Hydronic Radiant Heat System Question

[premis]

We just built a house. We had pex put in the basement and garage floor with the manifolds terminating in the mechanical room. I'm now working on building the plumbing (pumps, valves, boiler, etc) to get the system to work. As you can see the manifold for the garage pex is mounted high on the wall, where the pex comes through the wall is the height of the garage slab. I'm basing my system on one of these pre-built kits you can buy. I just figure I can build it for half the price and have a little fun doing it. The hydronic plumbing system calls for an air separator in the primary loop. So, My question is, do I need to mount that air separator so that it is higher than the garage floor pex?

 

[PoorUB]

No, you can mount the air seperator most anywhere in one of the main water pipes. Higher up helps some as when the unit is off any air will migrate up, but as long as the seperator is mounted where all the water will eventually pass by it will remove air.

 

[premis]

No, you can mount the air seperator most anywhere in one of the main water pipes. Higher up helps some as when the unit is off any air will migrate up, but as long as the seperator is mounted where all the water will eventually pass by it will remove air.

Thanks! That makes me feel better! It was going to take some funky piping to make it higher than the garage floor.

 

[yeldogt]

1/2 pex ? What was the spacing? Loop lengths Insulation under slab ? Did you do a load for BTU's.

Electric boiler ?

Do yourself a favor before you start. Skip the copy of those panels and figure out what boiler you are going to use. You first want to follow what the boiler wants .... not try and stick on some panel that's designed for some other boiler.

Depending on the loop lengths and BTU's needed it may be best to use a low loss header. Electric boilers can be done a bit differently ..

Piping does not have to be crazy ... depending on the boiler you want to do it correctly using a few quality parts. Use a Spirovent .. a few other simple fitting available from Supply house can make things very easy.


How are you going to control the two different spaces .. are they both wide open? 16 loops of Pex is restrictive you will be needing primary secondary unless using a very unrestrictive electric boiler. Smart pumps like the Alpha II is the ticket. Maybe a An Alpha I on the primary of you want to save $30 ... I always use two of the II's

 

[premis]

1/2 pex? - Yep
What was the spacing? - 12 inches
Loop lengths - 249' (smallest loop) to 299' (longest loop). ~4,605 total feet of pex, based on the plan (attached)
Insulation under slab? - 2 inch foam board, plus 2 inch foam board between the slab and the wall
Did you do a load for BTU's. - Yep, I have 3 zones. Garage is ~67,000 BTU, basement is ~60,100 BTU, and basement garage (pre-cast under the garage) is ~18,500. Total is ~145,600 BTU.

Electric Boiler? - Nope, Natural gas. I'm planning to use this boiler. It will do 140,000 BTU with its internal pump, but I can add an external pump on the primary loop (they recommend a Taco 0013) to bump it to 199,000 BTU

Thanks for the Spirovent tip, I'll use that instead of just the basic air separator.

I have three zones (the installer combined two zones on one manifold, I plan to fix that and add a manifold), they will each have their own thermostats with slab sensors. I'm leaning towards the Honeywell T6. For two zones (garages) the radiant is the only heat source, but the basement also has a forced-air furnace that I can use to heat. The garages are wide open, the basement slab is not, it has a guest room, bathroom, mechanical room, exercise room, and then an open entertaining area.

I'm planning a primary/secondary loop setup. I'm going to design it like those pre-made panels but am also using some inspiration from the panel this guy used.

Thanks for the tip on those Alpha pumps! I kept thinking it would be nice to have pumps with more variable speed settings, but I couldn't find any. I'll use the Alpha2s.

 

[Kezorm]

Ideal location for air separator is at the point of highest temperature and lowest pressure. In other words, located between the outlet of the heat source and the inlet of the circulator pump. Height relative to rest of the system isn't critical, although a vent mounted at highest point can help purge bulk of air out of the system more quickly. Sufficient fluid flow rate is able to carry air pockets downward through pipes, but this "sufficient" flowrate may be beyond the ability of the system circulator. Using a separate, higher power pump for the purpose the initial fill / purge / flush solves this problem.

https://www.spirotherm.com/sites/default/files/JR-4.pdf

"In hydronic heating systems, the Spirovent should be installed in the boiler supply line where the temperature is highest. Should the circulator be located on the supply line as well, the Spirovent should be installed between the boiler and the circulator where pressure is also the lowest."

