New condensing boiler cycling too much

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  #41  
Old 01-19-13, 10:54 PM
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Questions....
( Because I forgot)

Whats your system PSI? Should be 15 psi cold min on that boiler.

What speed is the boiler pump on? Should be on the highest i believe. Or speed 2.... You need 10 gpm through that boiler I think.

Whats the temp difference or delta t on the system side.?

Is the DHW circ hooked up to the terminals in the boiler? Thats where it should go.

I could barly see the gas line to the boiler. Normally its a 3/4 inlet at the boiler. Thats would mean it should be piped all 3/4. Looks like you have 1/2". Possibly the unit can starve for gas.....

ODR hooked up right?


Next we will need to look at your settings......
 
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  #42  
Old 01-20-13, 12:24 PM
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Whats your system PSI? Should be 15 psi cold min on that boiler.
Pressure is at 15 psi cold. The auto fill valve is set at 12 psi.

What speed is the boiler pump on? Should be on the highest i believe. Or speed 2.... You need 10 gpm through that boiler I think.
I have the Grundfos UPS26-99Fc set medium speed -- recommended for PF-110 for a delta T of 20 degrees. I believe this setting provides the 10 gal requirement.

Whats the temp difference or delta t on the system side.?
The digital readout on the boiler often shows a delta T of about 15 degrees during the first few minutes of operation -- but this depends on the zone and the programmable thermostat (I lower the temp at night to 65). The return slowly creeps up to the return temperature up until set point is reached. Then the cycling begins.... temperature slowly drops down and then ignition and then set point is soon reached.

Is the DHW circ hooked up to the terminals in the boiler? Thats where it should go.
Yes, the DHW is connected to the boiler directly. When there's a DHW call, the boiler shuts off the CH circulators and gives priority to the DHW. After the DHW is satisfied the CH turn back on, if calling for heat.

I could barely see the gas line to the boiler. Normally its a 3/4 inlet at the boiler. That would mean it should be piped all 3/4. Looks like you have 1/2". Possibly the unit can starve for gas.....
The boiler came equipped with a preinstalled 1/2" gas c.o.c.k. Since it was preinstalled, I didn't question it. There's less than a foot of 1/2" pipe from the 1/2" valve at the boiler that feeds from a 3/4" pipe.

Moving from the 1/2" pipe to the gas meter is 2' of 3/4 pipe, 18" of 1" pipe, 3' of 1 1/4" pipe, a 3/4" x 3/4" x 1 1/4" elbow, one run of the elbow feeds the stove and dryer, whyle the other run goes to a 5" nipple that finally feeds the 30" x 1" pipe to the meter. I was thinking of removing that 3/4" nipple -- seems like an unnecessary choke point.

ODR hooked up right?
Other than today, the ODR ALWAYS read the outdoor temperature correctly. I have a outdoor digital thermometer which I can compare to.

Odd thing... at the present moment, it's 54F outside but the sensor is reading 75F. The sensor is located on our western wall, but it is shaded. It's sunny now (2 pm) -- perhaps the vinyl siding is affecting the readout. I can fish a wire and reinstall the sensor on our northern wall in less than an hour of work, if needed.

Next we will need to look at your settings......

This is how the boiler is set (begins on p 40 in manual)...

http://www.peerlessboilers.com/Deskt...hod=attachment

BOILER
1] Mode 2: Manifold for pump for DHW
2] Location: US (default)
3] Vent materials: PVC (default)
4] Freeze protection: starts at 50F (default)
5] Blower Post Purge Time: 30 sec (default)
6] Safety Functions: Set for Low Water Cutoff (I did not install a LWC) (default)

CH SETTINGS:
1] Mode 1: Thermostat and Outdoor Reset
2] CH Pump: Post Purge Time: 1 min (default)
3] Gen Circulator Post Purge Time: 1 min (default)
4] Ramp Delay Step Modulation: On
5] System Type: Finned Tube Baseboard
6] Warm weather shut down: 70F (default)
7] Reset Curve Design: Boiler = 180F, Outdoor = 17F
8] R. Curve Mild Weather: Boiler=140F, Outdoor=70F (default)
9] Reset Curve: boiler min = off, boiler max: = 195F (default)
10] Boost function: temp=18F, time=20min (default)
11] Anti cycling: time = 3min, Tdiff=30F (default)
12] Max allowable CH rate: 50%

DHW SETTINGS:
1] Mode 2: DHW Store with Thermostat
2] CH/DHW Switch: Time: 30 min (default)
3] DHW Heat Dump: ON, Max time= 1min, min Diff: 5F
4] Max allowable rate: 65%

The digital display of the User Menu shows the following:
System: 14F (It's always 14F -- I don't have the optional system sensor installed).

Thanks!

Lowjoules

 

Last edited by NJT; 01-20-13 at 04:13 PM.
  #43  
Old 01-20-13, 01:43 PM
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Odd thing... at the present moment, it's 54F outside but the sensor is reading 75F. The sensor is located on our western wall, but it is shaded. It's sunny now (2 pm) -- perhaps the vinyl siding is affecting the readout. I can fish a wire and reinstall the sensor on our northern wall in less than an hour of work, if needed.
You need to fix that. possibly the sensor is bad???

The digital display of the User Menu shows the following:
System: 14F (It's always 14F -- I don't have the optional system sensor installed).
That was optional??? It needs a sensor for the supply right? Is that reading correctly?

Its football tonight so I cant read all of your reply but I will revisit tomorrow...... Or later....







 
  #44  
Old 01-20-13, 03:42 PM
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Lawrosa,
Odd thing... at the present moment, it's 54F outside but the sensor is reading 75F. The sensor is located on our western wall, but it is shaded. It's sunny now (2 pm) -- perhaps the vinyl siding is affecting the readout. I can fish a wire and reinstall the sensor on our northern wall in less than an hour of work, if needed.
You need to fix that. possibly the sensor is bad???
the ODR seems to be reading correctly now (5:30 pm). Despite being in a shaded area, I think the indirect sunlight may have affected the reading earlier today. I'll move the sensor to the north side of the house tomorrow.


The digital display of the User Menu shows the following:
System: 14F (It's always 14F -- I don't have the optional system sensor installed).
That was optional??? It needs a sensor for the supply right? Is that reading correctly?
The boiler has a built in sensor for Supply and Return. Those seem to be operating. An optional System Sensor can be installed when using multiple boilers (Cascade system). p31 mentions the optional sensor, p48 talks about the multiple boilers. Diagram on p49 shows that the System sensor is used with the multiple boiler system.

Enjoy the game!

lowjoules
 

Last edited by NJT; 01-20-13 at 04:17 PM.
  #45  
Old 01-23-13, 08:23 AM
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Larowsa/NJ Trooper --

any thoughts on the the settings on my boiler? (posted earlier) Do you recommend that I change or tweak anything?

I've been monitoring the delta T the last couple of days. It seems to be about 11F for the first cycles during a heat call.

I also tried an experiment... I connected the basement zone (only 10k BTU) to the 2nd floor thermostat, which now turns on basement and 1st floor (25k BTU) at the same time. That seems to have knocked the cycling a bit.

thanks,

lowjoules
 
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