Calorifiers

[Alastair]

I asked a manufacturer (albion) of hot water cylinders what the difference between their domestic and marine calorifiers.

 

The response was this:

 

The marine calorifiers are smaller.

 

The connections on the marine calorifiers are smaller.

 

Most of the marine calorifiers have twin coils, and only some of the domestic systems have twin coils.

 

So there doesn't seem to be any technical reason to need a 'marine' calorifier over a domestic unvented tank.

 

I was surprised - I expected them to tell me that the marine ones were of heavier construction etc (they do a heavy-duty stainless-cased marine range).

[John Orentas]

I asked a manufacturer (albion) of hot water cylinders what the difference between their domestic and marine calorifiers.

 

 

It used to be said that as water pressures on boats is so much higher than on domestic systems the construction is that much more robust to cope with the higher pressures. Sounds logical but don't know how true it is.

[Alastair]

I think that was true when domestic were all vented tanks, but they now build unvented ones; i.e. running at full mains pressure. Gut feeling tells me that mains pressure is going to be higher than 12V pump pressure.

[Gary Peacock]

The cheap one like Albion probably are no different but the true marine ones tend to be of a better spec.

 

We used to fit cheap one but the amounts of failures proved it a mistake in the long run we now fit Surejust and touch wood haven't had a failure for over 3 years.

[Alastair]

Thanks for the link, Gary. However, their brochures only show up to 50l cylinders, with just one coil. I'm unconvinced that they offer anything not offered by that a major manufacturer of domestic hot water cylinders.

 

What brands did you have problems with (pm me if you don't want to state it in a public forum).

[Theo]

I think that was true when domestic were all vented tanks, but they now build unvented ones; i.e. running at full mains pressure. Gut feeling tells me that mains pressure is going to be higher than 12V pump pressure.

 

I am sure that your gut feeling is correct. I bet your pump could not push water to the top of School Hill!

 

Nick

[Gibbo]

I think that was true when domestic were all vented tanks, but they now build unvented ones; i.e. running at full mains pressure. Gut feeling tells me that mains pressure is going to be higher than 12V pump pressure.

 

Are there any plumbers on this forum?

 

I thought the unvented house hot water systems didn't store hot water in a tank? ie they use combi boilers.

 

I've only ever seen house hot water tanks fed from a header tank with *very* low pressure.

 

I know one boat builder who put a domestic hot water tank in a boat (to save money) and it burst the instant the water pump was switched on. Like, within about 30 seconds.

 

Again I know nothing of this field.

 

Gibbo

[bottle]

Hi Gibbo

 

There is a 'high' (mains) pressure hot water storage system. The storage tank has something similar to an accumulator built in to the top.

 

I did look into having it fitted but the cost, at the time, was prohibitive.

[Gibbo]

Hi Gibbo

 

There is a 'high' (mains) pressure hot water storage system. The storage tank has something similar to an accumulator built in to the top.

 

I did look into having it fitted but the cost, at the time, was prohibitive.

 

Right, so I guess they must use a special high pressure hot water tank (like a boat) which will not be a normal one and will cost more.

 

Which makes sense.

 

I can see the advantages in it. I mean the shower on the boat is like a power shower. Much better than the weak trickle I get at home.

 

Gibbo

[Tony Brooks]

I asked a manufacturer (albion) of hot water cylinders what the difference between their domestic and marine calorifiers.

 

The response was this:

 

The marine calorifiers are smaller.

 

The connections on the marine calorifiers are smaller.

 

Most of the marine calorifiers have twin coils, and only some of the domestic systems have twin coils.

 

So there doesn't seem to be any technical reason to need a 'marine' calorifier over a domestic unvented tank.

 

I was surprised - I expected them to tell me that the marine ones were of heavier construction etc (they do a heavy-duty stainless-cased marine range).

 

 

Having cut a hole in the side of a Stone Boat Building calorifier last year and also having cut copper sheets from a number of domestic cylinders I am sure the marine one is much thicker. The scrappy I took the calorifier to had a good poke about because he thought it contained a load of scale it was so heavy.

 

When I was on the hire fleet we did try "dumpy" domestic indirect cylinders, and although they coped with pump pressure they evetually went ball shaped because of the PRV pressurea when the water inside expanded. We did have pressure switches on the pump that we adjsured to about 15 psi.

 

It is worth noting that domestic cylinders are available in different letter designated "grades" and the grade signifies the head of water it is designed to cope with. Unfortunately the plumber chaps at college never gave me a conversion for head to psi that I understood.

I suspect a higher grade cylinder would work well.

 

Tony brooks

[bottle]

Right, so I guess they must use a special high pressure hot water tank (like a boat) which will not be a normal one and will cost more.

 

Which makes sense.

 

I can see the advantages in it. I mean the shower on the boat is like a power shower. Much better than the weak trickle I get at home.

 

Gibbo

 

To solve the low pressure/flow in the domestic shower situation , fit one of these

 

 

Come in various pressures from nice to take the skin of your back.

[Gibbo]

It is worth noting that domestic cylinders are available in different letter designated "grades" and the grade signifies the head of water it is designed to cope with. Unfortunately the plumber chaps at college never gave me a conversion for head to psi that I understood.

 

Why did no one else think of that?

 

I think the normal "vent valve" (is that the right name) on a marine calorifier is usually about 2 bar? (Mine is set at 1.8 bar and "pops" occasionally when the Mikuni is on)

 

2 Bar is a head of 66 feet of water! Who's gonna make a domestic hot water tank to take that (plus a safety margin) when the header tank is usually about 5 feet maximum above it.

