Finally -- Bus Heater Install!

[MJH]

Originally Posted by Dockhead

I scrubbed my lithium battery install, and still feeling bad about it. But I pushed forward something I've been thinking about for a long time -- the bus heater plumbed into my calorifier loop. I ordered the heater today but would love to hear what the CF brain trust thinks about the system design.

It looks kind of like this:

Attachment 214865

The existing loop uses 1/2" heater hose. So here are the design issues:

1. Parallel, not series. Right? The feed to the heater is just downstream of the pump for maximum pressure. Do I need a balancing valve on the main line to the calorifier? The heater I ordered (https://www.t7design.co.uk/3-8kw-sta...eater-24v.html) has a water valve in it so I can reduce the flow through the heater.

2. Air removal. The pump should help with this, right? Do I need valves at the top of the loops?

I will be grateful for any comments! This will live under my companionway stairs, and will blast heat out whenever I'm motoring in cold wet weather. Especially delightful when the cockpit enclosure is up and the companionway hatch is open!

I installed a REAL 5014 Hydronic Heater in the salon prior to going to Alaska for the Admiral...she loved it. I ran directly off the engine to the heater and then reconnected back to the water heater line; only added another five feet to the overall hose. Runs great, happy Admiral. My only concern is the high amperage for higher blower settings so only run on the lowest setting which is fine.

~ ~ _/) ~ ~ MJH

[wrwakefield]

Hi DH,

I'm coming late to this party.

I installed our bus heater in parallel right at the engine [T's out of in and out ports, with a small ball valve on each of the other two ports on each T- for flow control (none needed) and damage control in the event of a leak in the hoses running to the water or bus heaters.] Lots of heat arrives at both.

RE: Bleeding air from the hydronic loops [something I used when I retrofitted hydronic heating to my home...]

Bleeding air from hydronic loops can be quite a chore as the top of each loop is not always conveniently accessible. [I know ours aren't...]

We installed air bleeders on our water and bus heaters. They eliminate manual bleeding- even when first commissioning a hydronic system...

We use small, float style [vs. Schrader valve; e.g., Watts brand] automatic air bleeders used in home boiler heating systems. [Cheap at ~US$10-15/each]

These require no interaction once installed, and keep the engine coolant loop air free as well...

I installed a T at the top of each hydronic core [water and bus heaters] then the the air bleeder in the highest port of the T. [i.e., Where the coolant return line to the engine exits the core.]

Best wishes with your bus heater install.

Cheers! Bill

[Bill O]

Originally Posted by wrwakefield

RE: Bleeding air from the hydronic loops [something I used when I retrofitted hydronic heating to my home...]

Bleeding air from hydronic loops can be quite a chore as the top of each loop is not always conveniently accessible. [I know ours aren't...]

We installed air bleeders on our water and bus heaters. They eliminate manual bleeding- even when first commissioning a hydronic system...

We use small, float style [vs. Schrader valve; e.g., Watts brand] automatic air bleeders used in home boiler heating systems. [Cheap at ~US$10-15/each]

These require no interaction once installed, and keep the engine coolant loop air free as well...

I installed a T at the top of each hydronic core [water and bus heaters] then the the air bleeder in the highest port of the T. [i.e., Where the coolant return line to the engine exits the core.]

Excellent recommendation on the automatic bleeders. Never seen them before and will add it into the system!

[kmacdonald]

Originally Posted by wrwakefield

RE: Bleeding air from the hydronic loops [something I used when I retrofitted hydronic heating to my home...]

Bleeding air from hydronic loops can be quite a chore as the top of each loop is not always conveniently accessible. [I know ours aren't...]

We installed air bleeders on our water and bus heaters. They eliminate manual bleeding- even when first commissioning a hydronic system...

We use small, float style [vs. Schrader valve; e.g., Watts brand] automatic air bleeders used in home boiler heating systems. [Cheap at ~US$10-15/each]

These require no interaction once installed, and keep the engine coolant loop air free as well...

Bill

MaineSail uses the hydronic vents for dripless shaft seals.

Link: https://pbase.com/mainecruising/pss_shaft_seal&page=2

[Brewgyver]

Originally Posted by kmacdonald

Dont run 4 lines like you have drawn it.

I think those "4 lines" are just roughly drawn hose runs. And it is drawn in parallel.

