I'm also thinking I will need expansion tanks in the ST90 portion of the primary circuit and in the secondary coil circuit to enable this to function safely. Is this also correct?
Hydronic vs. Non-Hydronic Heating. (Air & Water)
- Thread starter waveslider
- Start date
Joe917
Explorer
Your plan looks good, I wish we had an underfloor heating circuit.
The Webasto st90 is probably too large. We have a larger living space (approx 26 cu m, foam sandwich construction, 60mm walls, 80mm ceiling, 100mm floor). We have a Thermo Top C, it puts out plenty of heat (even at -20C) and does not short cycle.
How will you control temperature when parked?
Webasto sells a multitude of timers and thermostats, but they are not all compatible. Timers are of no use for a living space you need a thermostat. I spent a lot of time (and wasted money on a Webaso tstat that was not compatible) before i found the Heatmiser thermostat. It does a perfect job controlling the Thermo Top C.
A small radiator in the storage accessible through an exterior hatch is a good idea.
Spa Isotemo hot water heater 20 l (never run out of hot water for 2). This is the second unit in the truck, the first lasted 23 years. 750watt element so that the solar can be used(the 1500 watt element is too big a draw).
A radiator in the bathroom makes life really nice!
We have a large radiator by the door, a medium unit in the bathroom and a small unit in the storage area. The truck holds a very even heat.
The heat from the aircon is a bonus if it comes with the unit, but I really don't see any need for it.
The Webasto st90 is probably too large. We have a larger living space (approx 26 cu m, foam sandwich construction, 60mm walls, 80mm ceiling, 100mm floor). We have a Thermo Top C, it puts out plenty of heat (even at -20C) and does not short cycle.
How will you control temperature when parked?
Webasto sells a multitude of timers and thermostats, but they are not all compatible. Timers are of no use for a living space you need a thermostat. I spent a lot of time (and wasted money on a Webaso tstat that was not compatible) before i found the Heatmiser thermostat. It does a perfect job controlling the Thermo Top C.
A small radiator in the storage accessible through an exterior hatch is a good idea.
Spa Isotemo hot water heater 20 l (never run out of hot water for 2). This is the second unit in the truck, the first lasted 23 years. 750watt element so that the solar can be used(the 1500 watt element is too big a draw).
A radiator in the bathroom makes life really nice!
We have a large radiator by the door, a medium unit in the bathroom and a small unit in the storage area. The truck holds a very even heat.
The heat from the aircon is a bonus if it comes with the unit, but I really don't see any need for it.
luthj
Engineer In Residence
There are many different variations on the hydronic and air heating system. Engine integration or not, water heating, etc. It is critical that a detailed usage case be made up. Hopefully you have a good idea what your needs are. This is one of those situations where a system must truly be engineered (if not going with an off-the-shelf unit).
Some thoughts.
Being able to pre-heat the engine, or supplement engine heat is really helpful in cold climates. With my Espar D5 I can rapidly preheat the engine, which allows nearly instant heat on start up. This adds some complexity though, as without some isolation loops, or a bypass valve, the hydronic heater will always be heating the engine block. The added plumbing adds coolant leak risks unless you isolate the loops with a heat exchanger. This causes its own problems, as you will need pumps on both loops for preheat. I have a 2in/2out bypass valve. This lets me isolate flow in the engine and hydronic heater loops (my build thread has details).
There are lots of minor design details that need to be addressed for a reliable hydronic system. Bleeding air, flow control etc. A standalone air heater like Espar D2 is much simpler to install and service.
Hydronic heaters have longer warm up times. This is due to the greater mass of the liquid in the loop.
Water can be heated on demand via a plate heat exchanger, or stored in a calorifier (isotemp etc). Or both (heat exchanger in series with calorifier). With a connection to the engine system, you can heat the calorifier when driving, or provide hot water on demand (engine running). I have an isotemp 4 gal unit, and heated to 180F, it will maintain shower temp water for 24 hours minimum, longer with extra insulation in mild temps.
