Problems with new dual hydronic heating system

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Old 11-13-18, 06:59 PM
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Problems with new dual hydronic heating system

Hi,

I moved from the eastern US to Las Vegas a few years ago, so I am unfamiliar with a "dual hydronic" heating system, which I think is what they call this thing...

Basically, my hot water heater doubles as my heating system in that there is a hot water outlet that goes up into the ceiling and must run through some coils and fans or something, which allows me to blow warm air throughout my condo.

Anyway, my hot water heater died a few months ago and I had it replaced. Hot water was flowing fine ever since, but about a week ago I finally turned on my heating system for the first time. That seemed to work fine also. I discovered the problem the next morning when I got in the shower and the water was barely warm...I thought the hot water heater went out and the water had just cooled over night, but when I checked it, it was fine -- for some reason the hot water just isn't making it directly through my faucets after running the heating system.

In doing some tests, I found that:

1) If I completely shut the valves that go to the heating system, then hot water will make its way to my faucets again, but then I can't run my heating system!

2) If I open the heating system valves AND the heating system is actually RUNNING, then it also seems like hot water makes it to my faucets.

3) HOWEVER, if I have the valves open to the heating system but the system is NOT running, then the hot water does not make it to my faucets... it appears that the pipes to the heating system are the path of least resistance when it's not running, so my hot water is mostly just running through there instead of going to my faucets (at least I think that must be what is happening).

I've read (after I had the hot water heater replaced) that it is very important for these systems to "bleed them" when installing a new water heater. As far as I know, the plumber that replaced mine did not bleed anything having to do with the heating system. Could that have created this issue? Is it something I can fix myself, if that is the case?

For additional information, it does NOT look like there are actually completely separate, isolated pipes going to the heating system. The hot goes out of the top of the water heater and there is a split--one goes into the wall (and to my faucets, etc. I guess) and one runs up into the ceiling to the heating system. Same with the cold side -- the pipe from the heating system runs down and connects into/meets with the cold water supply that connects to the cool water input to the water heater.

I though that was a bit strange too... does that mean I am washing dishes/clothes/showering in water that was running through the heating system?

Thanks in advance, and I'll try to supply any additional info I can.

In the meantime, while I try to figure this out on my own (for now), I just have the valves closed to the heating system and I am not running it (it's not THAT cold in Vegas) so I can still take a hot shower and do laundry, dishes, etc...

-Doug
 
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Old 11-13-18, 10:27 PM
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Welcome to the forums.

Dual hydronic is used everywhere.
It's one boiler that supplies domestic hot water and heating hot water.

In order for us to help you..... we need to know what the boiler is and pictures of the installation would be a big help too. How-to-insert-pictures
 
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Old 11-14-18, 07:05 AM
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Cont

I'll take a couple pics today, but I really don't have a "boiler" based on other pictures I've seen here. I truly ONLY have a regular looking water heater. It is a 65,000 BTU 50 Gallon power-vent water heater and it looks just like a regular water heater.

The only difference is that it has that hot water "out" that runs up into the ceiling and then the return that goes into the "cold" line by the top of the water heater. Up in the ceiling that single hot water line goes into a little box near the fan/blower and then the single return line leads back to the water heater.

If this diagram works, it looks pretty much just like this. The other pic is what I can see if I poke my head into the ceiling. Those go right into/out of where the blower is. It's something like if you had a baseboard type heater up in that one area of the ceiling, then the blower just blows that heat throughout the condo. I figured since that seems kind of a weak heating source they weren't used anywhere except where the temperatures don't get very cold. I certainly never saw anything like it in Pennsylvania! Only big gas furnaces, wood burners, or big water based systems with giant separate boilers, etc.

I'll take a pic of my water heater later, but I'm telling you... it just looks like a water heater

Thanks,

Doug
 
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Last edited by PJmax; 11-14-18 at 11:12 AM. Reason: reoriented diagram
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Old 11-14-18, 11:16 AM
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Okay, here are a few pics -- very uncomplicated for any of you, I'm sure -- I just am trying to figure out why, after the water heater install, hot water to faucets worked fine until I first ran heating system. Once I did that, if heating system is not actively running hot water no longer makes it to faucets (a little bit does, but even on full hot it is just mildly warm...so it seems it is being mixed with a lot of cold).

