two temps off Laars mini therm

CPHNed

3 zone valves consisting of 1 for baseboard(high temp), and 2 for radiant(lower temp).
also a side arm(high temp).
I plan on firing new Laars minitherm jx boiler(with low loss header) to 180 for baseboard and side arm, and
a caleffi mixing valve for the 2 radiants. How would you all
do this project?
What controls, ie. relays , zvc would be the simplest?

thx much folks for your input. Mark

EdTheHeaterMan

First step is to select the piping design. Do the radiant zones need to be different temperatures? For Example radiant zone 1 is concrete slab with tile floor and radiant zone 2 is staple up with wood subfloor covered with carper, that might be a 100° water temperature for the slab and 120° for the carpeted floor While the high temp zone is 180° and the side arm (DHW) is also 180°

If you truly have only 2 temperatures then the piping can be simple with only one mixing valve.

Once you have the piping design figured out then you can decide how to control it.

hot_rod

I'd sure like to see a buffer tank on a boiler like that. It's low mass and one speed boiler, not really good for micro-zoning:)

A 30- 50 gallon electric water heater could be used, or a Boiler Buddy style buffer.

A tank, three 15-58E circulators, 4 zone valves. One thermostatic mix valve for the radiant zones

An aquastat on the control to run the buffer tank off the boiler, maybe 160F to start.

EdTheHeaterMan

here is another option The DHW circulator would have priority over the low temperature circulator (radiant zones) and system circulator (high temp zone). Boiler circulator will operate when ever there is a call for heat or hot water.

clammy

How about a turbomax piped as a 2 pipe buffer. Set at 160 for the tank and pull your hi temp and low temp off it . Kills 2 birds w one stone ,buffer and indirect . Also the benefit of pull the lower temp radiant off the tank and when the aqua start drops It fires the boiler same applies for the high temp . You will have to check your flow rates and make sure you pipe the tanks boiler side correctly . Also consider using flow checks on the hi temp side and on the circulators to not have any thermal migration out of the tank for it would lead to short cycling and wasted energy . Same would apply to the low temp also . I personally would look into it a bit further ,I have installed a few turbomax just for domestic and find that they work very well and do not get lined up and if they due there are easy if installed w provision to descale and flush out and usually a few minutes of running water through them flushed out any descaler unlike descaling a indirect it’s some time difficult to flush all the descaler out and get rid of any odor or possible taste more time . Great product but not cheap but nothing is cheap any more
Peace and good luck clammy

CPHNed

thx for your input. appreciated.

hot_rod

What size is your boiler, and what is the btu load of the smallest zone? Copper tube boilers are great, but short cycling them is not a good idea.
Here is the formula for sizing a buffer tank. You want at least a 10 minute run time.