Twin Calorifiers

[Sean & Coral]

Due to the good lady insisting on a bath for the new boat, I am considering fitting two 55l calorifiers so that there is the sufficient hot water for occasional bath. At present I am planning on fitting a Webasto 5Kw diesel heating system; does any one know if it will cope with the additional heating coil on top of the planned 4 radiators, 1 towel rail and heating coil that would make a normal system up? Would appreciate any advice from anyone who has or is considering a similar set up.......Many thanks!

[koukouvagia]

It'll cope but will take an age to heat up two large calorifiers. I have a 55l calorifier heated by a 5kw diesel heater (a Refleks). It takes between three and four hours for the water to get hot in the calorifier if the radiators are isolated and all the heat goes into the calorifier. If I try to use the calorifier and the radiators simultaneously the radiators remain lukewarm until the calorifer is hot.. I get round this by heating the calorifier overnight when the radiators are not needed. I can heat up the water separately from the radiators, so this helps. Without the calorifier being heated, the radiators are all piping hot within half an hour.

 

On the butty we've got a calorifer half the size and it seems perfectly adequate, providing we stagger bath times. In fact, we use showers and there is no problem at all with the smaller calorifer. The 20l calorifier heats up in about an hour.

 

For every day small volumes of hot water – washing up etc. it's far easier just to have a kettle.

 

If I were going down the two calorifer route, I'd have a very small one connected to the radiator circuit and a larger one that can be heated separately, say overnight. I personally think two 55l calorifiers are a bit excessive.

 

 

 

 

 

 

[Robbo]

Feed the output of one cal. to the input of the other, this way the water should stay hotter for longer, also feed your boiler and engine to heat up the last cal. (The one that goes to the taps) up first so you get hot water quicker.

[BargeeSpud]

It'll cope but will take an age to heat up two large calorifiers. I have a 55l calorifier heated by a 5kw diesel heater (a Refleks). It takes between three and four hours for the water to get hot in the calorifier if the radiators are isolated and all the heat goes into the calorifier. If I try to use the calorifier and the radiators simultaneously the radiators remain lukewarm until the calorifer is hot..

 

Really? My 55ltr calorifier gets hot, along with the towel rail, within an hour of firing up my Eberspacher. But then my heater is, I think, a 7Kw one. Just goes to show what a difference 2Kw can make I suppose. Mind you, my calorifier will cool down quicker unless I keep the heater going for at least a couple of hours.

[Robbo]

The reflex (unless youve got the one for just heating hot water) doesn't put 5kw to heat te water , but more like 1-2kw.

[koukouvagia]

The reflex (unless youve got the one for just heating hot water) doesn't put 5kw to heat te water , but more like 1-2kw.

 

Yes, of course, I should have mentioned that. In that case, my advice is probably not much use to the OP .

[Sean & Coral]

Yes, of course, I should have mentioned that. In that case, my advice is probably not much use to the OP .

 

Yes, but all advice is most welcomed believe me!! I appreciate that having 2 calorifiers might be excessive; however, this boat will be our home, and thus I am wanting fit her out as best as possible within our budget. I can purchase a Webasto Thermo 90ST at a good price and having done my calculations, am happy that this would more than meet the needs of the system design. However, forum postings ref the 90ST are few and far between (unless I'm searching incorrectly); this is either a good thing because they are reliable (assuming regular servicing/de-coking), or because they're not so common.............feedback welcomed!

[smileypete]

A 4.2kW heater will heat 1 liter a minute by 60°C, so that's 100 minutes say for 100 litres. Probably won't need ALL of that for a bath once it's mixed with cold.

 

If you're living aboard you want to be able to heat the boat with a SF stove and not rely 100% on a diesel heater.

 

cheers, Pete.

~smpt~

[GUMPY]

Yes, but all advice is most welcomed believe me!! I appreciate that having 2 calorifiers might be excessive; however, this boat will be our home, and thus I am wanting fit her out as best as possible within our budget. I can purchase a Webasto Thermo 90ST at a good price and having done my calculations, am happy that this would more than meet the needs of the system design. However, forum postings ref the 90ST are few and far between (unless I'm searching incorrectly); this is either a good thing because they are reliable (assuming regular servicing/de-coking), or because they're not so common.............feedback welcomed!

