Finally -- Bus Heater Install!

[kmacdonald]

I'd take the time to get the air out without the circ pump. It adds expense, complexity, wiring, and it has to be able to take the coolant temp. It also draws a significant amount of power. I'm surprised you have an issue with air in the lines. Just add coolant very slowly, run it, and add more. Repeat until it stops taking coolant. Once you get the air out it shouldn't be any more maintenance at all to it. The engine circ pump will do fine. But like I said before, you have to tap into the engine cooling system at the right places. I assume that's already been done correctly for the water heater so you just add a hose from the water heater inlet to the air heater inlet and a hose from the water heater outlet to the air heater outlet. Add a shutoff valve to one of the hoses going to the air heater to completely turn off the heat. The valve can be on either the inlet or outlet, pick which one is more convenient to get to. I wouldn't bother with isolation valves since it's so easy to replumb to remove a heater if necessary. Just stick a 1/2" bolt in the hose end and clamp.

[kmacdonald]

To completely isolate a heater two valves are required, one on the inlet and one on the outlet. To turn off a heater requires one valve on either the inlet or outlet. That will stop the flow of coolant thru the heater. 1/2" hose is all that's necessary. Like I said before, adding a bus heater in parallel to the water heater reduces the flow resistance of just the water heater. Bigger hoses are not required! This is a dead simple job.

[jimbunyard]

Originally Posted by kmacdonald

...I wouldn't bother with isolation valves since it's so easy to replumb to remove a heater if necessary. Just stick a 1/2" bolt in the hose end and clamp.

Especially when one's bouncing around in 'calm' 15' North Sea swells....

[Dockhead]

Originally Posted by kmacdonald

I'd take the time to get the air out without the circ pump. It adds expense, complexity, wiring, and it has to be able to take the coolant temp. It also draws a significant amount of power. I'm surprised you have an issue with air in the lines. Just add coolant very slowly, run it, and add more. Repeat until it stops taking coolant. Once you get the air out it shouldn't be any more maintenance at all to it. The engine circ pump will do fine. But like I said before, you have to tap into the engine cooling system at the right places. I assume that's already been done correctly for the water heater so you just add a hose from the water heater inlet to the air heater inlet and a hose from the water heater outlet to the air heater outlet. Add a shutoff valve to one of the hoses going to the air heater to completely turn off the heat. The valve can be on either the inlet or outlet, pick which one is more convenient to get to. I wouldn't bother with isolation valves since it's so easy to replumb to remove a heater if necessary. Just stick a 1/2" bolt in the hose end and clamp.

The circ pump is definitely needed, and I already bought it. The round trip to the calorifier is about 6 meters, and the hose is only 1/2".


I cannot get all the air out with the method you describe because I cannot get to the high points in the system. I do my best but something is left, and circulation is unreliable.


I've been reading up on bleeding domestic hydronic systems and it does seem that with a circ pump in the system it's not essential to get right to every high point. The air apparently gets carried along as bubbles, so you bleed, replace, bleed, replace, til it's clear.


And if the air goes into the engine as bubbles it shoud get separated and end up in the header tank, I would think.

[kmacdonald]

I'm curious now. What engine do you have? Were the water taps on the engine factory installed? Is the water heater mounted higher or lower than the thermostat on the engine? 6 meter round trip isn't short but isn't excessive either. Can you post a picture of the water taps on the engine? If the water taps are not correct on the engine the results are exactly what you are describing. Little to no flow. If the taps are wrong on the engine it can damage the engine by inconsistent water flow. Beta talks about it in their install literature. Just trying to help and I know how frustrating problems like that can be. Lets make absolutely sure the water taps are plumbed correctly on the engine before proceeding.

[kmacdonald]

From Beta:

HOT WATER HEATER SYSTEM

If you are going to fit a hot water heater (calorifier) and let the coolant from the closed circuit of the engine heat the water for you, It is essential to get the plumbing correct so that you don’t have an overheat problem with your engine. Keep the supply and return lines between the engine and hot water heater as short as possible and avoid any big loops or dips in the hose. Remember that you fill the coolant at the cap that is on top of the manifold that is on the engine. This must be the highest point of the cooling system because you cannot pour water uphill. If the shape of the boat forces you to mount the hot water heater above the engine, then you need to follow the drawing (link below) to ensure that your cooling system works correctly.

