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joining two calorifiers in perfect matrimony


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following on from my "bath" post...

 

I've found room for an additional vertical calorifier which i can site next to the original horizontal one, between them both there will be  plenty of HW for my bath. It would be preferable to make use of this hot water all the time and not just for baths, so i want to connect the two.

 

I would also like to add an evacuated tube solar hot water system.

 

the existing calorifier has two coils, one of which is on the webasto, the other on the engine.

 

the new calorifier is also likely to have two coils one of which i could use for the solar hot water.

 

I would like to "mix" the hot water in the two calorifiers so they are both at the same temperature, but I'm at a loss as to the best way to do it.

 

It's probably blindingly obvious, but I would appreciate thoughts on the subject...

 

Bex

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I would plumb both calorifiers in series - cold water in to bottom of no. 1, out of top of no.1 and into bottom of no. 2, then out of top of no. 2 to the hot taps.

Connect both the engine and webasto coils so that hot water passes through the coil in no.2 then no.1. That way the water you are using first (from calorifier no.2) will be hottest, and if there is sufficient engine/webasto heat you will then also heat no.1.

Adding solar adds a level of complexity!

 

Edited by David Mack
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29 minutes ago, David Mack said:

Adding solar adds a level of complexity!

For a start, you need a differential thermostat. Ie, something to open a valve/turn on a pump only when the solar tubes are hotter than the contents of the calorifier. Without that, you'll just be radiating heat away on sunless days and at night.

 

MP.

 

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If you mix the water in both calorifiers at all times you will use far more energy than necessary for your normal daily needs. You will have to heat all of the water in both to your desired temperature and lose the advantage of thermal stratification (more relevant in vertical calorifiers) where the water at the top heats up first and can be used for washing dishes or a quick shower without waiting for the full tank to heat. 

 

I think I would keep the tanks separate except when water was needed for the bath and find a way circulating the water for that. This of course doesn't account for the solar but I'm sure you can use the same circulation system to transfer the solar heated water to the original tank. A solar circulation pump might be suitable for mixing between the two tanks:

 

https://www.ebay.co.uk/itm/DC-12V-Water-Circulation-Pump-Solar-Water-Pump-Brushless-Motor-3M-8L-H-UK-HOT/174016643721?_trkparms=ispr%3D1&hash=item2884334289:g:lsQAAOSwhvFdbOe9

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12 minutes ago, MoominPapa said:

For a start, you need a differential thermostat. Ie, something to open a valve/turn on a pump only when the solar tubes are hotter than the contents of the calorifier. Without that, you'll just be radiating heat away on sunless days and at night.

 

MP.

 

Yes, sussed that, maybe a solar circulation pump? 

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1 hour ago, David Mack said:

I would plumb both calorifiers in series - cold water in to bottom of no. 1, out of top of no.1 and into bottom of no. 2, then out of top of no. 2 to the hot taps.

Connect both the engine and webasto coils so that hot water passes through the coil in no.2 then no.1. That way the water you are using first (from calorifier no.2) will be hottest, and if there is sufficient engine/webasto heat you will then also heat no.1.

Adding solar adds a level of complexity!

 

I did this in my cottage in Scotland and it worked very well. Solar works well so while it adds complexity it does get you free hot water. I have used my excess drive solar to heat water by immersion heater, now because of lack of sun I use it to charge leisure batteries so my life doesnt change as for as electricity needed, Hot water now is taken care of by the Rayburn because its getting a bit colder 

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23 minutes ago, peterboat said:

I did this in my cottage in Scotland and it worked very well. Solar works well so while it adds complexity it does get you free hot water. I have used my excess drive solar to heat water by immersion heater, now because of lack of sun I use it to charge leisure batteries so my life doesnt change as for as electricity needed, Hot water now is taken care of by the Rayburn because its getting a bit colder 

No room for excess PV on a Nb though Peter or life would be a lot simpler, I'm thinking of perhaps another solar powered pump on a differential stat to mix the tanks when hot water is available, connect the engine circuit through a coil on both, leave the webasto on a single tank, and the solar on another. 