If you buy a heater bigger than you need it will give you trouble!

They dont like cycling

[GSer]

I use two calorifiers but for different reasons, i just have 2 x 1kw immersion heaters, i need to run the generator for a couple of hours a day for battery charging, then the quattro inverter manages power supply to the immersion heaters, ensuring they switch off when the generator does.

 

It works well for me, one calorifier is also connected to the engines heating system, the other is in the galley area this would remain cold if i were cruising then i just put the kettle on, or swap supply to use the inverter 240 output to warm it all up, but if i do that i need to remember to switch it off, this is not at all ideal and i've only once felt the need to do this.

 

In practice i've always got plenty of hot water

[BargeeSpud]

If you buy a heater bigger than you need it will give you trouble!

They dont like cycling

Very true.

 

I use two calorifiers but for different reasons, i just have 2 x 1kw immersion heaters, i need to run the generator for a couple of hours a day for battery charging, then the quattro inverter manages power supply to the immersion heaters, ensuring they switch off when the generator does.

 

It works well for me, one calorifier is also connected to the engines heating system, the other is in the galley area this would remain cold if i were cruising then i just put the kettle on, or swap supply to use the inverter 240 output to warm it all up, but if i do that i need to remember to switch it off, this is not at all ideal and i've only once felt the need to do this.

 

In practice i've always got plenty of hot water

A set up well worth considering. Going to file that for future reference when I finally get around to a new build.

[nb Innisfree]

When we planned our self fit out we decided on two single coil 50lt cals, basically because our bathroom is remote from the kitchen and we reasoned that drawing hot water from a distance of 30'-40' wasn't good practice and a waste of water. So we finished up with a cal right next door to the bathroom and one in the kitchen which has worked out really well and is one of our best solutions (shower takes 5 sec to get hot!) both are connected in parallel to the circuit same as the rads. We have a 7kw Mikuni which handles 5kw of rads, 2-3kw? of cals. and engine preheat with ease. All that lot takes about 2hrs from cold and the Mikuni stays on full output for those two hours before switching to half output, so I would guess 5kw would take, say, 3hrs to reach the same point? I think that taking the engine preheat out of the equation wouldn't make much difference to that time. Assuming your rads are already up to temp and you then bring in two 55lt cals it would still take the same time to heat them up, unless that is, they were twin coil ones which I guess would halve the time, theoretically, but in practice may be a little longer.

[bigcol]

there's me thinking I bought and fitted a 5kw thermo top

I've just been below to sort out a radiator fitting,

and have just read the label on the unit and its a 4.2kw

 

I imagine this is probably something to do why my radiators are taking a long time to heat and keep hot?

 

is there a difference between a 4.2/5kw

 

I bet there is

 

Col

[Robbo]

there's me thinking I bought and fitted a 5kw thermo top

I've just been below to sort out a radiator fitting,

and have just read the label on the unit and its a 4.2kw

 

I imagine this is probably something to do why my radiators are taking a long time to heat and keep hot?

 

is there a difference between a 4.2/5kw

 

I bet there is

 

Col

 

Maybe: 5Kw Input, 4.2Kw Output

 

Edit: Perhaps not looking at these tech details as they do a 4.2Kw output as well as a 5Kw. - http://www.webasto.com/gb/markets-products/marine/heating-solutions/water-heaters/water-heaters/

Edited December 9, 2013 by Robbo

[bigcol]

Thanks for the link

Wondering why would webasto make a heater so close in kw? ie 4.2 kw and 5kw

 

there's not a lot on Google re the 4.2 kw

and if I replaced my 4.2 for a 5kw what difference would it make, I wonder?

 

col

Edited December 9, 2013 by bigcol

[Ryeland]

The heat time of a calorifier is likely to be determined by the heating capacity of the coils fed by the engine, Webasto etc. This will be a lot less than the 5KW of a Webasto. Mine still cycles down to the low heat setting even with a small radiator as a heat sink when feeding the calorifier as well. The low heat setting is about 2.5Kw I think, so I would be surprised if the calorifier can absorb any more than 1.5KW.

