Unconventional buffer tank setup. Will it work?

Eureka

Feeling the Heat
Feb 4, 2018
336
NW Wisconsin
I want to add some buffer and outdoor reset into my current supplemental wood heat system. I got these tanks at a good price but haven’t done any work yet. They have decent 1-1/4 connection points (shown in drawing) for a 2 pipe arrangement, except for an upper supply header, so I came up with this entering into an existing top bung. I know it will mix more when recharging, but this would save me from chopping into brand new tanks to add a side connection, and I thought it could still work well for my needs: on demand DHW and low temp radiant slabs on outdoor reset injection.
33384C55-EADA-45A5-8D83-2D8A5A4E045C.jpeg
My sketch shows my idea for the supply header but all tank connection points shown are what is existing. Heat source is a small but capable Heatmaster C150 OWB with a low water capacity of 60 gallons. It recovers super fast then idles often. I’m hoping to help with that as well as help get me a better pad on the cold nights before I get outside to reload. It does surprisingly well now working as an on demand, inline FPHX setup but I see room for improvement and my wife will tell you I like to fix what isn’t broken :p

This isn’t a gasifier and I’m not trying to create a thermal storage; I’m after more convenience and maybe better efficiency at times of the season.

Will that supply header on top be a deal breaker?
Maybe the cross flow would help..?
 

Eureka

Feeling the Heat
Feb 4, 2018
336
NW Wisconsin
I also considered running the tank supply to the middle side connection and taking the loads out of the top ports. I’d think it would still stratify somewhat. Kind of becomes more of a large hydraulic separator then.

Not dead set on any of this, just exploring options that would cut out a lot of fabrication. It’s kind of a retrofit, so I’m ok with less than perfection if it ends up being better than stupid.
 

HardDrinkin'Lincoln

New Member
Nov 2, 2019
34
WA
I also considered running the tank supply to the middle side connection and taking the loads out of the top ports. I’d think it would still stratify somewhat. Kind of becomes more of a large hydraulic separator then.

Not dead set on any of this, just exploring options that would cut out a lot of fabrication. It’s kind of a retrofit, so I’m ok with less than perfection if it ends up being better than stupid.
Here's what I would do with the two tanks. You will double the amount of useful stratification.

1607961723000.png
 
  • Like
Reactions: Eureka

salecker

Minister of Fire
Aug 22, 2010
1,262
Northern Canada
Your picture shows bungs in the bottom.
My 500 gallon tanks are plumbed using the very top and bottom with reversing the tanks from top to bottom flows
 

Eureka

Feeling the Heat
Feb 4, 2018
336
NW Wisconsin
Your picture shows bungs in the bottom.
My 500 gallon tanks are plumbed using the very top and bottom with reversing the tanks from top to bottom flows
Yes they have bungs at the bottom too. I suppose I could use either depending on what fits the space better. I like the header arrangement that @HardDrinkin'Lincoln shows because it would split the flows up equally when pulling from either the side or bottom of the tanks.
 

Eureka

Feeling the Heat
Feb 4, 2018
336
NW Wisconsin
Is a Grundfos 15-58 on a temperature controller acceptable for the circulator that pulls heat off the OWB HX into the tanks, or is there a better option? Looked at Alphas but they don’t seem like they fit the bill.
 

HardDrinkin'Lincoln

New Member
Nov 2, 2019
34
WA
It depends on the flow rate and pressure drop through the heat exchanger for the desired number of BTUs transferred between the two system. Once that's known then you can look at the pump curves for the 15-58 to see if it's a good match.
1607985611218.png
 

Eureka

Feeling the Heat
Feb 4, 2018
336
NW Wisconsin
Sorry, I was referring to smarter delta T / P circs and the like. I’m not very learned up on how those work.
 

Eureka

Feeling the Heat
Feb 4, 2018
336
NW Wisconsin
I don't know how I missed it, but I just found the Tekmar 156. Looks like that is about the perfect fit for control of reheating a tank from a heat source like this. It would give me setpoint on and off of the circulator, minimum and maximum cutout when the heat source is offline/depleted, and looks like a little datalogging as a bonus. Sensors included for the heat source and tank. I think I found my control.

How do you mechanical room junkies here in the Boiler Room automate your storage?
 

maple1

Minister of Fire
Sep 15, 2011
10,656
Nova Scotia
I don't know how I missed it, but I just found the Tekmar 156. Looks like that is about the perfect fit for control of reheating a tank from a heat source like this. It would give me setpoint on and off of the circulator, minimum and maximum cutout when the heat source is offline/depleted, and looks like a little datalogging as a bonus. Sensors included for the heat source and tank. I think I found my control.