 

[premis]

@yeldogt have you used the Alpha II pumps? If so, are they compatible with a Taco 3-zone switching relay? I'm assuming the switching relay is sending/cutting 110V to the pump as heat is called for. If the relay cust 110v to the Alpha II pump will the pump lose it's setting?

 

[Kezorm]

Nope, Natural gas. I'm planning to use this boiler. It will do 140,000 BTU with its internal pump, but I can add an external pump on the primary loop (they recommend a Taco 0013) to bump it to 199,000 BTU

That seems a massively oversized boiler based on the information you've provided. Where are you located? Are you sure about the heat loads? Are you planning to keep garage at 70F? Will the boiler be used to provide heat to emitters other than the radiant floors (i.e. is there a bunch more house to heat with this hydronic boiler beyond the radiant floors)?

Working from other direction (heat output vs. heat load), a common design point for 1/2" tubing in radiant floor is 0.8GPM and 10F deltaT. This yields output of 4000BTU per loop. Looks like you have 16 loops, so total of 64,000 BTU. Even if you get 20F deltaT, it only comes to 128,000BTU.

Another way to look at it, assuming every 1' of tubing is essentially 1sq.ft of radiant floor (12" spacing), this means that you have 4600sq.ft. of radiant floor. 199,000 BTU into 4600 sq.ft of floor comes to 43 BTU/sq.ft. output. This is an unrealistic design point for radiant floor. Even assuming the lesser 145,000 BTU calculated load, this comes to 31.6 BTU/sq.ft. Also beyond realistic design conditions for a radiant floor.

 

[premis]

I'm located in Iowa. The boiler is only for the radiant floors. I'm also planning a 35% Ethylene Glycol mix, which will zap some efficiency.

I plan to keep the main garage (1,800 sq ft) between 60-70 degrees. The main garage has two large (18x9) insulated (R-18.4) doors, a side walk-through door, and 3 large windows. It has R-19 in the ceiling (I may improve that later) and R-13 in the walls

The basement garage (420 sq ft) will be kept at about 50 degrees. It has a single 7x8 insulated (R-18.4) door and a window. The two exterior walls have R-13 insulation. Another wall (14'x8') borders the basement, there will be R-19 insulation in the basement on that wall. The 4th wall (32'x8') is not insulated but borders the dirt under the garage. The ceiling is not insulated, but it's pre-cast with the garage above it. The garage will be warmer than the basement garage by 10-20 degrees, and there is 2" foam board between the pre-cast and the garage floor

The basement (1,910 sq ft) will be at 72 degrees. It has blown-in cellulose on 2x6 walls (R-20), a few windows, and a 8x8 sliding patio door.

I figured I'd need ~140,000 BTUs but I didn't want to undersize the boiler. It was only ~$250 more to go from a 140K BTU to a 199K BTU. Is it bad to oversize it by that much? Or is oversizing the boiler ok?

 

[Kezorm]

Oversizing the boiler is very bad, primarily from a standpoint of efficiency. Versus a right-sized boiler, you'll end up paying far, far more in energy costs over the life of the boiler. An oversized boiler will also need to cycle far more often than smaller boiler, with negative effect on the life of the boiler. Even a modulating boiler can only throttle down so far, so it ends up cycling far more often than a smaller boiler.

For reference, I'm in Minneapolis with a similar sized house built in 1955 (i.e. almost certainly far more leaky and lower design temperature). ALL of the heat for the house and (soon to be) 1500 sq.ft. heated garage is provided by a 86,000BTU output modulating/condensing boiler. And I'm probably oversized by 25% or more (I didn't know any better when I installed it and went similar output to the previous boiler).

 

[Kezorm]

I'm also planning a 35% Ethylene Glycol mix, which will zap some efficiency.

Might also consider a heat exchanger for the garage loops if you're really concerned about freezing. The extra cost of heat exchanger will probably quickly pay for itself by not having to run antifreeze in the basement radiant. 35% might be a bit higher than needed too, depends on design temp and how long it might ever go unheated.

