Installing a heat exchanger on engine for calorifier

[Cornishkiwi]

Hey all

I'm thinking of adding a plated heat exchanger onto my cooling pipes (like one in photo)of my engine which will keep the calorifier hot when I run the engine, I currently have a webasto thermo top to heat it up but would like a secondary means. I feel this is a cheaper and easier way rather than buying a twin coil calorifier.

I was wondering whether anyone else has a system like this? And finds it efficient or any problems??

Also once teeing into the existing hot water supply line (from the webasto) would I need to put non return valves in place to stop cooling water">engine cooling water back feeding to webasto? And would I need to put non return valves to stop webasto water entering engine, I feel this way won't be so important.

Thank you

Keiron

[Jamme]

Following

[sailingharry]

I use a very similar heat exchanger on my boat. One side has the hot water from my hydronic heating system. The other side is potable water. The unit is maybe 3 in by 6 in by 2 in high, very small. When my hydronic system is running, the domestic hot water is hotter than necessary. In other words, it works very well!

I am considering adding a small pump that takes water from the output of this plate heat exchanger and circulates it through the calorifier. I figure in 10 to 15 minutes (or less!), the calorifier would be toasty warm.

I'm not sure if this exactly aligns with what you have in mind, but I am impressed with these little plate heat exchangers.

[Cornishkiwi]

Originally Posted by sailingharry

I use a very similar heat exchanger on my boat. One side has the hot water from my hydronic heating system. The other side is potable water. The unit is maybe 3 in by 6 in by 2 in high, very small. When my hydronic system is running, the domestic hot water is hotter than necessary. In other words, it works very well!

I am considering adding a small pump that takes water from the output of this plate heat exchanger and circulates it through the calorifier. I figure in 10 to 15 minutes (or less!), the calorifier would be toasty warm.

I'm not sure if this exactly aligns with what you have in mind, but I am impressed with these little plate heat exchangers.

Ahh well I'm glad to hear that they work well then!! As they are reasonably priced!!

But yeah I think for the size of them it's a good idea as a back up on the engine, would your heating system pump not be enough to reach the calorifier??

[GILow]

Originally Posted by Cornishkiwi

Hey all

I'm thinking of adding a plated heat exchanger onto my cooling pipes (like one in photo)of my engine which will keep the calorifier hot when I run the engine, I currently have a webasto thermo top to heat it up but would like a secondary means. I feel this is a cheaper and easier way rather than buying a twin coil calorifier.

I was wondering whether anyone else has a system like this? And finds it efficient or any problems??

Also once teeing into the existing hot water supply line (from the webasto) would I need to put non return valves in place to stop engine cooling water back feeding to webasto? And would I need to put non return valves to stop webasto water entering engine, I feel this way won't be so important.

Thank you

Keiron

Attachment 264169

Do you motor a lot? If not, I cannot see the extra complexity being worth the effort. The Webasto is a VERY efficient and simple way of extracting heat from diesel. Engines are not.

I have a Webesto driven hot water system and I have never seen the value in incorporating the engine.

[Manateeman]

Plate heat exchangers are very efficient. We would check the numbers in and out because our plate exchanger is half that size. Some type of circulating pump is necessary and a pressure safety valve . We also have a temp gauge.

[Cornishkiwi]

Originally Posted by GILow

Do you motor a lot? If not, I cannot see the extra complexity being worth the effort. The Webasto is a VERY efficient and simple way of extracting heat from diesel. Engines are not.

I have a Webesto driven hot water system and I have never seen the value in incorporating the engine.

I try not to overly but I motor enough in and out of the harbour. I find the webasto efficient but does draw alot of power starting up and we're a live aboard with no shore power so to be able to get my hot water for the day without thinking about it I think would be worth it. Plus I like the idea of having a back up with minimal components to it especially now winter is edging closer.

[Cornishkiwi]

Originally Posted by Manateeman

Plate heat exchangers are very efficient. We would check the numbers in and out because our plate exchanger is half that size. Some type of circulating pump is necessary and a pressure safety valve . We also have a temp gauge.

Good to hear, but when you say numbers in and out do you mean flow rate etc??

But I think the circulation pump on the engine coolant would suffice, however I did overlook the prv, thanks for the reminder.

[GILow]

Originally Posted by Cornishkiwi

Good to hear, but when you say numbers in and out do you mean flow rate etc??

But I think the circulation pump on the engine coolant would suffice, however I did overlook the prv, thanks for the reminder.

I suspect you wii find that the engine circulation pump is not adequate. It depends on the engine I guess, but working on various engine driven hot water units over the years I’ve found there is very little pressure differential in the calorifier circuit and they seem to rely on low resistance circuits coupled with largeish hose bores.

People who have documented their success with plate style heat exchangers (and they have been successful) seem to have all had dedicated pumps driving them.

[GILow]

Originally Posted by Cornishkiwi

I try not to overly but I motor enough in and out of the harbour. I find the webasto efficient but does draw alot of power starting up and we're a live aboard with no shore power so to be able to get my hot water for the day without thinking about it I think would be worth it. Plus I like the idea of having a back up with minimal components to it especially now winter is edging closer.

I hear you on the power draw issue. Not only do they draw a fair bit of power starting up, but also a fair bit when running.

But if you end up having to add a pump, as I suspect you will, there’s a little bit more power to supply (probably not an issue with the engine running I guess) plus the whole minimal components thing is starting to get out of reach.

One of the reasons I dismissed the idea of incorporating the engine to heat my water relates very much for the desire for simplicity and minimal components. I felt that the extra engine plumbing was just that many more potential points of failure that could knock out not only my hot water system, but more importantly, my engine.

No chance of adding more solar perhaps? I got through winter at 42 degrees south by just festooning the boat with extra solar. Not pretty but a couple of secondhand panels to hang off the aft rails only cost me AU$100 for 380 Watts. I sold them in spring.

Anyway, if you do go down this path, the secret to good results from these plate style heat exchangers is pretty fast water flow on both sides of the system. The greater the temperature differential you can maintain, the more effective the heat transfer. They certainly do seem to work very well for those I’ve read about that chose to document their experience.

[GILow]

This thread had some references to plate style heat exchanger systems, or at least links to such setups, if memory serves me well.

Hydronic heating. cabin/water
https://www.cruisersforum.com/forums...d.php?t=149641

[CaptTom]

How old is your existing water heater? They have a limited life span. Replacing it with a two-loop version sounds so much simpler. Fewer parts to buy, fewer parts to fail, simple attachment, fewer fittings, etc.

Those plate heat exchangers are great, and I'm sure what you're proposing would work. It just seems unnecessary given that you can already buy a water heater which does exactly what you want, all in the one unit.

[Audeamus]

We have installed the exchanger set-up that you have in mind, Webasto to heat the hot water when we are short on solar and the boat/hot water when its cold. the thermo top should have an input for engine run. When this is connected and the engine is running it will run the circulation pump but if the water temp is high enough from the engine output it will not "fire" the webasto. You must plumb the exchanger into the correct part of the circuit. If you want to get tricky with a few relays you can incorporate the thermostat from the calorifier to control the webasto as well.
The fittings in the exhanger if its the webasto one will not restrict engine cooling flow as they are 1".(regardless the tappings on our Yanmar are bypass flow only) Truth is we are still in the tropics so have had plenty of solar and only run the hydronic occassionally for "maintenance" so have not commissioned the exchanger part as we have been busy with many other things on the refit so I cannot report on how it works. I have some wiring and plumbing schematics I can share if you want to PM me.