hot water from the engine for radiators

[DeanS]

ello

 

Last winter we just used the boat coal stove for interior heating and it was good, but the end of the boat got a little chilly, so we used elec heaters. If we were to one day CC....we would need something else. Our boat was new when we got it, and the engine has 2 pipes connected (but currently blocked off), for hot water from the engine (to connect to a calorifier perhaps if I remember correctly).

 

My question is....

 

If I installed 2 small radiators in the far end of the boat, and ran 2 pipes back to those engine connections....would it circulate water? Would I need a water storage tank such as a calorifier as well? I was under the impression that was for showers etc. Could you tell me what I would need to heat the radiators using the engine?

 

Secondly..would I need copper pipe runs, or would the white piping work ok (I use it for hot water piping in the boat at the moment...?)

 

ta

 

[nicknorman]

You should be able to connect a coupe of rads to your engine's connectors no probs. Of course, they will only get hot when the engine is running! Install the piping so that airlocks aren't created. Presumably you have a gas instant heater for hot water? If so, and you are planning to cruise more, it seems a shame to waste all that "free" heat from the engine! Maybe consider a calorifier, after all with a fat boat you must have the space!

 

Plastic piping should be good for the engine hot water, however be careful with the fittings, some are "not for CH " and only rated to 65 deg, some are for CH and rated to 100 or whatever. I suppose it would be sensible to check that the pipe is also rated for CH but all that I have come across has been. It will be printed on the pipe.

 

I would use metal pipe inserts at the fittings, the last thing you want is a leak in those pipes taking the engine down at a critical moment!

[Biggles]

Hello Dean

 

Yep done this totally successfully using a flat plate heat exchanger. It works a treat.

 

Blog Linky

 

 

I have a spare 22kw 10 plate heat exchanger never used. PM if interested.

.

[DeanS]

You should be able to connect a coupe of rads to your engine's connectors no probs. Of course, they will only get hot when the engine is running! Install the piping so that airlocks aren't created. Presumably you have a gas instant heater for hot water? If so, and you are planning to cruise more, it seems a shame to waste all that "free" heat from the engine! Maybe consider a calorifier, after all with a fat boat you must have the space!

 

Plastic piping should be good for the engine hot water, however be careful with the fittings, some are "not for CH " and only rated to 65 deg, some are for CH and rated to 100 or whatever. I suppose it would be sensible to check that the pipe is also rated for CH but all that I have come across has been. It will be printed on the pipe.

 

I would use metal pipe inserts at the fittings, the last thing you want is a leak in those pipes taking the engine down at a critical moment!

 

Thanks:)

 

By adding all the piping, I guess I would need to top up the engine water to accommodate....right?

Keeping shower hot water using gas, so would only use the engine for the rads...run the engine for an hour a night through winter...

 

If the engine stops....does the hot water just sit in the radiators....and still give off some heat...without being circulated....I assume it would...

Hello Dean

 

Yep done this totally successfully using a flat plate heat exchanger. It works a treat.

 

Blog Linky

 

 

I have a spare 22kw 10 plate heat exchanger never used. PM if interested.

.

 

howdy.

Why would a heat exchanger be needed....doesnt the engine water just travel through the radiator piping? If you use a heat exchanger...would you have a reservoir of cold water...(calorifier)...that circulates...seperately....and it's own pump?

[Biggles]

Keep the 2 systems separated using a heat exchanger and use a 12v CH pump to move water round the radiator circuit. Not sure running the same water around the CH and engine would be a good way to go. Not sure the engine water pump would be very efficient at this.

[DeanS]

Keep the 2 systems separated using a heat exchanger and use a 12v CH pump to move water round the radiator circuit. Not sure running the same water around the CH and engine would be a good way to go. Not sure the engine water pump would be very efficient at this.

 

ty. pm sent

[NB Lola]

We just fitted two rads. The rads are connected to the calorifier spare hot water coil and we have a header tank. We also have a pump and all connected with copper pipes. We also have cut off valves. The calorifier also has a heating element which we can use via shoreline/genny but 30 min engine running does the job. Pump used to circulate

Edited September 5, 2013 by NB Lola

[nicknorman]

Dean there are many ways to skin this cat as you can tell. I have gone for a heat exchanger with separate pump because I wanted to be able to run the rads from the engine or the Mikuni - and not heat the engine when the Mikuni was on. If you have a full suite of rads, its doubtful that the engine cooling pump would be sufficient. However in your case, you just want a couple of rads near the engine,I would have thought that the engine pump would probably cope. If not you could always add a small pump later. A calorifier only comes into it if you want to store hot water and heat it from the engine or an immersion heater.

