Virginia WaterFurnace Mystery

Discussion in 'Maintenance and Troubleshooting' started by tibs, Mar 23, 2021.

  1. tibs

    tibs New Member

    Hi, i realize that the title is unusual and contrary to other posts you will get very few specs. But please, finish reading and if you have any ideas post. BTW I am the home owner and very satisfied with the installer who is still my servicing my units.
    About 15 years ago we decided on geothermal and had 4 WaterFurnave units installed. 2 units have their own closed loop and 2 share a larger loop.
    About 2/3 winters ago - yes, it has been dragging on - i realized there was a problem with the 2-ton split system for the family room which is on the shared loop. If we had a cold night in the 20s or 30s I would come downstairs in the morning and find the auxiliary heat running most of the time. Once the room temperature, 74 degrees, was reached the auxiliary would switch off but the air coming out of the ceiling vent was a rather cool 82 degrees and it didn't take long before the auxiliary heat came on again.
    By the time the service guy came in mid-morning, the company is about 45 minutes away, the air coming out of the vent was back to the usual mid to high 90s and I was told everything checked out fine. As a precaution the insulation in the return air shaft was redone but that made very little difference.
    Winters are short in southside Virginia and once we got into the cooling season all was well again. Last fall though the situation deteriorated and now I had 60 degree air coming out of the vent in heating mode. This provided a clear-cut answer, the compressor had failed. Here a word of caution for owners of older WaterFurnace units, WaterFurnace no longer made these compressors and I was forced to go with a complete replacement and opted for a 2-ton WaterFurnace 5 system. I was assured this unit would take care of my problem but I was a bit skeptical. The unit at the coil produced 110 degrees but at the vent I was reading 96 degrees.
    The cold nights came and yes, still the same problem. Now all the ductwork in the attic was redone and again nothing changed. By now I had a ladder under the ceiling vent on a permanent basis to check the temp. here are some of the results from one morning;
    outside temp 25 degrees - room temp 73 degrees - H-2, Sp-6 - vent 88.2
    outside temp 43 degrees - room temp 74 degrees - H-2, Sp-6, vent 92.3
    outside temp 50 degrees - room temp 74 degrees - H-1, Sp-4, vent 104.1
    Before taking those temps the unit had been running at least 10 minutes and the second unit being supported by that same loop has no problems.
    Also, the return in the family room has been relocated from being close to the floor and adjacent to an outside wall to the ceiling toward the middle of the room.
    We are stumped, there was no problem for over 10 years and nothing has changed in the room. I'm really hoping someone will take the time to read this and come up with an explanation.
  2. tibs

    tibs New Member

    nobody at all who will venture a guess? i'm really worried whatever is going on did in the first unit's compressor and might affect the replacement unit
  3. gsmith22

    gsmith22 Active Member Forum Leader

    Not sure about others, but I didn't respond because I am having a hard time understanding what is "wrong". Is the room's thermostat temperature not being met - ie its set above 73/74 but only reaching those values?
    tibs likes this.
  4. tibs

    tibs New Member

    the room temp in the winter is always set on 74. the moment the outside temp drops in the low 30s the heat pump produces only about 88 degrees - that's what i get coming out of the heating vents in the ceiling. when the outside temp rises to 50 degrees the heat pump produces about 104 degree heat. a geothermal is not supposed to fluctuate with outside temps. my water temp is supposedly around 50 degrees and i doubt that changes very much, winters in southside virginia are mild. all the ductwork and the return airshaft have been redone. so why those drastic changes in output?
  5. tibs

    tibs New Member

    my 3 older units are producing about 95 degree heat no matter what the outside temp.
  6. wing

    wing Member

    Maybe your problem heat pump is not getting sufficient flow rate ? And it only manifests itself as an issue when you have high heat requirements and both the heat pumps on a single loop field have simultaneous heatings calls ? It is suspicious that your problem unit is the one sharing a ground loop, which can be somewhat tricky to manage.

    It would be extremely useful to have some basic data on that heat pump.

    What is the entry temperature of the loop field fluid going into the heat pump ?
    What is the return temperature of the loop field fluid after it exits the heat pump ?
    What is the pressure drop measured between the entry and return on the heat pump ? This will equate to a gallons per minute flow through the heat pump.
    What is the type antifreeze and concentration of antifreeze in your ground loop ?

    Try to adjust your thermostats so measurements can be taken with three scenarios- heat pump 1 on / heat pump 2 off , heat pump 1 off / heat pump 2 on, both heat pump 1 and heat pump 2 on.

    From all this, it is a trivial exercise to calculate how much heat your system is producing and narrow the issue down to

    A. Problem with the ground loop and/or loop circulating pump and/or whatever balancing or zone valve strategy you are using to split the ground loop flow between two heat pumps.
    B. Problem with the heat pump itself
    C. Problem with your ducting downstream of the heat pump.
    Last edited: Mar 25, 2021
    tibs likes this.
  7. tibs

    tibs New Member

    i'll try and do the 3 scenarios if we get another cold night. but i still don't understand why for 12 years i did not have this problem. and i don't see how the loop water temp could be affected so drastically within hours depending on outside air temp. for me, the main selling point was the pretty constant water temp with a geothermal.
  8. gsmith22

    gsmith22 Active Member Forum Leader

    If the room stays at its thermostat set point, what is precisely the problem? Why do you care what the temperature of the air coming out of the vents is so long as the room stays at its set point? how is the loop water temp drastically affected - there have been no measurements of the loop water temperature provided?