[Juho]

I've dreamed of installing a bus heater like system in my boat since it doesn't make much sense to flush all the heat of the diesel engine into the sea, and run a separate (air based) diesel heater at the same time. But I have thought of a serial installation. Hot water has the highest priority (always hot, no need for a bigger calorifier), and it doesn't cost anything (i.e. doesn't reduce the amount of heat flowing to the bus heater when hot water is not used) to run the hot water first through the calorifier, and only then either through the bus heater (cold season) or bypassing it (hot season). It would be enough to change the mode of the system once per season (or once per weather pattern), instead of continuously trying to find a balance between the two systems.

Warming up the bus heater first (and therefore put it also first in in the chain) could make sense when you arrive at a totally cold boat and want to quickly heat the cabin first and worry about the hot water only later. But maybe that is a special case. And your motor might provide sufficient heat already from the start to the bus heater too (the calorifier can not take it all in at once). In a parallel system you could heat those units in either order.

One more possibility would be to use a parallel setting and additional thermostats to control the flow of hot water to the bus heater and the calorifier. But that system could be already too complex. Maybe I'd satisfy with adding a bypass valve (in my original serial set-up) to the calorifier too (if anything, probably not), to support heating only the cabin and not hot water in some special situations.

You said that your motor will produce plenty of heat. In that case a parallel set-up with fifty-fifty flow to the two systems would do. But that system might still be more difficult to balance than a simple serial system (that would do the same thing).

In really cold environments you might consider also bypassing the heat exchanger (that wastes rest of the heat to sea). Probably with a thermostat to avoid overheating the engine. But maybe you will have enough heat in any case, always when the motor is running.

If you have a separate water based (diesel) heating system, that could be connected to the same loop.

[Dockhead]

Originally Posted by Juho

I've dreamed of installing a bus heater like system in my boat since it doesn't make much sense to flush all the heat of the diesel engine into the sea, and run a separate (air based) diesel heater at the same time. But I have thought of a serial installation. Hot water has the highest priority (always hot, no need for a bigger calorifier), and it doesn't cost anything (i.e. doesn't reduce the amount of heat flowing to the bus heater when hot water is not used) to run the hot water first through the calorifier, and only then either through the bus heater (cold season) or bypassing it (hot season). It would be enough to change the mode of the system once per season (or once per weather pattern), instead of continuously trying to find a balance between the two systems.

Warming up the bus heater first (and therefore put it also first in in the chain) could make sense when you arrive at a totally cold boat and want to quickly heat the cabin first and worry about the hot water only later. But maybe that is a special case. And your motor might provide sufficient heat already from the start to the bus heater too (the calorifier can not take it all in at once). In a parallel system you could heat those units in either order.

One more possibility would be to use a parallel setting and additional thermostats to control the flow of hot water to the bus heater and the calorifier. But that system could be already too complex. Maybe I'd satisfy with adding a bypass valve (in my original serial set-up) to the calorifier too (if anything, probably not), to support heating only the cabin and not hot water in some special situations.

You said that your motor will produce plenty of heat. In that case a parallel set-up with fifty-fifty flow to the two systems would do. But that system might still be more difficult to balance than a simple serial system (that would do the same thing).

In really cold environments you might consider also bypassing the heat exchanger (that wastes rest of the heat to sea). Probably with a thermostat to avoid overheating the engine. But maybe you will have enough heat in any case, always when the motor is running.

If you have a separate water based (diesel) heating system, that could be connected to the same loop.

In your climate, and with a motorsailer like a Nauticat, a bus heater is surely an absolutely natural thing to have. I remember spending midsummer at anchor at Kaunisaari in Eastern Finland, and there was snow! At 60N there are often not that many days even in the middle of the summer when you don't need heat, so it makes perfect sense.


As to series vs parallel -- I don't claim to have a profound grasp of the issues. I was talked into parallel by people with experience with house hydronic systems, which are all parallel. Series is called a "one pipe system" and it has enough drawbacks that it's not used any more, at least not in houses.