I have an overall pic of water heater, a close-up of the hot and cold where they meet with the pipes to heating system, and a pic of the label for the water heater model.

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Last edited by PJmax; 11-14-18 at 12:11 PM. Reason: reoriented pics
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Old 11-14-18, 11:17 AM
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It's not a terribly effective system but I guess it works ok with minimal heat requirements.
A little hard on a regular water heater.

There needs to be some way for a thermostat to operate a valve in the hot water line to the coil.
There wouldn't be hot water flowing thru the heat exchanger if it wasn't needed.
 
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Old 11-14-18, 11:59 AM
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Okay, that makes sense, but here's where I'm confused:

I usually have my heating system OFF, so most of the time, I guess, no water is even running through those pipes to the heating system. When I have it on, sure, there's a thermostat and when it kicks on, the valve opens or a pump runs or whatever and then hot water starts flowing through the heating system.

My issue is that after this guy put in the hot water heater, after the FIRST time I turned on the heating system, thus running hot water through it, hot water stopped going to my faucets when the heating system is NOT running.

Do you know what might have caused that just by changing the water heater out? He went nowhere near the heating system.

I read somewhere that with this type of system, when putting in a new hot water heater it is very important to bleed any air out of the pipes that got in due to putting in new lines at the water heater. If this was not done, could it cause the problem I'm having?

Keep in mind, in case it helps, if I completely CLOSE OFF the lines to the heating system, I get hot water again at the faucets. OR if the heating system is actively running, I can get hot water at the faucets. Once the desired room temperature is reached and the heating system kicks off.... no more hot water at the faucets (I watched a thermometer and saw the temp slowly drop almost as soon as the heat kicks off).

Thanks in advance for any insight!

-Doug
 
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Old 11-14-18, 01:13 PM
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Is it possible to take pics of the tank and piping all in one shot so we can see the tank and all connected piping before it leaves the room.
 
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Old 11-14-18, 01:22 PM
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The first pic in the group of them shows pretty much the whole thing.
There's no pump, no check valves..... nothing to direct the water flow.

I'm wondering what was removed when the water heater was replaced.
 
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Old 11-14-18, 01:34 PM
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What is telling you that the heating system is running? What is telling you that water is flowing through the heating system?
 
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Old 11-14-18, 01:34 PM
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PJ,
If that is the whole installation I can't see how the water circulates for the heat at all. That is nothing more than a feed and supply for hot water to me. I hope there's more.
 
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Old 11-14-18, 02:20 PM
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PJMax is correct - what you see is what you get That is the WHOLE thing... and up in the ceiling, there isn't much more -- that hot water line simply runs into the heating element / blower area, etc. And yes, I'm now wondering if something else was removed at the site of the water heater connections -- maybe there was a check valve at the hot water line there (is that ever done?) that he took out and replaced with just the new flex line?

What is telling me the heating system is running is I turn on the heat, turn up the temperature, and I hear it start blowing--I also got up on a chair and felt the warm air blowing out. At the same time, I can see the water temp start climbing again! Then, when the desired temp is reached (or I turn the thermostat down or turn off the heat), the blower stops and in a few seconds the water temp starts dropping.

And to spott: there is something up in the ceiling by the blower that I imagine has a pump that kicks on and/or opens some type of valve when the thermostat says to turn the heat on.

It is really small up there, I can only see it by removing the air filter for the A/C and sticking my head up there -- there is a pic I posted, but it doesn't show much... just water line running into the heating element thing by the blower...then the cooled water comes out other side and runs back down to the water heater.

This is apparently how they did a lot of the condos they threw up in Vegas in the 2000s before the crash.

-Doug
 
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Old 11-14-18, 02:28 PM
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What turns the hot water heater and what controls the temp of the water, first when you call for heat and 2nd when you just want faucet water.
 