 

The only way to get it to heat more quickly is to use multiple heat sources ie both coils, or to increase the temperature in one or both coils.

 

Richard

[raymondh]

Hi,

You need to rate your heater to the damand at max output, it can get realy cold on the cut and a 5Kw heater will never satisfy 10Kw of rads and hot water

We have a Webasto 90 and its now had over 5 years of live aboard use running on kerro, 4500 ish hours never missed a beat

and never had a service

Heats rads up realy fast in winter and hot water in summer 20 mins to reach 65c

We use a room stat to control the heating and a stat on the cal for when in hot water mode

This is for 7 rads 1 towel rail and the cal on a 57 x 10 wide beam

Actual facts not BS or war stories

Good Luck Ray

[smileypete]

The heat time of a calorifier is likely to be determined by the heating capacity of the coils fed by the engine, Webasto etc. This will be a lot less than the 5KW of a Webasto. Mine still cycles down to the low heat setting even with a small radiator as a heat sink when feeding the calorifier as well. The low heat setting is about 2.5Kw I think, so I would be surprised if the calorifier can absorb any more than 1.5KW.

 

The only way to get it to heat more quickly is to use multiple heat sources ie both coils, or to increase the temperature in one or both coils.

 

Or heat the calorifier water directly with a plate heat exchanger which offer excellent heat transfer for their size, maybe use it in conjunction with a suitable thermostatic valve (TMV).

 

 

Hi,

You need to rate your heater to the damand at max output, it can get realy cold on the cut and a 5Kw heater will never satisfy 10Kw of rads and hot water

We have a Webasto 90 and its now had over 5 years of live aboard use running on kerro, 4500 ish hours never missed a beat

and never had a service

Heats rads up realy fast in winter and hot water in summer 20 mins to reach 65c

We use a room stat to control the heating and a stat on the cal for when in hot water mode

This is for 7 rads 1 towel rail and the cal on a 57 x 10 wide beam

Actual facts not BS or war stories

Yes, but the same heater running on diesel in a narrowboat may be another matter!

 

If the rads are badly out of balance then a 5kW heater won't even heat 5kW of rads that well, you could fit a Thermo 90 which would work better but it'd be an expensive alternative to proper rad balancing.

 

10kW of rads is equivalent to a 20ft run of 2ft high finned double rad, which is a fair bit...

 

cheers, Pete.

~smpt~

[peterboat]

I have a wispergen in my boat and 5KWs or rads it has to be that much because the rads are the cooler for the wispergen (have a look on their site) It heats my rads and hot water up very well, however on really cold days takes longer. It cannot regulate itself other than if the batteries are fully charged then it will use less fuel and make less heat as a consequence. Because it is doing 2 jobs it is fairly cheap to run but the point is the 5 Kws is enough to do all my needs in my 57 x 12 widebeam so unless your boat is bigger you should be ok

 

Peter

[blackrose]

Yes, but all advice is most welcomed believe me!!

 

In that case my advice is get her to take showers on board. Baths are a waste of space, water and energy.

 

Twin calorifiers for free hot water from the engine isn't such a bad idea if you have the space, but if you're moored with shore power in winter then you'd probably only want an immersion heater on one of them and somehow you'd have to stop the hot water thermosyphoning from one to the other.

 

In my opinion too many people fit out their boats according to the daft desires of their other half, instead of what is practical on board. One bloke I know gave himself an unnecessary headache by fitting a deep butler-style sink in the rear galley of his new Tim Tyler sailaway because his girlfriend insisted that was what she wanted. He gravity drained the sink because that's the simplest way to do it, so his skin fitting ended up almost on the waterline. So in an effort to install a fashionable kitchen sink, he compromised the integrity of his hull. That's what I call style over substance. I've seen skin fittings knocked off in locks and if that happens to their boat they will have a hole on the waterline that they may not know about..