# Dometic HB2500 Aircon



## Vennwood

Hi All,

Does anyone have any experience on the Dometic HB 2500 underfloor airconditioning system? This supposed to be the answer to the Truma Saphir range and can be run off 12 volt batteries (via an inverter) with a feature called night mode. It is supposed to be significantly cheaper than the Truma unit and higher power. Any help or experience would be grateful


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## teemyob

*A/C*

Hello,

I would be interested in hearing from anyone who has this system or the Saphir. In particular would like to know if anyone runs the system off their won inverter rather than the expensive manufacturer kits.

Trev.


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## Vennwood

Hi Trev,

I researched this a fair bit, still am for that matter. The official report from Dometic regarding the night mode is that it only reduces the fan speed to lessen overall noise levels so doesn't reduce the compressor power. I have pretty much shelved the HB2500 as this needs too much power to realistically run from onboard sources. The bottom line is the only system I can find that will allow you to run sensibly from your own inverter is the Saphir Vario. This has 3 power settings - 600w, 1500w and 2000w (all the others seem to have 1) so depending on size of inverter/battery bank you can run the Vario on the lower 2 settings for whatever battery capacity you have. You don't need a pure sine wave inverter for the Vario so can avoid the expensive inverter. The major downside is the cost - £1300 for the unit then you have fitting kit and fitting (unless you do it yourself) so you are realistically looking at £2000 minimum.

As I say this is still an ongoing project for me as I need to find a system that can be run from an onboard inverter and doesn't drain too much power in the process

Pete


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## safariboy

Even 600W at 12 V will be over 50A into an inverter so that will flatten a fully charged 100A-Hr battery in less than 2 Hours. If you work on 50% discharge less than 1 hours running per battery.
Is this practical?


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## Vennwood

Hi Safariboy,

I agree there but anyone with a 2KW inverter will have (or should have)more battery power than a single 100AH battery. Forget aircon, even a kettle or toaster could deplete a single battery during the course of a day.

To make this work you would need a substantial bank of batteries maybe say 300ah+ total and you would need a reasonable recharge system of say solar panels/Efoy etc.

In my case I have a pretty hefty setup with 540AH dedicated battery bank, 260W solar panels and a genny with a 110a charging system and I'm still worried

Pete


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## PAT4NEIL

We looked at these at the Peterborough motorhome show, the company we were impressed with was Cool auto, they have a good web site with information. It does depend on size of motorhome you have because the smaller you have you can go for the smaller saphire unit.

Expensive if you have to have it fitted

Still researching, so interested in anyone else comments
Pat


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## Vennwood

Hi Pat,

The problem with the cheaper Truma Saphir units is that they don't have the multiple power settings so the Compact has a power setting of 1800W, the Comfort has a wopping 2400W while the Vario has 3 - 600W, 1500W and 2000W. EDIT: *Incidentally the smaller units are actually bigger in size which doesn't help either*.

 This piece of info isn't totally accurate I've just measured up and the Vario is the largest and the Compact the smallest

Does anyone know of a system that has multiple power settings and is reasonably cost effective.
Graham at Cool Auto is a first rate guy, extremely helpful and I would recommend him to anyone. I have been working with him for the past couple of months, always willing to look into things, always returns emails (even late at night). When I finally make my decision it will be through Cool Auto

Pete


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## PAT4NEIL

Hi thanks for your reply, dont know that much as husband did the research, That was the one we were looking at, but on cool autos site it says for vans up to 5.5metres, is there a saphire vario model that goes bigger as our van is 7.15metres

Thanks Pat


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## Vennwood

Hi Pat,

Yes the Saphir Vario is the top of the range unit that is supposed to be for MH's bigger than 5.5 mtrs. (As fitted as standard equipment in Hymer S Class and the Dethleffs Espirit range). Cool Auto use the Dometic volume calculator to assess the size of aircon unit you need

Pete


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## teemyob

*Aircon*

Hello Pete and Pat,

Our van is 7.3m, we have 3 x 110ah batteries coupled to 2 x 80w Solar Panels. However, the interior of the van is more like a 5.5m van as the living space is quite small, a lot of the van is taken over by the garage and under floor (we have a winterised double floor van).

I have a problem as to where to place the unit, more of a problem is where to route the ducts, as we have nowhere to route them. The option of a roof mounted unit is pretty much out as the Solar panels, Fiamma fan, Maxview and other units have taken all the space. Also do not like the idea of putting anymore weight on the roof of such a high sided motorhome with a very narrow track.

The thing I liked about the dometic is the option of electric heating. Our motorhome has a gas only truma boiler. In winter we pay for hook-up but only use the power to charge the batteries, power TV etc.

I am not bothered about the need to use A/C when wildcamping. The only reason I am looking at these units is that in extreme high temperatures, it is far to hot and stuffy for rear seat passengers. On a recent trip to the south of France, there was a heatwave, the temperature inland when traveling was around 45c, in the back of the van was 43c. Even the cab A/C was struggling.

The other option I have looked at is adapting a spare mobile a/c unit I have to work on the move.

