Pump Speed when Boiler Fires

hydronicsmike

If you could provide more info, that would possibly allow me to help you. Which Control do you use and what is the piping like? Can you provide a Piping Diagram by chance?

Could it be flow related? IE: Pressure (Ft of Head) Change? Thermal Actuators?

Or, just call tekmar at 250-545-7749 or Taco at 401-942-8000.

Best Regards,

Mike

Neil_5

Taco 007 Pump Speed

I have a gas fired hot water boiler installed Sept. of last year. All is well with the system but I noticed the following:

I have a Tekmar with the system and have notice that when the system goes into motion to fire (damper open etc) the pump speed tends to be faster? I can feel the pipe vibration increase and also the supply temp. feedback start to drop significantly.

An example: the traget temp is 175, boiler reaches 177 and shuts off. Circulator is on (stat calling for heat) the supply pipes are hot and convectors are coooking etc. The supply temp drops down to 176, 175 slowly, now say the temp. is at 164 and the Tekmar fires the boiler, at this point I see the supply temp. dropping off rapaidly as the boiler fires up and can feel the vibration on the pump increased.

Does the pump have two speeds? How is it possible for the flow to increase?

Thanks,
Neil

Neil_5

More Info

Mike:

Thanks for your info: some more on my system. Tekmar 256 unit, bascially I am reading the temp from this unit. No thermal actuators as far as I know unless they are inside the boiler. Units is a Burnham Series 2 gas fired boiler (M/N 205). Unit is plumbed very simply, circulator on return, into boiler and out from supply is expansion tank. Pressure reducer and LWCO etc. No bypass loop. For some reason when the system fires up the feedback temp from the Tekmar drops rapidly vs when the circulator is on alone, the supply temp drops slowly. Its like almost like the pump speed increased.

Neil

hydronicsmike

Interesting...

Does the Main/Boiler pump run all the time / permanently?? Does the Boiler ever short cycle (seconds vs minutes)??
The 256 does not operate a pump and can therefore have nothing to do with what you're seeing.

Does the pump get quite hot when (as you put it) the system is NOT fired up?? I am wondering if you are using Zone valves maybe and if the Pump is dead heading while there is no call. That would almost explain it. It seems like something is opening up on a call for heat, causing the temperature to drop. Have a look and see what is wired to terminal 7 on the 256 Control and tell me what it is connected to. If it is jumpered to terminal 9 and if you have Zone Valves, I would almost expect to see what you are describing and notice the Boiler Short Cycling. Got more info?

Either that, or just call me. 250-545-7749, Ext. 214.

I'll try to help as best as I can.

Regards,


Mike

Neil_5

Mike:

I appreciate your effort and time.

The unit is not constant circulation, the STAT is connected to thh zone valve and the output of the zone valve goes to the 256 and turns on the circulator when it receive a call from the stat. So the ciculator turns on when the zone valve opens.

The circulator is cool to touch all the time. Boiler is not short cycling, usually about 5-10 mins on and off about 15-20 mins depending on temp.

For some reason when the damper opens and the the sequence are lined up for the boiler to fire, the supply temp as indicated on the 256 drops off.

When the boiler shuts down and circulator is on, I do verify that the zone valve is still open (the manual arm is loose).

I have 2 zone valves, one for the main house and the next for the basement, MAYBE (will check tonight) when the boiler fires up, MAYBE its wired to open the second zone??? I have to verify that the second zone is not turning on when the boiler fires up.

Regards,
Neil

Neil_5

Second Zone

Does not turn on as a possible problem mentioned above ...

h-m-m-m-m

hydronicsmike

Neil,

If you call me, I may be able to help you further.

Mike

Joe Mattiello

Single speed

Hi Neil
The Taco 007-F5 is a constant speed circulator. However the flow characteristics will change based on the system dynamics. For example if zoning with zonevalve, 1 007 and only 1 zone is calling for heat you might get slightly more flow, then if all the valves were open. Centrifugal pumps are variable flow variable torque, but the speed is constant. Taco has recently introduced a couple of variable speed pumps that can vary flow based on outdoor temperature, or a set point temperature. For your reference I have attached some literature to read during half time of next Sunday’s game. Go Patriot's!!

Taco, Inc.
Joe Mattiello
Technical Service Technician
joemat@taco-hvac.com
401-942-8000 X 484
www.taco-hvac.com

Neil_5

Zone Issue

Joe:

That is a possiblity to my "temp flux" if you may. Will note if one or both zones are open and how fast the supply temp dips in each case.

Thanks for the info.
Neil