New hydronic AHU, no blower on heat call

TC83

Hey all,

My old r22 split system sprung a leak and forced me to upgrade. New system wiring has me scratching my head.
Tstat is ecobee 3 lite, ahu is comfort aire ahg60-0a, boiler is Weil McLain(existing setup up for 3 zone heat).

A/c works fine, as expected. Tested heating and this is the problem. The zone pump kicks on, boiler kicks on and ahu blower does not. I’ve waited 30s, 1min, 2min… thinking it needed hot water at coil to run, but that doesn’t seem to be the case. Boiler and pump do their job but ahu isn’t participating.

I contacted the manufacturer and inquired about a possible board issue, they had me jump the white ahu wire to the red and blower kicked on… they recommended I review my low field wiring.

Any insight on what I’m goofing up here?

ratio

IDK if the board is o supposed to turn on the fan itself during a heat call or if it notices hot water in the coil, but you should be able to set the stat up as 'electric heat', that will tell it to turn on the fan when it calls for heat. You can also add a relay to the W terminal (you'll need the C wire from wherever the Rh wire comes from) to turn on the fan, but that just moves the complications from stat programming to wiring.

EBEBRATT-Ed

You probably do not have a control to turn the fan on and off on heat. Simple way is a strap on aquastat which you can get at supply house.com. You need one that makes the contacts on a temp rise and breaks them on a fall very common issue. You wire the new aquastat to start the fan when the pipe gets hot.

But you could have other issues. What starts the circ pump? Do you have DHW off the boiler?

TC83

@EBEBRATT-Ed You're spot on. It WAS strapped on and junction box was dangling inside of unit.

I had my brother in law help demo the unit, while I moved and prepped new equip. He apparently just snipped wiring and hit everything with a hackzall, more or less as i asked him to. I called em, asked if there were any junction looking boxes or small boxes with wires spidering out and he said all small bits were in a cardboard box…. an aquastat and two transformers (one looked like an old one that was dead and left to rot)… I feel dumb now, but so grateful this forum is around to help with sanity checks. It was an L4008B, the old one switched 120v, i'll just copy and do that with the tstat wires now. Huge releif here. Thank you and @ratio for prompt responses. I seriously thought I had missed something on my low voltage wiring to boiler or pump.

HVACNUT

Does W from the thermostat go to W on the board? The freeze sensor looks like it's wired in parallel with W (from R on the other side of the board), so of your AC evaporator temperature gets too cold, it'll turn the heat on.

What is this White wire connected to? It should be W from the thermostat.

The simplest thing is to have the thermostat control the fan during a heat call. When going though the setup on the Ecobee, does it ask you "Thermostat or Equipment controls fan in heat mode"? It should. Or something to that effect.

If you have an electrical meter, you can check the fan speed terminals to see if you have 120 volts there. There might be a time delay in the board, so wait 5 minutes before checking. Can you check a manual to see what speed the factory setting is for heat?

If its in heat mode, and there's a call for heat, and the circulator is running, and the coil is hot, and there's no 120 volts at the blower speed terminals, then I'd think there's an internal open circuit for the fan in heat mode. I don't see an aquastat or temperature sensor for the hydro coil in the diagram, so we assume there isn't one. The board has Time Delay jumpers.

TC83

Yea, it does have a freeze sensor, but no, the white wire you pointed out does not connected to tstat. I believe that white wire goes to the blower molex plug. There is a white wire in that bundle there that does not connect to anything but is listed as w tstat wire from the AHU.

My current tstat wires for W and Rh go straight to the boiler aquastat for heat call and turn on circ pump, they dont come to the ahu at all. So, other than the tstat having fan turn on, i assume this board would turn it on or needs a field installed circ stat that @EBEBRATT-Ed and @ratio mentioned.

I can check the ecobee, but they;ve been installed for a few years, so i dont recall how to even get to those settings anylonger? perhaps just resetting the whole thing and setting up as new may solve this. I will try and update here. There was not 120v at molex plug in heat mode, but there was when in AC mode. I agree, i did not see any extra stuff like an aquastat on wiring diagram, which is why i assumed i goofed something or perhaps it needed to reach operating temp before kicking on, but this was not the case as i waited for several minutes and checked hw coil temp with thermometer and it was at approx 160F and nothing happening othat than boiler cycling off for setpoint.

I believe the time delay is for coil protection, before starting and after stopping. I tried moving them to 15 s and 0, while testing and nothing changed except in AC mode.

HVACNUT

Ok, so Rh and W go directly to the boiler from the thermostat. The old system must've had an aquastat on the coil to power the blower. The new one obviously does not.

I'm not too familiar with Ecobee, but I don't remember them being hard to navigate through. Go to settings, and scroll.

Or... if you can get a 2 conductor thermostat wire from the boiler to the air handler, it can be wired correctly using the boiler relay in the air handler circuit board.

TC83

@HVACNUT ill circle back once I get a chance to reset the tstat and go through the original setup prompts. I’d prefer not to add a circ aquastat to interface with ahu board and my tstat telling boiler to kick on… but $200 for the additional stat is far easier than fishing wire through finished spaces !

TC83

update time..

The old unit did what was recommended here. Photos below.

The ecobee does allow option for it to control the “furnace” fan, but only when under the ecobee pro menu’s. But wasn’t used in the former setup because the circ stat was providing power not signal.
This has been a great learning experience, I enjoy working with passionate and knowledgeable people. This place is an invaluable resource all is functioning now, the wife is asking why the heat is on now LOL!

HVACNUT

The only downside to having the thermostat control the fan in heat mode (instead of a time delay relay, or aquastat) is the fan will energize immediately, along with the boiler circulator. So for that first minute or two, the air out of the vents won't be warm until the hot water from the boiler gets to the coil. No biggie though.