Radiators not getting heat

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Hi. Just a confused homeowner but here's the puzzle. We have a hot water heating system (radiators and convectors on first and second floor) in a 1920s house outside Boston. Second floor hits the temperature designated on the second floor thermostat. First floor is cold -- set for 68 on first-floor thermostat and temperature reads 63. The flame icon appears on the thermostat indicating that heat is being called, but most of the first floor radiators & convectors remain cold. Viessmann boiler and normal room temp on that calls for 72 with 1.5 curve, which is more than sufficient to warm the house -- if heat makes it to the radiators. Has not been a problem in the past. We had radiant added for a new bathroom this past summer, and that's working fine. Work-around has been to increase the second floor thermostat above the second floor temperature, and for some reason when second floor calls for heat, that seems to kick on the radiators on the first floor. Maybe just coincidence.
Any suggestions for why the first floor is not getting heat to the radiators & convectors even when (1) first floor thermostat is calling, (2) second floor and radiant rooms are satisfied and not calling? (One ignorant question: any chance that when the radiant was installed that became the second zone in place of first floor, so first and second floor radiators are now treated as the same zone and turn out to be controlled from the thermostat on second floor?) Thanks.

Jamie Hall

Two thermostats. You did have two zones; you now have a third -- the radiant zone.

Can you take photos to show how the various zones are connected to the boiler? Or make a sketch to show the piping and any pumps and valves?

Also can you trace the wiring to find out just what is connected to what?

It's most likely a control wiring or valve/pumping problem, but to figure it out we're going to need more information and sketches and pictures!

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Thanks Jamie. Hopefully these help.

Ironman

Can you step back and take a pic that shows all the pumps and manifolds? Similar to the last pic, but more inclusive.

Also: a pic of your radiators?

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Here are a few more, including a panorama. The radiant controls are on far left on wall.

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Here's the panorama.

Ironman

Since I'm seeing the flow meters indicating flow in both manifolds, I'd say you may have air in some of the rads. Can you post a pic of them?

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Thanks Bob. Here are 4 of them



. Each has been bled individually and the whole system was bled in the basement ten days ago (not sure what that means but that's what the contractor told me the plumber did). Odd thing is that right now, temp is 65 on first floor, thermostat is set for 70, icon shows it's calling, but none of the radiators is warm to the touch.

Ironman

They will need to be bled individually. You CAN'T get the air out of them by purging at the manifold since that only pushes it through the bottom nipples of the rads. Once the air enters the rad, it goes right to the top and stays there until purged at the rad's key vent. You'll have flow across the bottom nipples, but not in the columns of the rads. That's why the flow meters are indicating flow at the manifold. You just need a radiator key.

Make sure the spout of the vent isn't clogged with paint.

Ironman

Whoever ran all the pex lines out from the manifolds should have properly strapped them up. The way they are now is totally unacceptable, unprofessional, and doesn't meet code.

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Thanks Bob. I really appreciate the advice. You don't happen to work in the Boston area do you?

Ironman

No, Central VA. But there are some good men on here that do. Check the contractor locator.

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Just checked everything again: (1) bled two radiators, and water came out right away; (2) flow meters in basement at or near 0; (3) temp at 65, set for 70, and icon on thermostat shows it's calling. Seems like something other than air in the rads. The photo above may have caught the flow meters when the second floor was also calling.

Ironman

Is the zone valve opening when the thermostat calls? It's the silver box near the manifold. There's a manual lever under the wire terminals that will move freely if the valve is open. If it has resistance, the valve is closed.

BBros

Guessing the photo of manifolds was taken when the 2nd floor was calling, thus flow is shown.

My amateur eye sees the left pump for the sunroom, the middle pump serving both 1st & 2nd floor, and the new right most pump (Taco) is for the radiant.

If the 1st floor is only getting heat when the 2nd is calling, that would tell me the 1st floor thermostat isn't getting pump action, but perhaps only the zone valve. Something in the controls got dropped, and needs investigation. The 1st floor thermostat needs to engage the (middle) pump...