Diagram if hot water heater is higher than heat exchanger: https://www.betamarinenc.com/wp-cont...-DRAWING-2.pdf

[Dockhead]

Originally Posted by kmacdonald

From Beta:

HOT WATER HEATER SYSTEM

If you are going to fit a hot water heater (calorifier) and let the coolant from the closed circuit of the engine heat the water for you, It is essential to get the plumbing correct so that you don’t have an overheat problem with your engine. Keep the supply and return lines between the engine and hot water heater as short as possible and avoid any big loops or dips in the hose. Remember that you fill the coolant at the cap that is on top of the manifold that is on the engine. This must be the highest point of the cooling system because you cannot pour water uphill. If the shape of the boat forces you to mount the hot water heater above the engine, then you need to follow the drawing (link below) to ensure that your cooling system works correctly.

Diagram if hot water heater is higher than heat exchanger: https://www.betamarinenc.com/wp-cont...-DRAWING-2.pdf

The calorifier is not higher than the engine.

[kmacdonald]

From Beta: https://www.manualslib.com/manual/90...page=15#manual

[Ivanvet]

Hi Dockhead,

I installed a heat exchanger between the main engine and our hydronic system. It’s a little different from what you are doing but we learned a few lessons that may apply to you.
We started with a parallel system on our hydronic and it was an absolute nightmare to get pressure regulated properly. We didn’t use flow regulating valves and we should have done that. We decided to change it into a series because we only have a single loop and the parallel design wasn’t going to benefit us much.
I installed something like this Heat exchanger ( https://www.supplyhouse.com/Bell-Gos...xoCYj8QAvD_BwE )to use heat waste from the main engine to heat the boat. In one loop I have the hose coming from the main engine, it goes through the exchanger, to the hot water tank and then back to the engine. On the other loop of the exchanger, the hose from the hydronic system. Ideally when we motor, we turn the diesel heater on, which turns the circulation pump on, but since the temperature through the system is high (thanks to the main engine) the diesel heater boiler would cycle once and then shuts off. This would heat the whole boat. I haven’t tried it yet so I can’t talk about how well it works.

Regarding bleeding. It has also been an absolute nightmare for us. For the hydronic, we ended up connecting city water to get all the air out at high pressure, then replaced with coolant. This still took a lot of run/bleed/run/bleed.
For the main engine, I ended up getting one of those vacuum systems that are used in automotive radiators and it worked like a charm. (https://www.amazon.com/GooMeng-Syste...9282949&sr=8-5)

Good luck,

I.

[DirtRdEarl]

Have used a bus heater for years. 5/8 hose, in series. I use a 3 way valve so I can bypass the heater in summer. Engine is adequate for circulation.

[Dockhead]

Originally Posted by Ivanvet

Hi Dockhead,

I installed a heat exchanger between the main engine and our hydronic system. It’s a little different from what you are doing but we learned a few lessons that may apply to you.
We started with a parallel system on our hydronic and it was an absolute nightmare to get pressure regulated properly. We didn’t use flow regulating valves and we should have done that. We decided to change it into a series because we only have a single loop and the parallel design wasn’t going to benefit us much.
I installed something like this Heat exchanger ( https://www.supplyhouse.com/Bell-Gos...xoCYj8QAvD_BwE )to use heat waste from the main engine to heat the boat. In one loop I have the hose coming from the main engine, it goes through the exchanger, to the hot water tank and then back to the engine. On the other loop of the exchanger, the hose from the hydronic system. Ideally when we motor, we turn the diesel heater on, which turns the circulation pump on, but since the temperature through the system is high (thanks to the main engine) the diesel heater boiler would cycle once and then shuts off. This would heat the whole boat. I haven’t tried it yet so I can’t talk about how well it works.

Regarding bleeding. It has also been an absolute nightmare for us. For the hydronic, we ended up connecting city water to get all the air out at high pressure, then replaced with coolant. This still took a lot of run/bleed/run/bleed.
For the main engine, I ended up getting one of those vacuum systems that are used in automotive radiators and it worked like a charm. (https://www.amazon.com/GooMeng-Syste...9282949&sr=8-5)

Good luck,

I.

I seriously considered and spent a lot of time designing a system with a heat exchanger to the main hydronic system. I ended up rejecting it because of the complexity. The only advantage over the bus heater would be that heat would get to the sleeping cabins and not just the main salon. I don't need this often enough (only good if ALL of the following are true (a) very cold; (b) overnight; and (b) motoring) that it's worth this complexity versus just running the Eberspacher a little more, in my case.


Reading your story I'm glad I didn't do it. I have zero issues with bleeding my hydronic system which other than the furnace has been bulletproof. Bleeds itself, circulates fine, has been bulletproof for 18 years. I'm glad I didn't touch it.


Really hot tip with the vacuum system!! Thanks for that. I'll give that a try

[kmacdonald]

A cars water pump will pump about 50 gpm at highway speeds. At idle it pumps about 8 or 10 gpm. What’s the flow rate of the electric circ pump you plan on using? I really don’t think the electric pump is beneficial if the water taps on the engine are plumbed correctly. In fact, it might even restrict flow.