 

[Kezorm]

Sizing a Modulating Condensing Boiler - GreenBuildingAdvisor

For the past few decades, an increasingly popular space heating option is a system with a modulating condensing (mod-con) boiler. Because these boilers can potentially have a high efficiency (90-95% or higher), they are often promoted by state and utility subsidy programs. In a well-designed...

www.greenbuildingadvisor.com

 

[premis]

Thanks, @Kezorm. I'll have to revisit my BTU calculations and try to nail it down a little better. I tend to live by "bigger is better".

 

[Kezorm]

I expect most that visit this forum are of a similar mindset . But this is definitely a case where "right-sized" is best. If fact, it can be argued that slightly undersized is even better than best. Slightly undersized, the result is that you might need to throw on a sweatshirt once or twice each year when temps dip below design temp for an extended stretch.

 

[HoosierBuddy]

Regarding the boiler in question, it is listed as modulating. I read that to mean that (like a similar wall boiler in my garage) it will throttle between some low input (mine comes on about 20,000 BTU/hour) and full capacity based on returning water temperature.

This makes oversizing the boiler less critical.

That being said, mine is 150,000 BTU in a 28 X38 with 13 foot ceilings, an attached 400 sf breezeway, and a 14 X 38 bonus room above. It never runs at 150,000 BTU's. There's simply not enough heat transfer from the pex to the concrete to get that much heat out of the water before it returns.

In 15 years of service, I've never noticed any issue from it technically being oversized.

 

[Firebrick43]

I run an alpha 2 pump, it does not lose its setting. It can be controlled by any controller that controls a 110v circuit.

Also don't use an air seperator, use a micro bubbler/spirovent.

 

[PoorUB]

The boiler is modulating ans probably fine with the 10 to 1 turn down. It will run at 20,000 BTU on low fire. In reality around 100,000 BTU is all you need. My numbers at a quick glance are roughtly 65,000 to 138,000 BTU and the 138,000 is probably not realistic. I doubt you need over 100,000 BTU.

 

[yeldogt]

The Alpha II pump has an "Auto" --- it learns.

Don't follow that guy on the video ... all wrong.

I would also rethink the boiler. I have a 4600sf house with 35 loops and it runs on 60k BTU boiler and two pumps.

You don't need a switching relay. My boiler uses ODR .. you set the curve and the boiler takes care of the water temp. The boiler can power the primary and the secondary pumps. With the Alpha II on the secondary --- set it to "auto" and it will automatically adjust when you open and close a zone. no need to make it complex.

You can zone a whole manifold with a valve connected to the T6 (zone valve) or use individual actuators on the loops controlled by the T6. to open and close some loops. I don't know how specific you plotted out the pex.

I used Cross manifolds on my last job and they allow easy thermostats hoop up to each loop ... zoning with pumps is silly and wasteful with new technology ... and needs the switching relay.

You will be better using a Low loss header with all the loops.

I think you need to redo the load -- is the basement underground ? 2K bellow ground have a delta based on 55 ground temp and no air leaking ... Very low BTU ... even bumping it up to 50 ground temp .... delta of 22.

The Sprirovent can be on the primary .... Yes. I typically do it after the LLH on my systems (secondary) .. with the expansion tank connected under it with the boiler feed and back flow all together. KISS rules. That guy in the video has the tank on a whip up in the air? He does not understand what it's doing.

Basically -- you want a set up that can purge the system most of the way using a hose .. the Spirovent will get the rest.

Why do you think you need glycol ?

 

[yeldogt]

@yeldogt have you used the Alpha II pumps? If so, are they compatible with a Taco 3-zone switching relay? I'm assuming the switching relay is sending/cutting 110V to the pump as heat is called for. If the relay cust 110v to the Alpha II pump will the pump lose it's setting?

Just to add .... with ODR and the system set up correctly ... it always running.. The alpha pump on Auto doing it's thing uses about 25 watts .... it is running when the boiler is "ON" running and if you have the boiler set up correctly .... it's always putting out some heat in the winter. that's what you want. You want 8k BTU all day long VS ... 20k BTU on and off all day long.

 

[fitter30]

Primary loop is the boiler side with back to back tees on the secondary loop. Air separator and expansion tank on the suction side of the secondary loop pump. How many loops ,lenght and pipe size. That is what what is needed to design a pump. How many zones? Glycol made for boiler minimum is 30% for the additives. Glycol doesn't need freeze protection just to slush. Glyclo manufacturers list both %. Did someone use manual j for your load or something else?

