Reverse cycle air con / heating info

[lanerboy]

Hi All

I am interested to know what people think of the heating systems on a boat that has heating / reverse cycle air con fitted in this country

Do you think that the heating is good enough to keep the boat warm on a cold winters night in the uk I have never used this system I have always had diesel heating so I suppose my question is do you find it as good as the eberspacher diesel heating or do you find yourself supplementing it with electric heaters of some sort

The system I am asking about is fitted on a 42ft sealine sports cruiser

cheers shawn

 

[IDAMAY]

On our last two boats (both UK based) we have had aircon AND heating. Both boats were bought second user.We would not have specified aircon for north European waters but have found it useful for cooling on a very few occasions. We have once in a while used it for heating (works OK provided water temp is 4C+) but mainly to give the aircon a run in the winter. It certainly kept the boat warm enough. However, the diesel heating seems to us more efficient and less noisy. I wouldn't by choice have only aircon for UK use, particularly if it won't run on a 16 amp shore supply. It is well worth checking this as our first system wouldn't sustain the start up loads at 16 amp whereas the later Cruisair system on Ocean Star does provided you start the air handling units in sequence.

Richard.

 

[jimmy_the_builder]

Nope. Reverse cycle not as good as Eber imho. I have both on the T40 and even in France in the winter months I use the Eber.

 

[KevB]

I don't know if boat aircon is specific to boats but the unit we have in our apartment kicks out an awful lot of heat for a total unit rating inc the outside condensor of only 1600 watts. Seems to be very efficient compared to normal instant electric heaters like a fan heater.

 

[kcrane]

Nope. Reverse cycle not as good as Eber imho. I have both on the T40 and even in France in the winter months I use the Eber.

+1

RCycle works to a point and our Cruisair does work fine off 16A but it shares with Eber the problem that warm air heating is only effective while it is blowing, it doesn't seem to heat the fabric of the boat. 5 mins after it cuts out the boat is cold again. We add in a small oil radiator and the combination works OK. Overnight, if needed, only the radiator stays on, the AC is too noisy. We did find you can alter the fan level that the pre-sets use, so we turned it down and now fan setting 1 is much slower and quieter, but not good enough for a cabin at night.

We also have Eber in the cockpit, which is quieter than the AC and means we can use the cockpit all year, but again, as soon as it goes off it feels cold.

 

[DAW]

I've found the same as kcrane - reverse cycle is fine while it is on, but as soon as it reaches temperature and the fan shuts down the air temperature in the boat falls quite quickly. The result is that the heating switches on and off frequently, which is OK during the day but can be irritating at night, particularly for light sleepers. Fortunately, we're in SoF and in the winter the boat is used only as additional accommodation for visiting teenage kids who seem happy with a combination of heating on all the time at lower settings and extra duvets/blankets. I wouldn't want to rely upon it for a UK winter.

 

[SEARANGER ANCASTER]

we have aircon which can be reversed plus a diesel heating system . We have used the aircon ( yes in Scotland !) and have only used the rev aircon for some heat on a chilly summer night , all other times is diesel heater. Our boat was specced for the Med , hence why fitted .It works well but is pretty noise.

 

[Nigelpickin]

Have had reverse cycle and diesel on previous boats, agree with above.

Current boat has some additional system that puts hot water round the ring main and blows warm air within minutes. Boat warms through very nicely and I'd be happy sitting on it anytime; in fact I'm here now

I'd say that a combination of reverse cycle and some low profile, attractive wall mounted panel heaters might be an idea...
Depending on the boat of course.

 

[Cathy*]

Much the same as others, we have diesel and AC (2 units) in a 10m powerboat. We've been sleeping on her for the past 2 weeks in Plymouth and have been warm enough. The AC is noisy, we've dealt with this by setting the bedroom temperature to 19 degrees at night which it will not achieve, so the fan is always on rather than cutting in and out. Electric is costing us about £2.50 a day. If we bought another boat without AC I wouldn't pay to have it fitted.

 

[superheat6k]

As mentioned above, when in heat pump mode the lower limit for the seawater from which the heat is extracted is about 4oC. Any colder and then the water pouring out will be in cube form. Even air to air heat pumps hit a lower effective limit of -5oC, below which the air simply runs out of much useful heat.

Having said all this, heat pumps gain an extra point of efficiency over the AC use, because the motor input energy is added to the heat rejected at the condenser, which in heat pump mode is into the space.

In warmer weather a heat pump can achieve as high as 6:1, that is 1 kW in gains you 6 kW out. This is not breaking the laws of thermodynamics, you are simply moving the heat in the water (by cooling it) to the air in the space warmed. But red diesel at zero duty / vat likely works out considerably cheaper per kWH than electricity, but bear in mind also that as a visitor most places charge a flat rate for overnight electricity - so in those circumstances then let the heaters blaze - you've already paid for it.

A particular problem with all heat pump aircon units not used much in heat mode is that the reversing valve that diverts the gas flows from the two heat exchangers from one mode to the opposite tend to stick in the cooling posiition. This is also a common reason why people find the heat mode not very effective.

I practice this subject for my living, and at home I recently fitted a condensing boiler, not an air source heatpump.

