12 Volt Central Heating Pumps

[alan_fincher]

The "new" boat is (in my view) too reliant on 240 volts, having I think spent many of the last few years not moving, and on shore power.

 

As part of my planning processes, I would like to extricate myself from needing 240 volts to run any essential services, particularly those that may need to run all the time.

 

One of the power consumers at the moment is a 240 volt (domestic) central heating pump, and I would like to consider options to replace in 12 volts.

 

I thought I remembered more discussions on this topic than I have easily been able to find, (particularly concerning reliability), so I'm asking again.

 

So what works, what does not, (and what has a habit of breaking expensively)? Any recommended pumps, or models to avaoid at all costs?

 

The central heating pump is in a circuit that can be supplied by either a (very large) diesel boiler or (equally large!) solid fuel stove. You throw various valves manually to route through whichever heat source you are using. Whilst convoluted pipework to the diesel boiler, (it's in the engine room), means I think it could never circulate under gravity alone, I do wonder if it may be possible to achieve a gravity fed system when running on the solid fuel stove, (which is far better located).

 

So to what extent do the various forms of pump allow water to pass through them relatively unobstructed if not running, or do the effectively cause enough of a constriction that nothing would flow? One option might be to have pipes that either pass through, or bypass the pump, then use an L port valve to choose which way the water flows - one way for gravity thermo-syphoning, on the solid fuel back boiler, if it can be made to work - the other through the pump when the diesel boiler is in use.

 

What do people reckon, please? I've never had any kind of boiler that drives a heating circuit before, so this is a bit of a learning exercise!

[TaffyRon]

http://www.canalworld.net/forums/index.php?showtopic=70727&hl=%2Bdemon+%2Btweeks+%2Bbolin

 

an old thread I stared, this pump is great

[nicknorman]

I've used the small, cheap plastic pumps from Solarproject. So far so good, but probably only have a couple of hundred hours total running time so far. These sorts of pumps are generally centrifugal types which don't block flow when they are not running, but will of course cause some reduction in x-sectional area which will have some flow restriction effect, depending on the rate of flow etc.

[John V]

Thanks for that link TaffyRon.....I have lots of changes needed for my heating system next spring so I'll be watching all these types of thread closely....that pump looks pretty good !!!

[Phil Ambrose]

Hi John, I have gas C/H run from an Ellis boiler,I replaced the original pump about 3 years ago with a Jabsco which is magnetic drive. So far it's held up OK, we only use it for an hour or so in the morning to provide hot water plus it takes the chill off things first thing while the fire kicks in again, having been damped down for the night.

Can't say how much of an obstruction it is to free flow though. It draws less than 1 amp and it's only down side is the hum which though not obtrusive can be heard when the boat is quiet ie no TV on etc.

Phil

[David Schweizer]

Hi John, I have gas C/H run from an Ellis boiler,I replaced the original pump about 3 years ago with a Jabsco which is magnetic drive. So far it's held up OK, we only use it for an hour or so in the morning to provide hot water plus it takes the chill off things first thing while the fire kicks in again, having been damped down for the night.

Can't say how much of an obstruction it is to free flow though. It draws less than 1 amp and it's only down side is the hum which though not obtrusive can be heard when the boat is quiet ie no TV on etc.

Phil

 

Do you have a conventional set up? According to the installation instructions, the Ellis Heatmaster does not require a circulation pump. We have one on our boat and it provides hot water by convection for both the calorifier and the radiatiors, without the need for a pump.

 

Edited to add :- You do have to use 28mm supply and return pipes to get an adequate flow, so if they are only 15mm a pump would probably be needed.

Edited December 5, 2014 by David Schweizer

[John V]

Thanks for that about the pump Phil. I'll make a note of that....I am finding that there are so many answers to the problems concerning central heating that you need input from people who have used some of these bits otherwise you are depending on spec sheets and advertising.....

[magnetman]

Might be worth using a Mikuni circulation pump ? Or a Johnson. I didn't realise the Bolin had been discontinued. thats a shame as I believe it was an incredibly efficient pump.

and it also might be worth getting a 24v one and just fitting a small dc dc converter to it - very low amp draw so a small circuitboard with a heatsink would probably do it and not be expensive

[Chalky]

I used an auxiliary coolant pump off a Jaguar to rum the heating off a heat exchanger. The pump is designed to cool a high performance engine and be reliable. The impeller is magnetically isolated from the motor so there's no danger of a leak. It draws about 2A when running and can move a lot of water. I got mine from a scrap yard.

[Detling]

A lot of cars use a 12 volt coolant pump for the heater circuit, readily available from a well known auction site or a good breakers yard. Life span may not be in the thousands of hours the Bolin seemed to give but the cost is more manageable.

 

Beaten by Chalky

Edited December 5, 2014 by Detling

[Keeping Up]

2A is a high draw, at least double that of a Johnson or Bolin.

[magnetman]

Yes, I think the Bolin was about 0.7amp at 12v or something, with the Johnson about an amp. That would add up if it was a full time system on a boat which is not connected to shore power.

[ditchcrawler]

I have a Johnson and find it a bit noisy, its a good job its not the end I sit by the radiator.

