Hydronic heating system - zone valve issue

[branimal]

I have 4 hydronic heating units in my condo rental property. Each has their own thermostat - the knob on the control panel. See pic. The condo's boiler (serving 14 units) brings hot water to my unit and my heating unit blows on the hot water pipe and heat is disseminated throughout the apartment.

There is no other thermostat in the condo unit.

Each of the 4 hydronic units has their own zone valve.

Each of the 4 hydronic units has their own set of water shut off valves.

2 out of 4 units are not working. They are just blowing cold air.

I tried bleeding the units to no avail.

I read up a little on zone valves and have a basic understanding why either the wiring on the zone valves have gone wonky or the zone valves themselves are faulty.

2 zone valves going bad at the same time seems strange. But possible.

It could be the wiring. I have a Harbor Freight multimeter (I know it's ****)

How do I use the multimeter to check for 24vac at the zone valve / motor? And what do I do if there isn't 24vac at the zone valve motor?

I think I kind of have a fuzzy idea of how the wiring works;
1. 240 volt power comes into the unit.
2. Transformer steps down the power to the thermostat (knob control panel)
3. Thermostat sends on/off signal to the zone valve via opening or closing the motor.

Is there a way to hot wire the zone valve open for now?

How can I manually override the zone valve? One zone valve appears to have the override lever broken. Maybe I can remove the cover and slide over the control with a flathead screwdriver. Will it stay in that position if I leave it like that? The tenant typically shuts the units off with the standby switch.

The other zone valve might have the controls on the bottom of the valve. Perhaps the installer installed it upside down.

 

[LS6 Tommy]

Why are the isolation valves shut? Another part of the problem is the air bleeders need to be at the highest point of the system, not down low on the unit like the way they are. You can try closing one of the isolation valves and bleeding. It might push some air out. Nothing will purge air out of the coil if you can't get the zone valves open. You should get 24VAC between TH and TR on a Honeywell zone valve and between 1 and 2 on a Taco if the T-stat is calling for heat.

Tommy

 

[branimal]

What does TH and TR stand for?

Ball valve was shut so I could bleed it. Bled out like 3 gallons on each.

I can't figure how to fix this elegantly - Can I go the ballistic route?

Shut off both ball valves, cut the section of copper pipe attached to the zone valve, replace with straight pipe and call it a day.

The tenants typically turns the heater on and off based on their needs. I feel like that thermostat never really worked anyway. Probably b/c that zone valve or the thermostat is wonky.

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[BD1]

Shut off both ball valves, cut the section of copper pipe attached to the zone valve, replace with straight pipe and call it a day.

Doing above will provide constant heat resulting in overheat space. The thermostat controls ZONE valve and circulating pump runs constantly.


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[yeldogt]

You should be able to tell if the valve is opening ... operating. If it's not opening ... no heat.

They call them fan coils .... typically two parts. The operator head and the valve -- you should be able to replace the head if it's bad. the valve can also stick and overload the head.

You bleed the unit with it running .... what's going on with the boiler ... how many feeds?


As stated -- you don't want to cut out the valve

 

[LS6 Tommy]

Shut off both ball valves, cut the section of copper pipe attached to the zone valve, replace with straight pipe and call it a day.

Doing above will provide constant heat resulting in overheat space. The thermostat controls ZONE valve and circulating pump runs constantly.

The circulating pump comes on when the zone valve end switch closes. It doesn't run constantly. Replacing the zone valve with pipe will result in that zone getting heat any time any of the other zones calls for heat.

Tommy

 

[fitter30]

That style of valve operator has a metal lever that sticks out of one end. Just move it to its detent. Looks like the valve is a straight through design and if it doesn't have a lever it's normally open, heating valves fail in full heat so you don't freeze up a building. TR is transformer TH is thermostat. Google model of the valve for a manual. Could have a system problem not enough water, dirty pump strainer, did these units work last winter?

 

[yeldogt]

The circulating pump comes on when the zone valve end switch closes. It doesn't run constantly. Replacing the zone valve with pipe will result in that zone getting heat any time any of the other zones calls for heat.

Tommy

I'm sure there are different types .. but all the ones I have run across don't have individual circulators.

 

[BD1]

I'm sure there are different types .. but all the ones I have run across don't have individual circulators.

Individual circulators are used inplace of zone valves. Definitely at a increased cost .


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[yeldogt]

Guess this depends on building age/design .... those I have live in use/used pressurized mains. Basically a big bypass system.

 

[branimal]

Posting a follow up:

I went to the rental property Friday and got the units working. Sort of.

As soon as I pulled the motor off I could instantly feel all pipes get hot. I guess the motor on the zone valve kept the valve closed. Is the valve a binary valve. Just on or off?

Or does throttling that lever in the open direction widen the opening for hot water to flow to the coils? Forgot to bring my heat gun to measure the surface heat.

I ended up zip tying the lever in the fully open position. Using my hand as a heat gauge, the system felt hotter in the fully open position.

Perhaps the tenants will feel the apartment is too hot on mild days, but b/c the tenants would turn off the blowers the heat shouldn't disseminate too badly around the room. Fingers crossed.

The building is a 14 unit condo with shared boiler. The boiler gets turned on and off once certain temperatures are hit. On in October and off in April or May.

I realize that having the valve wide open is wasting energy. Hot water is flowing constantly through those coils, when in should only be flowing when the system / user calls for heat.

Regarding the 24VAC being fed to the motor: I put the multimeter up to the two wires coming from the unit feeding the zone valve's motor. It read zero. Then I think I uncovered both wire-nuts and tested the bare wires - no reading.

So I guess there is an an issue with the transformer.

But how could two different transformers get blown out?

@fitter30 :

The lever that should be sticking out of the zone valve wasn't there on both zone valves. But I do see the detent where you can lock the valve into the open position.

What do you mean by this? "heating valves fail in full heat so you don't freeze up a building."

The system was working fine last season.

 

[86turbodsl]

Since this is a rental unit, and presumably is a business, can't you just get an HVAC tech out to fix this and write it off?

Obviously it worked in the past, and has issues now. Bypassing zone valves will cook some of your tenants. You'll get complaints and your wasting your energy. I had an appt like that once. Couldn't shut the heat off. Old guy downstairs had the thermostat. Liked it hot. We had windows open in the winter in the UP. It was always a balancing act. I hated it. Moved out as soon as i could.

 

[yeldogt]

Why don't you ask the super how they work -- they will know the proper operation.

There is not much to the system. Sometimes the thermostat can fail ... the motors can fail and the motors can be "killed" if the valve starts to stick.

Again -- it depends on the design. Typically two wire motor systems power one way and spring return. The motor can fail ..or the spring .... both causing "no operation". Mine have always been power "on" and spring return. So when they fail the heater is off.

But you can also have two way DC motors that reverse operation -- they have two wires or three depending on how the relay works.

I have also seen them installed backward ....

Again -- they are relatively simple. I would find out how they work -- ask about common failure points and just replace the parts. Fix it once and be done with it -- that's my rental property rule.

 

[LS6 Tommy]

I'm sure there are different types .. but all the ones I have run across don't have individual circulators.

Exactly. There is only one circulating pump for all the zones. The pump does not run unless a t-stat calls and the pump does not run until the zone valve end switch makes.

Tommy