Hydro Air Issues with Viessman Boiler

Steltz

Hi all,
I’m having some peculiar issues and would love some help with all of this. I’ve had several different people in and looking for some definitive guidance.

First, I have a Viessmann 100-W B1HE-199, combi boiler. The hot water zone is connected to a 50-gallon indirect hot water tank. For my heating zones, I currently have two hydro air zones set up that feed two air handlers (American Standard/Trane TAM7 – installed 6-7 years ago). One right next to boiler in basement and serves the first floor, and the second air handler is in the attic, which serves the second floor and attic (2 bedrooms in attic).

I am in Westchester, NY. Since the beginning of the heating season, the air handler in the attic isn’t working right and is barely blowing (stuck in a low mode). There were a variety of errors, which led us to think there were some circuit board issues. The hydronic control board is on back order, but I managed to find one on ebay. Long story short, the guy who installed the system initially thought there was air so he purged everything and did a refill (installed air handlers years ago, not the boiler, which was last year). And the heat was actually blowing this past Friday when he left, so he thinks air in the system was messing it up. Of course, this is the coldest weekend in New York this year and the house can’t keep up. Half of the 1929 house is non-insulated. And the upstairs zone has since stopped blowing (so it stopped within two days of the purge/fill fix). And to be clear, the circulators are working, and hot water is getting upstairs. But it seems air is in the system creating some kind of issue where the system stays on a low blowing mode (apparently air gets in the system somehow). The boiler was installed April 2022, so we've had a whole season of heating. Part of me thinks the air handler is the issue and not necessarily too much air in the system.

Second issue, though not as big of an issue, I have is the pipes for the first zone on the manifold (which is the upstairs air handler) gets much hotter than the second zone (which is the downstairs zone). And so, to account for this I have to throttle the shutoff on the supply (you can see in the pictures) so the second zone gets enough hot water flow. Otherwise the downstairs zone (second) does not get enough 180 degree flow to really warm up the coils. Everyone who looks at this says it doesn’t make sense, but there is no question it’s happening. I can grip the second zone when the first’s zone supply shutoff is fully open (and that first zone is super hot).

Currently, the circs are on the return lines. The HVAC installer who bled the system the other day said they should be on the supplies (he did not install this boiler). What I am looking to do is modify the manifold setup to hopefully address the upstairs air issues and optimize this setup for air scrubbing and serviceability. I can do this work myself, but would like some setup guidance from the wise community.

Thoughts on changes/upgrades:
1. Move circulators to supply side (this is my main concern that this is creating air pockets being on the return side).
2. Add Spirovent Jr. on the supply after the low loss header (open to less expensive options but really just confused)
3. Add filter at end of return line before low loss header (mainly want to do this because I’ll be adding an old cast iron radiator as a zone in the basement, and while I will flush it there will still be junk in there no doubt). Welcome suggestions on filters
4. Add shutoff and drain to bottom of the low loss header.
5. Add a T with an air vent (if appropriate) and maybe a pressure gauge to top of low loss header.
6. Add a T with a shutoff valve (for serviceability) and a temp/pressure guage to the expansion tank.
7. Add pressure/temp gauges on the supply and return if appropriate. Welcome guidance here
8. Please confirm I only need drains on the return lines.
9. And lastly, is it important that my Indirect have its own circulator? Currently it's running off the boiler. It's a relatively short loop (maybe 6-8 feet not including what is inside the tank).

Very much appreciate all your advice and help in advance. This is becoming a very stressful issue in the house....
Thank you,
David

Redbaran

Your cheapest way to add an air eliminator is to remove the coin vent in the top of the low loss header and add a float vent - tape and dope the nipple going into the low loss header; I believe the female tapping is 1/2" parallel thread. You should have a pressure gauge under the relief valve on the top of the boiler. If you are losing water in the upstairs zone you should "see" it on the pressure gauge; as long as you noted the pressure when it was running. Isolating is always a good troubleshooting tool - run just the upstairs loop to the air handler (make sure the indirect is satisfied and turn the thermostat for the first floor all the way down). With the circulator running for the upstairs air handler, feel the supply and return piping. If the air handler is not running you should have a relatively small temperature drop (just loss to ambient in the space the piping runs through). Big air issues are no heat; partial air issues show themselves with water fall noises in the piping. If the indirect is connected directly to the middle tappings on the bottom of the boiler you are using the internal circulator to load the coil in the indirect - this works well; especially if the pressure drop between the boiler and the indirect is relatively low. There is a three way diverter valve, so when you are in DHW production; no boiler water is flowing to the low loss header. This can be an issue if there are large DHW draws that "time" out the heating side of the system. 199,000 btus available to a 53 gallon indirect should make for pretty quick recovery time which would then switch back to heating (flow to the low loss header)