 

Another approach which might work is a plate heat exchanger on the solar in line with the first calorifier coil, with a small circulating pump which can remain switched off if I only need one tank of water. that way I don't lose all that lovely potential hot water when the sun is out (which obviously happens a lot in Manchester!)

 

I don't have a back boiler on the little boatman, been considering it but tbh, I need all of the heat it makes for keeping me, my missus, the cat and the fish warm!

 

 

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You have 3 possible heating systems, and 2 coils per tank.  You can add a third coil as well if you wish for max flexibility, or if cost is a problem then stick with 2.

If you add the third coil you will loose your immersion heater which you may want to keep.

 

Assumptions

1)  make max use of solar as it is free

2)  the webasto is main  heat source in winter

3) Engine is used occasionally, but again when used heat is free

4)  Don't use the immersion heater now, but want to keep it for the future.

 

So I would plumb in series so cold into caliorifier 1 out put into caloifier 2 out to hot system.

 

Calorifier 1 - Coil a = Webasto

                     Coil b = Solar

 Immersion / coil c = Engine

 

 

Calorifier 2 - Coil a = Webasto

                     Coil b = Solar

 Immersion / coil c = Immersion heater

 

This way you would keep the engine heat in Calorifier 1 but could not use it without heating up cal 2 using the webasto but you would only 'pay' to use the webasto for one calorifier.  Of course if you don't want the immersion heater then get a third coil for tank 2

 

Just an example of a third coil adapter

https://www.ebay.co.uk/i/272972899295

 

 

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19 minutes ago, Tash and Bex said:

No room for excess PV on a Nb though Peter or life would be a lot simpler, I'm thinking of perhaps another solar powered pump on a differential stat to mix the tanks when hot water is available, connect the engine circuit through a coil on both, leave the webasto on a single tank, and the solar on another. 

 

Another approach which might work is a plate heat exchanger on the solar in line with the first calorifier coil, with a small circulating pump which can remain switched off if I only need one tank of water. that way I don't lose all that lovely potential hot water when the sun is out (which obviously happens a lot in Manchester!)

 

I don't have a back boiler on the little boatman, been considering it but tbh, I need all of the heat it makes for keeping me, my missus, the cat and the fish warm!

 

 

Great little stove looking at one in Jaynes Bungalow, It can cook us at full bore so maybe a backboiler would give you hot water in the winter as its only at the rear? Speak to Eddie whether it can be added

All I can say is use the KISS principle where ever possible I have learned over the years that anything remotely complicated on a boat will go wrong!!

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Eddie would weld me one on, and he's only just down the road so it might work, just drawn up what I have in mind, which is pretty simple really, couple of plate heat exchangers and Bob is quite definitely your Aunty.

 

I'm kinda thinking this (see diagram) would do all I need it to do and is quite simple. I've obviously left bits of expansion and other exciting  differential stats and control gear things out of the diagram for clarity.

 

My only concern would be thermal syphoning, but if it's only minor it's probably liveable with.

 

Base model logic circuit to handle temp differentials and start pumps etc.

 

Feasible?

 

 

Slide1.jpg

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I think your circuit is too simple. The engine and solar collector only heat the vertical tank but you are drawing that hot water through the horizontal tank, which will be cold unless you heat it with the Webasto, so the drawn off water will start cold and only get slightly warmer as more is drawn. 

 

It would be better if (other than bath-times) you were able to draw the solar or engine-heated hot water from the vertical tank directly. The Webasto-heated tank doesn't care that its water has come through the other tank, so that's not a problem. 

 

Maybe you could have some kind of diverter valve at the top of the vertical tank and bypass the horizontal tank on sunny days or after the engine has been run. If the vertical tank is cold, the valve is directed through the horizontal tank and the Webasto is used. I assume from the drawing that on bath nights the Webasto and engine are used. 