 

[premis]

Air separator and expansion tank on the suction side of the secondary loop pump.

Shouldn't the air separator and expansion tank go on the suction side of the primary loop pump (the one that just loops in and out of the boiler)?

How many loops ,lenght and pipe size. That is what what is needed to design a pump. How many zones?

3 zones (8 loops, 6 loops, and 2 loops for 16 total). Pipe is 1/2". Length of each circuit is between 249' (smallest loop) to 299' (longest loop)

Did someone use manual j for your load or something else?

I'm just trying to calculate my load myself using what I find on Google. This thread has also helped a lot. I'm not sure what manual J is.

 

[fitter30]

So 16 zone average 275' x 16 x 35 btu's per ft = 154,000 btu's. Radiant floor heat run 5 - 10* over room set point. Manual j load program that engineers use. Are u thinking about using a combi boiler for domestic hot water? If so need to know gpm needs, coldest incoming water temp, have a garden tub or multi head shower, people all taking showers at the same time and dishwasher. What type of floor covering?

 

[premis]

Are u thinking about using a combi boiler for domestic hot water? If so need to know gpm needs, coldest incoming water temp, have a garden tub or multi head shower, people all taking showers at the same time and dishwasher. What type of floor covering?

I'm planning on this condensing natural gas boiler, or maybe the 140K BTU version. It is a combi boiler but I have no intention of using it for domestic water. I already have two 50 gallon hot water heaters. I also plan to use Ethylene glycol in the floor so I want to keep this system COMPLETELY separate of my domestic water.

 

[PoorUB]

As for air eliminator placement,
https://www.spirotherm.com/sites/default/files/JR-3.pdf

 

[Kezorm]

You should really get a handle on your load calculation first. Assuming insulation to code and reasonable efforts made at air sealing, I would be surprised if you end up needing much more than 50,000BTU. 100,000BTU would be an extremely conservative guess. I'm in Minneapolis, MN (-11F design temp) in a leaky 1955, 2200sq.ft house with full walkout basement, marginal wall insulation, and **** windows. My 86,000BTU mod con boiler is oversized by at least 25%. It cycles on and off (vs. running continuously at low firing rate) for probably 90% of the winter. Will an oversized boiler work? Most certainly. You'll never know any better from standpoint of comfort. But oversizing the boiler is just flushing money down the drain in long term energy costs. There's really no upside to an oversized boiler.

See what you come up with here. Not the easiest thing to use, but it's Manual J calculation under the hood (generally a
conservative result in my understanding).

HVAC Load Calculation - Maunualj - Whole House Loadcalc

ManualJ load calculator, HVAC calculation, Whole house, - www.loadcalc.net

loadcalc.net

 

[yeldogt]

The whole point of the boiler you picked is to use it to make hot water for domestic use.

It also does not have ORD

 

[premis]

You should really get a handle on your load calculation first. Assuming insulation to code and reasonable efforts made at air sealing, I would be surprised if you end up needing much more than 50,000BTU. 100,000BTU would be an extremely conservative guess. I'm in Minneapolis, MN (-11F design temp) in a leaky 1955, 2200sq.ft house with full walkout basement, marginal wall insulation, and **** windows. My 86,000BTU mod con boiler is oversized by at least 25%. It cycles on and off (vs. running continuously at low firing rate) for probably 90% of the winter. Will an oversized boiler work? Most certainly. You'll never know any better from standpoint of comfort. But oversizing the boiler is just flushing money down the drain in long term energy costs. There's really no upside to an oversized boiler.

See what you come up with here. Not the easiest thing to use, but it's Manual J calculation under the hood (generally a
conservative result in my understanding).

