How would you run this system?

[Golovkin]

I have a Garn jr. heating a 4,500 sq/ft home with 20 radiant floor zones. The first winter I just used one thermostat in the basement and manually dialed all the zones to heat the house as evenly as possible. To do this I had to dial many of the basement zones down, so that flow would be more even on the third floor. The basement has 7 zones that are pex in concrete on 12" centers while the rest of the house is 'sandwiched' pex in aluminum fin on 8" or 6" centers below 3/4" wood flooring. Some zones are short, others are 300' so I've had to dial down short zones and zones that are lower in the house that have less resistance.

I'm using a tekmar 356 to control mix temperature and now I just installed thermostats and Calleffi operators on all the zones.

Here is my question: Would you now turn all the manual dials to wide open and just let the thermostats and controllers and pump do its job, our would you keep the manual dial settings to choke off some of the flow to the easier zones?

Option 1: Wide open - this probably is the fastest and most efficient at getting heat from the garn into my house. but when all the thermostats are calling for heat (because I was lazy and didn't build a fire) the flow will go mainly into the basement until it is all warmed up, then those zones will shut off, and it will heat the main floor, until those shut off, then it will heat the upstairs...

Option 2: Keep the manual settings - this will cause the whole house to heat up more evenly, but it may not be the fastest way to get the house warm because most zones are restricted?

The only reason this is really an issue is because I use a wood fired boiler and sometimes the tank temperature dips below the target mix leaving me with a house that has to go from say 62 to 70.

how would you do it?

 

[Bad LP]

Is the basement finished living space?

 

[Fred61]

I personally try to choke the supply enough so that the return is 10 to 15 degrees lower than the supply. Less mixing in the storage tank.

 

[Golovkin]

Is the basement finished living space?

Yes, I have three kids and all their bedrooms are down there. Our bedroom is on the 3rd floor.

 

[Golovkin]

I personally try to choke the supply enough so that the return is 10 to 15 degrees lower than the supply. Less mixing in the storage tank.

So less mixing in the storage tank - what is the benefit of that? Is that better for the steel in the tank or does that effect efficiency somehow? I should know this stuff, but I've just been learning as I went and forgetting most of it...

 

[Fred61]

Stratification, lighter hot water migrating to the top while colder "heavy" water sinking to the bottom is the invisible advantage and is your best friend.
It allows you to take advantage of a given amount of stored BTUs. If you pump hot water from the top of your storage and return it to the bottom at close to the same temperature you are redistributing the hot water throughout the tank causing the average stored BTUs to be less useable.

My best explanation on short notice

 

[Golovkin]

Stratification, lighter hot water migrating to the top while colder "heavy" water sinking to the bottom is the invisible advantage and is your best friend.
It allows you to take advantage of a given amount of stored BTUs. If you pump hot water from the top of your storage and return it to the bottom at close to the same temperature you are redistributing the hot water throughout the tank causing the average stored BTUs to be less useable.

My best explanation on short notice

Got it, thanks for the info. I'm running the garn through a heat exchanger, so I'll watch what the supply and return are doing. Sounds like restricting the system isn't necessarily a bad thing, might even have an advantage by creating less stratification. I can also adjust this by means of the tekmar control and pump speeds if needed.

 

[TCaldwell]

Sounds like a great system being able to maximize storage. You might look at tekmar’s essays on radiant management, interesting they use thermostats that communicate amongst one another.
Is the radiant the only heat source.?

 

[Golovkin]

Sounds like a great system being able to maximize storage. You might look at tekmar’s essays on radiant management, interesting they use thermostats that communicate amongst one another.
Is the radiant the only heat source.?

Thanks! It does seem to do well heating the house even with the tank in the 90's. Lots of zones, lots of fins! The radiant is my only heat source, I will put a gas boiler into the house loop next winter. With the garn jr. I have to make two fires a day when its -40 to -20f. One fire if its -20 -0 and a fire every other day if its in the 20's. A bigger garn would have been nice but the space in my garage was tight.