To test the theory, see if you can tell if the middle pump is running when the 2nd floor is calling (turn the heat up and go check). Then turn the 2nd floor thermostat down while 1st is up, and check again if the pump in the middle is running... it should. If the 1st floor is never satisfied, that middle pump should be running full time. This assuming I've got it right that the middle pump is indeed for both 1st and 2nd floor zones. I could be seeing things wrong!

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Thanks again Bob. Here are two photos of the silver box marked "1st," which I assume means first floor. Thermostat is calling, flow meters at or close to 0.

Ironman

Does the manual lever move freely to the left when the stat is calling? If not, the valve is closed. You can rest it in the slot to the left to temporarily hold the valve open if needed.

If the valve's not opening, the motor could be bad or it may not be getting 24v when the stat calls. A digital multimeter would be needed to check it then.

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Thanks BBROS. Here's some more info. Left red pump is sunroom, which means radiant (feeds sunroom and bathroom above it). Middle red pump says 1st and 2nd floor. Right green pump is for basement baseboard heater (which works fine).
Just did the check you recommended. When both 2d and 1st floor thermostats are calling, flow meters go up and middle red pump feels to my hand like it is whirring inside. When only 1st floor thermostat is calling (2d floor thermostat is at set temp), flow meters are close to zero and the middle red pump feels (to my hand on top of it) motionless inside.
I did not see any movement on the lever on silver zone valve. Stays in the position in the photo when 1st and/or 2nd floor thermostat is calling.
Thanks for all the help and guidance. Hugely appreciated, especially during this holiday week!

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Ironman-
Thanks for the diagram.

Here are two photos I just took after cranking up the second floor thermostat (which caused the flow meters for the first floor to go up). Why would the silver zone valve lever for the second floor stay in that position too if that was the problem? Thanks.

Ironman

No, it's a manual lever; it doesn't move automatically, but if it moves freely, then the valve is open. Try and move it open. If it offers resistance, the valve is closed.

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Hi Everyone. The contractor, plumber, and Viessmann rep were out today. They've discovered a few things: (1) the first floor thermostat seems to be malfunctioning, though there seems to be a second problem that they cannot pinpoint until that is fixed; (2) the pump for the sunroom is not necessary since it duplicates what's going on over on the left with the radiant; (3) some unknown problem with how the relays from thermostat to zone valve to boiler are wired. Thanks for all the help. I'll update as we get to the bottom of this.

Paul48

Get a good HVAC contractor in there. Let's see......they came, and told you something's wrong. Rocket Scientists!

hot_rod

That does seem like a lot of talent in the room, and no solution?

Paul48

That's called the "run-around". Problem #1, that had to be fixed first......take it off the wall and separate the wires,,,it's off and out of the picture. Or twist the wire together...it's on and the stat is out of the picture. That's ridiculous!

hot_rod

And manually opening the Erie valve answers a lot of questions.

Granted we were not at the party, but it doesn't seem like that complicated of a troubleshoot.

Paul48

I suspect more was seen by the rep than could be done quickly, that day. The question is....when are they coming to fix it?

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The part that still does not compute for me is this. Why do the first-floor radiators kick on when the second-floor thermostat calls? So if problem #1 is that the first-floor thermostat (and maybe wiring) are broken, so it isn't really calling at all, why then would the second floor thermostat trigger the first floor radiators? Is something else also going on? They're coming back to swap out the thermostat and check the wiring.
If there's a good viessmann HVAC person in MA on the contractor locator, can you point me to them? thanks.

BBros

Because one pump is running both zones. See how you have two zone valves upstream of the middle pump? There is effectively a "fork in the road" for the water that is being pumped by that single middle pump. Each thermostat has the capability to make the pump turn on, and the pump doesn't know or care which one (or both). However, if the pump doesn't run, no water moves, and right now only the 2nd floor thermostat is exhibiting ability to turn the pump on. Even if the valve is open for the 1st floor (caused by the 1st floor thermostat calling), there is no water movement because the pump didn't get told to turn on (due to some malfunction). I suspect if you turn the thermostat for the 1st floor down (off) that it's zone valve will close and heat will not be supplied to that level, even while 2nd floor is calling (and heating).

