Lochinvar Noble Combi Boiler Problem with SH heating air when thermostat calls for cooling

darkside501st

Hello all,

I just moved into a new house that has a Lochinvar Noble Combi Boiler with a geothermal heat pump AC system. From my understanding, the boiler is supposed to provide a backup heat source when the temp outside drops below a certain level and the geothermal heating can't heat as efficiently. I am just starting to learn about this type of system. Unfortunately the previous homeowner's husband was the one that installed the system and he passed away. She doesn't know how any of it works. It seems he did some strange things with the system; for example, there are two thermostats, one for cooling and one for heating. There are also two zones (upstairs and downstairs) so there are four thermostats in total. So I am not sure where the problem is. Everything was working fine but recently the AC system has started pushing warm air when the thermostat calls for cooling. The boiler is sending warm/hot water through the furnace. The DHW seems to be working fine. The DHW pre-heat option is enabled. It seems to me that there should be a diverter valve that blocks off the SH side of things when the thermostat is not calling for heat. I am not sure how the system is supposed to work but if that is the case then it seems that there is a problem with that valve or maybe a sensor that controls that valve.

So when the DHW is at idle temp (125F) the boiler is on standby. Then if you turn the thermostat on with a call to cool the inlet temp starts to drop (105F) and the burner ignites and the outlet temp starts to rise (135F). The AC system starts blowing warm air. If you turn the thermostat off again then the boiler goes back to standby.

I disabled the pre-heat setting and that seemed to help but the system started blowing hot air again later. The only thing that worked was to close the shutoff valves going into the furnace but that causes a lockout in the boiler with a notice that the inlet outlet temp diff is too great. There is a sensor on one of the pipes going into the furnace. There is also a crossover pipe that is closed off but to my knowledge no one had messed with any of the valves before this problem occurred. No error codes have shown up besides the lockout and temp diff notice when we closed off the valves going to the furnace. Although, doing that means we don't have any hot water, of course. Any assistance is very much appreciated. Thank you in advance.

HVACNUT

Any chance theres a dial switch near the air handler and zone panel? It would be labeled "summer/winter" or "heat-cool-fan".

The fact that there's separate heat and cool thermostats with a zoned system is weird. 
You're sure the pipes to the heating coil are hot? It's not just the geo running in heat mode when it should be cooling? That would be a waaay easier diagnosis. 

I guess a good place to start is find the thermostat terminals on the boiler, and trace that wire back to the geo and tell is what its connected to.

Jamie Hall

Unhappily, you've hit a problem I've muttered about before: a custom designed and installed system with no documentation. I do wish people wouldn't do that...

There. That's said. Your basic surmise is correct -- that the boiler shouldn't run, and the circulators to the air handlers certainly shouldn't run if you are calling for air conditioning -- or, for that matter, if the heat pump thermostats are calling for heat.

Are you sure that the four thermostats are really two for heat and two for cooling? Or are the four thermostats set up with two for the heat pump (can call either for heat or cooling as needed) and two just for the boiler? That would be the first thing to verify. Then the next thing would be to locate the valves (or pumps?) for the two systems, and figure out how they are controlled -- probably by the thermostats -- and then make sure they are behaving. That is, if you turn on a boiler thermostat in one zone, does the valve open or the pump start? Does the boiler start? If you turn on a heat pump thermostat in one zone does its valve or pump start? Does it start? Does it provide heat or cooling as requested?

At some point you are going to need a diagram -- in fact, two of them, but just one to start. Put down all the components -- thermostats, valves, boiler, heat pump, air handlers, the works -- and then draw arrows to indicate what is connected and controls or is controlled by what. Without that, the next step -- if one is needed -- will be to do a wiring diagram, but you'll need this simple sketch first.