How do you mechanical room junkies here in the Boiler Room automate your storage?
I like simple. So just went with a lk810 loading unit. Thermostat and circ in one unit, the circ is a 15-58 3 speed. If I didn't have that, next choice would simply be separate thermo mixer and 15-58. Boiler gets hot it starts, cools off it stops. 15-58 is a very good reasonably priced fairly widely adaptable all around circ. I have a variable Alpha for my varying loads, set to constant pressure operation, usually on low speed.
 
  • Like
Reactions: Eureka

Eureka

Feeling the Heat
Feb 4, 2018
336
NW Wisconsin
I like simple. So just went with a lk810 loading unit. Thermostat and circ in one unit, the circ is a 15-58 3 speed. If I didn't have that, next choice would simply be separate thermo mixer and 15-58. Boiler gets hot it starts, cools off it stops. 15-58 is a very good reasonably priced fairly widely adaptable all around circ. I have a variable Alpha for my varying loads, set to constant pressure operation, usually on low speed.
Nice, so similar to the Caleffi 281. I looked pretty hard at those but decided against it because I don't need return temp protection, and I already have a 280 protection valve in use. I got the 280 protection valve and put it where my underground lines enter the house and although it does provide return protection, I'm using it to bypass the heat exchanger and related in house piping when the outdoor unit is cold. I ended up putting in the lowest temp thermostatic sensor they offer to squeeze a little more heat out before it bypasses.
 

salecker

Minister of Fire
Aug 22, 2010
1,262
Northern Canada
Mine is simple,near boiler pump for boiler protection...
then it's all going to storage,once it gets past the tee that feeds the house heat exchanger.The return from the house HX goes back to the boiler return
 
  • Like
Reactions: Eureka

Eureka

Feeling the Heat
Feb 4, 2018
336
NW Wisconsin
You can read about my control strategy in the post about my boiler project.

https://www.hearth.com/talk/threads/my-first-winter-with-a-new-vedolux-350.180481/
Great and informative thread. I'm surprised I missed it but I was away from Hearth for a year while life came at me fast.
Your setup is impressive.
I'm seeing more and more setups out there that might go against the norms of traditional hydronics, yet seem to work as well or better. Especially with sophisticated controls becoming more available. Fun stuff.
 

Eureka

Feeling the Heat
Feb 4, 2018
336
NW Wisconsin
A few deliveries have shown up with some of the supplies. The rest will arrive over the next week. I’m partial to black iron pipe, so I’m using that for the headers and supply/return piping off of the tanks and to the 2” headers, 1-1/4 between tanks, 1” to the loads.
9A7E7E22-5C23-4026-9152-553F9E6DA195.jpeg
4713569C-F629-42C7-A765-0820FCD2B971.jpeg
Nice tanks.
F06181DB-CC53-4F21-B94F-7F6C8405E4D7.jpeg
Brown truck left something else here today:
25D9984B-721B-479C-8A90-E00EF4C5CA72.jpeg
Because when you get a really good deal on tanks you can get yourself a really nice chain grinder just in time for Christmas with the money you saved.
 
  • Like
Reactions: HardDrinkin'Lincoln

HardDrinkin'Lincoln

New Member
Nov 2, 2019
34
WA
I've revised my diagram by moving the HX pump to the outlet of the tanks instead of the inlet. It's always best practice to be pumping away from the expansion tank, or the point-of-no-pressure-change as it's frequently referred to.

1608235949472.png
 
Last edited:
  • Like
Reactions: Eureka

Eureka

Feeling the Heat
Feb 4, 2018
336
NW Wisconsin
Your picture shows bungs in the bottom.
My 500 gallon tanks are plumbed using the very top and bottom with reversing the tanks from top to bottom flows
Do you know what the temperatures are like on your tanks and how they stratify?
 

salecker

Minister of Fire
Aug 22, 2010
1,262
Northern Canada
Do you know what the temperatures are like on your tanks and how they stratify?
I charge my tanks according to the temp,185 is about max the i got it to
The way my system is set up,i have pumps running 24/7
It works good for now so i haven't tweaked it for maximum performance
 
  • Like
Reactions: Eureka

Eureka

Feeling the Heat
Feb 4, 2018
336
NW Wisconsin
Currently I have a little 2 gallon expansion tank below a Caleffi Discal on a primary radiant floor loop. This is just downstream of my mod con combi boiler, which is piped in with close tees and has auto water feed. My wood heat secondary loop is piped in with close tees upstream of the combi boiler and Discal. Where should I put my new expansion tank now that I’m adding buffer tanks?
-Pipe new tank out of the Discal?
-Pipe new tank out of the bottom of one of the buffer tanks on the wood heat secondary loop?
 

HardDrinkin'Lincoln

New Member
Nov 2, 2019
34
WA
I connected my large expansion tank to the bottom of the storage tank. That way if I closed the isolation valve between the storage tank and the radiant heating the large expansion tank remains connected to the storage tank.
 
Last edited: