Model 700. The water runs constantly while the furnace is on despite what the humidistat is set to. Can you give me some tips on how to fix?

Is this a newly installed unit it sounds as if there's a wiring issue. Could you show a picture of the wiring terminals. If this is not a new install try turning of your furnace fan.

It sounds like it is just miswired. The low voltage wiring off the humidistat should be on W and C on the circ. board at the furnace. If you have it on R and C then it will power it constantly regardless if the heat is running or not. W is only energized on a call for heat which is typically when you want that type of humidifier to run

Hope this solves your problem, look for the humidistat, it should be located on cold air return duct near furnace, make sure it is not set in the on position, if it is, then this is why it is staying on, please set humidistat any where from 20 to 35%, never over 40%. If the humidistat is set properly and is still running, you may have a electrical problem, humidifier circuit should only receive power(24 volts) when the indoor blower motor of furnace receives power, also if you have galvanized plumbing in your home, you may have a piece of rust or lime deposit in the humidifier solenoid valve preventing it from closing, turn water off to humidifier and disconnect water supply line entering solenoid valve inspect & clean protector screen. Good luck.

Neither, even if the solenoid or humidistat stick, it should always drain properly. Is the unit mounted on the cold air return duct or the supply plenum? If it's mounted on the supply plenum, the water panel might be getting blown forward and spilling the water. High efficient furnaces also can leak water on the floor if its drain is restricted. If hum. is mounted on return duct make sure drain is clear by blowing through it. On Honeywell hum's I've seen the rubber hose from the solenoid valve to the distributor tray leak too, check the rubber 1/4" hose.

Have you measured the amount of water dripping into the drain? The specification is 1 quart in 2 and half minutes. If it is much less, get your solenoid checked. I had the same problem and got it replaced and it works as per specification now. You also need to see how many minutes in an hour your furnace is actually running. The humidifier runs only when the furnace is, so the more it runs the better. The specification is 35% with the furnace running at 70%.

the 760 humidifier does not need a transformer wired externally. the 760 has its' own 24v transformer inside the fan compartment. this transformer will provide the power to enrgize the water solenoid as needed. it sounds like to me the additional trasnformer is hot all the time. when the furnace comes on, the unit gets power and the internal transformer is cancelling the power from the external transformer. this would explain why it quits running when the heat is on. since the external transformer is hot all time, when the heat shuts off, the solenoid is getting energized by the external transformer. to make this run correctly, you need to get rid of the external transformer. leave the humidifier high voltage wires hooked up so they are only hot when the furnace runs. if you have a humidistat that has a r and c terminal, you will need to wire these directly to the r and c on the furnace control board and move the switch inside the humidistat to "power". make sure it is not on "bypass". then wire your 2 brown wires from the humidifier to each of the "h" terminals on the humidistat. if you have a humidistat that only has 2 terminals, wire one brown wire to each of the terminals. this should allow it to run properly.

the humidistat on this unit just acts as a set of dry contacts. with the humidifier plugged in, you should be able to touch the 2 brown wires by the water solenoid together and get the power fan to run and the water solenoid to enrgize. if you do this and water does not flow, you most likely have a bad water soenoid. it is either electrically bad, or just plugged with water deposits. sometimes you can pull it apart and clean it, sometimes you just have to replace the solenoid.

Thanks for your question,
Sounds to me like you have a bad solenoid valve in your Humidifier, this will need replaced, the solenoid is supposed to open and close when there is a call for humidity only when the furnace is running, then when the proper amount of humidity is sensed by the humidistat, then will it shut off, with the solenoid not working it will let water flow through like an open faucet, the solenoid is the componet that the 1/4in copper tubing connects to at the humidifier, has two wires running from it, you will need to shut the power off before changing this out, also shut the water off at the valve at the other end of the 1/4in copper line, or you might get soaked,please be careful when installing the new solenoid, making sure the water line connection is secure, or you will have leaks, hope this was helpful, please leave a rating, thanks again for your question,
mr.grzz

You want the humidifier to run in heat mode which is the r-w1 terminal on the stat.