Hydronic heat

[somewhereinusa]

Originally Posted by DrDanger

Now that fall has turned into winter in the inland PNW...





I have already purchased the Webasto and laid the PEX for the floor, battery box, and water tanks. Here is what I still need to figure out:
- Distribution: the outlet of the Webasto is designed for coolant hose, what is the best way to get from that to the PEX? I've seen people build copper manifolds but I've never dealt with copper so I'd like to avoid it if I can
- Thermostatic Valves: I've never dealt with thermostats or thermostatic valves before, any recommendations on sources? Is it sufficient to rely on the Webasto pump and just use valves or is it better to use pumps like Somewhereintheusa did?
- Coolant reservoir: This needs to be the highest part of the system, correct?
- Engine pre-heat: As far as I can tell right now, the easiest way to plumb this into the engine coolant system is through the driver heat/defrost loop that goes into the cab. The only problem I see is that I would need to put a circulation pump in the loop and I don't know if this would interfere with the normal engine heat operation (i.e. will the pump prevent coolant from circulating to the cab if the pump is off?)


I've probably got a lot more to figure out, but those are the big questions I have right now.

Just some thoughts.
Looking at your diagram, I think but don't know for sure, that using valves as you have drawn warm water is going to go take the path of least resistance. Meaning what ever loop has the least resistance is going to get the heat.
I had an occasion where my thermostatically controlled pumps lost power. I still had heat everywhere but, it tool a looooooong time and wasn't as warm. I had no way of checking to see if heat was even in each loop.

I changed all connections to pex by using JB weld to glue a brass pex fitting to anyplace that had a hose and clamp connection. It's been working for 7 years now with no problems.

The main loop is 3/4" PEX the heat/floor loops are 1/2"

I bought my manifolds on ebay

My system is basically built the same as an automotive cooling system. Reservoir does need to be the highest point. I had to get a little creative to achieve that.

The engines water pump circulates the water in the heater hose connections a pump in that loop shouldn't matter. If you use a plate type heat exchanger between engine and boiler the water will circulate by osmosis to keep engine warm. Also that method will take heat from the engine for when you are driving.

NOTE: I have three separate water systems. Engine, ethylene glycol (poison) heat, I believe propylene glycol (not poison) and fresh water. All are separated by by heat exchangers. Be sure to get the proper boiler antifreeze it is different if you have any aluminum in the system.

[DrDanger]

Originally Posted by joeblack5

Dory has a factory electric coolant pump that helps to bring the engine heat to the front window defroster and also the roof top hvac system..so that part is already taken care off.

I also have a factory electric coolant pump (but it is not currently connected, it seemed like most of the buses I looked at when I was shopping had them disconnected, I think a mechanic told me they went bad a lot but mine still seems to turn on). Are you saying that your coolant is somehow connected to your roof top HVAC? I don't have factory AC so I'm not sure how those work.

Originally Posted by joeblack5

Personally I would heat the tanks and batteries with electric heating pads and heat tape for the lines.

I would like to be able to be unplugged as much as possible so it seemed reasonable to me to use the heat I was going to generate already (and maybe use a bit more diesel) rather than increase the capacity of my battery bank to use electric heat.

Originally Posted by joeblack5

We added, are adding, our shower water heating to the loop.

I decided not to use this for my domestic water so I wouldn't have to run it in the summer.

[joeblack5]

I understand your dilemma with the freezing of your tanks and maybe if you spend most of your time in freezing conditions....
You will need to insulate your tanks pretty good otherwise your supplied heat will be wasted to the outside.. you might think about a hot fox tank heater as used in wvo fuel systems. Not sure if you are able to get by in that climate on solar or have a generator running.

Our bus Dory has the heating and cooling on the roof. So for heating hot coolant has to be piped up there. They used a pump and electric valve to turn the coolant flow on or off in case the ac was on.

These are industrial pumps. Not cheap stuff. I had a shaft seal leak.. but all is rebuild able.

For the shower we used a electric heater in the shower head...and with a recirculating shower the water stays warmer so less power is needed.
I like to have multiple system in place ..calling for the right system in the right situation...
Lots of sun...go electric... Want to shower after a long drive ...use the remaining heat in the engine... Cold and cloudy then go webasto.

It is just fun to design..engineer and build. For us the nice challenge is that it has to be very compact since there is limited space under the floor.. as such I had no space for multiple pumps..and so heating loops had to be designed so that the flow matches the webasto pump..

Good luck
Johan

[cadillackid]

the built in heater pump in most busses develop leaks.. ive replaced the pumps on both my busses because they started leaking around the seal.. really common issue.. those pumps do move wuite a bit of water.. but as others mentioned the water takes the path of least resistance.. if you have ebnough pump flow where you can have smaller lines off of the main 1 inch trunks you can run a true parallel flow system.. your floor loops might benefit from a manual valve to limit flow at the inlet.. you dont need a huge amount of flow on a floor loop as the amount of total heat draw in the loop is low compared to that of a fan coil.

[joeblack5]

Chris has it right. He advised me to add the radiator under the seat and I am happy I did.. floor heat is nice, quiet, efficient but not very powerful.

[DrDanger]

I saw some kits from Espar/Webasto have a header tank but they are pretty expensive ($100+ for a 5L plastic tank?!). Is there any reason that I couldn't just us an automotive coolant recovery tank like this one?


Also, still thinking through my distribution system...