 

Gibbo

[chris w]

I have an unvented hot water storage tank at home. It's a "Megaflow" brand which has become the kind of generic name for these types of tank. As someone above mentioned they have a built-in internal accumulator and a pressure release valve (PRV) set at 3 bar. It comes with a 25 year guarantee. Expensive but great performance.

 

The whole system works tremendously well. Mains pressure showers and drinking water at every tap. No water tanks in the loft at all. The boiler is also a pressurised system with an enormous external accumulator to handle the two boilers (60KW & 70KW). You do NOT want to pay my heating bills!!

 

Chris

Edited January 9, 2007 by chris w

[DHutch]

We have have a mains presure hotwater night storage imersion hot water cyclinder!

- When we had it fitted 20 years ago, we had to have a" specicaly trained" geezar to do it, as the normal pumbers wouldnt do it!!

 

Its just a big 210liter tank, with a pair of imersions on it, one-way valve on the inlet with a expantion tank jsut after it, and a PRV just after that.

- Then theres a second PRV, with a temperature probe, on the top of the cylinder as well, just incase it all goes tits-up.

 

We've just had the PRVs replace yesterday after one of them started frequently passing large amounts of water, too much of which ended up coming though the dinning room ceiling!!

- So i happened to know there exact rating off by heart.

- The primary one, on the cold feed, is a 3.5bar valve.

- And the tank-top one is a 4bar one, with a 90C probe.

 

We did ask him to replace them when he did the expantion tank about 2months ago, but he said they where fine...

 

 

Which tbh, is very much inline with the boats cal, which has a 3bar PVR on it i think.

- Also, i gather that the newer domestic cylinders are rated at a much higher presure, our plumber intially bought a 7bar pvr with him.

 

 

 

Daniel

[DHutch]

Here we go, i even took some holiday snaps for you! - Its that big i was having a hard time geting it all in.

 

 

 

As you can see, the replacent expantion tank now extends above where the shelf was (the origanal was a short and dumpy shape) taking the total high upto a excess of 7ft! - Only just under the ceiling.

[Tony Brooks]

Why did no one else think of that?

 

snip

 

2 Bar is a head of 66 feet of water! Who's gonna make a domestic hot water tank to take that (plus a safety margin) when the header tank is usually about 5 feet maximum above it.

 

Gibbo

 

 

I was told they are/were made for fitting in blocks of flats with the water tanks no the roof.

 

Tony Brooks

[NB Phoenix]

Why did no one else think of that?

 

I think the normal "vent valve" (is that the right name) on a marine calorifier is usually about 2 bar? (Mine is set at 1.8 bar and "pops" occasionally when the Mikuni is on)

 

2 Bar is a head of 66 feet of water! Who's gonna make a domestic hot water tank to take that (plus a safety margin) when the header tank is usually about 5 feet maximum above it.

 

Gibbo

 

Don’t try and mix metric with imperial and it will be much easier.

 

1 metre of head will give 1 bar of pressure, so 2 bar is 2 metres (6’6” not 66”).

 

For an open circuit domestic heating system. i.e. Header tank in loft with an expansion pipe above would be around 3.5 metres above a cylinder in a first floor airing cupboard. (3.5 bar of pressure at the base of the cylinder).

 

If the cylinder is on the ground floor, say 5 metres from header tank, you would get 5 bars at its base. On my boat the pump runs up to 2 bar and the PRV opens at 3 bar. So the pressures onboard are either the same or lower than a domestic Open circuit system.

 

As to why there are domestic and marine cylinders / calorifiers ? I don’t know…….Sorry.

 

Edit to add. I think I do now.. Thanks to Chris... See next posts. Ill get my coat and calculator!

Edited January 10, 2007 by NB Phoenix

[ChrisPy]

1 metre of head will give 1 bar of pressure, so 2 bar is 2 metres (6’6” not 66”).

NOT QUITE: 10metres of water head = 1 bar

[NB Phoenix]

Doh

 

Engage brain befor fingers.

 

 

Thanks Chris.

 

 

Note:- Please add zeros to my last post as needed. 000000000000000000000000000000

[Alastair]

Some real experts in central heating coming out of the woodwork here!

 

Another question:

 

Has anyone installed (either in boat or in house) a "Thermal Heat Store" type of cylinder? These seem so suitable for boat use, I can't understand why they wouldn't be used. The only disadvantage I can see is that they need to be larger than a normal calorifier. However, as they are unpressurized, they can be 'square' and make best use of available space. See Heatweb for some info on one type of heat store.

[DHutch]

Has anyone installed (either in boat or in house) a "Thermal Heat Store" type of cylinder? These seem so suitable for boat use, I can't understand why they wouldn't be used. The only disadvantage I can see is that they need to be larger than a normal calorifier. However, as they are unpressurized, they can be 'square' and make best use of available space. See Heatweb for some info on one type of heat store.

I think you just hit the nail on the head as to why no one uses them on a boat.

- I have heard of calorfiers that have "heat store" within them. But never seen any for sale, or heard of somone with one.

- In a house, if you want more hotwater storage, you tend to just have more hot water! Becuase space if much less of an issue. Our tank will do 5 decent showers, and leave water for doing the dishes after tea. Only very occtionaly do we put it on "boost" , using the second inmersion element which is place 2/3 of the way up the tank to heat a small amount of extra water.

 

Simualarly, you can also get fridges with "cold stores" in them.

- But we just replicate that with 6 of the blue ice-pack things in the freazer box.

 

 

 

Daniel