Primary/Secondary & outdoor reset ,indirect+zone valves

polyj79

<span style="font-size:12pt">If  you had a primary / secondary piping

loop on a cast iron  type FHW boiler

with a primary loop pump and the supplied Honeywell aquastat relay, a

indirect water heater teed off the primary loop(parallel) with it own

pump and the supplied

aquastat controler/ thermostat ,  4  Taco zone valves on the secondary loop

with it's

own pump and  a

Weil Mclain WM-ODR .  How would you wire in the the FHW boiler system

pump to run all the time during any type of call for heat but cycle the

burner on and off with the ODR , plus  wire in the indirect water

heater pump and aquastat along with the pump for all the space heating? </span>

polyj79

Hand drawing of heating system

This is what the system looks like.

JStar

...

First, I would put the air separator on the baseboard loop. Then I would pump the boiler loop away from the common piping. After that, I only run the boiler pump when the burners are on.

Charlie from wmass

Contact weil

They have wiring diagrams if you do not have the installation manual any more.

Charlie from wmass

Why are you doing primary secondary if I may ask?

a variable pressure pump or a delta T pump would steam line your wiring and piping.I could see doing primary secondary if you were using pumps to the zones but not with zone valves.

EricAune

Maybe another control?

I would prefer to use a Taco ZVC406EXP & PC700 boiler reset control.



You will get the boiler reset will full function parameters in a simple plug-in installation, along with control for three circs. (system, boiler and DHW) along with extremely easy wiring of all zone valves and thermostats.  Add built-in diagnostics and its a pretty nice package.



**Edit**  I tried to attach pdf's for the taco pc700 and ZVC406 manuals to show diagrams....didn't work

polyj79

Reason for primary/secondary

Reason for primary/secondary is, It short cycled and I tried to eliminate it. What is the the best way to wire the system as it is now?

CMadatMe

Wiring

Simple....Get a Taco ZVC Relayy. Open the cover and the diagram is inside.

Main end switch to TT at boiler to run the boiler pump and then use the extra end switch to run the system pump. Wire your zone valve to the control as shown.



PS. Boiler is short cycling because it's too BIG! Real fix..Get the manual down fire if oil, as Eric said plug in the PC700 card and off you go. Treat the pri loop now as boiler protection if needed.

JStar

Just a thought.

Wouldn't p/s looping make the boiler short cycle even more?

CMadatMe

Your probably Right

It may but alteast if he get's it on reset he has a better chance of slowing the rate of shorts down. Boiler probably needs to be downfired if oil, may even want to throw on an heat manager. Don't know if its oil or gas he never said.

polyj79

DV 100 UTICA BOILER

I cannot reduce the input to this boiler.

I not sure but wouldn't  I wire the reset in the low voltage side of the boiler  ( in series with the  limit )?

Jay_14

tekmar House Control 400

You may want to consider the tekmar House Control 400. It's designed specifically for this type of installation. Simple two-wires per thermostat, has communication so each thermostat can show the outdoor temperature, and its cost competitive to a Taco PC control with a ZVC.

Here's link to the design guide:

http://www.tekmarcontrols.com/literature/acrobat/a002web.pdf



Jay @ tekmar

Dave in QCA

short cycling

The effect of the outdoor reset limits the water temperature based on outdoor temperatures.  This greatly improves performance on zoned by prevent wild swings on water temperature which can cause room temps to overshoot.  However, since you do not have a modulating firing rate on your boiler, the observed operating characteristics in mild temperature will be short cycling.  This is simply becuase the boiler has warmed up to the variable ODR set point. 

Dave in QCA

Similar System in 1985

I installed a similar set up in 1985 using standard controls.  There wasn't much available in the way of electronics at that time.  There was no secondary loop.

The boiler was a WM 350,000 cast iron boiler, installed ca 1967, connected to ample CI radiation with a B&G Model 2" circulator with a 1/6 HP motor. 

The house was 4000 sq ft, divided into 5 apartments with wildly varying heating loads because of different wall construction and solar gain in different parts of the building.  Fortunately, the piping ran out in 3 separate loops from the boiler.  I ran 2 additional return lines so that the second floor could be zoned in 2 separate zones.  Thus, I ended up with a zone for each apartment, situated as 1st flr North, 1st flr South, 2nd flr North, 2nd flr South, 1st flr back (only one story), and a zone for the domestic hot water tank, 6 zones total.  After the building was restored to a single family residence, the system continued to work very well.

CONTROL SET UP

I used 1" honeywell 2-wire zone valves with built-in end switches, honeywell round thermostats, an adequately sized 24v transformer for the zone valves, Honeywell T475A1032 outdoor reset control, a 24 volt/24 volt relay,  a 24v/115v pump relay, second 24v relay for boiler controls and and gas valve.  The existing B&G 2" pump was used.

Zone valves were installed on the return line.  Room Tstats were wired to the zone valves and 24v transformer.  The end switches on the zone valves were all wired parallel.  If any zone was activated, the valve would open.  As the contacts on the end switch closed, they activated a 24v pump relay.  This also supplied 110v to a second 24 transformer.  This second transformer supplied 24v to the boiler firing circuit, connected in series through the high limit, ODR, and gas valve.  As the boiler would warm to ODR set point, the ODR would shut down firing until the boiler cooled, but the pump would continue to run as long as any zone was calling for heat.  At any point, if all zones were satisfied, the pump and boiler fire would deactivate. 

I Set the ODR which had a 1:1 ratio at 90F.  Thus at 50F Outside, the boiler was 110F, -20F outside, the boiler was 180F. 

The difficulty in the set up is that an ODR controlled boiler will not heat domestic water unless it is VERY cold outside.  Therefore, I used an additional 24v relay.  The coil side of the relay was wired parallel to the zone valve serving the domestic water tank.  The N.O. contacts were wired in parallel to the ODR contacts, thus creating a short around the ODR and overriding it.  Therefore, whenever the domestic water tank called for heat, its zone valve would open, the relay would activate, and the ODR would not have contol.  Boiler temp would rise up as high as the high limit setpoint, 180F.  When domestic water was satisfied, its zone valve would close, the shorting relay would deactivate, and ODR would again contol boiler temp.



This system worked great, and continues to do so.  A subsequent owner decided that the boiler looked old, and installed a new WM, but the controls and valves are still in use.