Don't think balancing will be an issue, because the precise rate of heat output into the calorifier is not really important. If I have a whole boat load of crew wanting to all shower at once I could balance down the bus heater for maximum output into the calorifier. Or I can just fire up the Eberspacher -- my calorifier has two separate coils. With both Eberspacher and heat from the engine I guess the calorifier will act like an instant heater -- will heat as fast as you can use the water -- useful if you have 5 cold, wet sailors at the end of a rough weather passage all wanting a shower. If I'm wrong and balancing is a problem then I'll just add one more valve in the calorifier side.


The thing with one-pipe is that you can't balance at all. Now that probably doesn't matter either -- because the calorifier will stop taking heat out of the circuit once it gets up to temperature. Then the bus heater will start to get the whole heat output. So I guess at the end of the day it probably doesn't make a big difference either way.

[kmacdonald]

It matters if you want or need to completely turn off the heater. You need parallel for that. It may not matter much in cold climates though. My hot water heats up in less than 15 minutes run time. It's only a 4 gallon heater though.

[Dockhead]

Originally Posted by kmacdonald

It matters if you want or need to completely turn off the heater. You need parallel for that. It may not matter much in cold climates though. My hot water heats up in less than 15 minutes run time. It's only a 4 gallon heater though.

Well you can turn off the heater with a bypass, in a one-pipe system.



But that's a bit more kludgy than just shutting it off, in a two-pipe system.

[FAST FRED]

A parallel setup will work best as some HW heaters use a thermostat in the HW heater discharge line , hopefully to prevent scalding .

Doesn't work as eventually the water in the heater box will become engine temperature,with even a tiny flow.

A series setup only would give cabin heat while the FW water is heating , then will shut down.

Don't ask how I know.

With a shut down larger engine with more mass the circ pump can keep a cabin warm for a few hours .

[a64pilot]

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.

Dock in response to your earlier question as to what to do in hot weather, the above is your answer. A circulation pump shouldn’t hurt, but shouldn’t be necessary either.

You certain you have 1/2” lines? I have never seen 1/2” 5/8” is standard, if you have 1/2” I bet it was reduced down from 5/8” for some reason.
Houses may be parallel, but I bet they feed from a header tank or accumulator whatever it’s called and not the same size hose.

[Dockhead]

Originally Posted by a64pilot

Dock in response to your earlier question as to what to do in hot weather, the above is your answer. A circulation pump shouldn’t hurt, but shouldn’t be necessary either.

Yes, and I'm thinking about leaving out the circ pump to begin with.


My main reason for having it was to deal with the air locks which have prevented circulation in the past.


But if I can get the air out with vacuum, perhaps it won't be necessary.


Also I worry that using a circ pump might somehow disrupt the flow inside the main engine. Or cool it off too much. Or something.

[a64pilot]

Pump won’t hurt, I’m sure it’s not a positive displacement pump, but a centrifugal pump like one used for air conditioning, however be sure it’s meant to circulate hot water, cause I suspect a regular pump may overheat the motor and burn out or trip a thermal breaker.
But water will flow if pump is on or not, maybe slightly restricted when off.
Pump on, engine off will most likely bleed the system, especially if it’s really 1/2” hose as the velocity will be much higher than if it were 5/8”, and maybe that’s why it’s such a small hose to deal with a hard to bleed system.
And believe it or not but you can actually flow water too quickly for it to effectively transfer heat, race car drivers years ago learned that when they removed the thermostats, the thermostat restricts flow even when it was open, the answer was to remove thermostat and install a simple washer to reduce flow, they first did that and later figured out reverse flow cooling.
The only “bad” thing that may happen is with both heaters removing heat, the engine will take longer to fully warm up, reason is the heater circuit bypasses the thermostat, that way a car will have some heat before the thermostat opens, but it will eventually fully warm up, if nothing else the water will hit a temp to where it’s no longer absorbing heat, then the heater gets it all.
This is an identical system to an automobile, it’s not a marine thing.
Sounds silly, but I leave a dock with the water heater hot, that actually warms the engine as of course heat flows both ways through the calorifier loop.

I still think with a serial connection you will get much more heat, as all water will flow though the Bus heater, with only partial water flow, you won’t get as much heat. If your concerned about heat in warm weather, do the three way valve, but realize almost no cars turn the water flow off to the heater, almost all use air flow, that’s how you get instant heat. Regulating water flow doesn’t give instant heat when you slide the heater control to hot.
The only vehicle I have seen that actually turned off the water flow was my Son’s Suzuki Samurai. Auto’s use an air door to block airflow through the heater core.