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I have a diverter valve on my system.  That is NOT a system like yours..... .but I thought if you had a change over valve on the hot outlets of your tanks...you could set it so that when the water temperature coming out of one tank drops.....it switches over to the other tank.

 

Maybe a little Raspberry pie board and a simple program to compare the tank temperatures … and operate the valve to draw water from the hottest one.

 

My system is not like yours.  My boat has a large tank with only a single coil from the engine.  That meant engine running in marinas.. I already had a small 3 gallon tank in my garage from another project...with single coil and a 1kw immersion.  I installed that...so that when the immersion is powered from a land hookup, the diverter draws water from that tank.

I Siamese the cold inlets...and the pressure relief outlets...and fed the hot outlets through the diverter.

I'm amazed that the little tank heats really hot in 20 minutes and despite running off water for showers etc...the immersion keeps up with it.

 

Not like your system, but you can see where I'm going with my idea above.

 

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2 hours ago, stegra said:

I think your circuit is too simple. The engine and solar collector only heat the vertical tank but you are drawing that hot water through the horizontal tank, which will be cold unless you heat it with the Webasto, so the drawn off water will start cold and only get slightly warmer as more is drawn. 

 

It would be better if (other than bath-times) you were able to draw the solar or engine-heated hot water from the vertical tank directly. The Webasto-heated tank doesn't care that its water has come through the other tank, so that's not a problem. 

 

Maybe you could have some kind of diverter valve at the top of the vertical tank and bypass the horizontal tank on sunny days or after the engine has been run. If the vertical tank is cold, the valve is directed through the horizontal tank and the Webasto is used. I assume from the drawing that on bath nights the Webasto and engine are used. 

quite right, it should show the solar/engine circuit passing through the horizontal tank as well, my error

Oh BTW I do have immersions, but I am not on hookup at all so they are rarely used

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I have a plate heat exchanger on the engine coolant circuit and the webasto heater circuit is on the other side, with an extra circulation pump. When the webasto comes on it works as originally fitted ,it pumps the water round the radiators and calorifier coil.  When the engine comes on it turns the new circulation pump on so the water in the webasto circuit is pumped through the heat exchanger and then through the radiators and calorifier .   If for some reason one wants both engine and webasto running it still works fine, because the wabasto pump and the 'new pump both pump the water the same way round.  Bonus is the radiators work when engine is running as well as hot water and I only use one coil in the calorifier.  I have thought of using the other coil for solar but haven't got round to it.

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I'd try to keep it simple.

 

Tank H has webasto and engine

Tank V has solar (with its own pump and controller) and spare coil.

 

Fit the Webasto outlet with a three way valve (including midway option) to feed H, V spare coil or both.

 

Cold feed to V comes from hot outlet of H. DHW feed comes from V.

 

Normal operation has Webasto going to V or use solar in V.

 

Bathnight has Webasto powering H (and V if solar hasn't done much).

 

It sounds as if you don't use the engine much, but otherwise you could arrange a small recirculation pump from hot side of V to cold side of H (with a NRV in the cold feed to H and an expansion tank) to get hot water to V.

 

I don't know if you can get three-way valves for 12 V with a midway option, but otherwise take the actuator off and operate it manually (Womanually? Gender-non-specificually?)

 

Some clever Arduino programming with sensors could help, or get very confusing!

 

Martin/

 

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Quite a few assumptions here so this might not be relevant:

Assumption 1:

You're going to use the bath occasionally rather than daily. 

Assumption 2:

At least one of the calorifiers has two coils and an immersion boss.

Assumption 3:

You're so rarely on shoreline that an immersion won't be missed. 

 

So. I think it would be best to concentrate on heating one calorifier for daily use and only use the second one on bath nights. Swap the immersion for one linked to by Chewbacka above and connect that to your solar collector. If you find yourself on a winter mooring with shoreline, it's not such a big task to swap it back. Use the two coils for engine and Webasto. 

