Do you have to use coils in the tank or can you just pump that water through your heater?

I have used a Ecobee with a 24 VAC relay to turn on pumps. You could also put an old style timer that enables the pump for the heater when the cheap rates are available.

Thus I would try having the therm turn on a relay. The relay has two contacts, one contact will power the heating pump. The other contact in the relay will get power from the timer only when the timer says the rates are cheap and will thus send power to your pump to heat the tank at that time when the therm is calling for heat.

Here is the type relay I am talking about.
https://www.amazon.com/URBEST-HH52P-Electromagnetic-Power-DYF08A/dp/B00NN5ABG2/ref=sr_1_2?keywords=dpdt+24vac&qid=1570014623&sr=8-2

I would also plumb the floor heating pump to pull the liquid directly from the outlet of the heater.

There are tons of cheaper options....

Seams like you are over sized on your tank....but I don't have much experience with that.

Think about heating a small tank during the day with solar and at night with the cheaper power.

Don't know if you are understanding this so ask questions.

I want to use coils so that I can have closed systems. The storage tank was just going to be well water and open.

I need to review the manual again for the boiler but I'm pretty sure it has a built in timer. I'm also pretty sure that it has a relay built in for pump control.

My math for the tank size went something along the lines of:

1000 gallons with a delta T of 70 degrees gives me
=1000 gallons x 70 x 8.33 btu/gallon
=583100 btu of storage

Peak time is 12 hours so
15000 btu/hr *12 hours
= 180000 btu

Oh good, it looks like you're right. I think I determined tank size when I was still planning on using an outdoor wood boiler and I only wanted to make fires every couple days. Thanks for pointing that out.

I think when I did the math I would need a 6kW PV array to fully heat my water during the day. I am still considering adding in some panels sized for the shoulder season.

If I am pulling the floor heat directly from the outlet of the heater, my storage isn't optimized due to stratification right?

I'm all for cheaper options, that's a big part of why I posted.

Sounds like you are figuring it out.... I change the configuration on my house all the time...like every season... I would size the water heater to heat in the dead of winter and there add other ways as you go...wood,solar.... I have been cooling the house with well water that goes to water the lawn the last two summers. I am in Michigan. Are you using the hot water heater also for showers? Is that why you want closed loop? Good luck.

My initial thought without running the numbers is that a 1000 gallon water heat storage tank is NOT a good approach unless you are perhaps planning to heat it using a solar collector. Have you run the numbers to determine how long it will take to heat the water in that tank using the boiler while heat is being extracted from it to heat the building? There is lots of info about constructing solar collectors and heat storage approaches at BuilditSolar.com.

Going from $0.12 to $0.065/kwh is only a cost reduction factor of 1.84. If you used a heat pump system heat source you would have a cost reduction factor of at least 3 on both $0.12 and $0.065/kwh.

Yes, closed loop is the proper way to do a HR heating system. Open loop is illegal in many places and should be illegal in all places in my opinion. Open loop is not worth the health risk no matter how low you can convince yourself it is and I would personally not want to be the one who constructed one or who owned the building with one and then sold it without first disclosing the risk to the new buyer in writing.

Yes, you need to keep the 1/2” PEX circuits under 300 feet in length and 250 feet or less is preferable to keep the required pumping head on the lower end.

I like the Uponor SetPoint 521 thermostats that have slab sensors. I like Tekmar thermostats too. Be sure to place some PEX for the sensors BEFORE you pour the slabs.

You first need to do a room by room heat loss analysis to properly design a HR heating system. Then you need to properly design it to determine the required circuit supply temps, flow rates and heads. Only after doing this can you properly size the pump. Get a copy of John Siegenthaler’s Modern Hydronic Heating to get educated on this subject. We have free DIY heat loss analysis and HR floor heating design software on our website if you are so inclined.

I looked into a heat pump and the numbers didn't make sense. I'd probably average a COP of 2 over the winter which would result in a savings of about $300 vs the storage idea. Considering the heat pump I'd be looking at costs $5300 (arctic heat pump), that would take almost 18 years to pay off. For that same money I could get PV panels and the payback period would be under 10 years. Still not great but if I was grid tied it would further reduce that number. If there are better options for my climate I'll definitely look into them though. Design temp here is -25c (-13f).

My main reason for wanting a closed system is so that I can use regular cast iron pumps and not have to worry about water evaporating and algae and bacteria and all that other nasty stuff. The storage tank will be open (meaning not pressurized) simply because it doesn't need to be pumped anywhere and if it gets gross I can drain it and refill it. I would not mix heating water with drinking water directly. The health risks negate any possible reasons for wanting to.

I'll spend some time on your website sailawayrb and get the numbers you are asking for.

Ah, I didn’t initially see your location. Yes, doing the ROI check is very important and I am glad to see that you did. Do checkout BuilditSolar.com and be sure to use O2 barrier PEX if you will be using ferrous metal components in your HR heating system. You may find this to be useful reading:

https://www.greenbuildingadvisor.com/question/thermal-energy-storage

Here are the numbers you asked for as well as a picture of how I think I want my plumbing laid out



I calculated that pump 3 would need 3gpm using a 20*F temp drop which would put the head at 5 ft.
I was thinking of using Taco 008-VDTF6-2 in Delta T mode.


QUESTIONS
Do these look like good pumps to use?
I'm still confused on how to actually control the temperature of my house. I need something to ensure my floors don't get too hot. How do I wire all this up?

Well, I can tell you how one typically controls HR. It starts by sorting out how to zone the house, i.e., what areas of the house will have separate thermostats versus a common thermostat. To properly zone a house, you first need to accomplish a room-by-room heat loss analysis (e.g., ACCA Manual J or ASHRAE). Rooms or areas that have a similar Btu/H/SF heat gain requirement, similar surface temp requirement and common supply temp are good candidates for a common zone. You also have to consider if you just want different indoor temps in some areas too which will require more thermostats. You are essentially trading preciseness of area temp control against increased expense of more thermostats and manifold valves. Once you have determined your zones and where the thermostats will be located, they will be connected to a control module that is used open/close the manifold valves for the associated circuits in the zone of the thermostat calling for heat and to tell the heat source to supply the heat (e.g., turn On and run pump) something like this:

https://www.supplyhouse.com/Uponor-Wirsbo-A3031004-Four-zone-Control-Module
https://www.supplyhouse.com/Uponor-Wirsbo-A3050050-50-VA-Transformer

Presumably, you will be using manifolds that have balance valves and flow meters for each circuit so you can set the required circuit flow rates and that can use valves that open/close something like this:

https://www.supplyhouse.com/Uponor-Wirsbo-A2700502-5-Loop-1-Stainless-Steel-Radiant-Heat-Manifold-Assembly-w-Flow-Meter
https://www.supplyhouse.com/Uponor-Wirsbo-A3030524-Two-Wire-Thermal-Actuator-For-Stainless-Steel-Manifold

Outdoor reset is typically built into the heat source. An outdoor temp sensor is used to modify the heat source supply temp in accordance with some programmed supply temp versus outdoor temp curve (e.g., a colder outdoor temp causes the heat source to supply a hotter supply temp).

All I can say with regard to pump selection is that you need to properly determine your maximum flow rate requirement and the resulting head (which comes out of a proper HR design) and then select a pump that places this operating point close to the center of its performance curve. The HR software and associated instructions on our website explain this in detail.