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Old 11-14-18, 02:34 PM
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Actually, now that I look at the photo -- I know he didn't remove/replace anything above the flex lines, so I don't think anything lacking there could be the problem if the cold water is running backward through the heating loop.

Since nobody mentioned it, I'm guessing that leaving some air in the line wouldn't cause something like I'm describing... if it's not that, then even if he didn't bleed it I guess that's irrelevant. Maybe in the installation of the new line he got some debris in the line and the first time I ran the heating system it caused a valve up there to get stuck open...

Regardless, IF the cold is running the wrong way through there, I think they can just come back, I pay another $200 and they put in a new one-way valve somewhere in the heating loop. There's no way I can take the system apart to see if his gum wrapper got caught in the check valve so I guess I just pay up...

-Doug
 
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Old 11-14-18, 02:38 PM
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Spott: The hot water heater is just like a regular hot water heater (actually, it IS just a regular hot water heater!). So I have the water temp set at the base of the water heater. So, let's say I have it set at 120... it just keeps it at 120. When I open faucet, I get 120 minus whatever it loses on the way. When the heating system kicks on, it gets 120 minus whatever it loses on the way, then it blows off some heat and sends the cooler water back to be heated back up to 120 again.

Or maybe I misunderstood what you were asking (I probably did... I'm no plumber, as you can all tell by now, lol).

-Doug
 
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Old 11-14-18, 03:11 PM
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Doug,
If you get 120 at the faucet no matter if you call for heat or not then where is the no hot water to faucets come from. I thought you had a lack of domestic (faucet) hot water after the new tank was installed.
 
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Old 11-14-18, 03:19 PM
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Spott:

Okay, I did misunderstand you I was describing how it is "supposed" to work and how it worked up until the time when I got the new water heater.

Now, I have 120 at the water heater, but if the heater is not actively running, I do NOT get 120 at the faucet because it is getting mixed with cold water, apparently.

If the heater IS running, I assume the pressure is higher due to the heater/pump calling for water so then the cold isn't making it's way through to my faucet lines, so I get 120 at the faucets.

If I completely shut the loop that goes to the heating system (and then obviously, I can't run the heating system), I also still get 120 at the faucet.

I'm only getting a cold invasion into my hot water faucet lines when I have the heater water line/loop open and the heater is not actually running. Then my water temp drops dramatically.

Hope that's clearer...

-Doug
 
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Old 11-14-18, 03:52 PM
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With your heat on, the water is forced to go to the heater to get reheated because of the pump circulating the water. When you shut the valves off to the heat the cold water has to go to the heater to get heated because it has no place else to go.

When you have all valves open but the heat not calling, so the pump is not forcing the water to the tank, without a CHECK VALVE in the return line of the heat what is stopping the cold water from going in both directions when you open your faucet.

Looking at your tank where the 2 ball valves are on the cold water inlet/heating return line are, if you installed a check valve above the ball valve on the heating line or you raised that ball valve and installed the CV in between the elbow and BV for maintenance reasons that would stop the water from going in both directions, simulating a closed ball valve but you could leave everything open and the pump would activate the CV when you called for heat.

You have to have something to stop the water flowing in all directions and backfilling through your heating lines and just into your tank.

Just a thought.
 
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Old 11-14-18, 04:29 PM
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Another thought is that the two valves supplying the heating system only need to be partially open.
It won't take much to heat the coil.
 
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Old 11-14-18, 04:38 PM
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Okay -- To start, I suppose I can try to open them partially and see if that works well enough.

As to the CV -- I agree, and that is likely what the plumbing company plans on coming out to do for $200.

I suppose what I'm wondering though is why it worked for the past 4 years but then stopped working when I got the new water heater installed -- any thoughts on that?

What do you think is more likely since it happened only after the new install:

1) Coincidence
2) Debris in line from repair/replace (he did have to install one new ball valve (the one that supplies the cold water to the hot water heater, NOT one of the ones on the heating loop) caused the CV (must be up in the ceiling, if there is one) to get stuck open,
3) Failure to bleed the air from the system somehow did something?
4) Something else?

