Central heating 12 volt Pumps

[Stevebd]

We have a pro build Boat . At some stage the heating pump has been changed and a pump with 15 mm connectors. Has been installed The original pump was 22 or 28 mm 

What would be the best replacement pump to help with the flow rate and an diesel stove on it also has a clarifier on the system . We. Don't like the idea of a back boiler in 28 mm copper to 15 mm though a pump then back to 28 mm copper tube.

Can any body help.

Kind Regards NB wild kitten. Tracey &Steve 

 

[Jen-in-Wellies]

Welcome to the forum.

If the system uses 28mm piping, then it was likely designed for gravity circulation, without a pump. Now, a pump might have been installed early on, if the builder found that the gravity circulation wasn't working properly, or might have been fitted later and may not actually be needed. Without the history, it's hard to tell.

Where is the calorifier installed? Is it under the stern deck, or elsewhere. The pump may just be to reach the cauliflower (official forum alternative spelling).

Can you post a pic of the pump and surrounding pipework?

[BEngo]

A scour  of the internet for solar hot water pumps will find you several possibilities.   Some will be chinese carp.

 

Features you want are:

Long design  life

Brushless

Magnetic drive

Quiet

 

I have a Johnson, backing up gravity circulation from a Morso Squirrel solid fuel stove.which ticks the first three but is not really quiet.

 

N

[MtB]

12 hours ago, Stevebd said:

Don't like the idea of a back boiler in 28 mm copper to 15 mm though a pump then back to 28 mm copper tube.

Can any body help.

 

Yes this will look clumsy and inappropriate but does it work?! 

 

'Not liking the idea' of it is not a good reason to change it in my personal opinion (and opinion is all it is). More practically, I don't think I've even seen a 12Vdc pump with connections larger than 1/2"BSP. Pumping fluids takes ENERGY and replacing a low energy pump that works with a bigger one that also works sounds a daft idea to me.

 

We here seem to be assuming you want a 12Vdc pump though. If you actually want a 230Vac pump then pretty much any central heating circulating pump will do. You can fit them with 22mm or 28mm isolator valves but beware, they typically draw about 50W all the time they are running. 

[David Mack]

14 minutes ago, MtB said:

 

We here seem to be assuming you want a 12Vdc pump though. If you actually want a 230Vac pump then pretty much any central heating circulating pump will do. You can fit them with 22mm or 28mm isolator valves but beware, they typically draw about 50W all the time they are running.

And will require your inverter to be on.

[MtB]

4 minutes ago, David Mack said:

And will require your inverter to be on.

 

However, noticing the thread title I see the OP wants 12Vdc....

 

There might be the odd circulator about with 3/4"BSP threads.

 

 

 

 

[David Mack]

13 hours ago, Stevebd said:

We. Don't like the idea of a back boiler in 28 mm copper to 15 mm though a pump then back to 28 mm copper tube.

Why not?

If its a back boiler system it was probably intended to be gravity circulation with 28mm pipe to provide minimum resistance. My guess is it didn't actually circulate properly so was converted to pumped circulation. If that had intended from the start it would have used 15mm pipe throughout anyway.

Edited March 26 by David Mack

[MtB]

In addition, the actual motive force produced by a little 15mm 12Vdc will be hundreds if not thousands of times bigger than the motive force of natural convection.

 

No matter how clunky it might look. 

 

 

[BEngo]

1 hour ago, MtB said:

 

However, noticing the thread title I see the OP wants 12Vdc....

 

There might be the odd circulator about with 3/4"BSP threads.

 

 

 

 

Our Johnson has 3/4 in hose connections and is fitted to 22mm pipe in the  main circ loop , with 15mm radiator drops and risers.  It sucks from the  return pipe.

The pump  is controllled by a cylinder thermostat on the stove output.  The stat has a bypass switch for test and bleeding purposes.  The stat switches the pump on when the stove outlet is above about 70C .   It spends most of its life off, because at low stove  firing rates the boat is warm enough from natural circulation.

 

N

[Ex Brummie]

Whilst you may have 28mm connections on the back boiler, your pump needs to be matched to the available heat capacity and the radiator output, so a smaller pump will be more than adequate. What rating is your back boiler?

[MtB]

8 hours ago, BEngo said:

Our Johnson has 3/4 in hose connections and is fitted to 22mm pipe in the  main circ loop , with 15mm radiator drops and risers.  It sucks from the  return pipe.

The pump  is controllled by a cylinder thermostat on the stove output.  The stat has a bypass switch for test and bleeding purposes.  The stat switches the pump on when the stove outlet is above about 70C .   It spends most of its life off, because at low stove  firing rates the boat is warm enough from natural circulation.

 

N

 

Is this the Johnson pump you are suggesting?

 

https://www.midlandchandlers.co.uk/products/johnson-compact-water-circulating-pump-12v-15lpm-16mm-10-24501-03#

 

 

 

 

[Machpoint005]

6 hours ago, Ex Brummie said:

Whilst you may have 28mm connections on the back boiler, your pump needs to be matched to the available heat capacity and the radiator output, so a smaller pump will be more than adequate. What rating is your back boiler?

 

If the water is circulating, it will be travelling faster through the smaller diameter pipework (volume flowrate will be the same, of course).

 

Does this means that less heat is transferred to the surroundings? 

 

 

[Ex Brummie]

No, If the flow is matched to the load, then that is efficient. However, with an uncontrolled heat source, that need not matter.

Edited March 26 by Ex Brummie