HVAC Load Calculation - Maunualj - Whole House Loadcalc

ManualJ load calculator, HVAC calculation, Whole house, - www.loadcalc.net

loadcalc.net

I'm trying to be conservative with my calc mostly due to the large garage I'm trying to heat, I figure those big garage doors can be leaky and the insulation in the garage is not as good as the house (foam batting in the wall and R-30 in the attic). A friend of mine just built a 2,200 sq ft slab house and he uses an 80,000 btu boiler. I figure I'm almost double the space and part of it (garage) will be leakier and less insulated. I've used several online calculators and I'm getting anywhere between 100K and 160K. I figure since that boiler is modulating that it will adjust the output based on the need. I'm leaning towards the 140K BTU unit, but for $200 more I can go to the 199K BTU unit, and if it modulates based on need I don't think I'll see a huge efficiency loss. Still, I'll probably just do the 140K unit.

The whole point of the boiler you picked is to use it to make hot water for domestic use.

It also does not have ORD

What is an ORD?

That boiler can be used to make hot water but it is also designed for heating. The manual for the unit has some in-depth info on using it for radiant heating.

 

[yeldogt]

Out door reset ..... boiler does it\s thing and the pump just runs.

Boilers make hot water .. most can do radiant

 

[premis]

Out door reset ..... boiler does it\s thing and the pump just runs.

Boilers make hot water .. most can do radiant

It does have an outdoor reset. It's referenced in the tech specs.

https://hw.menardc.com/main/items/media/HTPIN001/Prod_Tech_Spec/wbrctechspec.pdf

 

[Kezorm]

Modulating boiler can only go so low. Majority of the season is spent at relatively low load. Yes, modulating helps, but it isn't magic fix everything. Oversized boiler WILL cycle more often than right sized boiler at low load. It will impact efficiency (although admittedly you'll never know because nothing to compare it to). Have you confirmed that your friend actually needs 80,000BTU boiler? Does it run continuously, full fire at outdoor design temp?

 

[yeldogt]

It does have an outdoor reset. It's referenced in the tech specs.

https://hw.menardc.com/main/items/media/HTPIN001/Prod_Tech_Spec/wbrctechspec.pdf

I'm not seeing where you set the curves

 

[premis]

I'm not seeing where you set the curves

It looks like the curve is preset.

Have you confirmed that your friend actually needs 80,000BTU boiler? Does it run continuously, full fire at outdoor design temp?

He just moved into his house this fall. We haven't had cold enough temps for him to really test his.

I think I'm going to go with the 140K BTU model. I know I won't need all that all the time, but I'd rather oversize it slightly than undersize it at all. The 140K BTU Westinghouse seems to be the most reasonably priced condensing boiler with an outdoor reset.

 

[fitter30]

I'm planning on this condensing natural gas boiler, or maybe the 140K BTU version. It is a combi boiler but I have no intention of using it for domestic water. I already have two 50 gallon hot water heaters. I also plan to use Ethylene glycol in the floor so I want to keep this system COMPLETELY separate of my domestic water.

can't use automotive glycol in a heating system. reread post 20.

 

[premis]

can't use automotive glycol in a heating system. reread post 20.

I'm not going to, I'm using a 35% mix of ethylene glycol from these guys

DOWTHERM SR-1 Inhibited Ethylene Glycol 55 Gallon Drum

Buy ethylene glycol antifreeze online. DOWTHERM SR-1 distributor of bulk heat transfer fluid with corrosion inhibitors. Concentrations from 20% - 100%. No order minimum, ready to ship.

goglycolpros.com

I considered Propylene Glycol but it's twice the cost and not as efficient. This will be a closed-loop system with no contact with domestic water, so I should be ok with the Ehtylene Glycol.

 

[MongoTA]

Careful with ethylene glycol regarding it's acidity levelover time as well as potential oxidation of components in your system; cast iron, black pipe, etc.
Hope your installation goes well! RFH is terrific.

 

[premis]

Careful with ethylene glycol regarding it's acidity levelover time as well as potential oxidation of components in your system; cast iron, black pipe, etc.

Supposedly this Dowtherm SR-1 Ethylene Glycol is "inhibited" to prevent corrosion

Benefits of Corrosion Inhibitors in HVAC Heat Transfer Fluids

Glycol provides burst point and freezing point protection for HVAC systems, but not all glycol includes corrosion inhibitor. Learn about inhibited vs uninhibited glycol.

goglycolpros.com

 

[yeldogt]

That's not really ODR -- it's doing something based on the outdoor temp "IF" you buy the outdoor sensor ... but it's not telling you the "how" and "what" ... so --- we have no idea if that is "good". Also -- you are picking a boiler that has parts to do domestic hot water ... including a small tank. That's a nice way to go with one of those .. but -- you are not wanting hot water. Why buy a boiler with equipment for something that you are not going to use. Get a boiler with the proper ODR for what you want it to do.

