Radiator heating via engine

[MrsM]

Is there any reason why I can't use the same coolant in the engine cooling circuit and my Webasto water and central heating circuit, because they both contain an antifreeze and rust inhibitor? This would potentially give me the opportunity to pump the engine coolant through my radiator circuit either in parallel or as an alternative to the skin tank on cold days (ie get 'free' heating when the engine is running rather than just 'free' hot water). I recognise this would require an extra 2-way valve in the skin tank feed and a small circulation pump for the radiator loop. I am aware I would also need a non-return valve to avoid heating the engine from the Webasto! Your thoughts/feedback as to the viability or not of this please.

Edited September 11, 2020 by MrsM
Have previously contacted Webasto tech support for info about antifreeze etc but not heard back

[Tony Brooks]

9 minutes ago, MrsM said:

Is there any reason why I can't use the same coolant in the engine cooling circuit and my Webasto water and central heating circuit, because they both contain an antifreeze and rust inhibitor? This would potentially give me the opportunity to pump the engine coolant through my radiator circuit either in parallel or as an alternative to the skin tank on cold days (ie get 'free' heating when the engine is running rather than just 'free' hot water). I recognise this would require an extra 2-way valve in the skin tank feed and a small circulation pump for the radiator loop. I am aware I would also need a non-return valve to avoid heating the engine from the Webasto! Your thoughts/feedback as to the viability or not of this please.

Yes and no - that helps doesn't it.

 

It is unlikely but not impossible that the Webasto system is unpressurised where as the engine coolant will almost certainly, on a modern engine, be pressurised when hot at u to about 15psi. This means that if you simply linked the systems as the engine warmed up it would blow its coolant out f the central heating header tank.

Much safer to put a plate heat exchanger in series with the Webasto's outlet and heat the central heating water from the engine coolant via the heat exchanger.

 

[MrsM]

Thank you Tony. I'll check the pressures but suspect you are right.

[Tony Brooks]

It is so simple to plumb one side of a heat exchanger into the engine calorifier return pipe and the other side into the Webasto circuit its hardly worth checking the pressures. Without the heat exchanger a central heating leak would cause overheating or worse so for reliability a heat exchanger is a good idea.

[MrsM]

1 minute ago, Tony Brooks said:

It is so simple to plumb one side of a heat exchanger into the engine calorifier return pipe and the other side into the Webasto circuit its hardly worth checking the pressures. Without the heat exchanger a central heating leak would cause overheating or worse so for reliability a heat exchanger is a good idea.

That definitely sounds more straightforward, which is always my favoured approach! 

[Tony Brooks]

7 minutes ago, MrsM said:

That definitely sounds more straightforward, which is always my favoured approach! 

Several on here have done it and I have seen links to suitable heat exchangers in topics. f you cant find one via the search function I hope someone will post a link.

[MrsM]

Thanks again and yes I've now searched on heat exchangers and am sure all the info I need, and more, will be there. Are you aware of whether anyone has done what I suggested using a pressure reducing valve (as opposed to a pressure RELIEF valve - which wouldn't help) in the curcuit? Just out of interest, I certainly won't pursue it if it isn't a wise idea.

Edited September 11, 2020 by MrsM

[David Mack]

It's a water circuit. If you have a pressure reducing valve on one side you need a pressure increasing valve on the other!

[Tony Brooks]

6 minutes ago, MrsM said:

Thanks again and yes I've now searched on heat exchangers and am sure all the info I need, and more, will be there. Are you aware of whether anyone has done what I suggested using a pressure reducing valve (as opposed to a pressure RELIEF valve - which wouldn't help) in the curcuit? Just out of interest, I certainly won't pursue it if it isn't a wise idea.

As @David Mack implied as far as I can see it is simply not practical. Please forget it and go the heat exchanger route because its more conventional.

[MrsM]

3 minutes ago, David Mack said:

It's a water circuit. If you have a pressure reducing valve on one side you need a pressure increasing valve on the other!

D'oh!

