Sensor placement with a VT2218

[Cozy1234]

In Setpoint heat w/ boiler protection, can i place both sensors on the return side of my zone loops? I am zoned with circulators.

I believe this would allow me to set the boiler to 180, set the supply sensor to 160, and have the bp sensor at 140.

It should the run slow until i see the 140, then speed up to 160 giving me a 20 degree delta t over the distribution system.

Its my way of getting a 20 degree delta t, with boiler protection.

Anyone try this?

 

[Bob Rohr]

In Setpoint heat w/ boiler protection, can i place both sensors on the return side of my zone loops? I am zoned with circulators.

I believe this would allow me to set the boiler to 180, set the supply sensor to 160, and have the bp sensor at 140.

It should the run slow until i see the 140, then speed up to 160 giving me a 20 degree delta t over the distribution system.

Its my way of getting a 20 degree delta t, with boiler protection.

Anyone try this?

There are some piping arrangements out there that may be a bit misleading.

Here is the way to pipe a VS pump, along with the explanation, to provide absolute protection.

 

[Cozy1234]

There are some piping arrangements out there that may be a bit misleading.

Here is the way to pipe a VS pump, along with the explanation, to provide absolute protection.

Thanks Bob,

I dont have primary/secondary piping. Today, i have two zone circulators and a boiler bypass loop. It takes about 15 minutes to come to temp, which is unacceptable to me.

Based on the install doc (page 6) : https://s3.amazonaws.com/s3.supplyh...co-VT2218-HY1-FC1A01-Install-Instructions.pdf

"Set Point Heat Mode (with Boiler Protection (BP) option) (50°F - 220°F, default = 105°F, BP default = 140°F) In Set Point Heat mode, the VT2218 will start at the lowest speed. It then immediately switches to Variable Speed operation, increasing speed to raise temperature or decreasing speed to lower temperature and maintain the Set Point Heat target. If Boiler Protection (BP) option is used with Set Point Heat, the return sensor (R) will over-ride the supply sensor (S) and slow the pump down if boiler return water temperature falls below BP target (for example 140°F). Once the return sensor reads BP target, the pump will then speed up to reach the supply temperature Set Point target. In this mode the return sensor will read “BP” on the LCD."
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I feel like i should be able to put both sensors on my zone returns (of each loop before they meet common piping). The behavior i expect(and desire) is that:

1. Both zones are cold and boiler is cold
2. zone 1 calls for heat
3. zone 1 circ starts/ boiler comes on
4. zone 1 BP sensor detects low temp and slows the pump to min. speed
5. boiler heats up (cut off at 180)/ zone 1 BP reads 140+ and starts to speed up
6. zone 1 supply sensor reaches 160 (my setpoint) and circ speed varies to keep that based on distribution load
7. great, boiler came up to temp as fast as min. speed allowed it to (something much better than 15 min with my current 007e)
8. now zone 2 calls for heat (and is cold)
9. repeat 3-6 until both zones are hot.
10. I believe this should give me relatively fast boiler heat-up, 20 delta t and boiler protection.

Can anyone poke holes in this plan?