 

Yes, the hot water will linger in rads after you stop the engine, but it will cool fairly quickly as it heats the room, maybe cold after 30 mins in winter.

 

Yes, you will have to add coolant to fill the pipes and rads (ie water + antifreeze). Depending on whether your engine has a header tank or is pressurised might affect how easy it is to keep air out of the rads - if the header tank is well above the rads, it will be no problem. If no header tank, the rads may be the highest point and thus prone to getting air in which will stop the circulation. In that case a pump (installed fairly low in the system) may be needed.

[Ray]

I have to admit immediately that I'm not technically qualified but . . .

 

From my experience (at home and) on the boat, it takes a while for the engine to get up to temperature - and that will be extended slightly I presume with the additional water in the system to heat the radiators. I would anticipate about 30 minutes total.

 

I'd guess that it will take a while for the radiators to have an impact on the ambient temperature around them, possibly more than 30 minutes? If the radiators then cool quite quickly, say another thirty minutes, I can see you needing to run the engine more than once in the depth of winter when the temperature starts to drop mid afternoon.

 

I do wonder if this is the right way to solve the problem (although I can't think of an alternative)

[nicknorman]

I have to admit immediately that I'm not technically qualified but . . .

 

From my experience (at home and) on the boat, it takes a while for the engine to get up to temperature - and that will be extended slightly I presume with the additional water in the system to heat the radiators. I would anticipate about 30 minutes total.

 

I'd guess that it will take a while for the radiators to have an impact on the ambient temperature around them, possibly more than 30 minutes? If the radiators then cool quite quickly, say another thirty minutes, I can see you needing to run the engine more than once in the depth of winter when the temperature starts to drop mid afternoon.

 

I do wonder if this is the right way to solve the problem (although I can't think of an alternative)

I'm inclined to agree, but Dean asked about implementing his idea, not whether it was a practical one! As you say, it will take longer for the engine to heat up, and this will not be very good for the engine (running cool for a long time) - although that effect depends on how big the radiators are.

 

A better solution would be a back boiler on the stove to run the rads at the back.

[Trento]

Dean, as Nickorman says."there are many ways to skin this cat as you can tell."

To be sure your idea will work, just be aware of the differential head of water between the engine header tank and the high piont on the heating system.

For information, my central heating system is run by the Rayburn back boiler, with an Eberspacher back up for when the Rayburn is unlit, plus, the engine cooling water. They all work independently and can work simulatiously if required.

Sounds complicated but in reality its a bucket full of wood, a switch on the Eber, or start the engine...

Edited September 5, 2013 by Trento

[by'eck]

I have to admit immediately that I'm not technically qualified but . . .

 

From my experience (at home and) on the boat, it takes a while for the engine to get up to temperature - and that will be extended slightly I presume with the additional water in the system to heat the radiators. I would anticipate about 30 minutes total.

 

I'd guess that it will take a while for the radiators to have an impact on the ambient temperature around them, possibly more than 30 minutes? If the radiators then cool quite quickly, say another thirty minutes, I can see you needing to run the engine more than once in the depth of winter when the temperature starts to drop mid afternoon.

 

I do wonder if this is the right way to solve the problem (although I can't think of an alternative)

 

That's why the calorifier at least is usually fed from the thermostat bypass circuit. Some marine engines have twin thermostats effectively in series. Initially the engine bypass circuit just circulates water around the engine for quick warm up. When the first lower temp thermostat opens, water is allowed to flow through the calorifier. Eventually the second higher temp thermostat opens to allow normal (skin tank) cooling. The flows through each circuit are controlled by using different diameter pipes.

 

If you only have a single thermostat engine, you can still have a direct bypass for quick warm up with a manual valve, turning it to calorifier after the engine hits 60°C say. Forgetting to operate it won't be an issue since when the thermostat opens the main cooling circuit will be brought into play irrespective.

[Tony Brooks]

Ray & Nicknorman. The engine should heat up just as fast as it always did because it should be fitted with a thermostat. It will take a time for the radiators to heat up because as soon as a slug of cold water from the rads enters the engine the thermostat will close to degree to maintain engine temperature so only a certain amount of warm water will enter the rad system.