GroundUp

Does the boiler actually fire when this is happening? If you've disabled the preheat function and the boiler is still running without a call for heat, there is a wiring problem somewhere.

darkside501st

Thank you for the replies. I am a DIYer but not that well informed on geothermal or AC systems. I have a basic understanding of how it should work. I am really just starting to learn about them since we moved into this house. I have had a mini-split unit in my garage which utilized a heat pump operation and could cool and heat the garage. So I know basically how the heat pump works. I never had a problem with that unit though so never had to do any diag on it.

To @HVACNUT

I do not see a dial or other switch labeled summer/winter.

If the boiler was not the cause of the problem (if it was just the geo heating when it should be cooling) then the problem would still exist with the boiler turned off. However, when I turn the boiler off then the problem is gone and the AC is blowing cold air.

To @Jamie Hall

I was told that the heat pump AC thermostat is setup for cooling and the boiler heat is setup for heating. So apparently what they did was use the top thermostat for cooling during the summer with the bottom thermostat turned off. Then during the winter they turn off the top thermostat and turn on the bottom thermostat. The homeowner (widow) was unable to explain why or provide any information beyond that. I too thought that was very strange to use two thermostats for each zone. It is my understanding that one thermostat should be able to control the heat pump and the backup heat source (boiler). I have attached some additional photos.

I did a simple test on the system. I disabled the preheat function again. The boiler was in standby as it should be without a call. I started a hot tap faucet and the boiler ignited. It took about 10-15 seconds for the boiler to get the call and ignite. It took a while longer for hot water to start flowing out of the tap. I let it run for a few minutes. I could feel the DHW pipes getting hot but the SH pipes did not get hot. So it seems the diverter valve is working (at least during the test). I turned off the water and the boiler when back to standby and the inlet/outlet temps started cooling.

One thing I find strange is that if there isn't any water flowing through the SH pipes during a call for DHW then what does it matter if the SH valves are closed. But when I closed the SH valves the boiler goes in to lockout mode as described before.

Anyway, next I turned off the heat pump AC thermostats and turned on the boiler heat thermostats. The boiler immediately got a call for heat and the SH pipes heated up pretty quick and the system started blowing warm air through the vents. I turned off the boiler heat thermostats and the boiler went back to standby. So that all seems to be functioning as it should.

I decided to do an extra test to see if the heat pump would produce heat if I set the heat pump AC thermostats to heat. I did that and the system came on (boiler was off) and started blowing warm air then I went back to check on everything in the utility room and the boiler had come on and the SH pipes were hot. So I am confused about that. The heat pump AC thermostats cycle between off, cool, heat, and emheat. The boiler heat thermostat cycles between off and heat only. So if the heat pump AC thermostat can control all those and is connected to the boiler as well then why did they add the second thermostat?

To @GroundUp

Ok, it has been about 10 minutes while I type all this up. I left the boiler turned on (pre-heat disabled). I went back to check the system cycles of the boiler heat thermostat and noticed the boiler was fired up. No call for DHW and the DHW pipes were cool. The SH pipes were hot and the AC system was blowing warm air. The boiler heat thermostat was turned off and the heat pump AC thermostat was set to cool. The upstairs zone was calling for cool as confirmed on the honeywell control panel as well as the thermostat. For some reason is seems the boiler is getting a call for SH heat from the upstairs zone when the system is set to cool. So there is that but does that explain why the SH pipes are warm when the DHW is set for preheat.

Jamie Hall

First out of the box here -- do NOT set the two thermostats at the same temperature. They'll fight each other. I'd set the heat pump A/C thermostat somewhat higher -- 3 degrees at least -- than the boiler one.

Yes, ideally the one thermostat should be able to control both the heat pump and the boiler. What should happen is that if the heat pump thermostat is set to heat, the heat pump should run; if it's set to emheat, that should run the boiler. If it's set to cool, it should cool -- and if it's off, nothing should run except for domestic hot water. That's the theory With a two thermostat setup such as you have, however, there should be no connection between the two (which would mean the emheat function was disabled, among other things). I have a suspicion that you may need to trace out the wiring to see what is actually connected to what; there may even be some kind of cross connection in there somewhere which would cause the boiler to run when cooling was wanted, at least under some conditions.

