Storage tank placement

[MarkW]

I'm looking to build a new home next summer and properly integrate my boiler/storage into a radiant system.
I'd like to place the boiler/storage in the garage and to save space, place the storage below grade.
Outside of needing check valves to prevent drainback from the boiler, any negatives that I'd need to overcome in order for this to be feasible?

 

[peakbagger]

Yu would want to take into consideration thermosyphoning when the boiler is down. With the boiler off line, the hot tank is below the cold boiler heat is going to rise and cold water is going to sink so the storage will want to heat up the boiler. If you have isolation valves it will help but even long vertical runs will tend to radiate heat.

 

[MarkW]

I'd have the boiler placed immediately above the storage pit so there won't be much run. I've got a air vent in the line so there would be no complete circuit for a thermosiphon to get going.

 

[maple1]

What do you mean by 'drainback'? That's something not normally associated with a closed pressurized system.

And as peakbagger alluded to, when the fire goes out & storage is hot, the water will want to reverse flow back to/through your boiler via convection. I'm not understanding how an air vent would prevent that - a check valve or checked circ, maybe. IMO a 'proper' integration would have storage above boiler - that's not saying you can't do it though.

 

[MarkW]

Sorry, its not pressurised storage.

 

[maple1]

But your boiler is though, right? And the heat exchanger it would be tied to to heat up your storage? Or do you have something else planned? Might need more details.

 

[woodsmaster]

Sorry, its not pressurised storage.

Still wouldn't drain back. You have to have a hx if the rest of the system is to be pressurized.
pressurized storage above the boiler would be ideal. but dont see why unpresserized under wouldn't work.

 

[MarkW]

Not thinking too clearly this am. It's not the way I've got it going now so I was not quite right in my thinking about the future setup.
I'd like to have it over the boiler but that's not too practical for me.

 

[MarkW]

You have to have a hx if the rest of the system is to be pressurized

What do you mean about the rest of the system being pressurized?

 

[maple1]

Your boiler.

Your radiators/heat distribution.

Typical unpressurized storage has those pressurized, with the storage in between, separated by heat exchangers on each side.

EDIT: Or, maybe could tie both together using one heat exchanger for transferring heat from boiler to storage, and from storage to distribution. Getting a bit out of my league with this now though.

 

[altmartion]

What do you mean about the rest of the system being pressurized?

if it's connected to a pressurized system it will also be pressurized. if you use a pump, like the 15/58 or something, they have internal, replaceable and removable check valves. these are nice because they don't chatter.

 

[MarkW]

Oh, was under the impression that one just pumped from storage.

 

[altmartion]

a circ pump in reality is just a booster pump. they can't take the load of "drawing" for to long. but I have seen them work for a long time. what are you planning to use for tanks and plumbing?

 

[MarkW]

a circ pump in reality is just a booster pump

That's what I wasn't thinking about. As I should be all too aware from the troubles we have with the circs on our ground heaters at work when the guys in the field want to try to pump up hill.

Anyhow, I've got some bulk oil tanks that I came by new. I intend to place them together in a pit below the boiler. I'm thinking I'll have 4 in-slab loops in the house and one in the garage. A DHW tank above all for thermosiphon.

 

[maple1]

Oil tanks will be subject to increased corrosion if used for open storage. So keep ease-of-service in mind in the planning. They will also see pressure at a rate of 0.4psi/foot, from any water that is above them - so keep their pressure rating and that in mind too.

 

[MarkW]

I intent to keep up with corrosion prevention chemicals and ensure that I've got wetted surfaces by providing expansion into a sacrificial vessel. I should think that would help in that regard.
They're dual chambered and heavy walled so minimal pressure shouldn't be objectionable.

 

[altmartion]

That's what I wasn't thinking about. As I should be all too aware from the troubles we have with the circs on our ground heaters at work when the guys in the field want to try to pump up hill.

Anyhow, I've got some bulk oil tanks that I came by new. I intend to place them together in a pit below the boiler. I'm thinking I'll have 4 in-slab loops in the house and one in the garage. A DHW tank above all for thermosiphon.

try to coat the inside if possible and adjust the water balance, this will help to slow the tank rot. how much storage are we talking?

 

[MarkW]

Coat with?
1500gal

 

[maple1]

Expansion into 'sacrificial' vessel? Not sure what that means - I don't think I'd want any of my system components to be 'sacrificial'?

 

[altmartion]

Coat with?
1500gal

I cant remember the name. it comes in either gallon cans or spray cans with tube. is the storage sized or a guess. it seems like a lot. what are you heating it with?

 

[MarkW]

If I understand correctly, even with corrosion preventer kept in solution at time, one will experience corrosion above the wetted surface of unpressurized storage vessels. Have I got that right? If so, then I just fill the tanks completely and allow for expansion into a more easily replace vessel, thereby protecting myself from costly and difficult replacement of the large tanks.

 

[altmartion]

Expansion into 'sacrificial' vessel? Not sure what that means - I don't think I'd want any of my system components to be 'sacrificial'?

yea, it doesn't sound right. that's not a word you want to use when describing a pressurized vessel.

 

[MarkW]

I'm not pressurized but I get your trepidation.

Sacrificial isn't necessarily a bad thing when used to prevent damage/unneeded maintainence to other components.

 

[altmartion]

how do you plan on getting the water from the storage tank into the system? is this must be an open system?

 

[MarkW]

Yes, I was thinking open. I guess I didn't see any other diagrams when decided to go open that would have led me to think otherwise.