 

If he connects the radiators to the calorifier circuit and it is n the common position then it will act as you suggest, but not if he uses the main cooling circuit and uses a valve to bypass the skin tank.

 

I get so fed up hearing hull builders explaining that they can not fit a larger skin tank because it would over-cool the engine and it simply is not true.

[Chalky]

 

Why would a heat exchanger be needed....doesnt the engine water just travel through the radiator piping? If you use a heat exchanger...would you have a reservoir of cold water...(calorifier)...that circulates...seperately....and it's own pump?

 

On our engine the coolant pump is capable of running engine coolant circuit and the calorifier but is not capable of driving anything else. I rang up HMI marine who marinised the engine and was told in no uncertain terms that increasing the calorifier circuit beyond what was stated in the manual could adversely affect the engine's ability to cool itself.

 

I connected a plate heat exchanger in the calorifier circuit after the calorifier so I get hot water first then heat to the rads. It takes about 30 mins for the rads to start to warm up. I plumbed the rad circuit in 22mm plastic pipe and used a car secondary coolant pump to circulate the water. I had some lucky breaks with the parts (pipe was 50p for 3m in a B&Q clearance sale, plumbers merchants was selling small rads for between £2.50 and £5, pump from scrap yard for £20 etc)

[nicknorman]

Tony, I am aware of your points, but if you read the OP you will see that he is contemplating connecting the rads to the calorifier loop which is not protected by a thermostat. Therefore warm-up time will be lengthened.

 

I have always maintained that its a bad idea to run a CH system from the calorifier loop for this reason, however in Dean's case, a couple of smallish rads probably won't be much of an issue and no worse than a calorifier full of cold water.

 

Chalky, I really don't see how extending the calorifier circuit could reduce the ability of the engine to cool itself. A small loop to the calorifier presents a fairly low resistance path to the flowing water, but doesn't result in too much water being diverted round that loop. Increasing the loop length via some radiators can only increase the loop resistance and reduce the water flowing round it.

 

Therefore, either the company was making it up to avoid getting out of their comfort zone, or you misinterpreted. Are you sure they were not concerned about over-cooling, not under-cooling? The latter certainly could be an issue with a large CH loop from the calorifier (pre-thermostat)

Edited September 5, 2013 by nicknorman

[Biggles]

IMO keep the 2 systems separate. The flat plate heat exchangers are very effective at what they do, not massively expensive, and a 2nd pump to circulate the CH either manually switched or on a stat. This really is KIS principles but its 2 separate KIS systems cleverly linked but equally separate.

[Tony Brooks]

Tony, I am aware of your points, but if you read the OP you will see that he is contemplating connecting the rads to the calorifier loop which is not protected by a thermostat. Therefore warm-up time will be lengthened.

 

 

 

Sorry, I missed that.

[nicknorman]

Biggles, although engine failure is not usually critical in inland waterways, a good system will be one that doesn't impact on engine reliability. So the question is, does having the engine coolant circulating through pipework, fittings and radiatiors pose more risk to loss of engine coolant that having it flowing through the relatively short distance to a plate exchanger. But then what risk does the plate exchanger itself present? Thin plates brazed together, probably not very resistant to vibration.

 

I don't know, and also have done as you are suggesting, just not sure its the best solution if the system can be made to work without an exchanger. I suppose we don't know the long term reliability of the plate exchangers in a boaty engine environment.

[DeanS]

FOOD FOR THOUGHT.

THANKS EVERYONE

 

The thought of having to start the engine every day fills me with dread (which is why in summer we have solar panels for batt charging etc).

The coal fire really manages to heat the front of the boat, so I'm tempted to try a bunch of 12v computer fans and circulate the heat slowly , but consistantly to all rooms. The trick however, is to blow the ceiling air downwards into each room....so it's not just circulating at head height. This wouldnt be the greatest solution, but is fairly cheap and might just take the edge off (this winter). Last winter we had the coal fire on for 5 months solid....

 

Some of those 12V fans make a real racket though....I might have to buy proper ones.

[nb Innisfree]

We run 7 rads and 2 cals directly off the engine, same coolant, engine pump copes fine, only downside, the amount of coolant is doubled so a larger expansion tank is needed.

Edited September 5, 2013 by nb Innisfree

[Paul C]

As above, we run a single system with engine coolant circulating both the calorifier and 3x radiators (2 normal sized ones and a small one for the bathroom) and have seen no issues at all with the engine reliability. We did have an issue with the existing header tank being too small, but it was upgraded to a larger one and we keep it topped up so there's only about 1/2 - 1 inch coolant at the bottom - it needs the 2.5 litres or so space to expand.