The classy method:
$123 Manifold
$34 actuator (1 per zone)
$20 thermostat (1 per zone)

The mad scientist method:
$67 zone valve (1 per zone)
...and some kind of Arduino/Raspberry Pi to control it??? (I have never used these before but I want to learn)

The cheap-o method:
$5 gate valves adjust to modulate the heat between the zones (i.e. the main floor heat would be wide open, the valve to the water tanks would be open just a little since it only has to keep it from freezing)


Thoughts?

[DrDanger]

The Webasto Thermo Top C kit I bought came with their programmable timer which seems to be suited to the engine pre-heat function. I am not sure if this will allow me to control the Webasto with a thermostat to turn it on and off. Does anyone know if there is a way to have a thermostat turn the unit on and off, or is it better to just install an on/off switch for the Webasto and have a zone valve to control the heat?

[john61ct]

Webasto sells a variety of control modules, including one with a SIM card for remote operation

[DrDanger]

Originally Posted by john61ct

Webasto sells a variety of control modules, including one with a SIM card for remote operation

I saw that one, but unless I was looking at something different than you it only works in Europe

[DrDanger]

I've done some revision based on more research. No major overhaul, just tweaking details to conform to reality


I decided that the simplest/cheapest thing to do would be to simply use a thermostatic switch in the cabin to control the on/off of the boiler since that is where I'll want heat first (i.e. I'll want cabin heat if it is 45F outside, but I won't need to heat my water tanks yet).

I moved the loop for the battery box to just be a part of the main floor heat loop since the batteries should perform best around room temperature. I also decided to go with a manual valve for the engine pre-heat loop. I may just leave the valve open since it shouldn't suck up too much heat if the pre-heat circulation pump isn't actually on. That leaves the question of how to control the water tank loop. In an effort to reduce the electrical power draw of using conventional 24V AC zone actuators or solenoid valves I would like to use something that uses 12V DC. I toyed with the idea of attaching a servo to a manual valve, but I am told that would be challenging given the torque required to move valves. If there is some kind of 12V controlled valve out there someone please let me know!

Anyway, that brought me back to the method that somewhereintheusa used: pumps. I managed to find an inexpensive 12V pump that can handle hot water, the only thing is I don't know how it will hold up to the antifreeze agents. Has anybody had experience using this type of pump before?

[somewhereinusa]

If there is some kind of 12V controlled valve out there someone please let me know!

https://www.ebay.com/sch/i.html?_fro...e+12v&_sacat=0

[DrDanger]

Originally Posted by somewhereinusa

https://www.ebay.com/sch/i.html?_fro...e+12v&_sacat=0

Those are perfect, thank you!

[cadillackid]

My engine takes up a lot of heat , much more than I thought it would, wile the thermostat stays closed and quite a bit of circulation occurs even if I just open the valves but don’t turn on my pump .. now I’m directly heating my main coolant loops and not heat exchanger isolated , I get yours and another mixed up if you isolated your engine and cabin coolant or is part of same system).

My cabin is paralllel with my engine so the webasto isn’t looping through engine .. the whole engine gets warm and radiates a lot of heat away ..

[DrDanger]

I think I've got all my components assembled (or at least ordered). My question now is about fuel line access. The Webasto installation instructions indicate that I should install the fuel pick-up line on an auxiliary port on the fuel tank, but I have no idea if I have one or not. Do most people drill their own port or do most buses have an auxiliary?

[john61ct]

If you don't have one then you need one put in.

Ideally do that it can't drain the tank completely and leave you stranded

[rossvtaylor]

Originally Posted by DrDanger

I think I've got all my components assembled (or at least ordered). My question now is about fuel line access. The Webasto installation instructions indicate that I should install the fuel pick-up line on an auxiliary port on the fuel tank, but I have no idea if I have one or not. Do most people drill their own port or do most buses have an auxiliary?

Credit to Bus'n It for finding this. It would allow you to add a pick-up line without drilling.

[DrDanger]

Originally Posted by rossvtaylor

Credit to Bus'n It for finding this. It would allow you to add a pick-up line without drilling.
Attachment 52954

That is what I want to try to do, but I haven't found one of those ports on my tank yet. I really wish I had taken better pictures of the top of the tank through the access panel. I looked around last night from the side by the filler neck but didn't see any ports like that sticking up.

[DrDanger]

I think I saw somewhereinusa had mounted his Webasto/Espar in a storage bay under his bus, but I don't have one of those. Where have you all mounted yours? I have a dognose bus so I could try to find room in the engine bay, but that is not as convenient for connecting it to the rest of my system (floor, water tanks, etc). I am thinking of trying to find a spot under the driver area near the battery box and air tanks (I've filled up most of my space under the bus with water tanks, battery storage, and the like). Thoughts?

[Booyah45828]

WOW! What a system this is. Probably one of the best ones I've seen designed. I love it.

Do you have a picture of the heat exchanger setups, or a link to what you used?

Is your heat exchanger for the engine coolant to mail loop protected by a thermostat in case the engine coolant goes above the rating of the pex?

I tried to read through this quickly, but do you have a recirc pump for your hot water heater? I'm feeling that potable water is a limited resource in an rv, so it only makes sense to me to not waste it by running water in the sink waiting for it to get hot. So it would be valuable to have instant hot water at the turn of the valve. Or am I off base?

[somewhereinusa]

Originally Posted by DrDanger

I think I saw somewhereinusa had mounted his Webasto/Espar in a storage bay under his bus, but I don't have one of those.

I have a rear engine. Mine is mounted in a room I created above the engine compartment. Besides the Espar boiler my water heater, lithium batteries, inverter/charger, solar charger and engine air cleaner lives there.