Wiring question for indirect circulator

ALH_4

You're right, any DPST cube relay rated for the load from Grainger will work. However it's easier to use an Argo 822 or Taco SR501 single zone relay which provide isolated swiches to call the boiler. Plus both companies are supporters of this site. ;-)

Charles_8

OK so now I need a relay...

Working out the control wiring now (steam boiler, tankless coil, adding indirect hot water tank).

I need the boiler to fire when either the thermostat OR the aquastat calls for heat. However, I only want the circulator pump to the storage tank to come on when the aquastat is cold, and shut off when it is satisfied.

The aquastat could easily control the 1/25-hp pump directly, but then needs a separate relay (to call for fire) whenever the pump runs. Any SPST relay would work, with a 115VAC coil and the ability to close a 24VAC 0.3 amp circuit, but it'd have to be in an approved box.

Another solution appears to be to have two "zones" (aquastat and thermostat) either of which can start the fire. But the Taco relays (SR501 or 502, for example) look like they'd turn on the circulator pump if either one calls? That's no good because the water in the tank would get too hot while the boiler is making steam for the house.

Please help me straighten this out. I am an EE among other things and have rewired many old houses in the last 30 years, so understanding the electricity isn't a problem.

I have little HVAC experience though, so I don't know what UL-Listed relay boxes are available...

thanks

-Charles

Unknown

The 501

has a set of "dry contacts" that you could use to turn on the burner.

Dave

Charles_8

One zone or two?

Yes, I saw that all the SR's have the T-T contacts, presumably the dry circuit to which you refer. That would go to the thermostat contacts on the boiler's control.

Initially I thought an SR502 two-zone relay would be required: The wall thermostat would be zone 1 (with nothing connected to its circulator contacts). The aquastat would be zone 2, and its contacts would turn on the pump. The T-T circuit from the SR502 in either case then would call for heat.

But on further thought, it *could* be done with a SR501 single zone, with both the wall thermostat and the SR501 outputs parallel-connected to the T-T control lines, Then the aquastat can trigger the SR501, which lights the fire independent of thermostat call.

But the simplest way is still the SPST relay, or DPST if the L2 (white) power line is broken along with the L1 (black). I could just mount a relay in a deep junction box, but is there a particular enclosure that is "legal" by code?

-Charles

Leo

Keep it simple

Charles,

Not being engineers we use what they (engineers) have designed and gotten approvals on. In this case the Taco or Argo as previously mentioned or the Honeywell equivlant. In order to keep the labor time down and use a warranted part we use the parts mentioned as they can be used in other applications also.
Hope this made some sense,
Leo

Hvacman

If you want a rated relay...

The good ol' RIB1 never lets me down...

http://www.functionaldevices.com/pdf/RIBU1C.pdf

Has it's own enclosure and a cute indicator light!

John@Reliable_14

Charles, keep it real simple............

From your last post I think you have a storage tank and not a in-direct. Real simple to control, aquastat at tankless will control burner, thermostat on new tank will control pump. When temp in tank is below set-point pump will turn on, when aquastat at tankless goes below setpoint burner will start due to water pumping thru tankless coil.Do them like this all the time