 

When it's bath time, circulate the water around the two calorifiers using a pump with non-return valves to prevent pushing the water back to the main tank (probably not an issue) or sucking air from an open tap (again, probably not an issue). The circulation pump might need to be weaker than the main pump to prevent problems (not sure about that). 

 

Anyway, here's my expertly rendered diagram of how it might look. Not sure if either, both or none of the NRVs (marked as diodes) are actually needed and if they are, clack valves might be better given the relative weakness of boat pumps. As Onewheeler said, an expansion vessel might be needed:

 

 

IMG_20190929_201621.jpg

 

Edit: Needs an NRV in the pumped circuit to prevent the cold water bypassing the calorifiers and flowing through the pump. 

Edited by stegra
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3 hours ago, stegra said:

Quite a few assumptions here so this might not be relevant:

Assumption 1:

You're going to use the bath occasionally rather than daily. 

Assumption 2:

At least one of the calorifiers has two coils and an immersion boss.

Assumption 3:

You're so rarely on shoreline that an immersion won't be missed. 

 

So. I think it would be best to concentrate on heating one calorifier for daily use and only use the second one on bath nights. Swap the immersion for one linked to by Chewbacka above and connect that to your solar collector. If you find yourself on a winter mooring with shoreline, it's not such a big task to swap it back. Use the two coils for engine and Webasto. 

 

When it's bath time, circulate the water around the two calorifiers using a pump with non-return valves to prevent pushing the water back to the main tank (probably not an issue) or sucking air from an open tap (again, probably not an issue). The circulation pump might need to be weaker than the main pump to prevent problems (not sure about that). 

 

Anyway, here's my expertly rendered diagram of how it might look. Not sure if either, both or none of the NRVs (marked as diodes) are actually needed and if they are, clack valves might be better given the relative weakness of boat pumps. As Onewheeler said, an expansion vessel might be needed:

 

 

IMG_20190929_201621.jpg

Try this: remove the pump and related pipework. Take the returns from each coil in the lefthand calorifier to the inlets of the coils on the righthand calorifier. Use two 3 port valves to change from lefthand only to both. Link the valve handles (or use a duplex valve) to change from grubby day to bath day.

edit to add the theory.

The left hand calorifier will heat up until its contents are at the same temperature as the hottest coil. At this point the temperature drop across the coils of the left hand calorifiers is effectively zero; meaning that the available heat transfers  to the second calorifier automaticaly once you select “both”.

On grubby days the righthand calorifier is nothing more than a fat cold water feed pipe for the lefthand calorifier.

Buy a triple coil calorifier and plumb it in as the lefthand calorifier, and replumb the existing calorifier as the righthand one.

disclaimer: typed under the influence of “Birra Maretti”

Edited by Eeyore
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11 hours ago, Eeyore said:

Try this: remove the pump and related pipework. Take the returns from each coil in the lefthand calorifier to the inlets of the coils on the righthand calorifier. Use two 3 port valves to change from lefthand only to both. Link the valve handles (or use a duplex valve) to change from grubby day to bath day.

edit to add the theory.

The left hand calorifier will heat up until its contents are at the same temperature as the hottest coil. At this point the temperature drop across the coils of the left hand calorifiers is effectively zero; meaning that the available heat transfers  to the second calorifier automaticaly once you select “both”.

On grubby days the righthand calorifier is nothing more than a fat cold water feed pipe for the lefthand calorifier.

Buy a triple coil calorifier and plumb it in as the lefthand calorifier, and replumb the existing calorifier as the righthand one.

disclaimer: typed under the influence of “Birra Maretti”

Lol, have to say "grubby days" are few, there is plenty in the existing system for a shower, so really it is only the two calorifiers for a bath, however if the heat is "free" ie engine or solar, I'd rather have it.

 

When it is just the webasto running, I just want to heat the minimum of water.