Anyway, I'll try a partial opening of the two ball valves in the heating loop (what would happen if I turned on the heat but both of those ball valves were completely closed)? Would that damage the heating system since the pump would be running but there'd be no water flow? I'm just wondering what would happen--I don't plan on doing that!

If that doesn't work, then I'll just have them come and install a CV. I'll just leave it to them to determine where to put it unless you think one of the two locations you mentioned is superior. It won't cost much more to replace and move up the ball valve in order to put the CV below it, if that's better for some reason.

Thanks a lot for your suggestions and help,

Doug
 
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Old 11-14-18, 04:39 PM
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Pete,
The only thing with that is it would also cut the flow down to the pump and might cause cavitation and even with partially opened valves, when calling for domestic hot water the cold water supply would still be able to feed both ways instead of just into the tank.
 
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Old 11-14-18, 04:52 PM
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If you ran the pump with the valves closed you would burn out the pump, plus it would do you no good because without circulation you would have no heat. Even partially open valves might cause cavitation. Those pumps are made to run with fully open valves and lines.

AS far as the CV goes, looking at your pics again, it could involve some repiping because you cannot install a CV on a vertical pipe. Must be installed horizontally because of the design of the valve.

As far as air in the system, there is air in fresh water every time you turn on your faucet you let fresh water with air into your tank. If you had air in your coil, water would not circulate and you would have no heat.

As to why it worked before nobody can tell because we don't know how your last one was installed. Next time you'll have to take pics before you have anything replaced.
 
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Old 11-14-18, 05:06 PM
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I didn't see a confirmation there was a pump in line.
 
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Old 11-14-18, 05:22 PM
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That's what I was trying to get at with:

What is telling you that water is flowing through the heating system?
 
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Old 11-14-18, 05:58 PM
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Pete,
Post #11 about half way down when he addresses my response. It sounds like it's in the ceiling or part of the unit, so he thinks, which is why I mentioned it.

Z,
I'm guessing the water is getting to the coil because it's activating the blower and blowing warm air so the water must be getting to the coil somehow.

Everything at this point is just an assumption based on what is happening with the unit.
 
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Old 11-14-18, 07:23 PM
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Okay, so if there was air in the lines where he made the connection, if the air somehow got forced into the heating loop, then I'd have no warm air coming through. Since I do have warm air, I guess that's not the case.

I actually can get pictures to show how it was set up before the water heater replacement since I have another condo here that is exactly the same as it was. That said, I'm almost positive it looks exactly like the pics I've attached, except with an older water heater!

I will not try the partial valve opening because I don't want to risk burning out the pump (assuming there is one). I'll get some pics probably tomorrow just to be sure nothing is different.

Thanks again,

Doug
 
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Old 11-15-18, 07:04 AM
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I find it hard to believe that you are getting any space heat without a pump (circulator) somewhere in the loop up into the ceiling. Such a pump would probably switch on and off together with the blower.

I find it easy to believe that when the space heat zone is not calling for heat, used (cooled) water is coming back down from the ceiling and commingling with the hot water coming out of the heater and going to your faucet.

Some water heaters come with "heat trap" nipples that might add resistance to the in and out of water causing a greater back flow through the loop in the ceiling.

Yes, the faucet (potable) water is the same water that made a trip up into the ceiling and through the space heating loop. Possibly many trips, being reheated in the water heater each time.

An ordinary tank water heater is the same thing as an ordinary FHW boiler (which is the same thing as a counter standing plug in tea kettle) , burner/heating element and all. It is just that the typical water heater has a far smaller BTU per hour output and can only handle a very small room.

Some manufacturers do not honor/offer warranties of water heaters used for space heating, as described here.
 

Last edited by AllanJ; 11-15-18 at 07:20 AM.
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Old 11-15-18, 08:06 AM
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Shouldn't there at least be a "scoop tee" installed to keep the cold from flowing backwards towards the faucets? Or does the circulator STOP flow (or does it freewheel?) when there's no call for heat?