Next: If I am reading this correctly ------ One of the spaces is the lower level of a residence that obviously will have other heat in the building ..... What temp is the space w/o any heat? Many basements will only drop into the lower 60's when the rest of the house is 72 .. even when there is no heat in them (or leaks from ductwork) So all you need is 10 or 12 degrees of heat ..... you can't use a load calculation that assumes an outside temp of 10 degrees. Basements even if they are in unheated buildings need a different calculator as they are heated by the ground and don't leak. There is no way you need 60k for a typical basement .... I'm heating a whole building over 4000sf in PA with 60k and it's a converted church

Finally: You have three totally different spaces to heat ... needing three different water temps. Ideally this can be done automatically (expensive). In a house one typically picks two water temps and goes from there .. this still requires a boiler with two ODR curves (you don't have any). So ----- one is forced to pick an output temp. Your largest load is the upper garage .. that's what the boiler is going to have to be set to do. With the proper boiler it can be set up so the garage is always at whatever temp you want based on the outside temps -- it does not even need an inside thermostat .... once it's set up it just runs. The second garage space then becomes a slave to this temp and often you can restrict the flow to those loops and get that area at the temp you want based on the ODR curve of the upper. It's trial and error ... but can often work quite well. The basement is a different story and depending on the piping you may have to play with the manifolds with zone control.

One more. If I was doing this project knowing how you were going to use the space I would have piped the lower garage so that there were loops that covered the space in a way that I could turn some off. If you do serpentine loops in a garage you can set them up so the whole space gets ... lets say 1/2 the BTU's based on just turning on and off some zones. The loops parallel each other ..... you could have run the lower garage with 1/2 the loops running and if you wanted to make the upper .... just turn more loops on.

Same with the basement ... many times wide space tubing running with ODR works great in these situations and all you have to do to up the temp is open more of the zone.

When you price out a boiler -- make sure you do the cost of the intake and exhaust piping -- some require special pipe and can get expensive. Same with how you are going to control the various zones. A zone valve on a full manifold is not expensive ($100) another ($100) for the thermostat and the wire -- but that's opening the whole thing and it can only work with what water temp the others are getting. All manifolds will take individual heads -- but -- this gets expensive. That why you have to add up all the parts.

Properly done .... one pump on the secondary can make this work with ODR and the manifold to to upper garage all open. The other spaces are slaves to this and the pump can react accordingly as the zones open and close. Get the manual online for the Viessmann 200 boiler and look over how they recommend the piping .. it's a great reverence. Don't follow the videos online -- they are all hacks. There is a guy in the UK that is very good ... but technical

 

[fitter30]

Ideal location for air separator is at the point of highest temperature and lowest pressure. In other words, located between the outlet of the heat source and the inlet of the circulator pump. Height relative to rest of the system isn't critical, although a vent mounted at highest point can help purge bulk of air out of the system more quickly. Sufficient fluid flow rate is able to carry air pockets downward through pipes, but this "sufficient" flowrate may be beyond the ability of the system circulator. Using a separate, higher power pump for the purpose the initial fill / purge / flush solves this problem.

https://www.spirotherm.com/sites/default/files/JR-4.pdf

"In hydronic heating systems, the Spirovent should be installed in the boiler supply line where the temperature is highest. Should the circulator be located on the supply line as well, the Spirovent should be installed between the boiler and the circulator where pressure is also the lowest."

Not if your running a primary secondary loop. Primary is the boiler loop secondary feeds all the heat emitters.

That's not really ODR -- it's doing something based on the outdoor temp "IF" you buy the outdoor sensor ... but it's not telling you the "how" and "what" ... so --- we have no idea if that is "good". Also -- you are picking a boiler that has parts to do domestic hot water ... including a small tank. That's a nice way to go with one of those .. but -- you are not wanting hot water. Why buy a boiler with equipment for something that you are not going to use. Get a boiler with the proper ODR for what you want it to do.