All-in-one units (Dual-top etc). These units have a air heat exchanger combined with a boiler which share the same burner assembly. When heating air they will be slower to heat up water as they split the BTUs. These are fairly complicated units, and servicing can be a bit of a chore depending on how they are mounted. They are compact and much easier to install compared to separate air and water heaters, or a hydronic only system.
Power consumption/Noise
A D5 will use about double the power of a espar D2. The water pump is the main difference. The D5 has two outputs (low/high) with the lower output still being 2.4kw. For most small/medium sized rigs 2.4kw is a lot more heat than you need continuously, so the unit will be cycling on and off. Starting with a cold water tank it takes about 12 minutes for my D5 to heat 4 gallons of water to shower temp using the isotemp built-in coolant exchanger. When heating the interior of a vehicle, the D2 (and D4) heaters continuously vary the output to avoid cycling. The lowest output on the D2 is 800W, which is pretty reasonably for a medium sized vehicle in mild temps. On this setting the fan is fairly quiet as well, and power consumption is around 1.5A at 12v. The D5 is much louder, even at low power.
These diesel heaters do not like cycling on/off often. And running on high for 10-20 minutes now and them helps keep them clean. The Espar heater should have the (overpriced) high altitude sensor added if operating above ~6,000ft for extended periods.
The hydronic heaters are a bit more involved to clean/service. The D2 for example is readily serviced in place with good access from above. The glow pin screen will needed changed on occasion, and that is quite simple.
Expansion tanks would be required is the hydronic loop is not connected to the engine system. If you are connection in series with existing engine coolant circuits, you need to size your hoses to prevent reduced flow.
For large rigs, hydronic is generally the easiest way to get heat to different (and far apart) areas. Lines can be run to storage areas, or tanks to prevent freeze up as well. Floor heating is also an option if the weight isn't an issue.
Some thoughts.
Being able to pre-heat the engine, or supplement engine heat is really helpful in cold climates. With my Espar D5 I can rapidly preheat the engine, which allows nearly instant heat on start up. This adds some complexity though, as without some isolation loops, or a bypass valve, the hydronic heater will always be heating the engine block. The added plumbing adds coolant leak risks unless you isolate the loops with a heat exchanger. This causes its own problems, as you will need pumps on both loops for preheat. I have a 2in/2out bypass valve. This lets me isolate flow in the engine and hydronic heater loops (my build thread has details).
There are lots of minor design details that need to be addressed for a reliable hydronic system. Bleeding air, flow control etc. A standalone air heater like Espar D2 is much simpler to install and service.
Hydronic heaters have longer warm up times. This is due to the greater mass of the liquid in the loop.
Water can be heated on demand via a plate heat exchanger, or stored in a calorifier (isotemp etc). Or both (heat exchanger in series with calorifier). With a connection to the engine system, you can heat the calorifier when driving, or provide hot water on demand (engine running). I have an isotemp 4 gal unit, and heated to 180F, it will maintain shower temp water for 24 hours minimum, longer with extra insulation in mild temps.
All-in-one units (Dual-top etc). These units have a air heat exchanger combined with a boiler which share the same burner assembly. When heating air they will be slower to heat up water as they split the BTUs. These are fairly complicated units, and servicing can be a bit of a chore depending on how they are mounted. They are compact and much easier to install compared to separate air and water heaters, or a hydronic only system.
Power consumption/Noise
A D5 will use about double the power of a espar D2. The water pump is the main difference. The D5 has two outputs (low/high) with the lower output still being 2.4kw. For most small/medium sized rigs 2.4kw is a lot more heat than you need continuously, so the unit will be cycling on and off. Starting with a cold water tank it takes about 12 minutes for my D5 to heat 4 gallons of water to shower temp using the isotemp built-in coolant exchanger. When heating the interior of a vehicle, the D2 (and D4) heaters continuously vary the output to avoid cycling. The lowest output on the D2 is 800W, which is pretty reasonably for a medium sized vehicle in mild temps. On this setting the fan is fairly quiet as well, and power consumption is around 1.5A at 12v. The D5 is much louder, even at low power.