Without following the wiring, though, about all one can say is that it isn't doing what it's supposed to do -- but not why.

darkside501st

Jamie Hall said:

First out of the box here -- do NOT set the two thermostats at the same temperature. They'll fight each other. I'd set the heat pump A/C thermostat somewhat higher -- 3 degrees at least -- than the boiler one.

This is true if you had both turned on at the same time but it shouldn't have any problem if only one thermostat is turned on, correct? I mean, if one of them is turned off then it can't do anything, right?

Jamie Hall said:

I have a suspicion that you may need to trace out the wiring to see what is actually connected to what; there may even be some kind of cross connection in there somewhere which would cause the boiler to run when cooling was wanted, at least under some conditions.

Without following the wiring, though, about all one can say is that it isn't doing what it's supposed to do -- but not why.

Yes, it would seem that there is a problem in the wiring and that is the root of the issue. But it doesn't make sense to me why they would have two thermostats... especially if the first thermostat is connected to everything anyway.

Jamie Hall said:

Yes, ideally the one thermostat should be able to control both the heat pump and the boiler. What should happen is that if the heat pump thermostat is set to heat, the heat pump should run; if it's set to emheat, that should run the boiler. If it's set to cool, it should cool -- and if it's off, nothing should run except for domestic hot water.

This is the way it seems it should be setup as you described. However, the boiler turned on when the first thermostat was just set to heat. I did not test the EMheat function. So it seems to me that the guy that installed this system was doing something strange and I don't understand why someone would want to set it up like he did.

Have you all seen two thermostat systems like this before (four thermostats for two zones)? Why would someone want to do that? Is it some sort of obscure but not unheard of method, common, or just downright ridiculous?

darkside501st

Ok, I thought I would see what the EMheat function does. So first off, I left the boiler off so I could see how much heat the heat pump can put out by itself. I set the thermostat to heat. On the hub it came on and the Heat 1 and Heat 2 lights lit up. Then after a while the Heat 2 light went out. The air was warm but felt more like a lukewarm temp. Eventually it would probably heat up the space but it didn't do much in about a 30 min time window. Also, since it is still warm outside I obviously can't really test how it would function in the winter time. I am not sure if it should become more or less effective at heating in colder temperatures (limited knowledge of heat pumps showing).

Then I switched it to EMheat. The furnace shut off, went into purge mode for a little while and then came back on in EMheat mode. The EMheat, Heat1, and Heat2 lights all lit up on the hub. The air coming out of the vents actually felt a little cooler than in regular heat mode on the thermostat but that could just be my faulty impression because I am just feeling with my hands. It certainly wasn't warmer than regular heat mode.

Then I turned the thermostat off, turned on the boiler, and turned the thermostat to EMheat again. The boiler did not ignite in SH mode. I thought that was a bit strange... like what the heck is the EMheat mode even there for? So I put the heat pump AC thermostat back to the regular heat mode and checked the boiler... it was not igniting. The lights on the hub don't seem to have any effect on whether or not the boiler turns on.

I think when the boiler turned on before when I had the heat pump AC thermostat set to heat it was in fact the boiler acting up and turning on when it shouldn't be. The entire time I was running the most recent tests when the boiler was turned on it was in standby mode. So the heat pump AC thermostat is not connected to the boiler in anyway so it seems. The boiler is only connected to the Boiler heat thermostat. Any for some reason it is turning on when it should not be. So we are back to the wiring problem. Not sure if wires are crossed somewhere or if the boiler heat thermostat is faulty. I will start tracing the wires and making the diagrams as suggested earlier.

Another thing to note is that I don't think the zones are truly zoned. When the downstairs thermostat is shut off and the upstairs thermostat calls for heat or cool I can still feel the air coming through the downstairs vents. So it seems there is no diverter valve setup in the ducts... or that is not functioning. They are set up as two different zones on the hub. The downstairs thermostats are connected to the Zone 1 light on the hub and the upstairs thermostats are connected to the Zone 2 light on the hub.