13 hours ago, stegra said:

Quite a few assumptions here so this might not be relevant:

Assumption 1:

You're going to use the bath occasionally rather than daily. 

Assumption 2:

At least one of the calorifiers has two coils and an immersion boss.

Assumption 3:

You're so rarely on shoreline that an immersion won't be missed. 

 

So. I think it would be best to concentrate on heating one calorifier for daily use and only use the second one on bath nights. Swap the immersion for one linked to by Chewbacka above and connect that to your solar collector. If you find yourself on a winter mooring with shoreline, it's not such a big task to swap it back. Use the two coils for engine and Webasto. 

 

When it's bath time, circulate the water around the two calorifiers using a pump with non-return valves to prevent pushing the water back to the main tank (probably not an issue) or sucking air from an open tap (again, probably not an issue). The circulation pump might need to be weaker than the main pump to prevent problems (not sure about that). 

 

Anyway, here's my expertly rendered diagram of how it might look. Not sure if either, both or none of the NRVs (marked as diodes) are actually needed and if they are, clack valves might be better given the relative weakness of boat pumps. As Onewheeler said, an expansion vessel might be needed:

 

 

IMG_20190929_201621.jpg

 

Edit: Needs an NRV in the pumped circuit to prevent the cold water bypassing the calorifiers and flowing through the pump. 

liking this a lot, strikes me that I could make use of the coils in the vertical calorifier, rather than the replacement coil in the left one. the temp would be evened out by the circulation surely? the pump would only circulate when either the engine was running, or the solar was producing heat.

 

not sure I would need any non return valves at all? wouldn't water pressure prevent mixing??

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56 minutes ago, Tash and Bex said:

Lol, have to say "grubby days" are few, there is plenty in the existing system for a shower, so really it is only the two calorifiers for a bath, however if the heat is "free" ie engine or solar, I'd rather have it.

 

When it is just the webasto running, I just want to heat the minimum of water.

So plumb the “engine” coils in series, with the flow going to the calorifier nearest the tap first. No need for a valve on this circuit as any excess “free” heat will automatically go to the second calorifier. You just need a single valve in the “webasto” coil plumbing to change between single calorifier nearest the tap and both in series on bath day. A single valve to achieve your stated aim. Pumped recirculation is fine in large installations like hotels where you need hot water fairly quickly at all taps, but seems a little complex for what you want?  

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1 hour ago, Eeyore said:

So plumb the “engine” coils in series, with the flow going to the calorifier nearest the tap first. No need for a valve on this circuit as any excess “free” heat will automatically go to the second calorifier. You just need a single valve in the “webasto” coil plumbing to change between single calorifier nearest the tap and both in series on bath day. A single valve to achieve your stated aim. Pumped recirculation is fine in large installations like hotels where you need hot water fairly quickly at all taps, but seems a little complex for what you want?  

that would certainly work, but wouldn't get me both full of solar hot water? and while I agree regarding recirc, (I installed it at home) but only on a single HWC 

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14 minutes ago, Tash and Bex said:

that would certainly work, but wouldn't get me both full of solar hot water? and while I agree regarding recirc, (I installed it at home) but only on a single HWC 

A triple coil in the new calorifier, and one of those immersion boss adaptors in the existing calorifier. Feed the “solar” heat to the coil of the calorifier nearest the tap first. Add a valve to choose between this calorifier coil or both in series as per the “webasto” circuit. You could link the two valve handles to give a single action changeover for bath day, although experience may favour individual control.

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2 hours ago, Eeyore said:

A triple coil in the new calorifier, and one of those immersion boss adaptors in the existing calorifier. Feed the “solar” heat to the coil of the calorifier nearest the tap first. Add a valve to choose between this calorifier coil or both in series as per the “webasto” circuit. You could link the two valve handles to give a single action changeover for bath day, although experience may favour individual control.

After all these good ideas the op is going to need a bigger bath to take advantage of all this hot water ?

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