Advice on System Setup (Tarm 40, Storage and Oil Boiler)

[DenaliChuck]

Attached is a diagram of my present system.

I'm planning to integrate a Tarm 40 that uses a flat plate hx to heat 1,200 gallons of unpressurized storage. I would like the house to receive heat from the Tarm first (when hot), the storage tank second and the oil boiler last. Since the radiant floor heat wants 100* water, I would like to be able to use the storage tank heat even if it is as low as 100*.

I also would like to begin heating a hot tub also using a flat plate hx and would like the heat to come from the Tarm first (when hot) and the storage tank second. I do not want to heat the tub with the oil boiler (or have somebody else mistakenly do this).

In the top of the storage tank I plan to run a home made copper tube hx to preheat DHW before running it into the current 40 gallon tank heater.



Where do I connect the new components to the existing system?

How do I control these different systems?

Thanks!

Chuck

 

[Bob Rohr]

That's not the correct way to install a 4 way, really. It has two functions when used for radiant. First it mixes down the boiler temperature for the radiant.

Secondly it watches the return temperature to the boiler and adjusts to keep the boiler from running too cold, in condensing mode. But it needs a motor, control and sensors on it to be able to adjust.

tekmar has some excellent application diagrams, essays, and wiring at their site for free. www.tekmar.com

Also the 26-64 seems like a lot of pump for your system? And why the ball valve throttled 50%? A pressure bypass may be a good addition if you need that much circ. it bypass some flow when only one zone calls.

The control logic to make all the things you want to happen gets pretty involved. Various sources and loads switching on and off, priority, etc.

I prefer the primary secondary show in the sticky above. Other piping methods work, but P/S covers all the various coming and going both hydraulicly and from a control wiring.

You want various loads and sources to be able to switch on and off based on priority, but also based on temperatures.

Neither boiler should ever see low return temperatures, below 140F for extended periods. I feel 10- 15 minutes before it gets above condensing mode.

That can be accomplished with 3 way thermostatic valves, 4 way mixers with operators, or as I prefer with sensors that trigger the boiler pumps off and on. I'm not sure my method is the best, or better than others. But I know it well and it does safely accomplish all the tasks.

Start with a drawing of all the various components. Then write out what you want to happen, when, and how.

I doubt you will find an off the shelf control to plug and play all that. Really it needs to be custom built to your specfic application. Smart folks like NoFo can do it with PLCs (programable logic controls) Find someone with control experience to write a program to use that type of control.

Or it can be done with off the shelf setpoint and differential controls. It will be a big wiring project, double throw relays to drop one load as the priority calls, etc. Again a control expert could draw that up quickly. a DIYer will need some trial and error time and money

tekmar controls come pretty close to being right for what you intend to do. If you find a willing tekmar installer, rep, or dealer they certainly could draw piping and wiring digrams. It a bit of a time consuming job. It might be worth you while to hire someone to at least configure it for you.

Here is the tekmar 4 way piping from their website. Thanks to tekmar for making it available!

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[Nofossil]

Thanks for the post, MOS. I was trying to figure out how to distill it all down, and I chickened out.

Bottom line, a system with oils, wood, and storage is a complex beast. I think I have the lowest cost solution, but likely the most complex and least maintainable.In my initial setup, I did everything with relays and snap action thermal switches. I didn't have storage at that point, but you can embody some pretty complex logic in relays, and they're cheap.

 

[DenaliChuck]

Yikes. Thanks for the reply MOS and NOFO. I've always been one to ask (and give) a lot, but I didn't realize how much I was asking regarding this project.

Your opinion of the Tekmar 4way is interesting to me. I know very little about this subject which is why I (we) hired the "best" from around here and he did the whole design and install. This being a manual valve the adjustment is strictly made by watching the gauge supplying the 100* loop; there are no other gauges installed. As I understand it the ball valve at 50% is to be sure the circuit is not short circuited and that the water actually makes it through the RFH tubes while allowing some to bleed back to the valve, but I'm not sure why - I don't know what a pressure bypass valve it (but can guess) and it seems like the right tool for the job. Since the 4-way is completely manual, it doesn't change based on changing conditions. This one has only one control, me (and that may not be worth much!). In reading the Ipex Manual for Modern Hydronics I just found a quote

For proper control, the valve must react to both the supply and boiler return temperatures. To do so, it must be directed by a controller that senses both supply and return temperature. It’s pointless to install a 4-way valve body while omitting the actuator / controller it needs for proper operation.

I think this manual will go a long way to teach me what I need to know.

As far as the pump being over sized, I certainly don't have a clue. I did leave off a few zone circuits for clarity, there are five total on the 100* side, one active on the 180* side with the infrequent use of one additional 180* loop running through the sewer line, tank and septic system in case the frost level gets below 10 feet.

Ultimately I'm looking for the simplest, effective, low maintenance, lowest tinkering needed system. With drawings, the internet, and email, I should be able to find a pro to help me design a system. Any advice on a designer? I don't have the luxury of a trial and error system, even thought thats what I'd like to do. And to get a full picture of the cost, I need to have a full system design prior to starting down this path, even with heating oil at $3.80/gal.

So, it just occurred to me that switching off the oil boiler (using the "off" switch) could simplify the controls. Does automating the switch-over between the wood boiler and storage tank get easier without having to prioritize them over the oil boiler?

Is there a website or book you could recommend to begin learning about controls? I know so little...

Thanks!

 

[Bob Rohr]

Here is one idea. This allows any source or load to work independently. Boilers could switch manually or with an complete automation system. I'd configure it so the oil fired boiler could never fire when the wood fired one is running. I'd also configure it so the oil fired could never charge the buffer.

The oil fired should only supply directly to the loads. No reason to turn oil to hot water until it is needed and at the rate it is needed. The 4 way really, really needs an actuator. With a reset control it would provide excellent radiant comfort and control, and protect the boiler against cold return temperatures.

Protect the wood fired with a strap on sensor at the return piping connection, set at 130F

Only the wood fired could heat the hot tub via the pool HX in the boiler loop.

The other HX, inn the primary loop could be a properly sized plate type to charge the buffer.

You might send this to tekmar for control options and critique. If they send back wiring, please buy their products.

To pipe, supply HX and controls,pumps etc and wire this if you supplied the boilers and tanks, probably a weeks worth of labor, upwards of 8 grand possibly.

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