was incorrect afterall.

 

Chris

[Smelly]

yes please, you give some waffle about stratification and cold water at the bottom of the cylinder which I find a bit difficult to accept but with additional heating from the CH coil AND the engine heating coil there is no way that the calorifier water temperature wont be uniform throughout. Also I had the problem of hot water back feed prior to fitting the accumulator as the factory fitted NRVv had failed.

 

I'd wonder whether nobody's mentioned convection...

 

Regarding backfeed, Graham Booth had the same problem on his horizontal calorifier during his fitting out of Rome, as documented in the third edition of the narrowboat builder's book. he fitted an NRV and it was fixed. I hope that's cleared it up.

 

yes please, you give some waffle about stratification and cold water at the bottom of the cylinder which I find a bit difficult to accept but with additional heating from the CH coil AND the engine heating coil there is no way that the calorifier water temperature wont be uniform throughout. Also I had the problem of hot water back feed prior to fitting the accumulator as the factory fitted NRVv had failed.

 

I'd wonder why nobody's mentioned convection...

 

Regarding backfeed, Graham Booth had the same problem on his horizontal calorifier during his fitting out of Rome, as documented in the third edition of the narrowboat builder's book. he fitted an NRV and it was fixed. I hope that's cleared it up.

[chris w]

Regarding backfeed, Graham Booth had the same problem on his horizontal calorifier during his fitting out of Rome, as documented in the third edition of the narrowboat builder's book. he fitted an NRV and it was fixed. I hope that's cleared it up.

Ah, but does Graham Booth have a heating engineer's license (sic) like TerryL claims he has? Different league mate.

 

Chris

Edited November 5, 2008 by chris w

[Guest TerryL]

yes please, you give some waffle about stratification and cold water at the bottom of the cylinder which I find a bit difficult to accept but with additional heating from the CH coil AND the engine heating coil there is no way that the calorifier water temperature wont be uniform throughout. Also I had the problem of hot water back feed prior to fitting the accumulator as the factory fitted NRVv had failed.

Only one person genuinely interested then? Hardly worth the effort if the only one has a closed mind and thinks hot water stratification is waffle! Learn about it and I won't need to repeat myself. http://wiki.diyfaq.org.uk/index.php?title=...#Stratification

 

BTW we might as well accept the ineviable and use the U.S spellings and terminology for things like licence/license much the same as someone claiming to be a math and physics major when they mean they've got two "O" levels!