Some questions ...Cast Iron Radiators

[dook]

New construction, plan on getting EKO 25 or EKO 40 boiler.
If it's economically feasible to excavate the rock on this site to build a stem wall foundation rather than slab, I was thinking of using cast iron radiators inside the house and pex in the garage slab.
I'm new to the idea of radiators. When I get ready to purchase old radiators, does it matter if they were originally designed for steam or hot water? Will I have to have a pressurized system?
Since this home is going to be off grid, I was thinking it will take less electricity to move water through those radiators than to push it through many hundreds of feet of skinny pex tubing. Is that correct?
The home will only be about 1400 square feet. Should I simply have one house zone and a manifold directing flow in parallel with 3/4" pex tubing?

 

[Bob Rohr]

New construction, plan on getting EKO 25 or EKO 40 boiler.
If it's economically feasible to excavate the rock on this site to build a stem wall foundation rather than slab, I was thinking of using cast iron radiators inside the house and pex in the garage slab.
I'm new to the idea of radiators. When I get ready to purchase old radiators, does it matter if they were originally designed for steam or hot water? Will I have to have a pressurized system?
Since this home is going to be off grid, I was thinking it will take less electricity to move water through those radiators than to push it through many hundreds of feet of skinny pex tubing. Is that correct?
The home will only be about 1400 square feet. Should I simply have one house zone and a manifold directing flow in parallel with 3/4" pex tubing?

Not sure about you foundation question? The footing, below frost level, is what spreads the weight of the structure to the ground. The foundation walls stack onto the footing. Or the slab, if it is on grade.

I'd get a structural engineer involved if you plan on any other method.

HW rads with two ports work best. Steam radiators can also work, you may need to drill some holes to add air vents at the top.

Todays ECM pumps can easily move radiant loops with 10- 27 Watts of energy.

I'd use 1/2" loops on a tight spacing 6- 8". This allows you to use very low supply temperature.

But start with a heat load calculation first, even before you break ground, or rock

Todays super insulated homes do not need much heat. An accurate load calc is critical. Some over heat just from the gains from lights, appliances and people inside them.

 

[dook]

Thanks, Bob. Even 27 watts is a lot when you have a few pumps running as well as the boiler fan and there is snow on the panels or no sunshine. I think 1/2" tubing is no-go for solar, takes too much energy to push anything through it. I would go with at least 5/8", maybe even 3/4" in the garage slab. I'll most likely use 12 or 24 VDC ecm pumps. I've looked at some of the pump curves and they're really pathetic, though. Hopefully there is newer technology in the last few months since I checked.

 

[BoilerMan]

Consider a natural draft gasser like a Varm like what maple1 has. One less electrical consumer. I think you can easily design a hydronic system that will draw 50watts or less total. One ECM circ and very energy efficient zone valves like the Taco Sentry (broken link removed to http://www.taco-hvac.com/products/hydronic_accessories/zone_and_flow_control_valves/zone_sentry_zone_valve/index.html)

What are you going to run for an inverter? I've designed and installed an off-grid system which runs very well. 120V ECM pumps, the 12Vdc ones are just as you said pathetic........

TS

 

[Bob Rohr]

Thanks, Bob. Even 27 watts is a lot when you have a few pumps running as well as the boiler fan and there is snow on the panels or no sunshine. I think 1/2" tubing is no-go for solar, takes too much energy to push anything through it. I would go with at least 5/8", maybe even 3/4" in the garage slab. I'll most likely use 12 or 24 VDC ecm pumps. I've looked at some of the pump curves and they're really pathetic, though. Hopefully there is newer technology in the last few months since I checked.

My buddy Larry Weingarten built a gravity circulated radiant wall for his off grid home in CA. Google house on hummingbird hill

 

[dook]

Consider a natural draft gasser like a Varm like what maple1 has. One less electrical consumer. I think you can easily design a hydronic system that will draw 50watts or less total. One ECM circ and very energy efficient zone valves like the Taco Sentry (broken link removed to http://www.taco-hvac.com/products/hydronic_accessories/zone_and_flow_control_valves/zone_sentry_zone_valve/index.html)

What are you going to run for an inverter? I've designed and installed an off-grid system which runs very well. 120V ECM pumps, the 12Vdc ones are just as you said pathetic........

TS

I couldn't find a website for Varm. Didn't know anyone made a gasser without a blower. That would save me 75 watts!!
I was planning to have an Outback VFX3524 inverter, but was hoping to have 24 VDC components like pumps. I'd rather not run the inverter 24 hours a day. I've been trying to find info on the Caleffi and Liang pumps.
There's not much sunshine here in Western Montana in December, January and February so regardless of my PV array, I need to keep things minimal. I'll be limited to 8) Trojan L-16 REB batteries.
The garage will be about 1700 square feet so several loops meaning several pumps. I looked into El-Sid pumps but they seem to only have enough head to circulate the nearest loop.
It seems a cast iron radiator system in the house would have much less restriction than pex so couldn't the house be run with one single pump? I'm thinking 3 small pumps for the garage and one larger pump for the house.