Just now, Tony Brooks said:

As @David Mack implied as far as I can see it is simply not practical. Please forget it and go the heat exchanger route because its more conventional.

Will do. Thanks for the advice, it is very much appreciated. Mx

[Sea Dog]

If it helps, I've done a compromise solution and added a small towel rad in my bathroom, plumbed into the calorifier return circuit. It dries towels and keeps the chill off the bathroom a treat and has had no detrimental effect on the engine running temperature. It's valved on flow and return with a bypass valve between the legs to allow isolation and adjustment of flow (all valves are full bore type). It works perfectly. Quite frankly, if it's cold enough in the boat to need the rads on when running, the stove is already on, making the expense of a heat exchanger a bit academic (in my case at least).

[dmr]

Don't do it, a lot of trouble and potential problems for very little gain. A diesel engine pushing a boat along at 2.4mph does not make much spare heat. It might work on a river but on a canal it will likely result in the engine never getting up to temperature. Canal cruising is bad enough but running well below temperature will just make the engine very unhappy.

 

We had this system when we got the boat and once I fitted a temperature gauge I realised it had to go. It used a system of ball valves and if I got these wrong the engine pressure blew all the water out of the Alde header tank.

 

............Dave

[TheBiscuits]

58 minutes ago, dmr said:

Don't do it, a lot of trouble and potential problems for very little gain. A diesel engine pushing a boat along at 2.4mph does not make much spare heat. It might work on a river but on a canal it will likely result in the engine never getting up to temperature. Canal cruising is bad enough but running well below temperature will just make the engine very unhappy.

 

We had this system when we got the boat and once I fitted a temperature gauge I realised it had to go. It used a system of ball valves and if I got these wrong the engine pressure blew all the water out of the Alde header tank.

 

............Dave

 

I'd argue against that, but on the understanding the heat exchanger is not in the calorifier loop, but is instead on the skin tank loop.  Only "waste" heat that would be going to the skin tank and into the canal/river gets used for the CH circuit and the engine/calorifier loop maintains it's correct working temperature.

 

I've not done it (yet) but I got the idea from @nicknorman I think.

[MrsM]

8 minutes ago, TheBiscuits said:

 

I'd argue against that, but on the understanding the heat exchanger is not in the calorifier loop, but is instead on the skin tank loop.  Only "waste" heat that would be going to the skin tank and into the canal/river gets used for the CH circuit and the engine/calorifier loop maintains it's correct working temperature.

 

I've not done it (yet) but I got the idea from @nicknorman I think.

That's what we were thinking. Our understanding is that the water jacket thermostat remains shut until the engine is up to temperature so there should be no issue that the engine will run cool. We would simply be ditching heat into the radiators via the heat exchanger rather than into the skin tank. We are aware that our skin tank is marginally undersized anyway, so this gives us a useful extra but of heat sink. That's the plan ...

Edited September 11, 2020 by MrsM

[TheBiscuits]

9 minutes ago, MrsM said:

That's what we were thinking. Our understanding is that the water jacket thermostat remains shut until the engine is up to temperature so there should be no issue that the engine will run cool. We would simply be ditching heat into the radiators via the heat exchanger rather than into the skin tank. We are aware that our skin tank is marginally undersized anyway, so this gives us a useful extra but of heat sink. That's the plan ...

 

Yes, that's what I'm going to do when my round tuit arrives.  

 

2 hours ago, Sea Dog said:

Quite frankly, if it's cold enough in the boat to need the rads on when running, the stove is already on, making the expense of a heat exchanger a bit academic (in my case at least).

 

Nice for those chilly days in spring and autumn (or even summer this year!) though, and it's waste heat from diesel that's been burned already.  Greener and cheaper, what's not to like?

 

I suppose a lot of it depends on individual cruising/mooring patterns.  It's not much cop if one tends to spend a few days stationary, but useful if one tends to cruise most days.

[MrsM]

Our thinking exactly. Not strictly 'free' heating as it depends upon running the boat engine, but good as if one is already running the engine for cruising. 

[Alan de Enfield]

19 minutes ago, TheBiscuits said:

Yes, that's what I'm going to do when my round tuit arrives.  

