Dual Thermostats - 1 system Pump/Zone

TerrS

pecmsg said:

Are you ASSUMING or measuring?
you also need water temperature in and out. 

So btus charts do a lot of assumptions, because mine are around 50 years old.

So yes to fully understand I need.to buy a temperature clamp to check my supply and returns at the boiler but then at several fins.

Because let's assume for a second the water is 170+ water. Does that mean my water is moving to fast to pull out the heat?. I mean my fins are mostly only 8ft, a few 10ft and attic 2 at 20ft

Jamie Hall

If your differential was or is only 5 degrees or so, you are way overpumped -- in addition to all your other woes, which you seem to be resisting doing anything positive about.

TerrS

HomerJSmith said:

To get back to the original question--running one zone (two floors) off of two thermostat, you can be sure that one or the other floor is going to be incorrect temperature wise because only one thermostat can effectively have control.

So I was still thinking about this. But like someone else said, what if I used a system to avg both thermostats?

TerrS

Jamie Hall said:

If your differential was or is only 5 degrees or so, you are way overpumped -- in addition to all your other woes, which you seem to be resisting doing anything positive about.

Thats not even true, I am spending $5k on insulation next Monday on areas that I know are cold. I asked Ray to look at my boiler because things others have said didn't make sense. So not even sure what you are talking about!!!!. But I am still on my own here, Ray doesn't do residential boilers. So until I pinpoint where to spend even more money possibly I need them to be in right direction, the 4 hvac people I had here throw up their hands and say go buy another boiler at $$$$$$ and then cant even tell me that will heat my house better..

So ummm yeah..

KC_Jones

TerrS said:

@Jamie Hall yes but that's the issue and has been, my water is 180 degrees and using a 4gpm or 1gpm fin heat output. It's around 600-625btus per ft at those gpms.

So if you start asking, are they really giving off those btu's.  I start asking how fast is my hot water moving.

You are not getting 600-625 regardless of flow, this has been told to you on several occasions, but you still aren't getting it.

You get 600 BTU if the flow is continuous for a full hour during all the hours of the day, any time less than that and you get less output. You have stated, by your own observation, that you will run 40 out of 60 minutes which means the baseboard output is only 400 btu/hour, not 600. This is why we keep trying to tell you that you don't "need" 180° water. 150° water flowing continuously would give you the same output, and should be more efficient.

This is why a heat loss is so important. Your conclusions based on your observations are incorrect and contributing to you not understanding what is being explained, as near as I can tell.

You are moving BTU's, not hot water. You have to think BTU's, not water temperature. TIME is a paramount criteria here as much as flow and temperature, and all three matter when figuring this out.

ChrisJ

TerrS said:

HomerJSmith said:

To get back to the original question--running one zone (two floors) off of two thermostat, you can be sure that one or the other floor is going to be incorrect temperature wise because only one thermostat can effectively have control.

So I was still thinking about this. But like someone else said, what if I used a system to avg both thermostats?

https://www.supplyhouse.com/Honeywell-Home-YTHX9421R5101WW-Prestige-IAQ-Kit-with-RedLINK-Includes-White-Thermostat-EIM-Wireless-Outdoor-Sensor-2-Duct-Sensors

And here's the wireless sensor that goes with it. You can use a bunch of these but I don't remember how many. Like I said, I have 3.

https://www.supplyhouse.com/Honeywell-Home-C7189R1004-RedLINK-Enabled-Wireless-Indoor-Air-Sensor-Wireless

HomerJSmith

How does RedLINK solve the problem? Does RedLINK avg both thermostats (sensors)?

"You are moving BTU's, not hot water."

KC_Jones, it's nice to know that BTUs have nothing to do with hot water. How do you separate one from the other? Btu's and hot water marriage go together like a horse and carriage, me thinkith. It's like a coin, you can't have one side of a coin. But...to be fair water is the carrier of heat energy and the capacity of liquid water to carry heat energy is limited. I think what you are saying is that it is the temperature of water that counts. However, it's the flow of water that moves the heat energy from one point to another.

You can't measure energy and you can take that to the bank. You can only measure the effects of energy. -- Whoa, Homer, deep thinking, there.

TerrS

Jamie Hall said:

If your differential was or is only 5 degrees or so, you are way overpumped -- in addition to all your other woes, which you seem to be resisting doing anything positive about.

So originally yes, with my old l8124 set temp was 180degree always, and in looking at the control, it had either a 5 or maybe 10 degree deferential.

 Introduce the Beckett 7610 and now my water fluctuates but on cold days always sits at 180. It's been warm here in Pittsburgh and looks like another week yet of warmer temperatures.

Saturday I will have a clamp-on temperature Guage and I will monitor pipe temperature entering and exiting one of the 8ft fins, 10ft and possibly the 20ft if I can get to those pipes in the attic. I will also monitor my supply and returns at the boiler. Right now my water temp set on the 7610, is at 165, so I should see that or close to it entering the fins. Unfortunately my fins are not labeled, so I can't tell first, middle or end of a loop, but I will see.

But If my gpm calculation is even close with head pressure, at .5, and even if I quadruple it at 4 even. A 10 gallon pump at 9 head should work to get closer to my 4gpm number.

I have yet another boiler guy coming Tuesday, but not holding out any hope, but who knows and I am going to hope.

Lastly to@KC_Jones. According to Ray's chart he gave me, after 30 minutes of firing time, the water is 168.2 degrees and the loop has around 41870 btus. That includes around 875 btus lost in pipes and overall heatloss due to air temperature.

Assumes boiler  is providing 1875btus per minute. He did those calculations at 42 degrees which it was Tuesday 9am and when watched when the boiler stopped firing and pump running. But he forgot his clamps to see supply and return temps.

