Results 1 to 10 of 10
  1. #1
    Join Date
    Nov 2016
    Posts
    5
    Post Likes

    Question High Rise Fan Coil System Help

    I moved into a high rise condo recently and have run into some issues with the HVAC. The condo has two separate 4 pipe (cool/hot) fan coil units. I live in Canada and the outside temperature is now dropping to freezing some nights. The condo building has had the heat turned on centrally.

    Each fan coil has the following features:
    1. Honeywell T8575D2003 24v thermostat.
    2. Temspec TVS 800 fan coil.
    3. Honeywell VU844A1003 24v actuators
    4. Two Omron LY2F-24VAC 24v relays.

    What I've noticed is the air that comes out is pretty much at room temperature. The overall apartment temperature stays around 72F (22C) but it's impossible to get it higher. The units will work but they can't really warm up more.

    I opened one up and noticed the following things:

    1) The hot and cold pipes coming into the unit are very hot and very cold respectively.
    2) Setting the thermostat to heat makes the fan run, there are no obstructions. When heating 24v are applied to the W (orange) heat call wire as expected (I measured it).

    However, both the cold and hot actuators are set to "Open" instead of "Auto". The manual for them (I found it online) says they should return to Auto when energized. They're not.

    Additionally, the way the hot valve relay is wired, when eletricity is applied to it, it will actually *disconnect* the actuator from the 24v hot wire coming from the transformer. That makes no sense to me, but I ignored it for now.

    The radiator itself is lukewarm to the touch. Is it possible that it's feeding both cold and hot water at the same time? Is it normal for both valves to be manually opened and left that way?

    Thanks for any advice.

  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    18,268
    Post Likes
    Contact the building engineers and see if they can help. I wouldn't change anything until i knew how the System is designed.

  3. #3
    Join Date
    Jul 2011
    Location
    Dallas, TX.
    Posts
    640
    Post Likes
    It's possible that you should call the maintenance man or a hvac company to look into this u issue.


    Sent from my LGLS991 using Tapatalk

  4. #4
    Join Date
    Nov 2016
    Posts
    5
    Post Likes
    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Contact the building engineers and see if they can help. I wouldn't change anything until i knew how the System is designed.
    Thanks for the reply.

    I'm not changing anything - but I also can't really call anyone as I'm renting the unit and I'm not the owner. I have contacted the owner, but evidence is always helpful when presenting an issue to a landlord.

    I'm not looking for DIY advice, but some confirmation on whether it makes sense that both valves are set to manually open state.

    Reading the manuals indicates that is not normal.

  5. #5
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    18,268
    Post Likes
    Quote Originally Posted by Rideau View Post
    Thanks for the reply.

    I'm not changing anything - but I also can't really call anyone as I'm renting the unit and I'm not the owner. I have contacted the owner, but evidence is always helpful when presenting an issue to a landlord.

    I'm not looking for DIY advice, but some confirmation on whether it makes sense that both valves are set to manually open state.

    Reading the manuals indicates that is not normal.
    Someone needs to be there to see the design. Valve and controls come in Normally Open & Normally Closed configurations and theirs reasons for that!

  6. #6
    Join Date
    Nov 2016
    Posts
    5
    Post Likes
    Thread Starter
    Thanks for the replies!

  7. #7
    Join Date
    Nov 2016
    Posts
    5
    Post Likes
    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Someone needs to be there to see the design. Valve and controls come in Normally Open & Normally Closed configurations and theirs reasons for that!
    For the record and in case someone has the same problem here is how this turned out. I opened the second fan coil up and saw the exact same behaviour (i.e. cold coil when set to heat). I observed the following:

    1) The system is actually under voltage when off. Turning the heat on disconnects the heat valve via a relay.

    2) All the manual bypass levers were loose and flopping around.

    I cut the power to both fan coils at the circuit breaker and noticed both cold valves' levers now provided lots of resistance.

    I turned the circuit breakers back on, all levers became loose again.