[BD3Bill]

The "new" boat is (in my view) too reliant on 240 volts, having I think spent many of the last few years not moving, and on shore power.

 

As part of my planning processes, I would like to extricate myself from needing 240 volts to run any essential services, particularly those that may need to run all the time.

 

One of the power consumers at the moment is a 240 volt (domestic) central heating pump, and I would like to consider options to replace in 12 volts.

 

I thought I remembered more discussions on this topic than I have easily been able to find, (particularly concerning reliability), so I'm asking again.

 

So what works, what does not, (and what has a habit of breaking expensively)? Any recommended pumps, or models to avaoid at all costs?

 

The central heating pump is in a circuit that can be supplied by either a (very large) diesel boiler or (equally large!) solid fuel stove. You throw various valves manually to route through whichever heat source you are using. Whilst convoluted pipework to the diesel boiler, (it's in the engine room), means I think it could never circulate under gravity alone, I do wonder if it may be possible to achieve a gravity fed system when running on the solid fuel stove, (which is far better located).

 

So to what extent do the various forms of pump allow water to pass through them relatively unobstructed if not running, or do the effectively cause enough of a constriction that nothing would flow? One option might be to have pipes that either pass through, or bypass the pump, then use an L port valve to choose which way the water flows - one way for gravity thermo-syphoning, on the solid fuel back boiler, if it can be made to work - the other through the pump when the diesel boiler is in use.

 

What do people reckon, please? I've never had any kind of boiler that drives a heating circuit before, so this is a bit of a learning exercise!

 

It's best to fit full bore valves either side of any pump so you won't need to drain the system if you need to replace the pump, having a bypass too is only a little extra work/money.

 

I use the Solarproject pump, cheap, low consumption, doubt it flows enough for you very big boiler though.

I'm guessing you have 22mm pipes ?

 

Hopefully smileypete will look in, he knows you know....

[MoominPapa]

Yes, I think the Bolin was about 0.7amp at 12v or something, with the Johnson about an amp. That would add up if it was a full time system on a boat which is not connected to shore power.

 

I have a Bolin pump fitted. It uses much less than that. More like 0.15A. That's the great advantage of Bolin pumps. Their disadvantage is that they're expensive and have limited life. Mine is starting to leak a bit and get more noisy, unfortunately.

 

MP.

[Phil Ambrose]

2A is a high draw, at least double that of a Johnson or Bolin.

The Jabsco draws about .8amp oh and David you were correct about the pipework,my set up has 15mm , it was on the boat when we bought it and as it worked OK I left it alone.

Phil

[Chalky]

2A is a high draw, at least double that of a Johnson or Bolin.

 

Yes it is however the rads run off a plate heat exchanger that's heated by the engine. I only ever have it running when the engines on so it's not a problem - the control circuitry is partly controlled by the oil pressure switch so I can't leave it on by accident.

[SamKingfisher]

 

It's best to fit full bore valves either side of any pump so you won't need to drain the system if you need to replace the pump, having a bypass too is only a little extra work/money.

 

I use the Solarproject pump, cheap, low consumption, doubt it flows enough for you very big boiler though.

 

As above. I reckon the solarproject pumps would do a fairly large boiler, certainly worth a try.

 

If you think how a 1.5a bilge pump would fling it around, totally unnecessary, an 0.8w ish solarproject pump should be ok.

[alan_fincher]

As above. I reckon the solarproject pumps would do a fairly large boiler, certainly worth a try.

 

If you think how a 1.5a bilge pump would fling it around, totally unnecessary, an 0.8w ish solarproject pump should be ok.

I'm a bit confused by references to 'a' and 'w', which I assume are Amps and Watts respectively?

 

Googling SolarProject pumps shows ones rated at 6, 8 or 14 watts, so perhaps the reference to 0.8w is meant to be 8.0 Watts. At a nominal 12 volts 6, 8 & 14 watts would equate to 0.5, 0.67 or 1.17 amps respectively.

 

SolarProject pumps linky.

 

Can I really hope to introduce something into long pipework runs that are currently 22mm or 28mm that is only 1/2" bore, and expect it to be OK? I can't really get my head around whether it will work, but if it circulates water reliably at anything like the rates stated, I can't see why not.

[John V]

I am not sure on this as it is something that puzzled me..

.I came to the conclusion (rightly or wrongly) that in a pump the hydraulic flow is higher as the liquid is being forced through .

Any extra "drag" due to the higher velocity is more than compensated by the extra pressure of the pump, whereas in the pipe runs the larger diameter gives a lower flow rate thus reducing drag.

In a thermo-syphon system the larger diameters are used to allow higher flows at a lower velocity as the pressure pushing the water round is lower than a pumped system.

(something I have never worked out and that is what is the advantages of a microbore system apart from cheaper copper pipe?)

 

Hopefully someone with knowledge of fluid dynamics can point out if I'm a plonker

[nicknorman]

I'm a bit confused by references to 'a' and 'w', which I assume are Amps and Watts respectively?