Next: If I am reading this correctly ------ One of the spaces is the lower level of a residence that obviously will have other heat in the building ..... What temp is the space w/o any heat? Many basements will only drop into the lower 60's when the rest of the house is 72 .. even when there is no heat in them (or leaks from ductwork) So all you need is 10 or 12 degrees of heat ..... you can't use a load calculation that assumes an outside temp of 10 degrees. Basements even if they are in unheated buildings need a different calculator as they are heated by the ground and don't leak. There is no way you need 60k for a typical basement .... I'm heating a whole building over 4000sf in PA with 60k and it's a converted church

Finally: You have three totally different spaces to heat ... needing three different water temps. Ideally this can be done automatically (expensive). In a house one typically picks two water temps and goes from there .. this still requires a boiler with two ODR curves (you don't have any). So ----- one is forced to pick an output temp. Your largest load is the upper garage .. that's what the boiler is going to have to be set to do. With the proper boiler it can be set up so the garage is always at whatever temp you want based on the outside temps -- it does not even need an inside thermostat .... once it's set up it just runs. The second garage space then becomes a slave to this temp and often you can restrict the flow to those loops and get that area at the temp you want based on the ODR curve of the upper. It's trial and error ... but can often work quite well. The basement is a different story and depending on the piping you may have to play with the manifolds with zone control.

One more. If I was doing this project knowing how you were going to use the space I would have piped the lower garage so that there were loops that covered the space in a way that I could turn some off. If you do serpentine loops in a garage you can set them up so the whole space gets ... lets say 1/2 the BTU's based on just turning on and off some zones. The loops parallel each other ..... you could have run the lower garage with 1/2 the loops running and if you wanted to make the upper .... just turn more loops on.

Same with the basement ... many times wide space tubing running with ODR works great in these situations and all you have to do to up the temp is open more of the zone.

When you price out a boiler -- make sure you do the cost of the intake and exhaust piping -- some require special pipe and can get expensive. Same with how you are going to control the various zones. A zone valve on a full manifold is not expensive ($100) another ($100) for the thermostat and the wire -- but that's opening the whole thing and it can only work with what water temp the others are getting. All manifolds will take individual heads -- but -- this gets expensive. That why you have to add up all the parts.

Properly done .... one pump on the secondary can make this work with ODR and the manifold to to upper garage all open. The other spaces are slaves to this and the pump can react accordingly as the zones open and close. Get the manual online for the Viessmann 200 boiler and look over how they recommend the piping .. it's a great reverence. Don't follow the videos online -- they are all hacks. There is a guy in the UK that is very good ... but technical

Post 5 in a attachment has loop layout. Floor coverings are going dictate floor temps hardwood and carpet less than cement or ceramic tile. Don't need a hot floor if its design correctly 5-10*f over room setpoint.

 

[yeldogt]

Not if your running a primary secondary loop. Primary is the boiler loop secondary feeds all the heat emitters.

Post 5 in a attachment has loop layout. Floor coverings are going dictate floor temps hardwood and carpet less than cement or ceramic tile. Don't need a hot floor if its design correctly 5-10*f over room setpoint.

But you need to supply the correct water .... W/O ODR and constant circulation using the lowest temp possible ... it overheats areas.

He is a bit off on the 10% zone length ... but, unless unlucky it should be OK.

He needs a lot of flow on the secondary side and I woudl be making sure the math is right for close T vs a LLH

 

[premis]

But you need to supply the correct water .... W/O ODR and constant circulation using the lowest temp possible ... it overheats areas.

He is a bit off on the 10% zone length ... but, unless unlucky it should be OK.

He needs a lot of flow on the secondary side and I woudl be making sure the math is right for close T vs a LLH

I don't plan to use the DWH part of the combi-boiler but it seems like every boiler I find is a combi-boiler so I figured I'd just get one of those and not use the DWH part. If I could find a heat-only boiler I'd be all for it. I know I want condensing and something efficient, all those seem to be combi-boilers.

I see your point on the basement. I suppose something 100K or less would be fine. Is there a boiler that you recommend?

If I supply too hot of water to the basement will it just overheat the space? Wouldn't the zone just run for shorter periods if it had the hotter water? Would you recommend making my secondary loop similar to this pre-made panel that mixes the return water with the supply water for one of the zones?