    With respect to "constant water temp with a geothermal" if you are talking about the ground loop, and it is a closed system, the water temperature varies greatly with the season typically in the 30s during heating and maybe near 70 during cooling (for a heating dominated climate - not sure where you are). An open loop geothermal has near constant temp incoming water because the loop water tis constantly being replaced with new ground water which will be the temperature of the ground. So an open loop might have 50 degree incoming water temp year round regardless of heating/cooling mode.
  9. wing

    wing Member

    Bear with me.

    Say your ground loop pump delivers fluid to the heat pump at a constant 5 gallons per minute. That five gallons per minutes goes to your two heat pumps. Normally there are zone valves that will direct the flow to either heat pump number one or heat pump number two. So if only one zone valve is open and the other closed, the heat pumps will operate with the full 5 gallons per minute. But what if both heat pumps are operating and both zone valves open, then the 5 gallon per minute fluid Flow will be split at some percentage between the two heat pumps. If the fluid flow drops to say 2 gallons per minute in your ‘problem unit’ then that’s not enough fluid flow to have the heat pump generate the rated heat output.

    Sometimes this is handled by a variable speed ground loop pump and having this pump ‘ramp up’ to say 10 gallons per minute if the system detects both heat pump number 1 and number two operating simultaneously. But I’m not sure if this is your case or what your setup actually is with the ground loop pump, zoning valves and balancing valves. Operating two heat pumps off a single loop field can be done, but it takes special planning and hardware.

    Maybe some of this kit has been working for 12 years but now it’s not.

    Thus the request for entry/ exit water temps and pressure drop under the three scenarios.
    tibs likes this.
  10. tibs

    tibs New Member

    thank you for taking the time to explain :)
    to your first question - the reason i care, at an output temp in the mid-80s the set room temp of 74 can't be maintained which means the auxiliary heat is coming on at a constant basis. also, air blowing at 80some degrees feels cool and makes the room uncomfortable.
    i'm in southern virginia and our frost line is about 14'' the trenches for the horizontal loops were dug a good 6' deep.
    as to valves and zoning i'm at a loss. i hope i don't make a fool of myself but all i remember from the original discussions is that that loop was large enough to support 6ton and could handle a 2ton and 2.5ton easily.
    what sticks in my mind is the reading the tech got once the replacement unit was installed. apparently, the waterfurnace series 5 units have a temp sensor right at the coil. that sensor (supposedly pretty accurate) gave the temp as 110 degrees. what i got coming out of the ceiling vent was 95 degrees. that's a loss of 15 degrees which can make a world of difference. i have no idea what the spread is after all the ducts for that unit were reworked. i was never given that reading again. but the readings that fluctuated so wildly within hours and seemingly tied to the outside temps i gave in my first post were taken after all the work was completed.
  11. Deuce

    Deuce Member

    I am also in Sothside VA at the VA Outer Banks My temps stay about 104. Is it possible that your attic is cooling the ducts when it is colder? I have an enclosed attic without any ventilation. Maybe you need to check your duct runs for gaps in the insulation or have more blown in.
    tibs likes this.
  12. tibs

    tibs New Member

    i'm more toward the middle of the state but, as i said, my older units put out about 95 degrees reliably. the new unit is producing better results but only if the outside temp is not below freezing. deteriorated ductwork in the attic was the first guess that's why all that was reworked but it did not help.
  13. gsmith22

    gsmith22 Active Member Forum Leader

    Comparing vent temperature output of different units is not helpful and is likely counterproductive. each unit is responding to its own thermostat set point. What you should be focused on is can the unit in the family room maintain the thermostat set point. If it does that then there isn't a problem per se. If it is doing that using auxiliary heat and you don't want it to use auxiliary heat (just the heat pump) to do that than that is an entirely separate issue.

    Is the 80F temp output at the vent with the auxiliary heat on or off? Heat pumps aren't furnaces. they aren't going to produce 160 degree air and are more than likely going to be producing 80 to 100 degree air. if 80 degree air from the vent keeps the room at its thermostat set point, then I don't know what to tell you - its working properly see above.

    There is an aspect of residential HVAC design (ACCA manual T) that delves into vent size and placement so vents aren't blowing on people creating a wind chill effect. But presumably that would have been a problem all along. Its certainly more of a problem with a heat pump than a furnace due to the general difference in output temperature of the air.

    A 15 degree drop in air temp from unit to vent is troublesome, but that isn't a heat pump problem, that is a ductwork and likely a ductwork through the attic issue (which is a terrible way to duct anything but half the country does it so...). Wing might be onto something with the shared loop if this unit isn't getting enough flow. i don' think you have provided enough background data or system layout to figure that out though.
  14. tibs

    tibs New Member

    thanks to everybody for the input - maybe one of the suggestions will pan out.

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