Bosch Greenstar 151 boiler for radiant heat system, not working consistently

megmcg7

I live on the south shore of LI, NY and had a complete radiant heat system installed after a post-fire rebuild. Originally, a Prestige Triangle Tube boiler was installed with 3 manifolds (one for each floor) and multiple zones (12 total thermostats, plus a Vaughn Top Performer indirect water heater).

After the aquastat on the water heater failed in 2019 and was not replaced soon enough (separate long story), the indirect water heater started leaking and was replaced Sept 2020. When the boiler stopped working properly, it was replaced with a Bosch Greenstar 151 combo boiler in Oct 2021. The heat has not worked properly, consistently since then.

The 2nd floor has one zone/manifold (wood floors), the 1st floor (with all tiled floors), plus the two tiled bathrooms on the 2nd floor, are on another zone/manifold, and the basement (all tiled) has a separate manifold with a zone valve relay off of the 1st floor manifold.

Note: the tiled rooms have slab sensors that are on and set to min ~ 72, max ~81.

The original boiler had an outdoor sensor wired up, but the wires were never connected to the new boiler, they are just hanging in the basement; I was told that "this boiler does not need/have an outdoor sensor."

I have replaced Taco relay boxes, circulators, fuses, and re-plumbed the circulator for the main floor; spent several thousand dollars on "experienced" plumbers/electricians…and still have inconsistent heat. The hear generally works well during the day and when the outside temp is above 30F. Overnight, when the temp drops below 30F, I will awake to find my bathroom at 60F with the thermostat indicating that it is calling for heat, the Viega actuators indicating that heat is being called for (little blue thing popped out)…but no warm floors. Sometimes, it seems that some of the rooms have warmish floors, while others are cold.

This morning, at 7:30 am, all of the tiled floors, including the basement, were cold. It was 25F outside and 64 everywhere on the 1st floor. Even the basement floor was cold. At around 8:30 or 9 am, I turned all of the thermostats except for the basement off (since they were all calling for heat but not getting it…). The boiler was running and the circulator for the tiled floors was cold. The wood floor rooms and circulator were running fine. I figured that the circulator must be bad, but then, at about 10:30 am, the cold circulator kicked on and the temperature gauges on the pipes nearby started moving higher and the heat was back working! Coincidentally, my tenant had come in (after being away for a week) and the cold air from the open door as she moved packages back in must have triggered the thermostat which is only about 12' from the door. She did NOT touch her thermostat.

So, all parts of the system are working, just not properly. PLEASE help me figure this out! As a single mom, this has been torture and I am not trusting anyone to come in and $$$ "fix" this.

Could the problem be related to the way the basement zone is running via a zone relay to the same circulator that my 1st floor uses? Could it be that the outdoor sensor needs to be attached? (can the existing one's wires be hooked up to this boiler?) Could it be the wiring in the Taco relay box for the 1st floor is not quite correct??

The problem is generally overnight, but not always in all of the 1st floor rooms plus the basement, and I have never noticed it taking until 10:30 to start working again. HELP! THANKS!!!!

tcassano87

hi I’m a plumber in Queens & Long Island area, this is definitely a tough one to figure out without being there and seeing everything

Can you take and post pictures of your boiler, pumps, manifold etc

Also has anyone ever used a thermal imaging camera to see the lines heating up in your floor when the heat is being called by chance

megmcg7

The Bosch Greenstar 151 boiler is 199k btu's. All parts ARE working, because I have days when there is generally no issue, even first thing in the morning. I think that the issue is related to the zone valve (2nd pic) that was put in originally to send heat to the basement. It works off the same circulator pump that is used for the rest of the tiled floors. All of the tiled floors (entire 1st floor, basement, and 2 bathrooms on the 2nd floor) are getting hot water (hydronic radiant heat) via the same circulator pump.

This past Sunday, I would have sworn that the circulator had died - all of the afore-mentioned tiled floors were cold, as was the circulator, when I checked them ~7:30 am. The circulator for the bedrooms on the 2nd floor (bamboo floors) was working fine. When someone entered the basement from outside around 10:30am, letting cold air hit the basement thermostat, the circulator kicked on and sent hot water to all of the rooms that had been calling for heat for hours.

I need someone who really knows how the wiring in the Taco relay boxes should be, as well as how the settings for the Z-one Caleffi relay thing should be. Somewhere/ somehow, the messages from the 1st floor thermostats are going to the Viega actuators, but not getting to the circulator.

tcassano87

For Some reason the pictures aren’t uploading for me and I can’t see them if you’re able to upload them another way.

I don’t think you said, what kind of thermostats do you have?