Anybody's boiler just heat the storage?

I thought about doing it at one point. Here's why I decided not to - Say the tank is at low temp, ex. 140*. You just started a fire and the water coming out of the boiler is 180*. Your zones are calling for heat because the programmable thermostats just switched from 65 to 70. If it is pretty cold out you will have a tough time getting the zones warm with the 140* water from the tank so you might have to wait until the boiler heats the tank, which could be awhile. If the boiler can directly heat the zones, then you can immediately take advantage of the 180* water.

There's another thing I never understood - the design is apparently intended to use separate coils for charging and discharging. I've seen this approach many times and I just don't get it.

Does that mean that you have two separate water systems with fill valves and expansion tanks?

Using two coils also means that you have two heat exchangers and intermediate fluid between your boiler and your zones. That's two heat exchanger temperature drops between your boiler and the zones, in addition to the extra thermal mass. I have to believe that if your boiler outlet is 180, you'd never see 180 going to the zones. Does anyone have a system set up this way? If so, what do you see for temperature out of the boiler vs. temperature to the zones?

Since there's never a time when you need to put heat into and out of the tank at the same time, that means that you could use the two coils in parallel and double your coil surface area.

Still scratching my head.

My system is set up this way. I'm not going to say it's right or wrong but it's working for me. The supply out of my wood boiler is piped to the bottom of my two 200 gallon tanks, then out the top of the tanks to the system. My wood boiler pump shuts off when the water temp drops below 135 at the boiler. But the tanks are alway 10-15 degrees hotter. I have a wc-130 and if all 5 zones are calling and boiler running full tilt the tanks will rise 20-25 degrees an hour. I went this route because I have radiant heat some my max water temp on a -10 day is only 140, if I had baseboard or high temp heat this would not work. But so far it's been working good for me.

Here are a couple of pics showing the setup. I can also bypass the tanks if I need to.

My GARN only heats the storage water, but I don't think that is what you meant.

BRL - that's not really the same as if the boiler was heating an stss type of tank. It looks like you have closed/pressurized tanks. With an stss type of tank you have a problem where heting just the tank with the boiler requires an extra heat exchanger which is bad, but i don't think you have this problem.

I'm also curious as to how well heating only through storage would be. I think having less storage, like 500 pressurized gallons might be a plus for this setup.
I believe Hansson from Sweden submitted a link to a video showing something like this.

Free75, yeah I figured that out after I posted. I was going to erase it but decided to leave it as another option.

I'll know soon how it works. When I planned out my system I decided to use this method. I was worried about the tank temps as well so the output from my heat exchanger ( to heat the tank ) is fed directly to the load source so that if the boiler is on the heat would go right to the load first allowing heat while the tank is still getting up to temperature. My boiler will go to a flat plate exchanger only and the rest of the system will rely on the tank "side" of the exchanger. I am using an EKO 60 and 1600 Gal homemade tank.

I have a hand made sketch of my original plan. But the concept was simple for me to understand and believe in enough to build. I have loop A from boiler to HX with the pump A just as the EKO install pictures show, I have loop B that circulates from the bottom of the tank to the HX thru Pump B and back to the top of the tank. I have Loop C that taps into the return to the tank after the pump B and cycles using pump C to the furnace(s) and back to the bottom of the tank.

3 Pumps, 1 Flat plate HX, 1 Tank, 2 water to air HX - for furnaces. I'll be firing it up next weekend so I am hoping for the best. Due to the thread on this forum about the temperature differential controllers I will be adding that in the plan to stop the tank pump B when the loop A side is cooler than loop B but for now the EKO controller will spin up both A & B.

My set up is much like anyone else, my boiler is piped so that is constantly circulates through my oil boiler, in that loop I have a flat plate hx that I use to charge my tank. The house is heated with baseboard from the oil boiler, my tank heats the house with a forced hot air system, and also radiant floor heat soon to be all radiant floor heat. I rarely use the baseboard unless the storage is to low in temp, and that is not very often. My wood boiler spends most all of its time heating the storage only.

Steve

I'm still trying to get my head around the return water from the storage tank being 132 and shutting off the main taco circ. seems like a catch 22 type deal. Ive tried for several days to reach 165 degrees top level of my sstc 806 gal storage tank. this cold weekend the 1st and only in-floor radiant zone used the majority of the heat to keep the structure warm 68 degrees. Now with the warm up and less demand to the 1st zone the tank temps are 169 top 147 mid and 102 bottom. I can't go above 150 because that is the limit for the top main heat pipe coming out the top back of the tarm 40. Today I just turned the thermostat from 120 to 150, seemed to help burn much hotter with less idle. Quite the learning curve but when this is done I'll still be glad I purchased this system. How many different possibilities are their? my system has only 1 zone for radiant infloor and 806 gal. open storage. :lol: sweetheat

My system is setup to heat only the storage tanks. But I do have a valve that allows me to send heat right to the house.

My system has a 3000 gallon non-pressurized tank. Essentially, the temp of that tank is very stable. A 4 hour burn can add as much as 18 Deg F, at the high end, all conditions perfect.

Part of my reason for this is that my boiler and tank are in a shed away from the house. I didn't want the boiler to be pushing water to the house any time the boiler is running, expecially if the house is not calling for heat. The split system does this very well.

I also plumbed the system with all sorts of cross connects and hand valves in place, so I can change the water flow to a lot of different things. Primarily, I leave the boiler pushing through the "tank heat" coils and the house pulling from the "house heat" coils.

The boiler return header does have a connection to the return from the house. That allows me to have one fill valve and one expansion tank.

I am in the process of adding a controlled valve at the outlet of the pump off the boiler. This valve will open a cross connection to the pipe that supplies hot water to the house. In addition, I'll be putting a controlled valve in the house that will stop flow if the house is not calling. This will give me water direct from the boiler if/when the boiler is running AND the house is calling for hot water. If the house is not calling for hot water, the boiler pump is able to push through the "house heat" coils in reverse and make use of the extra surface area for heating the tank.

This helps me, because it reduces the losses to the ground by only allowing flow to the house when the house needs water. I've tried just opening the valves all the time, but the pump off the boiler pushes water to the house and back to the return header rather than through the coils. Likewise, when the boiler is off and both valves are open, the house pump pulls through the boiler, not the tank coils, which results in not using any of the stored heat.

I can't say for sure that this is the best way to go forward. But it works for me, in my unique situation. I've also got a lot of radiant heat, and I run with outdoor reset for my inside heating water temps, so most of the year I'm running 120 deg water for heating.

very nice pics BRL. what kind of tanks are those? i'm in the design process(hopefully up and running for next season) using only radiant floor systems.