 

Has it not arrived yet ? (I sent it some time ago)

 

Here is another for your delectation.

 

 

 

[TheBiscuits]

1 minute ago, Alan de Enfield said:

 

Has it not arrived yet ? (I sent it some time ago)

 

Here is another for your delectation.

 

 

 

 

Thanks Alan.

 

Now I just need an appropriate heat exchanger and some plumbing fittings.  I already have the pump installed on the CH circuit.  Oh, and I need to move all the crap out of the engine room to get to it.

 

Probably not this week then!

[MrsM]

Can I have one too? Been looking for a round tuit for ages. I blame Covid.

[Alan de Enfield]

19 minutes ago, MrsM said:

Can I have one too? Been looking for a round tuit for ages. I blame Covid.

Your wish is my command - and in view of the current situation, a little help with C19 -  Just for you ....................................

 

 

 

 

 

 

 

 

Edited September 11, 2020 by Alan de Enfield

[smiler]

42 minutes ago, TheBiscuits said:

.........Oh, and I need to move all the crap out of the engine room to get to it.....

A word of warning.....

A get tuit is different than a round tuit.

Normally you need a round tuit to do the get tuit.

I think you will need 2 round tuits.

 

[Cas446]

6 hours ago, MrsM said:

Your thoughts/feedback as to the viability or not of this please

Don't connect the circuits together for all the good reasons already mentioned. You need one of these with the cover.

https://www.ebay.co.uk/itm/263272702860

Install in series with the Webasto, you can use the Webasto pump by cutting the wiring and inserting a changeover relay. Install a push button to power the changeover relay and the pump at the same time. With the switch off the Webasto is connected back to its pump. Alternatively add another pump in series, these pumps have a high flow rate when not running. Or connect in parallel with the webasto, with the flow in the opposite direction and use non-return valves (draw it out and you will see how that works - although you need spring type non-return valves). I connected my heat exchanger on the clarifier return, and run it when the engine is up to temperature, never a problem with over cooling, Beta 38. Although conceptually better on the skin tank, but for me would have been a messy install. Best mod I ever made to my boat, radiators will get very hot! 

[Tony Brooks]

There is a problem with plumbing the heat exchanger into the skin tank circuit unless its something with twin thermostats like a Shire and that is to ensure the skin tank which would be in parallel with the heat exchanger you need to fit it in series and that involves the much large size of pipes. No great problem if the Webasto is in the  engine  room with enough pipe run to break into but if the accessible pipe run is small or the Webasto is elsewhere you will end up with long runs of large bore pipe.

 

 

If you just want the chill off the rads then the calorifier will act as a heat exchanger with the central heating pump running.

[Sea Dog]

2 hours ago, TheBiscuits said:

Nice for those chilly days in spring and autumn (or even summer this year!) though, and it's waste heat from diesel that's been burned already.  Greener and cheaper, what's not to like?

Nice to have, yes.  However, on those (rare, I think) occasions out cruising when it was cold enough to need the chill taking off the living space but too warm to warrant lighting the stove, I'd just give it a burst of the Eberspacher before I went below. At about 50p for an hour, it'd need a lot of this occasions before the heat exchanger (and associated pump?) earned their keep I think. Of course, other folk may have a different temperature threshold and different needs.

[ditchcrawler]

6 hours ago, Tony Brooks said:

Yes and no - that helps doesn't it.

 

It is unlikely but not impossible that the Webasto system is unpressurised where as the engine coolant will almost certainly, on a modern engine, be pressurised when hot at u to about 15psi. This means that if you simply linked the systems as the engine warmed up it would blow its coolant out f the central heating header tank.

Much safer to put a plate heat exchanger in series with the Webasto's outlet and heat the central heating water from the engine coolant via the heat exchanger.

 

Our share boat with an eberspacher the engine cooling and heating system were all on one circuit, one header tank, it even included a back boiler. As well as the eberspacher it had a second pump which would pump hot water from the stove or the engine round the rads, the Eberspacher would heat the engine as well