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A few questions on my hydro air setup

giantsean Member Posts: 61
Hey All,

I have a new hydro air setup and have had enough problems with my installers that I basically cut them loose (problems ranging from leaky ducts to mismatched boots to "forgetting" to install a filter in my attic air handler). I am thinking about how to correct everything they messed up myself. Most like swapping ducts/boots is easy enough, but I could use some sound technical advice on some of the other items. Fortunately I don't think any of it needs special tools and most is within the realm of possibility of doing.

Background - 2 x Trane/AS AAM7/TAM7's with factory hydro coils (1 basement, 1 attic, 2 story home - 2 ton cool/42K heat down, 2.5 ton cool/50K heat up ), Navien CH-240 combi boiler

1) The first problem is that when they plumbed the hydro coils, they did so backward (hot water goes in the out hole and cold to the in hole - doesn't sound like it maks a difference in a closed loop but there is an actual "right" way that apparently makes a difference). I'm pretty adept at PEX connections so right now the only thing I need to worry about is how to drain and refill my system without leaving a whole bunch of air inside. Draining should be fairly easy, and the boiler will refill the water by itself once I re-open the auto-fill, but how can I be sure I am getting all the air out of the system? The system does not have any bleeders. It does have an air remover in the piping but that's in the basement. I'm going to need to ensure no air in the coil/lines that are all the way in the attic. Is it as easy as closing the gate valve on the return and just running water into it until all the air is out?

2) The zone controller they gave me does not support multi-stage heat (it's also for a heat pump so it always reads "EM heat" when it's on lol), nor do my thermostats currently. However the TAM7 does. W1-W3 are currently jumpered so as to give me max CFM (I did it, not them). I know multi-stage heat is more for heat pumps with supplemental electric heat coils, but can/should a hydro install also take advantage of multi-stage? If it is seldom done I'll just let it go (and save a few bucks on a new zone controller and stats in the process)

3) I also have the problem of the handlers blowing cold when the boiler makes a DHW call. The AAM/TAM7 has an aquastat on the supply inlet of the coil (currently piped backwards, but will be right once I switch them). Does anyone know what this thing does for sure? It may be telling the system something but it does not appear to be to shut down the fans. If so, what is the proper method of installing a third party aquastat that will shut down the fans when the supply water gets too cold?

Sincere thanks for any help! It's hard to get any sort of support from Trane/AS unless you are a dealer. In this case I'm not trying to take money out of anyone's pocket. I already paid lol



  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    1) the basement piping should be such so water can be forced thru the loop and push air out a drain. Yes, the supply orientatation nmatters on the TAM7.

    2) Not sure of your control strategy but A/S has a dual fuel kit to accomplish what you want.

    3) The DHW appears to be on priority, stopping flow to the TAM's, they still see a heat demand. If the air is bothersome in that period, un-prioritize the DHW and see if there's any negative effect on recovery. Would not mess with auxiliary aquastats, the 925 HW control does so much. Make sure the dip switches are tailored to the TAM model and the delays are right for you.
  • giantsean
    giantsean Member Posts: 61
    Thanks Bob. I have attached a couple of photos of the setup. The Tacos are running on the supply side. With this setup, would closing both the large gate valves and opening the drain eventually force out all the air? I read a trick from an old timer about attaching a hose into a bucket either outside or in a sink, running the circulators, and watching for when the bubbles stop, then closing the drain when done. I am not sure if I have to increase the pressure while doing this

    As for the dual fuel suggestion - I do not have (or plan on getting) a heat pump. This is just to see if the TAM7 with a hydro coil will work in a multi-stage (individual W1-W3 calls) setup. If I'm reading it wrong, my apologies :)

    Finally yes, the Navien puts DHW on priority and there is no way around it unfortunately. I am not familiar with the "925" you mention... is that part of the TAM7 controller? At this point I'm just looking for somethign that will tell the TAM7 to stop blowing... if I only shut off the circulators it will still try to blow cold air. Ain't technology grand?

    Thx again!
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    Your purge valves are the yellow getups on the return pipes. The valves get closed and the drains opened to push air out and until you get a solid, non burbling stream of water. The problem I see is the installer used the Nav boiler feed tap. It's a real pain to purge at low pressure thru this method. Far better to feed it conventionally at the expansion tank junction, with a typical water feeder that lets you "fast fill" at house water pressure. As it is, you'd have to back feed the heat loops via a hose going from some cold water tap to one of the heating drains on the secondary loop. Annoying. If you're successful in purging as it is piped then let it be.

    I see the 925 control in the HW coil section. Tailor it to the TAM7 model re CFM in heating. I took it that you had a HP. If you didnt jumper W'S, as you discovered, the blower wouldn't ramp up.

    Correct. There's no interface between a DHW call and blower operation here. Is this an NCB?
  • giantsean
    giantsean Member Posts: 61
    edited September 2015
    Ah I see. In that case does the air come back through the supply side (as it has nowhere else to go?) and through the secondary loop then up and out the yellow drains on the return? As for that loop in general, what's the purpose of having two large gate valves and two drains in the first place? Just curious is all.

    if the 925 is what the manual for the coil kit calls the Hydronic Control Board, yes it does have some DIPS and the supplied aquastat attaches to this board (see attached pics). I did not see anything in the manual to indicate it could be tuned to turn off at a particular temp - I think it was just to ID the air handler sizing. Interestingly the manual for the board and the manual for the coil itself seem to have a contradiction in graphics... the coil manual shows the inlet clearly but the board manual tells you to hook up the aquastat to the inlet BUT show it on the outlet pipe in the illustration. If you know of any resources that I could use to further tune it, that would be outstanding

    If by NCB you mean the Navien Combi model, it is a CH series not NCB (for better or for worse :P). So the $64K question is now how to establish an interface that will kill the heat call when DHW calls are active. That question originally led me to the external aquastat question but if there is a way to do so with what I already have, also fantastic

    thx yet again!
  • giantsean
    giantsean Member Posts: 61
    sorry as per last post