I would like to replace the line voltage thermostat that controls the circulator pump on my hot water heating system with a programmable one. I found the Honeywell TL8100 (http://www.forwardthinking.honeywell.com/products/thermostats/thermostat_products.html) and even called Honeywell for a recommendation and the overly polite Indian gentlemen informed me they were only trained on resistive and not inductive applications. Anyone offer other suitable thermostat recommendations?

It would not be a problem at all if you use a relay between the stat and the pump.

What is a relay? I wanted to install the same type of thermostat. I have hydronic heat with fan-coil heaters and was considering installing the HWP 120 by King Electrical. You can see the thermostats here:
http://www.king-electric.com/hydronics.asp

Will I need to use a relay?

It would not be a problem at all if you use a relay between the stat and the pump.

If you mean for a low voltage thermostat, the problem would be sourcing the relay and 24V power supply, mounting them somewhere, and then running low voltage wiring back to where the thermostat is currently mounted, but maybe I'm making it harder than it has to be. Would this be the type of thing Lowe's or Home Depot would have sitting on the shelf?


...was considering installing the HWP 120 by King Electrical...

Those look like what I'm looking for.


What is a relay?

A relay (http://en.wikipedia.org/wiki/Relay) is an electromechanical (or solid state) switch that allows a small current flow to control a larger current flow. In an HVAC application, a low voltage thermostat (24 V?) would control power to the electromagnetic coil of a relay which when energized would close a set of contacts that complete a circuit to power a larger load, such as a 120V or 240V motor. The advantage of this type of control is large power wiring does not have to be run to the thermostat's physical location. It may also simplify and reduce the cost of the thermostat as the electrical components that comprise the thermostat do not have to be sized to handle the current draw of the large load.

To start with there is not a real big selection of 120 volt thermostats so I thought it would be better to have a larger selection and to do that you have to go with 24 volt units. The relay is added for two reasons. First to remove your fears of overloading the 120 volt thermostat with a motor load. Bt adding a relay you can buy a relay that will take any load you could impose all you have to do is pick one that is rated as high as you need. The 24 volt transformer or wiring is not a problem and you could actually use something like a fan center and a 4X4 handy box to add a 24 volt control system which would allow you to use a low voltage transformer and a relay at the same time. I use this setup on my boiler here at home.

The gismo as pictured is called a "fan center". There are a few specs that you need to be concerned with like # of poles and primary voltage(s).

He has 120 volts available at the boiler and the fan center pictured has both normally open and normally closed contacts and that is all he will need to run his pump is the normally open contacts since the thermostat will close the relay contacts on a call for heat.. This will work out well if he wants to use a 24 volt thermostat.

They are cheap also and it has a 3/4 hp relay rate so it will service that pump

NEWWHITE ROGERS FAN CONTROL CENTER 90-113 - eBay (item 250530262211 end time Dec-13-09 13:34:36 PST) (http://cgi.ebay.com/NEWWHITE-ROGERS-FAN-CONTROL-CENTER-90-113_W0QQitemZ250530262211QQcmdZViewItemQQptZLH_Def aultDomain_0?hash=item3a54c46cc3)

I like this idea more now that I've slept on it as this option would allow also me to reuse any thermostat I purchased when/if I update the burner/boiler as I remodel the house. I'll have a look at the pump motor when I get home tonight, but I think it is only 1/4 or 1/3 H.P.

You can take a look at Honeywell's focus pro series, Vision Pro series and the Prestige series of thermostats.


The Prestige is a pretty bizarre stat. http://customer.honeywell.com/techlit/pdf/PackedLit/69-2057EFS.pdf

I think it can control the temp based on where the remote is.

Honeywell Prestige is nice but too much money. Venstar remote is cheaper and just as good. But for this guy a regular priced digital will work just fine.

any thermostat I purchased when/if I update the burner/boiler as I remodel the house.

If you change over to the 24 volt system you will be able to use just about any digital thermostat out there or any standard unit for that matter.

Honeywell and White Rodgers don't even come close to the capabilities that the programmable PECO T180 has. The stat can range from 24VAC to 277VAC. This product is rather elusive on the web, but I did find one source at http://thermostatlinevoltage.com

Overpriced junk.