what is the best way

Paul S_3

To control a boiler with a buffer tank?....on my next project im thinking of using a buffer tank (2 pipe setup) with a mod con....can i use a tekmar 152 setpoint controller? Never did this before just read on idronics and coffee with caleffi

aircooled81

Dont think this answers your question, but we have started using buffer tanks with high e raypaks. We have found these help absorb the shock of boiler overshooting when secondary flow cuts down too far.
I haven't put any thoughts into how typical boiler operation should change. Have Just plugged the ol system sensor into the tank and ran it like it was a normal decoupler. Works well, no more worry about the boiler staging down quick enough for low flow in the secondary loop, which has been known to trip these style boilers on high limit.
These are the tanks,
http://media.wix.com/ugd/88b2fd_5a2428b066e247dfa522f9e3dec87df5.pdf

Paul S_3

do I have the boiler maintain tank temp only? I'm designing 4 zones in total with indirect...2 baseboard zones....one zone under tile radiant with 3 way iseries with tstat...one zone under tile radiant for all 2nd floor bathrooms with another iseries 3way but this will be constant circ. buffer 2 pipe method. just want to know best way to control it....smallest zone is the constant circ its really for floor warming....smallest zone with tstat is 18,500 btus....boiler is laars neotherm 80....thank you

wogpa67

I use the 256 on buffer tanks.

Paul S_3

So just install supply sensor from the 256 in a well on the buffer...and use the outdoor sensor with the boiler as well

wogpa67

that's what i've been using for years. Geo , infloor, micro zones. Doesn't matter. Your zone panel will energize the heat demand when needed to fire the boiler. Otherwise it draws off of the tank until the differential is met.
Plus you have all the settings in the 256 to adjust to that small or radiant zone.
What type of system is this going to be used on?

Paul S_3

Gas fired 80k modcon....2 basboard zones (3)infloor radiant zones...two with a tstat...one on constant circ( for all bathrooms on 2nd fl )....all with taco 3way iseries....there will be an indirect....i will use a 25 gallon thermocon from caleffi....i have 4 small bathrooms on 2ndfl that will have radiant in floor that is my smallest zone....when you say my zone panel will turn on boiler when needed how is that wired?what control do i put on tank with a differential or is this the differential on the 256?...never used a buffer before and want to give my customer most savings with the least short cycling

wogpa67

ok this all depends on the boilers inputs.
What boiler are you going to use?
The dhw will come off of it as it's own zone.
Let me know what boiler you are going to use, I'll pull up the specs on it to work it out with you.

Paul S_3

Laars neotherm 80k....indirect before the zones, off boiler loop with priority ....boiler modulates to about 15k btu...well above the 4 bathroom heat losses..each bathroom will be in a bedroom....i really want to use the bathrooms mostly for floor warming there will be baseboard in the bedrooms sized at a lower water temp lets say 140f

hot_rod

Some good control info here, along with piping and wiring schematics.
http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_14_0.pdf

I think the system on page 63 is close to what you have in mind. There are plenty of ports in the buffer tank to insert a well and the boiler operating sensor.

The Caleffi Gen 2 controls have even more features to help with these type of systems, like an end switch attached to zone one for multi temperature systems.

Paul S_3

Could i use this with the 2 pipe tank setup

hot_rod

sure, the control logic will be the same regardless of two or four pipe tank connections.

Paul S_3

Thank you hotrod much appreciated