 

[maple1]

I couldn't find a website for Varm. Didn't know anyone made a gasser without a blower. That would save me 75 watts!!
I was planning to have an Outback VFX3524 inverter, but was hoping to have 24 VDC components like pumps. I'd rather not run the inverter 24 hours a day. I've been trying to find info on the Caleffi and Liang pumps.
There's not much sunshine here in Western Montana in December, January and February so regardless of my PV array, I need to keep things minimal. I'll be limited to 8) Trojan L-16 REB batteries.
The garage will be about 1700 square feet so several loops meaning several pumps. I looked into El-Sid pumps but they seem to only have enough head to circulate the nearest loop.
It seems a cast iron radiator system in the house would have much less restriction than pex so couldn't the house be run with one single pump? I'm thinking 3 small pumps for the garage and one larger pump for the house.

Watch for the Smokeless Heat banner on here, or just Google it. My gasser has no fan, uses a 15-58 circ on low for boiler pump, and one Alpha for my 4 zones. Not much juice being used there.

 

[dook]

Found their website (broken link removed)

It seems all but the largest ones use a 50 watt suction fan. Those boilers ain't cheap, either.

 

[Bob Rohr]

Laing is now part of B&G Xylem. Those Eco circs are detailed there
http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2012/07/A-175.pdf

You should be able to move 30- 40,000 BTU/hr with the 24V system, even in a radiant system

 

[dook]

Laing is now part of B&G Xylem. Those Eco circs are detailed there
http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2012/07/A-175.pdf

You should be able to move 30- 40,000 BTU/hr with the 24V system, even in a radiant system

It's my understanding that some pumps which are designed to be hooked directly to solar panels are different from pumps which are designed to be run by batteries of the same nominal voltage. I like the numbers on this pump. I wonder if it could be used in a hydronic heating application rather than solar hot water circulation.

 

[BoilerMan]

Found their website (broken link removed)

It seems all but the largest ones use a 50 watt suction fan. Those boilers ain't cheap, either.

Swedish quality.........

TS

 

[BoilerMan]

If you use storage a large output boiler is not a problem, and I'd say an advantage. One loading and you can charge storage quickly, opposed to several loadings (think no daylight to run boiler pump) over a longer period.

If setup correctly with elevated storage, large piping to storage (2") you could have no fan, no boiler pump, and minimal wattage running ECM circulator and very low wattage zone valves.

TS

 

[ewdudley]

If setup correctly with elevated storage, large piping to storage (2") you could have no fan, no boiler pump, and minimal wattage running ECM circulator and very low wattage zone valves.

I worked this out once and I concluded that in order to have return temperature protection with pure gravity flow, then the mixing valve needs to be elevated a couple feet or more above the boiler and then storage can be immediately above the mixing valve.

Another way of looking at optimizing boiler output relative to storage might be to prefer a smaller output boiler with a relatively large firebox, which might be preferable in many cases.

If the boiler output is more closely matched with system load and if the firebox is relatively large, then the burn time of the boiler can be longer and during that time more heat is stored in the wood in the firebox. This way storage can be smaller because there's less need to store heat because the rate of heat production is not as great.

In particular Varmbaronen and Froling have relatively short, narrow, and tall fireboxes that make this easier.

 

[dook]

If setup correctly with elevated storage, large piping to storage (2") you could have no fan, no boiler pump, and minimal wattage running ECM circulator and very low wattage zone valves.

TS

Forgive my ignorance, but what are the zone valves for? It would seem that when the circulator pump is off, there wouldn't be enough flow to make a difference. What power are mixing valves operated by? Do they make them in 24 VDC?

 

[maple1]

Zone valves are used to control flow to multiple zones when using one zone circulator.

 

[BoilerMan]

If you only have one zone, then just the one circulator and no valves is all you need.

TS

 

[dook]

If you only have one zone, then just the one circulator and no valves is all you need.

TS

Forgive my ignorance, but what are the zone valves for? It would seem that when the circulator pump is off, there wouldn't be enough flow to make a difference.

My thinking is that the DC pumps are so pathetic that most won't carry more than one loop, let alone a whole zone, so I may not need any of those zone valves.

 

[BoilerMan]

Do the math on if you will use less total wattage using a 120V ECM through your inverter vs. using several DC pumps directly from your batteries.

This depends on your lifestyle and what your plans are for inverter run time.

TS