New to hydronic heating

rkurtz85

I just built a garage with an additional 14x16 room off back and I was talked into putting in floor heat.
I purchased Prestige 9.0 GPM Propane Liquid High Efficiency Combi Boiler with 180000 BTU to heat with 2 zones (main garage and additional room) and domestic water. I don't know what else I need to heat these 2 zones. Do I need 2 circulation pumps and a taco zone control with 2 thermostats and an expansion tank?

Zman

What are your heating requirements? You need a heat loss calc before you purchase anything.
What are the hot water needs? Again, do the math first, then buy the parts.
It is usually a good idea to start with the manufactures recommended piping diagram and make tweaks as needed.

Jamie Hall

Oh dear. Well, for starters unless you live in Point Barrow or someplace like that, the boiler you bought is about 10 times as large, give or take, than what you need or, with floor heat, even can use. If I assume the total structure is around 30 by 16, with the garage, you'll not be able to put more than 15,000 to 20,000 BTUh through the floor.

So... as @Zman said, your first step should have been to calculate the heat loss from you structure. There ae several easy to use calculators out there -- I like this one: https://www.slantfin.com/slantfin-heat-loss-calculator/but there are others, but using the back of an envelope and a dull pencil suggests about that same 15,000 to 20,000 BTUh with decent insulation, so you may be able to do it with floor heat.

Now keep in mind that floor heat does not play well with temperature changes (people running the thermostat up and down), but assuming that the two spaces have different desired temperatures, yes, you will need two zones. which may need two different supply temperatures. If so, you will need two pumps and two thermostatically controlled mixing valves which, ideally would be adjusted by outside air temperatures. Your total flow rate through the system is going to be on the order to 2 gallons per minute, more or less, divided between the two zones (that's very rough -- not for use in design!).

Now since you already have that huge boiler... you will also need a huge buffer storage tank which the boiler will heat and from which you will draw the warm water you need to heat the structure.

rkurtz85

I was told by a local heating and plumbing contractor I needed at least 130,000 BTU.
My main garage is 32x32 with 10 foot high ceiling and the back addition is 14x16 with 12 foot ceiling.

rkurtz85

I have 3 loops in main garage and 1 loop in back room which I was told to buy a 4 loop manifold and now that I want to regulate the 2 areas separately I am going to have to get a single loop manifold for my back room and have 2 thermostats. The heater has a circulating pump in so I will need one for a zone and my pressure tank should pump my domestic water correct?

HVACNUT

You were told you need 104 BTU per sq ft? 
Download the free Slant/Fin heat loss app and do it yourself. 

KC_Jones

rkurtz85 said:

I was told by a local heating and plumbing contractor I needed at least 130,000 BTU.
My main garage is 32x32 with 10 foot high ceiling and the back addition is 14x16 with 12 foot ceiling.

I wouldn't listen to what that contractor said anymore.

@HVACNUT has it right, use the Slant/Fin app and calculate the heat loss, that information is needed for the entire design process and is always the first step. It actually should have been done prior to putting the tubing down and pouring concrete, but that ship has set sail I'm guessing.

rkurtz85

Dangit. Yes it has. I have no clue what I'm doing! Ive been trying to read up on this as I feel like I can do it but all the components are confusing on what I do and dont need.

GroundUp

What do you have heating the domestic hot water currently? As far as the space heating is concerned, your heat load isn't likely to be any more than about 25,000 BTU but maybe they told you that you'd need 130k+ for the combi aspect due to the volume of hot water that is used in the household? If the manifolds you bought are compatible with zoning actuators, you can keep what you have and use them with a single pump. To be frank, this is not really a DIY job and you'll likely spend more money trying to figure it out yourself than simply hiring out the job or at least a designer to give you a parts list and piping diagram.

Zman

HVACNUT said:

You were told you need 104 BTU per sq ft? 
Download the free Slant/Fin heat loss app and do it yourself. 

That number is pretty close if you are trying to melt snow off the floor of the garage
Do you need hot water in the garage? What would it serve?
I would work on returning the boiler and have someone put together a proper design.

rkurtz85

I have (2) sinks (1) in bathroom with shower and another in back room since it will be used for processing deer.

rkurtz85

In my house I use electric to heat my entire house. Water, stove etc.

Jamie Hall

rkurtz85 said:

In my house I use electric to heat my entire house. Water, stove etc.

So?