Here is a random question for you that I never really thought about before. What happens if one thermostat in a zoned system is calling for cooling and the other thermostat is calling for heat?

GroundUp

The Noble comes with an outdoor sensor which, if connected, will prevent the SH from firing even during a heat call if the outdoor temp is above setpoint. I believe factory setting is 70 degrees. This should stop your issue.

Jamie Hall

In answer to your random question -- in most cases, the heat pump can either heat or cool -- but not both at once. Trying to get both at once may get an error message, or may simply result in whichever call came in first -- or both.

A bit of explanation may help here. A heat pump is basically a stunningly simple machine (albeit with lots of bells and whistles). It consists of three components: a compressor, a coil or coils which are fed compressed refrigerant, and a coil or coils which are fed liquid refrigerant. The cycle is this: In the coil or coils which are fed liquid refrigerant (which is cool), heat is absorbed from the air passing over the coil, and this heat boils the refrigerant liquid, so you now have refrigerant gas and the air in turn is cooled. This gas then goes to the compressor, which does just as it says -- raises the pressure. But -- the boiling point of a gas changes with pressure, and is much higher at high pressure than it is at cold pressure. So that compressed gas now goes to the other set of coils where air is blown over it again -- but now the air is cooler than the boiling point of the refrigerant, so the refrigerant condenses and releases heat to the air going by, warming it.

Now it's not really quite that simple -- there are various pressure reducing valves involved, and often other metering valves. But that's the basic principle.

Dep0ending on one's choice of refrigerant and pressures, clearly one can have various temperatures at which the refrigerant will boiler (the low temperature side) and others at which it will condense (the high temperature side. The same principle is used in freezers and refrigerators -- and air conditioners and heat pumps.

What makes heat pumps a bit odd is that they contain valves which allow the two sets of coils to function either evaporators, while the other set is condesers, or the other way around -- so you can either chill the inside air and heat the outside air, or heat the inside air and chill the outside air.

But. You can't do both at once.

The choice of refrigerant and pressures also determines what the minimum and maxiuum temperatures which can be used will be, and to some extent the efficiency of the unit -- but that's another topic entirely.

All of which is probably more than you wanted to know...

Which brings us back: your system is not operating as it should, and I think you will need to trace out the wiring very very carefully to find out two things: first, to make certain exactly what circuits are closed in the thermostats when they are in various operating states, and similarly and second what those circuits do to that hub, what circuits are closed at the hub for various signals from the thermostat, and finally what circuits (direct from the thermostat or through the hub) do to the boiler, the heat pump itself, and to the various zoning valves. You won't be able to be sure of what's happening either by depending on what lights are on at the hub, or the visible state of the thermostats. It will be very important when going through this that neither the boiler, nor the hub, nor any zone controls, nor the heat pump will do anything on their own ("act up" as you would put it). There must be a signal from somewhere telling them what to do, and that's almost certainly a wiring problem -- which very likely won't be obvious until you have a complete circuit diagram.

darkside501st

@GroundUp

I will look into that and see but that still is only a workaround since there is a deeper problem here.

@Jamie Hall

Thank you for the explanation. I wouldn't say it is more than I want to know but maybe more than I can currently understand, lol. I am eager to learn so thank you for a more in depth look at the functionality. I had a more basic understanding of how it works, I knew about the coils and that a heat pump can reverse the process. I understand what you are saying about the refrigerant and pressure making a difference in the way the system will work. Question... does the heat pump heat more effectively when it is colder outside? Does the outside/inside temperatures have an effect on the system efficiency? I can't seem to wrap my head around that to come to a logic base conclusion. From your explanation it sounds like it will have an effect. If the outside air is not that much cooler than the boiling point of the refrigerant then it won't heat as effectively, correct?

