Outdoor reset

[Deleted User]

I have a WM HE-5 boiler, nat. gas, running fin tube and CI zones with Honeywell ZV's. I am not taking domestic hot water off the system and the only future plans for the system is poss. add some floor warming and set up for constant cir. I would like to first add a outdoor reset to the system. What make and model do you recommend for my needs?

Bob Haley

Outdoor reset

Both Argo and Taco make outdoor reset controls which integrate easily with their circulator relay panels. My experience has been that they are appropriate with cast iron baseboard and radiators but fin tube ought to be run of high temp if possible.

Bob Haley

Outdoor reset controls

Both Argo and Taco make outdoor reset controls which easily integrate with their circulator relay panels. We have had good luck running cast iron baseboard and radiators with reset but fin tube should be high temp if possible.

[Deleted User]

What little fin tube I have will be replaced with panel rad's for a higher output. I have read alot about Taco, but what model # would best suit my needs?

Larry (from OSHA)

Fred

I also have a Weil Mclain HE5 series 2 boiler with fin tube convectors. I added a Honeywell AQ475A reset controller last season and saw improved comfort and economy. The output of the fin tubes drops off quite a bit as supply temp decreases. However, during shoulder season we have been very comfortable with supply temps in the 150 - 160 range. Some points you need to consider are prolonged return temps below 135, as flue gas condensation could be an issue. I suspect that it would not be with the baseboards. The Honeywell unit works well for an inexpensive unit, but with your future plans for radiant, you might want to look into a Tekmar control.

I am only a homeowner, so I suggest that you consult a pro to assess your situation. Best of luck.

Larry

Bob Haley

Reset controls

Taco PC700, Argo DPM-2. Both have adjustable minimum setting

Jay_12

tekmar 256

Hello Fred,

Consider using a tekmar Boiler Control 256. I have attached some application drawings to this posting.

A mixing control for radiant floor heating can be added at a later date. Suggested mixing controls are tekmar 356 or 360.

If you have any questions, please contact me.

Jay www.tekmarcontrols.com 250-545-7749

[Deleted User]

Thanks for the replys, the Taco pc-700 & Tekmar 256 are the units that I have been considering. My son in law that is serving his apprenticeship with a local company feel confident that he can install the reset. Not that I dought him but I am just checking thing out. I am leaning towards the Tekmar just because of what I have read here. One question , would the cir. relay on the WM be compatable with eather of these units or should we install a rely of the same manufactor?

Jay_12

relay

Relays can have either have a 24 Vac coil a 120 Vac coil. The application drawing A256-2 shows a 24 Vac coil relay.

Your Weil-McLain relay may be reusable if you can determine the coil voltage.

If you are unsure about the existing relay I would suggest installing a tekmar 003 24Vac relay.

The relay is required since the 256 may determine that the boiler is still warm and will not activate the boiler burner. The relay ensures that the boiler pump activates when a zone calls for heat.

Jay

Reynz_2

Reset Curve

Is it true, that if the reset curve is correctly set to adjust heat input for the higher temps (35*-50*) that, in theory, it should be correct all the way down to the lowest set temp? Meaning if it works great at 35*, should it also work the same at 10*, if the curve is correct?

Roger M

Reset Controls

Take a look at the Caleffi iRadiant controls. This has a self adjusting curve so there is no guesswork and callbacks. Automatically adjusts the output based on both outdoor reset and indoor feedback. A curve based on outdoor temperature cannot take into account the actual thermodynamics of the indoor space. Without the indoor feedback feature you're guessing. I've been at this for 25 years and believe me, this is the easiest reset control system I have seen. Look at the web site at caleffi.com and then go to the US section. Click on iradiant controls in the building automation section.

Roger M.

george_17

Roger, the Caleffi U.S. National Distributor perhaps???

Jay_14

reset curve

If outdoor temperature was the only factor, then setting the reset curve should work at all temperatures.

However, due to other factors such as wind loading, solar gain, internal heat gains, ect, the reset curve may provide too much or possibly not enough heat for the building.

Also consider that heat output of heating terminals units is not linear. tekmar compensates for this by bending the reset ratio, thus we call it a heating curve.

Indoor feedback can correct for all this. Basically a signal is sent back to the heating control (boiler or mixing device) to adjust the water temperature. tekmar makes several controls that use indoor feedback.

If you are interested on more info on outdoor reset, tekmar can some great essays on it at www.tekmarcontrols.com
Click on downloadable literature and then click on E brochures.

Jay www.tekmarcontrols.com 250-545-7749

Reynz_2

Reset

Thanks Jay!