Hydronic Heater/Engine Loop

[gpeacock]

Hi all
I am in the midst of planning an Espar D5 heater install for hot water and heat using a few bus heaters.
I am having trouble conceptualizing how to use my existing hot water tank (with only one heat exchanger) to get hot water from both the engine and Espar.
The current coolant run from the engine to the hotwater tank is long... too long. I would like to add an external engine heat exhanger and change the hot water tank heat exchanger to run off the Espar.
Getting hot water and heat from the Espar is easy but how do I automatically make the Espar loop flow through the external engine heat exchanger when only the engine is running?
The logic I want is this: Is engine on. If yes is Espar circuit coolant temp low. If yes turn on external Espar circuit pump. When coolant temp is high, shut down pump. I want this to happen even if the Espar is turned off. If this is too complicated then I'd settle for just running the circulating pump whenever the engine is on.
Thanks
Gary

[Jd1]

Run the engine through a heat exchanger that has the other side in the Espar loop. The hot water tank heat exchanger is fed off the Espar loop. You will want some valving to switch to summer operation where the Espar loop only runs through the hot water tank and not through all the heater cores.
The only down side - you need to run the Espar external coolant pump if you want hot water but you can't (shouldn't) run the Espar pump automatically when the engine runs since you want the engine at operating temp before turning the pump on. A thermal switch of some kind that operates the Espar pump whenever the engine is at operating temp in parallel with the Espar control of the pump (so the Espar can turn on the pump when it is running) would be ideal. do the job

[gpeacock]

Originally Posted by Jd1

but you can't (shouldn't) run the Espar pump automatically when the engine runs since you want the engine at operating temp before turning the pump on. A thermal switch of some kind that operates the Espar pump whenever the engine is at operating temp in parallel with the Espar control of the pump (so the Espar can turn on the pump when it is running) would be ideal. do the job

Currently the engine cooling loop runs a long way through to the hot water tank. If in the new design the external coolant pump runs when the engine isn't up to temp am I not doing the same thing I was doing before?
Regardless I understand that aquastats and relays can do the job, what Im struggling with is exactly what I need and how to combine them with the already engineered out of the box espar system.
Questions like:
Will coolant flow through the espar when it's not on. (The newer models seems to have some sort of electronic valves built in to control flow).
How do you wire the pump relay so it can be controlled by the engine circuit aquastat and the espar unit.
Do they make aquastats that have a high and low settings (on at desired low temp and off at desired high temp) or do I need to wire two up in series.
If someone has done this and documented their set up, I'd love a link. Google doesnt seem to be my friend in this case.
Thanks
Gary

[UNCIVILIZED]

This is a SWAG on my part (Scientific Wild Ass [educated] Guess). But you're better off keeping the engine cooling system as a completely seperate system.
- It runs on a mixture of coolant & water, which neither the Espar, nor hot water heater do.
- Every extra foot of plumbing, & turn/corner you add to an engine's cooling system boosts the probability of the engine overheating.
- Finding any leaks in an engine's cooling system that is run though an enclosed heat exchanger inside of another system would be a nightmare. Read expensive.
- Plumbing the engine's cooling system as you're describing could get pretty pricey.

Now, educated guesses & common sense aside. Could you kindly post some schematics of how you're thinking of plumbing things. It'll let us see much more easily, what you're trying to do, where any problems may lay, & whether or not the idea as a whole is good, bad, or other.

Also, maybe it's just me. But a bit of spacing & punctuation in between your info dumps, & rapid fire questions, would make things a lot easier to read. And thus form coherent answers there to.

