Heating Help

unpressurized floor loops

hey y'All,
I have an application where I'd like to pump out of a large (solar heated) unpressurized tank.  it'll be going to 3 floor zones (thru 3 zone valves) of 2 loops each.  I'd like to be able to pump tank water directly to the floor zones (with  pressure diff by pass) with a 00R or similar.  I think this'd be OK, as I've seen a number of unpressurized floor systems installed around here, but I'm looking for tips anyone out there has for this sort of application.  we could also put $500 worth of copper into the tank, and lose some efficiency at the same time, but why bother if we don't need to?  because it's unpressurized, it doesn't need a PRV, expansion tank, air eliminator an all that other stuff that is needed on another closed loop system.

thoughts?  



 

hey Karl

just put up another thread about my scheme for my own unpressurized (or pressurized-lite via closed loop drainback) floor loops. must be in the spring air.

I ran my floor out of an atmospheric tank tank for several years without troubles, even used a cast iron pump which didn't fail. bronze/stainless would probably be the way to go long term & the added cost of that slightly offsets the cost of a HX coil, but coil savings plus all the other components that go away - I think unpressurized makes a lot of sense.

Roy

Bronze pumps

Or stainless steel may eat up the savings. Open mean oxygen and that means no iron body pumps. Unless you like changing them every other year. are they all of the same or lower elevation as the tank? Because bleeding out floor loops is not what one wants to do after each pump shut down.

unpressurized

the floor loops are above the tank.  I was hoping that everytime only one zone was calling for heat, the pump would have enough head to flush out any air in those lines. 

a float air vent wouldn't work up there, due to the fluid being below atmospheric when the pump is off. 

hmmm

K

so a drainback radiant system

Could it be a "sealed" unpressurized system, or is this an open tank?

Pumps like a little NPSH to prevent cavitation, as long as the pump is low on the system it should work.

I've seen cast pumps in DHW recirc, it's not the approved method but I have seen them last for many years installed in open systems.

hr

I feel that coil may be money well spent

maybe you can get a large heat exchanger from an indirect or a tankless coil from a boiler? or something of that nature than an extrol and an air scope? you can do the old hook a garden hose to fill it idea to save hard piping it and installing the boiler feed backflow preventer. Floor tubing is not that easy to bleed out and with it being open will drawn more electrical current to move the same amount of water,

loops

I'm probably just going to put some coils in the tank.  it's only for spot heating, so I won't need to make them sized for the entire house's heat load, so they' won't be too expensive. 
 I usually do systems like this without hard piping them.  I fill them with a transfer pump or hose, and oversize the expansion tank so there's a little extra fluid in the system, and call it good.  haven't had a problem yet.

it's an open unpressurized tank, and I can't punch holes inthe liner.   that's the downside of lined tanks, as opposed to fibreglass tanks.  those the MFG will put as many ports in as we want.  

does anyone have a source or name for immersable HX's that could take the place of coils of copper in the flooded tanks?   when copper prices go up, it might make sense.

thanks
karl

Wolverine Tube

www.wlv.com builds and sells all sorts of finned and HX tubing. For that small job I'm not sure it would be worth the cost over bare copper tube HXers??

hr