Though it's possible the 1st floor isn't responding to anything, and the valve is always open and the pump signal off, in which case it will heat with the 2nd floor regardless of 1st floor thermostat setting. That's why other posters were asking about the pressure of the manual over-ride lever on the zone valve (silver box) for the 1st floor. Is it's stiff or loose?

I still contend there is a control issue, and it isn't the thermostat. I don't know enough to tell you where the issue is specifically.

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Thanks. Just checked the zone valves, but right now, for some bizarre reason, the first floor is getting heat even with the second floor off (last night this was definitely not the case). With the first floor getting heat now, the first floor zone valve lever is tight; second floor zone valve lever is loose. I'll test again when first floor goes off (don't want to mess with it when it's miraculously getting heat).

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Conclusion.
Hi everyone. I want to circle back with how this ended up. Once the Viessmann expert showed up, they all discovered that the first-floor thermostat was not working and that some wires were loose. Once those were addressed, and after the elecritician re-wired the zone valves so that each controlled only one floor (versus the second floor also calling for first floor radiators), the first floor still was not getting heat. That's when they discovered that indeed, the first floor zone valve was broken. So I still don't know if the thermostat was really broken or if it all stemmed from the zone valve. The took 3 days to iron out and get in the right parts.
It was humming over the weekend.
On Monday, our coldest day of the winter so far, the heat went out completely in the wee hours of the morning. When I alerted my contractor, I indicated that I thought we'd need a Viessmann expert. But I'm not usually listened to, so only when the two plumbers could not locate the root cause, did they call a Viessmann tech. He had to call in the Viessmann rep, and in early evening they discovered a fuse was blown in the boiler control (something that the Viessman tech had tested, but his equipment turned out to be faulty). We got heat back around 5:00 pm, with the house down in the 50s.
Thanks everyone for your help and insight. My question for everyone is whether there are HVAC/plumbing contractors whose staff could have figured all this out without calling in a separate Viessmann expert, or is this how it typically works, that at some point with certain challenges, plumbers and HVAC folks call in the manufacturer's local rep or technical expert. Thanks.

hot_rod

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Conclusion.
Hi everyone. I want to circle back with how this ended up. Once the Viessmann expert showed up, they all discovered that the first-floor thermostat was not working and that some wires were loose. Once those were addressed, and after the elecritician re-wired the zone valves so that each controlled only one floor (versus the second floor also calling for first floor radiators), the first floor still was not getting heat. That's when they discovered that indeed, the first floor zone valve was broken. So I still don't know if the thermostat was really broken or if it all stemmed from the zone valve. The took 3 days to iron out and get in the right parts.
It was humming over the weekend.
On Monday, our coldest day of the winter so far, the heat went out completely in the wee hours of the morning. When I alerted my contractor, I indicated that I thought we'd need a Viessmann expert. But I'm not usually listened to, so only when the two plumbers could not locate the root cause, did they call a Viessmann tech. He had to call in the Viessmann rep, and in early evening they discovered a fuse was blown in the boiler control (something that the Viessman tech had tested, but his equipment turned out to be faulty). We got heat back around 5:00 pm, with the house down in the 50s.
Thanks everyone for your help and insight. My question for everyone is whether there are HVAC/plumbing contractors whose staff could have figured all this out without calling in a separate Viessmann expert, or is this how it typically works, that at some point with certain challenges, plumbers and HVAC folks call in the manufacturer's local rep or technical expert. Thanks.

Certainly a well trained, qualified troubleshooter should be able to find all those problems. A blown fuse is often one of the first places to look for trouble

It helps if the contractor has some manufacturer specific training, Viessmann does offer plenty of training classes.