aqua hot

Try giving the check valves a whack. sometimes they stick closed and stop the flow of heated fluid from circulating. You shoould see them just after the circulating pumps.

Usually the check valves for those cold zones are stuck shut. The easiest way is to whack them gently with a hammer to free them up. very common problem on Hydronic systems that are not cycled regularly on heat. You should cycle the heat zones at least once a month for a few minutes to prevent this from happening. Doug

I'll second rapping the check valves. I've had more than one stick. You can feels the pipe on both sides of the check valve to verify which one is stuck.

I will third that. Don't "beat on them" just a smack with the handle of a large screwdriver and depending on the ambient noise, sometimes you can actually him the "click" and then the flow of glycol. They will be coming right up out of the top of the enclosed unit and are merely a brass union looking part with the PEX line coming out of the top. They may have a small cap on one side. You can either feel the lines or use an infrared gun to see the temperature differential on either side of the check valve. Or just give all of them a tap and call it a day.:)

They will stick if not used for an extended period of time. Also, whenever you flush your glycol system try to keep the mixture as close to 50/50 (boiler glycol/distilled water) as possible. Too much glycol can magnify the sticking issue.

Mike.

New Year's Resolution for all AQH owners...run at least once a month even just for a tank of hot water. They need the exercise...valves, pumps, burner, etc... :) :)

Twomed wrote:
New Year's Resolution for all AQH owners...run at least once a month even just for a tank of hot water. They need the exercise...valves, pumps, burner, etc... :) :)

Running to get a tank of hot water does NOT excercise the HEAT check valves. You MUST run all the heat Zones for a few minutes to get the check valves to function. Running also keeps the fuel nozzle from gumming up. Doug

x4 on giving the valves a good whack. Have had this happen twice over the past three years and one tap solved the problem. Will take longer to take the cover off than anything else.

Okay, I'll ask a dumb question...where are the heat/check valves?

You need to remove the shrouding from your unit to get to them.

If you look at your owner's manual (or better yet, download the service manual for your model), they give you all the detail you need.