These diesel heaters do not like cycling on/off often. And running on high for 10-20 minutes now and them helps keep them clean. The Espar heater should have the (overpriced) high altitude sensor added if operating above ~6,000ft for extended periods.
The hydronic heaters are a bit more involved to clean/service. The D2 for example is readily serviced in place with good access from above. The glow pin screen will needed changed on occasion, and that is quite simple.
Expansion tanks would be required is the hydronic loop is not connected to the engine system. If you are connection in series with existing engine coolant circuits, you need to size your hoses to prevent reduced flow.
For large rigs, hydronic is generally the easiest way to get heat to different (and far apart) areas. Lines can be run to storage areas, or tanks to prevent freeze up as well. Floor heating is also an option if the weight isn't an issue.
waveslider
Outdoorsman
Thanks luthj. Great summary and appreciate that detail.
Even though the Espar Hydronic was about the only thing that truly lived up to our expectations in our SMB, our other challenges taught us to value accessibility, ease of service, and fewer complications. So we chose to go with an all-in-one dual-top unit.
Even though the Espar Hydronic was about the only thing that truly lived up to our expectations in our SMB, our other challenges taught us to value accessibility, ease of service, and fewer complications. So we chose to go with an all-in-one dual-top unit.
Dannyboyski
New member
Joe,
In your arrangement, what would happen if the vehicle engine was on, diesel heater off and the valve was closed?
Would this by chance shut off heat to your vehicles heater matrix?
Just trying to determine if others have configured there system like I am planning!
Many thanks
Dan
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Dannyboyski
New member
This is a plumbing schematic showing the flow with the engine. I think this is pretty much what you have.
Im going to follow a smilier setup I think, except I will also have an underfloor loop.
EDIT - I believe, there is a mistake in this attached circuit. The vehicle matrix appears to flow the wrong way. I was just using it for inspiration for using a single valve to halt flow through the engine.
Im going to follow a smilier setup I think, except I will also have an underfloor loop.
EDIT - I believe, there is a mistake in this attached circuit. The vehicle matrix appears to flow the wrong way. I was just using it for inspiration for using a single valve to halt flow through the engine.
Attachments
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Neil
Observer
I have an Eberspacher m10. It heats hot water , warms the cabin and pre heats the engine brilliantly. It has altitude adjustment built in
However, we are currently in chile and have spent quite some time at over 4000 meters and minus 20 at night.
My truck doesnt have glow plugs.
At this altitude and probably crap diesel it will not run. It fires up then shuts down then tries again.
At 3500m its perfect.
I dont know what the solution is but i think most combustion type heaters , gas or diesel, will struggle in these conditions.
Its been a problem but luckily the truck has started even at that height at minus 20.
Apart from this its been good.
However, we are currently in chile and have spent quite some time at over 4000 meters and minus 20 at night.
My truck doesnt have glow plugs.
At this altitude and probably crap diesel it will not run. It fires up then shuts down then tries again.
At 3500m its perfect.
I dont know what the solution is but i think most combustion type heaters , gas or diesel, will struggle in these conditions.
Its been a problem but luckily the truck has started even at that height at minus 20.
Apart from this its been good.
Joe917
Explorer
Yes that set up would cut all heat to the camper, why would you not want to heat the water though?
Joe917
Explorer
Our set up is similar but the valve placement is different, it should be on either of the two lowest lines in the schematic. The way that is drawn, closing the valve would shut off the flow to the fan matrix demist. Where is the engine radiator in the diagram?
Here's my schematic - sorry for basic graphics, I did it in power point. The thick three way arrows are one in/two out valves - ignore the arrow direction of the T itself but the connecting red/blue/purple arrows show hot/cold/both flow directions. Whilst this uses 4 valves I will use a multistack unit with a single actuator. This will probably be actuated by a relay linked to engine start up so that the engine is connected into the calorifier circuit any time it is running and disconnected when not with a manual override for engine pre-heat. This means when parked we are not unnecessarily wasting energy heating the engine up. If the valve system works the engine side return loop is redundant but I think it is an important safety feature to ensure that there are no circumstances that the engine can run "dry".