Anyway, now I have a lot of work ahead of me to get this sorted out. I want to thank you all for helping me work through the issues and offering your advice and explanations. I very much appreciate it. I will come back and report my findings once I get it all sorted out.

hot_rod

Do either of the thermostats have the ability to do cool and two stages of heat.
What is your design temperature around there? The geo, properly sized and installed should heat down to the teens or maybe lower depending on the coil in the air handler 
Ince you know that break point, have the second stage call on the boiler

Pick a stat and read up on the wiring. It may em require an isolation relay since both the boiler and air handler gave transformers 

I know Ecobee can handle systems like this, probably some Honeywell models

When the boiler is running and you think it should not be, disconnect the wires from TT

Are you sure the two stats are set far enough apart? Could the cooling be dropping the air temperature to the boiler kick on temperature?

Sometimes you need to disconnect everything and start from scratch. It may take a pro to help you through a 3 stage system

Ecobee has some good you tube tutorials for wiring complex system. Probably Honeywell also

Try to get to one stat if possible

Then draw a wiring schematic, laminate it and hang a copy by the boiler and air handler

GroundUp

There may be a deeper issue, or there may not. If your stats are both set near the same temp, they will certainly fight each other and the only issue would operator error in that case. It could be as simple as turning off the heating stat or connecting the ODR.

Jamie Hall

Briefly, on the efficiency vs. temperature thing -- yes, both the high side and low side temperatures have an influence. For a given system and refrigerant, the less the difference is the more efficient the system will be, as the required pressure difference to make it work is smaller and so the compressor doesn't have to work as hard. So the colder it is outside, for instance, for a heat pump the less efficient it will be. Again, for a given refrigerant and compressor choice, there will be a minimum cold side temperature which can be used at all, as the compressor won't be able to lower the pressure cold side enough, and a maximum high side temperature -- as the compressor won't be able to raise the high side pressure enough.

HVACNUT

In a perfect world, you'd have 2 thermostats. One up, one down. With the geo as first stage heat and the hydro coil as auxiliary and emergency heat. 
I would start at the boiler and what's connected to the thermostat terminals on the boiler. Trace that wire back. It'll go either to an isolation relay, or the zone panel. This might be a long process, but maybe with some pics and descriptions we can figure it out. 

darkside501st

Sorry it has been a while since I replied. Again, thank you to everyone that is helping me to figure out this system. So I had a little help from someone with more AC system experience and we took a look under the hood of the Zone control panel and behind the thermostat panels to see what wires were hooked up to what. First, the boiler was hooked up to the fan on the controller. Those wires went to a relay in the boiler which my guy says is not stock on the boiler. So every time the AC system calls for anything the relay is triggered because the fan comes on whether you call for heat or cool. So Since this was an intermittent issue with the boiler heating when we call for cool I am guessing that the temperature probe on the boiler was set to override the SH function depending on the outside temp. Maybe there is an issue with the temp sensor? Or possibly the setting was not ideal for example if it was 75 degrees F outside and that was the threshold in the boiler but we still wanted to cool because the sun heats up the 2nd floor then it would cause the SH function to come on. I haven't checked the temp sensor probe or the setting yet. To 'fix' the problem we disconnected the red wire that was connected to the fan terminal on the zone panel so the boiler SH function is currently disabled.

Another thing we found was that even though there are 4 thermostats (2 up/2 down) there are only two sets of thermostat wires running to the zone controller. These are connected to the main thermostats (1 up/1 down). They have a brown sleeve. The wires connected to the secondary thermostats have a white sleeve and they disappear behind the wall. I can't find them coming out anywhere. So it seems like they were spliced into the main wiring with the brown sleeve somewhere inside the wall. Those wires from the thermostats come in from the bottom and hook up on the right side. The wires with the brown sleeves coming in from the top and hooking up to the right side go to the sensor and humidifier.