The good thing is that the heater circuit isn’t required for normal engine operation, you can close it off completely with no ill effect on engine cooling.

[Juho]

Originally Posted by Dockhead

Or I can just fire up the Eberspacher -- my calorifier has two separate coils.

If you have a hydronic heating system and two coils in the calorifier, a separate loop for the Eberspächer sounds good. (I guess there is no need to heat the bus heater with the Eberspächer.)

Would it make sense to push also the motor generated heat in the hydronic heating system (or is it already that way)?

... useful if you have 5 cold, wet sailors at the end of a rough weather passage all wanting a shower

Five 30min hot showers take a lot of heat and water. I could recommend building a sauna somewhere in the middle of the boat. That heat would move slowly to the rest of the boat too. But if you have lots of extra heat from the motor, and an efficient water maker too, then you could be ok with the five 30min hot showers without the sauna too.

The thing with one-pipe is that you can't balance at all. Now that probably doesn't matter either ... ...

Yes, at least balancing will be done in a different way. Some additional comments follow:

As you say, maybe there is no need to balance since when hot water is not used (and it is already hot), the calorifier gets 80°C coolant in, and pushes 80°C coolant out. There are not many situations where one would want the system to behave in some other way.

In some sense a serial set-up provides "automatic balancing". If hot water is already hot, the calorifier "steals" energy from the bus heater only when hot water is used. For most of the time both units will get 100% access to the available heat, not 50% and 50%.

If one wants to balance things in a serial system, the calorifier could have a bypass valve that would give all the heat directly to the bus heater. Also "serial style balancing" is thus possible.

One benefit of a serial arrangement is that one can use the leftover heat of earlier units in latter units. But if your motor produces lots of extra heat, this may not be important to you. (Same with the 50% - 50% problem above.)

One more thing that I have sometimes dreamed of is to store some of the extra heat (of the motor) in water or some other substance for later use in the boat. In this way short motoring out of a marina or anchorage early in the morning could provide heat for the rest of the day. That would however add also some weight to the boat.

[Dockhead]

Originally Posted by Juho

If you have a hydronic heating system and two coils in the calorifier, a separate loop for the Eberspächer sounds good. (I guess there is no need to heat the bus heater with the Eberspächer.)

Would it make sense to push also the motor generated heat in the hydronic heating system (or is it already that way)?

I designed a way to do that. It's straightforward -- just need a couple of plate-type heat exchangers.

But when I started to make up a bill of materials and plan exactly where I would put those heat exchangers I realized that it was a lot of trouble and complexity for relatively little gain and decided it wasn't worth it just to save a fairly small amount of running the Eberspacher.

The bus heater will heat up the main salon by itself. The only benefit from heating up the hydronic system would be to heat up sleeping cabins fore and aft. It's rare this would be needed -- only if all of the following are true at the same time (a) overnight passage (so that people are using the sleeping cabins); (b) motoring not sailing; (c) really cold weather (just "pretty cold" weather and warm blankets are enough). I decided for those rare occasions I'll just run the Eberspacher. And the Eberspacher works while sailing, and most passages long enough to involve an overnight I do under sail anyway.


But in an ideal world where complexity didn't matter, or perhaps for a new-build boat, I would use waste heat from both main engine and generator as heat sources alongside an Eberspacher furnace, in a single hydronic circuit which does everything -- hot water and space heating everywhere.



And if you could store the heat, it would be even better. There is someone on CF who did come up with some kind of storage. I have an 8 tonne lead keel I thought about using for this, but lead has very low specific heat.

Originally Posted by Juho

. . . Five 30min hot showers take a lot of heat and water. I could recommend building a sauna somewhere in the middle of the boat. That heat would move slowly to the rest of the boat too. But if you have lots of extra heat from the motor, and an efficient water maker too, then you could be ok with the five 30min hot showers without the sauna too.

I have a friend who used to have a 90' Swan I spent a lot of time on. It had a sauna. I used to laugh at that as a great extravagance. No more! I would LOVE to have a sauna on board, and it would not be hard to create if you have a large shower space.


Of course if you're cruising the Swedish or Finnish archipelagos, you will find saunas in most harbors. And I do! Just that the Swedish idea of a sauna is not quite up to Finnish standards . . .