Joe917
Explorer
Two observations.
Don't use electric valves, they will fail at the wrong time, (they will fail, not might fail). An easily accessed manual valve is far better. Failure of one valve in your diagram could shut off the engine cooling loop.
You don't need 4 valves, just 1. Change your valves in the diagram to "T"s and add a single manual valve between the two loops. The single valve stops coolant circulating in one loop from circulating the other loop while allowing fluid to expand into the header tank. It does not matter which side you put the valve. you could put two valves (one between each T) for maintenance, but you only need to close one for operation.
That is our set up, the shut off valve is placed behind the driver's side front wheel.
Don't use electric valves, they will fail at the wrong time, (they will fail, not might fail). An easily accessed manual valve is far better. Failure of one valve in your diagram could shut off the engine cooling loop.
You don't need 4 valves, just 1. Change your valves in the diagram to "T"s and add a single manual valve between the two loops. The single valve stops coolant circulating in one loop from circulating the other loop while allowing fluid to expand into the header tank. It does not matter which side you put the valve. you could put two valves (one between each T) for maintenance, but you only need to close one for operation.
That is our set up, the shut off valve is placed behind the driver's side front wheel.
Dannyboyski
New member
Ok this is the circuit I have planned for my hydronic install. I would be grateful if those in the know could critique it.
Having spent weeks researching hydronic systems, I think this is my final plan.
Note my idea is made more complicated by my desire to utilise the vehicle heater matrix as a heater for the camper circuit. If you chose not to do this, you could move the motorised ball valve lower in the system and then the vehicle blowers belong to the vehicle. This isn't a concern for me as I plan to have the engine disconnect valve open while driving and closed while in camper circuit mode. I may even link it to an ignition feed or just manual 2 way switch on the dash.
Highlights:
Free heat from the engine (both water and heat in the back)
The option to remove the engine when parked so you don’t have to heat that up just to get some hot water.
Quiet radiant loop for milder conditions.
In cold weather, Utilise secondary high power rear blowers 4kw ish
Free use of the vehicle OEM matrix and blowers I read somewhere they are circa 4KW, but that is with the fans on full whack, and I know the speed setting is the lowest setting… so maybe 1Kw? Who cares, its free!
Single header tank - no additional weight.
Engine pre-heat at the flick of a switch (assuming the camper circuit is on)
Only single coil cal required, smaller & lighter in size & ££ Much easier for me to undermount due to size!
Many thanks all.
Having spent weeks researching hydronic systems, I think this is my final plan.
Note my idea is made more complicated by my desire to utilise the vehicle heater matrix as a heater for the camper circuit. If you chose not to do this, you could move the motorised ball valve lower in the system and then the vehicle blowers belong to the vehicle. This isn't a concern for me as I plan to have the engine disconnect valve open while driving and closed while in camper circuit mode. I may even link it to an ignition feed or just manual 2 way switch on the dash.
Highlights:
Free heat from the engine (both water and heat in the back)
The option to remove the engine when parked so you don’t have to heat that up just to get some hot water.
Quiet radiant loop for milder conditions.
In cold weather, Utilise secondary high power rear blowers 4kw ish
Free use of the vehicle OEM matrix and blowers I read somewhere they are circa 4KW, but that is with the fans on full whack, and I know the speed setting is the lowest setting… so maybe 1Kw? Who cares, its free!
Single header tank - no additional weight.
Engine pre-heat at the flick of a switch (assuming the camper circuit is on)
Only single coil cal required, smaller & lighter in size & ££ Much easier for me to undermount due to size!
Many thanks all.
Attachments
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Dannyboyski
New member
The idea behind the whole engine disconnect is In the summer time, when you want to run the D5 to make hot water, you don't also have to heat the engine mass as well!
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