My guy says the geothermal air handler has electric heat strips as the secondary heat function. However, there is only one white heating wire in the brown sleeve wiring (from the thermostat to the zone panel). So apparently that means that you can't setup a supplementary backup heating function with the thermostat... at least that is what my guy said. Which is why they used the secondary thermostats? But the secondary thermostats are somehow connected to the primary thermostat wiring in the walls so that doesn't make sense to me. There is an Emergency heat function on the main thermostats and when that is activated on the thermostat then it shows up on the zone control panel. I am not sure how that works. Maybe it is like the garage door openers and the thermostat sends a certain voltage that is detected by the zone panel and it knows whether or not to trigger the emergency heat function. Or maybe it is one of the other colored wires. If it is one of the other colored wires then maybe there is a way to make it so the boiler is only activated when the emergency heat function is used? If I can do that and it is a good idea then can one of you tell me how to set that up?

I guess what I am trying to figure out is why they would setup the boiler as a supplementary heat source in the first place. Also, since it is just activated when the fan comes on and presumably when the outside temp is below a certain threshold then why have the second thermostats?

Also, trying to figure out; if it is a good idea to use the supplementary heat source (the boiler) then is there a different, better way that we can activate the boiler SH function so that it would only come on when the heat or emergency heat function is used on the thermostat.

I am just looking for what is the proper way to setup the geothermal system with the electric heating strips as secondary and the boiler as supplemental. Like, is there a thermostat that can control all those functions? If so, how does it work (IE only turns on the supplementary heat source if the temp differential is a certain number of degrees below the thermostat setting)? Do I need to run a new set of thermostat cables with extra wires to make that work?

On a side note, we have been running the geothermal on heat recently and our electric bill is pretty high already and growing. Could that be why they said not to use the geothermal for heat and to just use the thermostat that (they said) only controls the boiler heat? Like would using the boiler for heat be less expensive than using the geothermal?

FYI, this system we have been talking about is in our accessory building. They also have a similar setup in the main house but only one zone. So I don't see a zone control panel like what is in the accessory building and the boiler is a different one too. So it is hard for me to compare the two systems but we have not had the same problem in the main house.

hot_rod

What is you outdoor temperature this time of the year. Geothermal can be one of the most energy efficient system IF it was sized and installed properly. The issue is often trying to run high temperatures from them. They match up nicely with radiant requiring below 120F. If the air handlers need 140 and higher. GEO cop drops. Strip heat kicks in electric bill will go up considerably
So you want to determine when to switch away from geo and go with the boiler

It should be easy enough to have a stat select the switch over if it has an outdoor sensor, -1st stage, 2nd stage. I’d use the strip heat only if there is no other option, it’s probably the most expensive energy source.

It sounds like a control wiring nightmare. Often you need to disconnect everything, trace wires and start from the beginning. It could be a labor intensive task, but the only way to get back to square one.  It’s nice to have 6-8 wires at each stat that controls multiple heat sources and reads outdoor temperature. The Ecobee website has good tutorials on wiring multi source systems

It would still be good to do a load calc and see how the equipment matches up.Controls will not fix a system that is under sized or improperly installed.

mrhemi

I have read through this whole thread and feel your pain. A control system nightmare that you have no documentation for. All the responses appear right on and should be investigated. I will ad a personal experience I had to work through on my own system that you might want to look into. The installing HVAC contractor was no help in this instance.
Make sure the hydronic coil in the duct work (from the boiler) does not have a "freeze protection" feature enabled, or the boiler itself. I ran into situations when the A/C came on the temp in the air handler would drop to the point of activating the "freeze protection" and fire the boiler, providing hot air with the A/C. The solution was to disable the feature in the air handler (jumper) and also in the boiler control parameters. In my case, the system is filled with glycol so freeze protection for the hydronic system is not an issue. I am not suggesting this is your problem for sure, but should be looked into.

darkside501st

@hot_rod I live in Oxford, Michigan. Right now it is 15 to 35 degrees Fahrenheit. Back when we were having this issue, before we disconnected the wire that turns on the burner, it was closer to 65-85 degrees Fahrenheit.

I guess I am going to have to do a lot of research to learn how to fix this issue and get some controllers and wiring setup correctly so the system can manage itself better. I will take a look at those Ecobee tutorials. Thanks.