And when there IS a call for heat what keeps the warm return water from flowing towards an open Cold faucet?
 
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Old 11-15-18, 10:40 AM
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Is it possible that the cold supply is connected to the wrong side of the water heater (WH)? In other words, the cold is coming in to the hot side of the WH, and the hot is coming out of the cold side of the WH? It looks like you could run the WH backwards but I wonder if that would increase the resistance that the water heater would present, that is, with water coming in the anode side and flowing out of the dip tube side could there just be more resistance to flow?

It was mentioned before that its seems like when the heat loop is open there is less resistance than there was before in the heat loop and more cold water is traveling through the heat loop than with the old WH. If all of a sudden the new WH is offering more resistance than compared to the previous WH, it seems to me that more water might now take the easier path through the heat loop.

Im assuming that there is a pump in the heat loop that pumps toward the cold side of the WH, and that if the pump is NOT running, water can then go backwards through the pump through the heat loop. But if the pump is running that would not happen and water would be forced through the WH and things would look OK.

Lot of ifs lol!
 
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Old 11-15-18, 05:45 PM
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Here's another piece of info: I just went out to ensure the cold water line was indeed connected to the cold side of the WH and it IS connected in the right place.

Odd thing though, that flex line going into the cold side (as well as the one on the hot side) are BOTH WARM. Is that normal? Heat has NOT been turned on and the heat loop is actually closed, so doesn't seem that hot could be running through that loop and into the cold flex line. Nevertheless, both connection lines just above the water heater (the flexible ones) are warm to the touch.

There is probably a pump of some sort built into the thing up in the ceiling, but I really can't get a good look at it and don't know what to look for anyway. All I see is that one of the lines has a drain valve on it with one of those round twist valve things...like for a regular hose sized connection.

Why would the cold water line feel warm, particularly if the heating loop is closed?

Also, I have the plumber coming tomorrow morning to install the check valve, so I'll see what he has to say and if he fixes it.

-Doug
 
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Old 11-15-18, 06:37 PM
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Okay, from doing some searching it sounds like that cold water flex being warm isn't that out of the ordinary...just the hot pushing up a bit from the tank, correct?
 
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Old 11-15-18, 07:38 PM
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I believe it is. As soon as you open a faucet that line will get cold from the entering water. If the water is off for a while the cold line near the tank will get warm by conduction.

Nothing unusual.
 
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Old 11-17-18, 07:26 AM
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Well, plumber came yesterday and installed a CV and "hose bib" (I think that's what he called it) over on the cold return side of the heating loop.

He said he was putting the hose bib there to ease bleeding air from the system as opposed to trying to do it up in the ceiling near the actual heating unit (where the original hose bib is).

It seems like everything is working correctly now, so apparently there is a check valve up in the ceiling somewhere or within the heating unit that failed for some reason. That being said, I still wonder if the first guy not bleeding the system played a part in the check valve failure since this second plumber also stressed how important it was to bleed the system after doing any work on it.

Maybe it was all just a coincidence and the first plumber not bleeding the system didn't harm anything though... no way for me to know as I can't seem to find out what the possible ramifications of leaving air in these systems do to them. I see many places where it says NOT to leave any air in them, but nowhere actually says why!

-Doug
 
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Old 11-17-18, 08:54 AM
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Doug,
Air in the system PREVENTS the circulation of water which PREVENTS the coil from producing warm air and you getting heat.

Also, if the water doesn't circulate it could cause cavitation in the pump and burn it out.

Air in the system WOULD NOT cause a check valve to fail.

Good to hear everything is working again, thank you for the update. Have a good Thanksgiving,
 
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Old 11-17-18, 10:13 AM
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Thanks, Spott.

Good to know -- must have just been coincidence then. We do have REALLY bad water out here, so it's certainly possible that over the several months we didn't use the heat things got funky in there.

Take care,

Doug
 
 

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