Googling SolarProject pumps shows ones rated at 6, 8 or 14 watts, so perhaps the reference to 0.8w is meant to be 8.0 Watts. At a nominal 12 volts 6, 8 & 14 watts would equate to 0.5, 0.67 or 1.17 amps respectively.SolarProject pumps linky.

Can I really hope to introduce something into long pipework runs that are currently 22mm or 28mm that is only 1/2" bore, and expect it to be OK? I can't really get my head around whether it will work, but if it circulates water reliably at anything like the rates stated, I can't see why not.

I selected the smaller 6W one I think, for the plate heat exchanger into about 4 kW-worth of radiators. It is barely enough and next time I would select the 8 or 14w one. I say barely enough because with the radiators balanced for the mikuni's pump, with this little pump the far end radiator doesn't get as hot as the others, so clearly the flow rate is a bit less. That you are feeding from a 15mm pump into 22 or 28 mm pipe work is not an issue (in fact, a good thing) - all that will happen is the fast jet of water coming out of the 15mm pump will slow to something more sane for a heating loop in the wider diameter pipe.

 

Anyway, if you try the 14w one first, they can be turned down by feeding with a lower voltage eg via a cheapo Maplin PWM controller. I remain unclear whether the higher wattage ones are the same mechanics, just running faster, or whether there is some mechanical difference. If the former, I guess the 14w one might be a bit noisier but again, it can always be turned down.

[TaffyRon]

Theres a thermowotsit pad available seen them on egay only low amps at present, I wonger how many you would need stuck to your fire to power a central heating pump?

[smileypete]

The central heating pump is in a circuit that can be supplied by either a (very large) diesel boiler or (equally large!) solid fuel stove. You throw various valves manually to route through whichever heat source you are using. Whilst convoluted pipework to the diesel boiler, (it's in the engine room), means I think it could never circulate under gravity alone, I do wonder if it may be possible to achieve a gravity fed system when running on the solid fuel stove, (which is far better located).

 

Might be helpful to attempt to make a diagram of what's there, make it easier to see if it can be improved.

 

For mixed pumped boiler and gravity on a narrowboat, best I could come up with was the last two of these basic layouts, but it does sounds like your existing is quite different:

 

In a house the gravity and pumped circuits would often be combined with a 'neutraliser' such as made by Dunsley, but that can't really be done on a narrowboat.

 

cheers, Pete.

~smpt~

[alan_fincher]

 

Might be helpful to attempt to make a diagram of what's there, make it easier to see if it can be improved.

 

For mixed pumped boiler and gravity on a narrowboat, best I could come up with was the last two of these basic layouts, but it does sounds like your existing is quite different:

 

Well broadly I have......

 

1) A large Much Wenlock stove with back boiler at the back of the accommodation cabin

2) A Kabola E7 gravity fed diesel boiler in the engine room, next to the Lister.

3) A series of gate valves that determines which of these feeds everything - depending on which way pointed, water passes through one or other of above.

4) Wide bore pipes (but see (8) below),along the length of the boat, with flow below gunwale, return above floor.

5) Hot water cylinders under bed at the very front, probably 11 or 12 metres from nearest heat source, (the Much Wenlock). I'm told there are two, but have not yet got under there to see what is hidden away.

6) 3 radiators strung between the feed and return pipes, some of which we may need to move, to suit a better boat layout.

7) A domestic central heating pump in the return, close to boiler, and through which all water passes, because all rads and tanks are forward of it.

 

8) A further complication is that bottom pipe is diverted in the bathroom area to provide under floor heating through some arrangement I have not seen, (because it is under the floor). We want to plumb this out, because it can't be helping the flow, and because it is not possible to heat tanks at front without wasting heat to heat bathroom floor, (the radiators can all be shut down, but these underflow pipes are simply part of the return circuit).

 

When the Much Wenlock is used, I think we could establish a circuit where gravity does much of it - at least the boiler is at the "downhill end of the boat).

 

The convoluted pipework to connect the Kabola in the engine room, that has to get past engine bearers, fuel tanks, and under the main water tank to enter the main cabin will, I think, always be far more reliant on a pump, if we keep it, and, unlike the solid fuel stove, of course, has to lose all its heat by pumped water, rather than just the back boiler in the Much Wenlock, which of course also lets a lot of heat directly into the main cabin.

 

I'll try and get some pictures, and maybe do some drawings, once we can get back to the boat.

[smileypete]

Might be able to replace the single domestic pump with a couple of solar project type pumps, one on the backboiler, one on the kabola, with a swing check valve just before/after each pump.

 

That should make it possible to do away with the various gate valves, just switch either pump on according to the heat source that's used, and the check valve by the other pump should stop unwanted back flow though the other heat source.

 

A priority would be making sure there was a wide bore pipe from top backboiler outlet to header tank vent with NO valve in between, in case a pump fails and the stove boils. Could have wide bore pipes also feeding a gravity rad or two, then tee in the pumped circuit right next to the back boiler.

 

The last of the above layouts shows how the gravity rads may also be connected to another pumped circuit, eg the Kabola. Bit of a compromise way of doing it, but can't really see a better way without getting even more complicated.

 

cheers, Pete.

~smpt~

Edited December 6, 2014 by smileypete