[Bill O]

Originally Posted by DirtRdEarl

Have used a bus heater for years. 5/8 hose, in series. I use a 3 way valve so I can bypass the heater in summer. Engine is adequate for circulation.

+1 to the 3 way valve to close off the loop for the summer and put the bus heater in series at the end of the run after the calorifier.

While late to the party, will add my 2 cents. Maybe your diagram doesn't show all the valves, etc. in your loop and you've already designed it with them in. From the motor you will want valves to shut the system off if something starts leaking. Typically these may be ball valves, but you may want to consider a different type of valve to no go full flow if your bus heater is robbing the motor of too much heat (especially in your cold NS water). The Raritan water heater installation manual has a nice diagram of a metering valve set up to help maintain better motor temps.

Having the calorifier in series w/the bus heater, IMO has some advantage w/a better/more consistent flow in the system. The calorifier will eventually reach a steady state of temp (if no cold water is added), then the bus heater will be the main heat extractor from the system. How the series is set up is your priority of hot water or heat. Don't have any data, but would think once the calorifier reaches a steady state, the bus heater would provide more consistent heat vs. the colorifier after the bus heater.

Have seen other setups (in colder water) w/the bus heater in the "summer" loop (not cut off) and unless the blower was turned on it didn't add any appreciable heat to the cabin.

[Dockhead]

Originally Posted by Bill O

+1 to the 3 way valve to close off the loop for the summer and put the bus heater in series at the end of the run after the calorifier.

While late to the party, will add my 2 cents. Maybe your diagram doesn't show all the valves, etc. in your loop and you've already designed it with them in. From the motor you will want valves to shut the system off if something starts leaking. Typically these may be ball valves, but you may want to consider a different type of valve to no go full flow if your bus heater is robbing the motor of too much heat (especially in your cold NS water). The Raritan water heater installation manual has a nice diagram of a metering valve set up to help maintain better motor temps.

Having the calorifier in series w/the bus heater, IMO has some advantage w/a better/more consistent flow in the system. The calorifier will eventually reach a steady state of temp (if no cold water is added), then the bus heater will be the main heat extractor from the system. How the series is set up is your priority of hot water or heat. Don't have any data, but would think once the calorifier reaches a steady state, the bus heater would provide more consistent heat vs. the colorifier after the bus heater.

Have seen other setups (in colder water) w/the bus heater in the "summer" loop (not cut off) and unless the blower was turned on it didn't add any appreciable heat to the cabin.

Thanks for these comments. I've now ordered all the parts and am now committed to parallel. There will be a valve in the heater branch which will allow me to balance down the flow through the heater if necessary. I can't imagine I would need to balance down the calorifier loop, since it's much longer, but if I do, it will be simple to add a valve.



There are two more valves where the hoses are attached to the engine.


I can't imagine I'll have any problem with cooling the engine down too much -- a diesel engine produce at least twice as much waste heat compared to its mechanical power output. So even barely ticking over at say 10kW, there will be at least 20kW of waste heat. The heater is only 5.5kW.



But I can easily balance down the flow through the heater if I need to for any reason. The temperature of the seawater has nothing to do with it, as there is a thermostat regulating flow across the heat exchanger. Fresh water circuit temperature is maintained to 80C within less than one degree, from the icy waters of the Arctic Ocean to the tropical-like waters of the Bay of Biscay in the summer. In fact the temperature control is so precise that I can see when there is even a little bit of seaweed in the strainer, because the temp goes up by a few tenths of a degree.

[SV__Grace]

Originally Posted by Dockhead

Another question -- about the air. The current system flows unreliably, and I presume because I can't get the air out of the high point. I think the circ pump should solve this, and just blast the air out of that, no? I know I could put bleed valves in those high spots, but I don't want to chop the hose more than necessary. The spot is difficult to reach, so not keen on it from that point of view, either.

Dockhead, our ITR hydronic heating system is a big circle with the circulation pump pushing coolant in one direction and through each heat exchanger/register in/out connections and returning to the unit.

We recently added a couple of zones and while each has a bleed valve we didn't need to use them. The ITR has a "bypass pump" that acts like the circulation pump but doesn't require the unit to be fired up, and by opening up the radiator cap to let air bubbles escape and running it as long as needed (we ran it for 3 hours, probably more than necessary) that was all that was needed to bleed the system.

My simple brain doesn't quite get the parallel vs. series setups, but I assume bleeding might be different between them. If the filling point is the highest in the system (and it should!), just having that open seems to be enough for bleeding, same with our hydraulic steering system.