    I set the thermostat really high and both coils got nice and hot within 20 minutes.

    I don't have a technical explanation for why this worked, but everything is well now.

  8. #8
    Join Date
    Sep 2002
    Posts
    23,146
    Post Likes
    Try setting both valves back to auto. Maybe someone inadvertently left them set manually.

    Th Honeywell valves I am familiar with will reset themselves to auto the next time they are powered and then unpowered again - the OPEN position setting is only temporary.

    Does each valve have two pipes connected to it? Or do they each have three pipes connected to them?

    PHM
    ------



    Quote Originally Posted by Rideau View Post
    I moved into a high rise condo recently and have run into some issues with the HVAC. The condo has two separate 4 pipe (cool/hot) fan coil units. I live in Canada and the outside temperature is now dropping to freezing some nights. The condo building has had the heat turned on centrally.

    Each fan coil has the following features:
    1. Honeywell T8575D2003 24v thermostat.
    2. Temspec TVS 800 fan coil.
    3. Honeywell VU844A1003 24v actuators
    4. Two Omron LY2F-24VAC 24v relays.

    What I've noticed is the air that comes out is pretty much at room temperature. The overall apartment temperature stays around 72F (22C) but it's impossible to get it higher. The units will work but they can't really warm up more.

    I opened one up and noticed the following things:

    1) The hot and cold pipes coming into the unit are very hot and very cold respectively.
    2) Setting the thermostat to heat makes the fan run, there are no obstructions. When heating 24v are applied to the W (orange) heat call wire as expected (I measured it).

    However, both the cold and hot actuators are set to "Open" instead of "Auto". The manual for them (I found it online) says they should return to Auto when energized. They're not.

    Additionally, the way the hot valve relay is wired, when eletricity is applied to it, it will actually *disconnect* the actuator from the 24v hot wire coming from the transformer. That makes no sense to me, but I ignored it for now.

    The radiator itself is lukewarm to the touch. Is it possible that it's feeding both cold and hot water at the same time? Is it normal for both valves to be manually opened and left that way?

    Thanks for any advice.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  9. #9
    Join Date
    Nov 2016
    Posts
    5
    Post Likes
    Thread Starter
    Quote Originally Posted by Poodle Head Mikey View Post
    Try setting both valves back to auto. Maybe someone inadvertently left them set manually.

    Th Honeywell valves I am familiar with will reset themselves to auto the next time they are powered and then unpowered again - the OPEN position setting is only temporary.

    Does each valve have two pipes connected to it? Or do they each have three pipes connected to them?

    PHM
    ------
    The auto/manual thing turned out to be a red herring. The bypass levers are loose on all four valves and they were simply resting near the open position due to gravity (they're installed at an angle). The other fan coil is a mirror image and there they were resting near auto.

    Cutting the power off at the circuit breaker made the two cold valve bypass levers have resistance and they would spring back if pushed on both coils. The hot valve levers remained loose. All four valves (both coils) have loose levers once the power is turned back on.

    I'm not sure why cycling the circuit breakers would make a difference, but it seems to have worked. After leaving the heat on for 20 min with the covers off both coils were hot to touch.

    Each valve has 3 pipes coming into it.

    This system is confusing to me because turning on the heat actually disconnects the valve from the 24VAC line. The only way to actually cut power to the valves in idle mode is to trip the circuit breakers.

    I don't think there is actually any issue at this point.

  10. #10
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    8,676
    Post Likes
    You Are NOT going to be able to discover
    the control logic of a 4-pipe system.

    One only needs to call appropriate service personnel.

    If I was the owner, I would post ...
    _ _ _" You touch it, YOU OWN IT
    & ALL Subsequent Repair cost$$$$
    . "
    ____________________________ Directly adjacent to this t-stat.

    https://customer.honeywell.com/resou.../95c-10897.pdf
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Related Forums

Plumbing Talks | Contractor MagazineThe place where Electrical professionals meet.