Still researching,
Trev.


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## Vennwood

Hi Trev,

Like you we have double floor and plenty of space to put the unit but would have difficulty in routing ducts to the roofing area. I spoke to Truma themselves and they said that floor mounted ducts would be ok , however not as efficient as roof mounted. The engineer mentioned that circulation was the issue and that a 12 volt fan would help to circulate the air and make it more effective.

We haven't experienced a problem yet with hot temperatures in the van but with a windscreen as large as ours I guess it won't be long before we do. We do a lot of wild camping or Aires without EHU and need a cool van to sleep in. It's a vicious circle - windows closed to keep the flies out and you are too hot, open windows and the flies buzz in etc.

I'd be interested in your mobile idea as all the units I have looked at are either too big or too power hungry and on the move I'd be worried about spilling the water collected.

Like you we are still researching all options

Pete


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## teemyob

Vennwood said:


> Hi Trev,
> 
> I'd be interested in your mobile idea as all the units I have looked at are either too big or too power hungry and on the move I'd be worried about spilling the water collected.
> 
> Like you we are still researching all options
> 
> Pete


Hello Pete,

There are two types of mobile, one that throws the condenstate out with the condenser air and the more common, where the condensate collects in a removalable resevoir.

My idea is to strip a mobile of the latter type, and fit a drain tube out under the van. Again, finding a place for the inner evaporator is an issue. The one I have in mind also has a rotary compressor and is filled with the more effecient R407C.

Trev.


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## teemyob

*Dometic V Truma*

Hello,

I think we are going to make a decesion on the air conditioning in the next few days.

I like the idea of the Truma Vario for the compact height and the variable compressor consumption, 600w, 1500w and 2000w.

However, I also like the idea of being able to heat the van via the heat pump on the Dometic HB2500. Especialy as we are often forced to pay for EHU and then have to heat by gas or fall over electric heaters.

Our set-up is...

2x 80w Solar panels
3 x 110ah batteries
1 x 2kW inverter

Question is,

Will I be able to run the Dometic HB2500 in A/C mode on the move by way of inverter?.

Spec for HB2500 is

Link To Dometic Spec< click this line

Trev.


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## Vennwood

Hi Trev,

The straight answer to your question is the HB2500 can be run while on the move with your present kit *IF* your alternator is man enough for the job. You may need to get this upgraded.

Dometic recommend their DC3 kit (approx£750) for using the HB2500 but that is just a pure sine wave version of any 2000W inverter. I have it from their engineers that the HB2500 doesn't need a pure sine wave invertor so....

You wouldn't be able to run the HB2500 for long when stationary and on battery alone but I guess you know that already.

I will PM you later today with more details on both running the HB2500 and the Vario

Pete


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## eddievanbitz

Ducted air con systems are very involved to retro fit. 

We try to dissuade our customers from having it installed, as getting adequate ducting to the places you need is near impossible.

Ducted systems do take a lot longer to cool the interior of the motorhome.

Don't count on using the heat pump as a serious heating system. The output is limited and of course hot air rises so to pump warm air out above head height is inefficient. In effect you sit down trying to ignore the noise of the fan shivering and when you stand up to get a jumper, you realise that the air is warm in the ceiling :lol: 

I had the Truma frost air, two, or three vans ago, and it just about lowered the temperature a few degree's in Spain with all the blinds closed, a silver screen. 

In my opinion, ducted systems have little going for them unless you have height issues and loads against them.

I would also politely suggest that to attempt to run a AC unit on inverter should be measured in minutes instead of hours, irrespective of battery bank. 

Just my opinion bearing in mind I always have AC on motorcaravans and we do fit quite a lot of AC systems :lol:


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## teemyob

*Replies*

Morning,

Thanks for the replies Pete and Eddie.

As I said, the Vario seems the better option for cooling, the Dometic for heating due to lack of electric on the Truma Boiler.

The roof is already very congested and would invlove a lot of work trying re-locate panels and a Maxview that is probably not only stuck like muck To a blanket with Sikaflex but would also leave a hole in the roof needing to be pulgged.

The other thing is that Roof mounted units of a similar capacity to the Saphir/Dom HB2500...........

More expensive, 
Heavier,
Top Heavy - effects handling,
Decreases Interior height around indoor unit by around 50mm.

As I said eariler in this thread, I was going to modify a portable unit to do the job. Or fit the type of split used in the US Truck market, getting hold of one is the problem. The other issue is that is very time consuming. So decided to go along the lines of the Saphir/HB2500 units.

Like anything in the Caravan And Camping Industry, these things cost the earth over the usual domestic/commercial products. I can buy a Mitsubishi/Daikin/Fujitsu or similar quality Split Heat pump for a Small office or Large Living room for around £225+VAT (Trade). However, these units are starting around the £900 mark inc VAT.

Thanks again,
Trev.


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## teemyob

*HB2500*

I did find and translate this.

HB2500 Install

Click "Dometic air conditioning installation and a member of our reconstructions"

Towards bottom of Page


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