 

The boat also previously had a back boiler on its stove which fed the same circuit, but this was removed.

 

There are a few downsides:

 

- if ever you need to drain/refill the coolant, there's a lot to store or lose/replace.

- hot water (calorifier) takes longer to warm up, typically 2 hours to get piping hot instead of an hour or so.

- the radiators aren't that efficient

 

Also, in autumn/spring the days are warm but the nights are cold, this means you don't want the heating on in the day, but it gets chilly around......8pm......and of course you can't really run the engine then!

 

But in the winter or colder days of spring/autumn then its a no-brainer to turn the radiators on and get "free" space heating.

[Guest]

ello

 

Last winter we just used the boat coal stove for interior heating and it was good, but the end of the boat got a little chilly, so we used elec heaters. If we were to one day CC....we would need something else. Our boat was new when we got it, and the engine has 2 pipes connected (but currently blocked off), for hot water from the engine (to connect to a calorifier perhaps if I remember correctly).

 

My question is....

 

If I installed 2 small radiators in the far end of the boat, and ran 2 pipes back to those engine connections....would it circulate water? Would I need a water storage tank such as a calorifier as well? I was under the impression that was for showers etc. Could you tell me what I would need to heat the radiators using the engine?

 

Secondly..would I need copper pipe runs, or would the white piping work ok (I use it for hot water piping in the boat at the moment...?)

 

ta

 

Briefly, I think far end of boat might be too far for the engine cooling pump. We have a fan assisted rad at the back of the boat right near the engine which is superb. 4KW of heat whenever the engine is running. We often have to open the doors to dump heat even in colder waether. I used 22mm copper pipe which works really well.

 

Edited September 5, 2013 by Guest

[DeanS]

I've decided I'd prefer to slowly assemble the bits n bobs I need to run a rad system, through a heat exchanger with a seperate pump, which makes a lot of sense to me. The 2 systems would then be seperate from each other, and a leak inside the boat wouldnt cause an engine failure.

 

So, I think I've managed to source a heat exchanger from Biggles, and I'll just try and find some cheap rads, piping, and a pump at some stage.

 

I assume I just fill the pipes with water, and it'll remain a closed system of it's own?

Am I missing anything? (like bubbles/airlocks etc)

ok , me confused

 

Do I need a storage container, or can I just have the following:

 

heat exchanger.

input pipe (from rads)

output pipe (to pump)

output of pump (to rads).

[Paul C]

 

 

I assume I just fill the pipes with water, and it'll remain a closed system of it's own?

Am I missing anything? (like bubbles/airlocks etc)

 

1. How are you going to fill the pipes?

 

2. Water expands (same mass of water will gain in volume) as the temperature rises, therefore you MUST have some kind of allowance for thermal expansion

 

3. Radiators will have bleed valves, which are useful to bleed them and eliminate airlocks. Slope your pipework as appropriate or keep it more or less level (don't have wavy bits up and down, etc!) to make bleeding easier.

 

The easiest way to achieve all of this is to have a system with a header tank, which is some distance above the highest point of the radiators and other pipework. It doesn't need to be a pressurised system (well, beyond the pressure from the head of water in the header tank) but you could pressurise it if you want to (no real advantage, but its just a case of using an aftermarket header tank which might have a pressure cap!)

 

Midland chandlers do header tanks, one has a pressure cap and the other is an open one.

[Guest]

I've decided I'd prefer to slowly assemble the bits n bobs I need to run a rad system, through a heat exchanger with a seperate pump, which makes a lot of sense to me. The 2 systems would then be seperate from each other, and a leak inside the boat wouldnt cause an engine failure.

 

So, I think I've managed to source a heat exchanger from Biggles, and I'll just try and find some cheap rads, piping, and a pump at some stage.

 

I assume I just fill the pipes with water, and it'll remain a closed system of it's own?

Am I missing anything? (like bubbles/airlocks etc)

ok , me confused

 

Do I need a storage container, or can I just have the following:

 

heat exchanger.

input pipe (from rads)

output pipe (to pump)

output of pump (to rads).

That was always my plan, though doing it the way I did required nothing other than a couple of valves and a couple of lengths of pipe plus sundry copper fittings; job done. Of course using a heat exchanger you will have the advantage of being able to tee in a boiler at a later date.