Quick question about Eberspacher

[snigsnig]

Does anyone know what the rule of thumb is regarding what Eberspacher unit is (realistically) best for what length of boat please?

 

I've been told 1kw per radiator and 2kw for the calorifier. I have a 70ft boat with 5 rads and a calorifier, have ripped out a knackered Hydronic 10, and would like to replace it with a D5WSC. But will it provide enough heat? We obviously have a stove too although its effect on our boat is quite limited as its right up front.

 

There's a lot of talk about these heaters underworking which is why they pack up, so surely its best to work it to its max?

 

Cheers

 

Neil

[RobinJ]

I've been told 1kw per radiator and 2kw for the calorifier. I have a 70ft boat with 5 rads and a calorifier, have ripped out a knackered Hydronic 10, and would like to replace it with a D5WSC. But will it provide enough heat? We obviously have a stove too although its effect on our boat is quite limited as its right up front.

A long time ago, we used to calculate the size of radiator required in a room, based on volume and conductivity of the walls (or windows). The radiators then were measured in BTU, but they tend to use KW now, so the principle will be the same for a boat.

Its not so much the number of radiators but there heat capacity and what heat can be supplied to them, so you need to calculate how much heat is required to heat the boat, what heat the radiators can provide and then match that to the capacity of heating unit!

[snigsnig]

That's great, thanks. And thanks to Peter for his PM.

 

Thinking about it all the radiators are single panel finned ones, 3 of them are small, and the one on the bathroom is tiny, so I don't reckon they are anywhere near 5kw total. Its easy to forget how little heat it really takes to heat a narrowboat!

 

I'll do some rough measurements on my next visit and see if I can find a chart online to calculate what kind of kw they really need.

 

Neil

[ChimneyChain]

It's not necessary if it will heat all the rads up on a 70ft boat it's whether the pump will be able to pump the water round over such a long distance. On my last boat the eberspacher was at the back of the boat and there was a pump situated at the front to assist in keeping the flow going.

 

Darren

[musicman]

In theory, the "pump" is a circulating device and it matters not where it is situated. In a sealed system, it merely provides a constant pressure to enable the liquid to flow around the system. However, most domestic central heating circulators are situated close to the heat source - sometimes on the "return" and sometimes on the "feed" side. I guess it is for convenience more than anything.

[ChimneyChain]

I know, on the eberspacher ( water version as opposed to the blown air version ) there's a pump under the boiler but it wasn't man enough to pump the water around a 62ft boat that's why a second pump was installed at the front to assist in the flow.

 

Darren

[smileypete]

That's great, thanks. And thanks to Peter for his PM.

 

Thinking about it all the radiators are single panel finned ones, 3 of them are small, and the one on the bathroom is tiny, so I don't reckon they are anywhere near 5kw total. Its easy to forget how little heat it really takes to heat a narrowboat!

 

I'll do some rough measurements on my next visit and see if I can find a chart online to calculate what kind of kw they really need.

On the Screwfix website they give the kW ratings for all their rads, just pick what is similar to yours.

 

From memory I think a 6' x 2' double rad is 3kW, a single rad is just over half less, and it roughly scales to rad size.

 

If space is short you could always swap the singles for doubles.

 

cheers, Pete.

~smpt~

[Bobbybass]

I know, on the eberspacher ( water version as opposed to the blown air version ) there's a pump under the boiler but it wasn't man enough to pump the water around a 62ft boat that's why a second pump was installed at the front to assist in the flow.

 

Darren

I have a D5W Eber.....(water only) ..that is now 15 years old on my 60 foot boat..

It feeds 5 rads and the calorifier..

 

There is no second pump...just the one on the unit..and it has never had any problems heating us up quickly.

 

Bob

[snigsnig]

Cheers guys.

 

From doing some quick research its clear the "1kw per radiator" thing is nonsense, everything has its own particular rating.

 

And the guy who told me that claimed he worked for Eberspacher for 20 years! Errr.. o-kayyyyyyyy.... no wonder they've got such a bad rep.

 

N

[NMEA]

Cheers guys.

 

From doing some quick research its clear the "1kw per radiator" thing is nonsense, everything has its own particular rating.

 

Even the individual ratings need to be taken with a pinch of salt as they are usually quoted at optimum temperatures of the fluid, especially true of this are matrix units. Length is entirely irrelevant, volume is the only measurement to be considered and then only as a start datum, glass area, type and condition of insulation, seasonal usage, live aboard / leisure, hull material, supplementary heating present, and most important of all in many respects, owner expectation. I usually have at least an hour discussion and survey of a vessel before I can give an accurate estimate and often have to manage customer ecpectation -v- buget.

[smileypete]

If there's a number of rads don't forget they need to be balanced against each other, briefly it means adjusting the lockshield valves while they're all fully on, so that temperature on the radiator return pipe is about the same compared to the other radiators.

 

Otherwise the radiator nearest the heater can 'short' the others and cause short cycling, particularly if it's a small radiator.

 

Might also be worth having a valve on the calorifer return pipe and balancing that a bit too, might be better to throttle it back for quicker rad warmup (this may be why the 5kW ones have a reputation for not being powerful enough.) But not so much the heater cycles off or to half power before the calorifer is heated enough.

 

cheers, Pete.

~smpt~

[snigsnig]

Well, by some miracle I actually managed to fit the new D5 without too much hassle, fitted it to the existing rads that were hooked up the previous Hydronic 10, and pleased to report it works beautifully. I have a 70 footer with 5 rads running the full length of the cabin and a calorifier, and the whole system heats up really quickly, about 10 or 15 mins for full heat to the rads and about 40 mins for the hot water. Bloody chuffed

 

N

Edited February 2, 2013 by snigsnig

[bowten]

Ah!Some good news on here at last.

[smileypete]

Well, by some miracle I actually managed to fit the new D5 without too much hassle, fitted it to the existing rads that were hooked up the previous Hydronic 10, and pleased to report it works beautifully. I have a 70 footer with 5 rads running the full length of the cabin and a calorifier, and the whole system heats up really quickly, about 10 or 15 mins for full heat to the rads and about 40 mins for the hot water. Bloody chuffed

Nice one

 

Would worth servicing/decoking at very conservative intervals, at least initially, to see how it's faring.

 

cheers, Pete.

~smpt~

[snigsnig]

Will do. I've already bought myself a spare set of gaskets, lol :-)

 

N