[Jd1]

Originally Posted by gpeacock

Currently the engine cooling loop runs a long way through to the hot water tank. If in the new design the external coolant pump runs when the engine isn't up to temp am I not doing the same thing I was doing before?
Regardless I understand that aquastats and relays can do the job, what Im struggling with is exactly what I need and how to combine them with the already engineered out of the box espar system.
Questions like:
Will coolant flow through the espar when it's not on. (The newer models seems to have some sort of electronic valves built in to control flow).
How do you wire the pump relay so it can be controlled by the engine circuit aquastat and the espar unit.
Do they make aquastats that have a high and low settings (on at desired low temp and off at desired high temp) or do I need to wire two up in series.
If someone has done this and documented their set up, I'd love a link. Google doesnt seem to be my friend in this case.
Thanks
Gary

First, the very end of my post 'do the job' was not supposed to be there, please disregard.
Coolant may or may not flow through the Espar, it seems to do so in my install.
If you use the factory install kit, the Espar will turn on the pump when it starts up. There might be a seperate control in your install kit to switch between engine heat or Espar heat. When this is switched to engine heat it will run the pump without the Espar being on. You could wire a relay that parallels the switch and which is controlled by the ignition circuit and a temperature switch.
I can't say much about the 'aquastat' ... I would use an off the shelf temperature sensor that closes at a certain temperature and mount that someplace on the thermostat housing or in that area.

[Jd1]

Originally Posted by UNCIVILIZED

This is a SWAG on my part (Scientific Wild Ass [educated] Guess). But you're better off keeping the engine cooling system as a completely seperate system.
- It runs on a mixture of coolant & water, which neither the Espar, nor hot water heater do.
- Every extra foot of plumbing, & turn/corner you add to an engine's cooling system boosts the probability of the engine overheating.
- Finding any leaks in an engine's cooling system that is run though an enclosed heat exchanger inside of another system would be a nightmare. Read expensive.
- Plumbing the engine's cooling system as you're describing could get pretty pricey.

Now, educated guesses & common sense aside. Could you kindly post some schematics of how you're thinking of plumbing things. It'll let us see much more easily, what you're trying to do, where any problems may lay, & whether or not the idea as a whole is good, bad, or other.

Also, maybe it's just me. But a bit of spacing & punctuation in between your info dumps, & rapid fire questions, would make things a lot easier to read. And thus form coherent answers there to.

Not complex at all - engine coolant runs through a heat exchanger who's other side is in the Espar loop. The total engine coolant circuit length is considerably reduced and easier to trouble shoot. Engine heats up quicker because it doesn't have to heat the water in the hot water tank - better for the engine.

The engine coolant is antifreeze which also protects metal bits, the same coolant mix (but completely separate) is run in the Espar loop through the hot water heater and all the heater cores.

As already stated, trouble shooting is easier but yes, you add a few dollars but not near as many as the Espar system and it's install. Since you are installing extra bits in the boat, by definition things will get a bit more complex. I would suggest that the Espar system is a heck of a lot more complicated than the slightly modified engine coolant loop (but still not rocket science)

[Jd1]

Originally Posted by gpeacock

Currently the engine cooling loop runs a long way through to the hot water tank. If in the new design the external coolant pump runs when the engine isn't up to temp am I not doing the same thing I was doing before?

Yes you would .... but why would you want to when you know how to do it 'properly'.

[gpeacock]

Sorry if my posts are confusing... Hopefully the attached diagram is a start to show the layout of what I want to do. Now I just need to source the aquastats (thermostat controls based on water temp) and sort out anything else I need.

- JB1, you mention coolant flows for you if the pump is running but the system is off. Thats good. Question 1 answered.

You also mentioned there is a "Engine heating on" setting on the control unit. Any idea which control unit I should look at that has this feature? I can't seem to find quality documentation as everything is locked behind a dealer login on Eberspacher's site. Just sorting out the difference between D5m, c lmc, e has been hard enough.
Thanks for the replies so far!
Gary

[sailorchic34]

If it was me I would put the water heater loop on the Esper put a small brazed plate heat exchanger (https://www.amazon.com in the Espar loop and run the engine loop to the heat exchanger.

Then add a separate pump that runs on a dtdp relay that is energized on engine key. the Esper is attached to the other side of the relay to disable it when the engine is running.

Then when the Esper runs it heats the water heater too (good at anchorages) and when the engine runs the Esper is bypassed with check valve. No fancy logic controls or temperature sensors. Only issue is selecting a LOW head pump as the Esper system does not have much in the way of pressure rating. (very low at least to my eyes)

[gpeacock]

Originally Posted by sailorchic34

If it was me I would put the water heater loop on the Esper put a small brazed plate heat exchanger (https://www.amazon.com in the Espar loop and run the engine loop to the heat exchanger.