Make the most of AC anyway - the recent law revision (F Gas Directive review) governing what we can use mean that most available refrigerants we currently use will be non available over the next 10-15 years anyway, and the implications for this not just for boat cooling, but all cooling are not yet fully appreciated. The replacements the EU want us to use instead haven't all been invented yet, and for some applications it is unlikely safe non flammable gases will be available much after 2025. This isn't just the recently banned R22, but all gases with R134a in - effectively all R400 series gases.

 

[rubberduck]

We have reverse cycle which is very effective but takes a while to heat up, so we added a plinth heater to supplement & provide quick warm up. Once up to temp we use fan only on air con & the plinth heater, works well & nice & quiet.

 

[Sdpaddler50]

Interesting, I was always curious about a reverse cycle in cold water, when using it for heat.

I am in San Diego, sitting on my boat right now, in 59F water, and i have the reverse cycle on to heat our 44 ft. cabin. It works, but runs a lot trying to get the heat out of that water. I think high 50F water is about as low as you can go, and still have some efficiency with a reverse cycle.

 

[Nigelpickin]

As mentioned above, when in heat pump mode the lower limit for the seawater from which the heat is extracted is about 4oC. Any colder and then the water pouring out will be in cube form. Even air to air heat pumps hit a lower effective limit of -5oC, below which the air simply runs out of much useful heat.

Having said all this, heat pumps gain an extra point of efficiency over the AC use, because the motor input energy is added to the heat rejected at the condenser, which in heat pump mode is into the space.

In warmer weather a heat pump can achieve as high as 6:1, that is 1 kW in gains you 6 kW out. This is not breaking the laws of thermodynamics, you are simply moving the heat in the water (by cooling it) to the air in the space warmed. But red diesel at zero duty / vat likely works out considerably cheaper per kWH than electricity, but bear in mind also that as a visitor most places charge a flat rate for overnight electricity - so in those circumstances then let the heaters blaze - you've already paid for it.

A particular problem with all heat pump aircon units not used much in heat mode is that the reversing valve that diverts the gas flows from the two heat exchangers from one mode to the opposite tend to stick in the cooling posiition. This is also a common reason why people find the heat mode not very effective.

I practice this subject for my living, and at home I recently fitted a condensing boiler, not an air source heatpump.

Make the most of AC anyway - the recent law revision (F Gas Directive review) governing what we can use mean that most available refrigerants we currently use will be non available over the next 10-15 years anyway, and the implications for this not just for boat cooling, but all cooling are not yet fully appreciated. The replacements the EU want us to use instead haven't all been invented yet, and for some applications it is unlikely safe non flammable gases will be available much after 2025. This isn't just the recently banned R22, but all gases with R134a in - effectively all R400 series gases.

Funny you should mention valves sticking
Do you know of anyone in my area, Falmouth, who services cruisair? Could do with a good looking at....

 

[superheat6k]

Funny you should mention valves sticking
Do you know of anyone in my area, Falmouth, who services cruisair? Could do with a good looking at....

The reversing valve set up is common to any reverse cycle split type AC unit. If you can find an experienced AC or Fridge engineer or local AC or fridge firm they should be able to help, but be wary of split only installers, as many of these guys have no clue what happens inside the boxes they fit.

A word with the local fishermen to who they use for their ice makers might help locate someone.

 

[Nigelpickin]

The reversing valve set up is common to any reverse cycle split type AC unit. If you can find an experienced AC or Fridge engineer or local AC or fridge firm they should be able to help, but be wary of split only installers, as many of these guys have no clue what happens inside the boxes they fit.

A word with the local fishermen to who they use for their ice makers might help locate someone.

Well a good bit of googling and a couple of hours faff and I have hot air coming from each of the 5 head units

The valve in one was struck but it pushed across and down and seems to be working well now...

I have one thermostat that is reading 10 c above actual...trying to find a cruisair spares dealer in the UK seems like fun

 

[Asm]

Well a good bit of googling and a couple of hours faff and I have hot air coming from each of the 5 head units

The valve in one was struck but it pushed across and down and seems to be working well now...

I have one thermostat that is reading 10 c above actual...trying to find a cruisair spares dealer in the UK seems like fun

Try http://www.marineairspares.com - no connection !

 

[Nigelpickin]

That's much appreciated

 

[Cathy*]

Funny you should mention valves sticking
Do you know of anyone in my area, Falmouth, who services cruisair? Could do with a good looking at....

We recently had ours regassed by these guys http://ballandballfarmservices.co.uk/ in Gunnislake

 

[Nigelpickin]

We recently had ours regassed by these guys http://ballandballfarmservices.co.uk/ in Gunnislake

thanks Cathy.
Just checking, they seem to be a farming machinery firm, it's not some Ex tractor fan joke is it...

 

[lambohill]

As QUOTE by superheat6k

"I practice this subject for my living, and at home I recently fitted a condensing boiler, not an air source heatpump."


I am Agreed. The technology has not yet reached the efficiency / life span cost benefit needed.

Incidently, your username, I used a product called just that many moons ago, originally available on a floppy way back then, to calculate building heat loss, is that yours?