Then add a separate pump that runs on a dtdp relay that is energized on engine key. the Esper is attached to the other side of the relay to disable it when the engine is running.

Then when the Esper runs it heats the water heater too (good at anchorages) and when the engine runs the Esper is bypassed with check valve. No fancy logic controls or temperature sensors. Only issue is selecting a LOW head pump as the Esper system does not have much in the way of pressure rating. (very low at least to my eyes)

Thanks for the link to the heat exchanger...thats cheap!

I will do a second pump if I have to but there are already too many pumps on board so I'd love to keep it to one. On my diagram, where would you put the check valve you mentioned to bypass the espar? Are you talking about running the second pump in the other direction?
Thanks
Gary

[Jd1]

Originally Posted by gpeacock

Sorry if my posts are confusing... Hopefully the attached diagram is a start to show the layout of what I want to do. Now I just need to source the aquastats (thermostat controls based on water temp) and sort out anything else I need.

- JB1, you mention coolant flows for you if the pump is running but the system is off. Thats good. Question 1 answered.

You also mentioned there is a "Engine heating on" setting on the control unit. Any idea which control unit I should look at that has this feature? I can't seem to find quality documentation as everything is locked behind a dealer login on Eberspacher's site. Just sorting out the difference between D5m, c lmc, e has been hard enough.
Thanks for the replies so far!
Gary

Yes, your diagram is exactly right.
As mentioned, I would not use an 'aquastat' ... sounds too expensive when a simple temperature switch for about a dollar from Ebay will do the trick.
I can;t help on the 'control unit' part as this came with the boat. I 'assumed' it was part of the heater package.

I have been running without the thermal switch myself (turning on the pump when the engine is at operating temperature) but this exchange may be enough to just install the damn thermal switch and get it done and over with <sigh> .... procrastination ....

[Jd1]

Originally Posted by sailorchic34

If it was me I would put the water heater loop on the Esper put a small brazed plate heat exchanger (https://www.amazon.com in the Espar loop and run the engine loop to the heat exchanger.

Then add a separate pump that runs on a dtdp relay that is energized on engine key. the Esper is attached to the other side of the relay to disable it when the engine is running.

Then when the Esper runs it heats the water heater too (good at anchorages) and when the engine runs the Esper is bypassed with check valve. No fancy logic controls or temperature sensors. Only issue is selecting a LOW head pump as the Esper system does not have much in the way of pressure rating. (very low at least to my eyes)

A second pump is extra complication that is not needed. You could use relay logic to prevent the Espar from running when the engine runs, that would make sense (although usually not an issue with me). It is much more important to start the pump automatically because if you are like me and forget, you get to the anchorage and have no hot water

[sailorchic34]

Originally Posted by gpeacock

Thanks for the link to the heat exchanger...thats cheap!

I will do a second pump if I have to but there are already too many pumps on board so I'd love to keep it to one. On my diagram, where would you put the check valve you mentioned to bypass the espar? Are you talking about running the second pump in the other direction?
Thanks
Gary

The check valve is installed after the Esper and the second pump and bypass connects before the Esper unit and espar pump. The bypass also has a check valve. Both pump the same direction otherwise there would be issues.

[Jd1]

Gary, a couple of things that you may want to consider .... in my setup there is a flow splitter before the hot water tank. Some of the Espar loop byasses the hot water heat exchanger. I do not know the implication if that is not present as per your diagram. It could reduce the flow because of the restriction in the hot water tank heat exchanger and at minimum it would prevent boat heat until the hot water is up to temperature.
You may also want to have diverters in front of every heater core so as to be able to bypass that particular core if you want no heat from it (and consequently have more heat available for the other heaters.
Better yet, you may want to arrange the heater cores in parallel with just a shutoff valve for each heater. If you have the heaters in series as per your diagram you will get lots of heat from the first heater but none from the last.