More to follow

pecmsg

Also get supply and return at the boiler. When the boiler is at or near 180*

KC_Jones

HomerJSmith said:

How does RedLINK solve the problem? Does RedLINK avg both thermostats?

"You are moving BTU's, not hot water."

KC_Jones, it's nice to know that BTUs have nothing to do with temperature. How do you separate one from the other? Btu's and hot water marriage go together like a horse and carriage, me thinkith.

First, show me with a quote where I said they have nothing to do with one another? Those exact words. You can't because I didn't say it, so I'd appreciate you not partial quoting me to try and change my message. What do you get out of that anyway?

I guess you chose to completely ignore this part:
"TIME is a paramount criteria here as much as flow and temperature, and all three matter when figuring this out."

The OP has been obsessing over the water temperature and not looking at the other factors, those include time and flow. You must look at all 3, at least, to have an understanding.

Or is it your assertation that we aren't trying to move BTU's here? Because that is the counterpoint to my statement.


If you are going to quote someone, quote everything.

TerrS

pecmsg said:

Also get supply and return at the boiler. When the boileri  is at or near 180*

I might not be able to get the water thst hot, because of the Beckett HM, but will see. After next week it's supposed to get colder and that will drive my water temperatures up.

ChrisJ

HomerJSmith said:

How does RedLINK solve the problem? Does RedLINK avg both thermostats?

"You are moving BTU's, not hot water."

KC_Jones, it's nice to know that BTUs have nothing to do with hot water. How do you separate one from the other? Btu's and hot water marriage go together like a horse and carriage, me thinkith. But...to be fair water is the carrier of heat energy and the capacity of liquid water to carry heat energy is limited.

You can't measure energy and you can take that to the bank. You can only measure the effects of energy. -- Whoa, Homer, deep thinking there.

As I said earlier,
That thermostat and those sensors can be setup to average multiple locations.

I didn't say anything about Redlink. Redlink is how it all communicates wirelessly.

TerrS

@KC_Jones so ummm I am not going to argue with you, but once my water temperature hits 180degrees, yes my fins according to specs should be giving off those btu's. Yes I will concede that for only as long as my water is at temperature. On cold days that's like 30 extra minutes, as the first 40 my water was not that hot.

I will also agree with you on the 3 aspects, we know but yet proven with a Guage that on cold days my supply water hits 180 degrees because I can see it on my Beckett and my boiler internal guage, so we also know we are firing for 30 minutes minimum on those cold days, as I have seen that last year. Yet to be cold enough to drive my boiler that long to get to those run times and water temperature. The last component you mentioned is flow, as we can't monitor that directly. If the water entering a fin and exiting are close in temperature, we could deduce that that water is flying thru and not transferring those BTU's to the room.

So again I will see.

ChrisJ

Have you actually measured the water temperature coming back from the radiation before it goes back to the boiler?

Jamie Hall

" If the water entering a fin and exiting are close in temperature, we could deduce that that water is flying thru and not transferring those BTU's to the room."

Nopd. If the fins are at that water temperature, they are transmitting the rated BTUh (power) to the room. Fear not. What is happening is that the flow is so great that there is far more power available in the water than is being transmitted to the room, and the rest goes on to the next emitter -- or back to the boiler.

It will help you, if you care to work on it, to contemplate three things: first, it takes a certain amount of power to maintain the room temperature. That's in BTUh, and it's a function of the heat loss rate of the room. Second, your radiation will deliver a certain amount of power -- again BTUh -- at a particular water temperature. That's a function solely of the design and amount of radiation. Third, that power transmitted from the water to the radiation and thence to the room will show up in the output water temperature being less than the input water temperature. The actual formula, which you misused, is BTUh is equal to 500 times delta T (inlet minus outlet(degrees F) times flow in GPM.

This is basic Physics 101.

The other thing you might contemplate is that you must not confuse energy (BTU) with power (BTUh).

Now to go back to the original problem here. Your complaint was and I presume remains that the temperature on the second floor was cooler than that on the first floor. That is because you are providing more power to the first floor, in relation to its power requirement, than you are to the second floor. End of story. Now there are two ways to fix that. Reduce the power being supplied to the first floor, or reduce the power required to heat the second floor. There are a number of ways to do that, but no amount of fiddling with thermostats is going to accomplish either of those things.

HomerJSmith

Sorry if I offended you KC_Jones, but what am I to think, KC with the following sentence?

"You are moving BTU's, not hot water. You have to think BTU's, not water temperature."

BTU=is defined as the amount of heat energy required to raise the temperature of one pound of water by one degree Fahrenheit. Dang, there's that temperature thingy worming its way into the conversation.

"TIME is a paramount criteria..."

not so much! Flow and Temperature are more paramount in delivering BTUs in this case, although I must agree that time is inescapable.

I don't claim to understand everything, half the time I don't know what I'm doing or where I am and I'm grateful for any help I can get.

TerrS

@Jamie Hall agreed. Hopefully the insulation I am adding to the 2nd floor and basement will cut the BTU's needed to keep the 2nd floor at temperature.

You are correct about my true issue, and not to beat that dead horse, was if there was another t-stat it would force the boiler to run more to meet the demands of the 2nd floor,  heat loss. If I speculate based on everything stated, the 1st floor must not have as much heat loss than the 2nd floor. So first step add Insulation to areas I know are colder and have issues.

Thanks for the explanation, but I am really curious, why if you look at the slant-fins btu specs they only State values for 1 and 4 gpm?  What happens at higher gpms?

I have also contacted a company that does infrared room scans. I don't understand truly how to calculate my room by room heat loss. if a given room is 12x14, 1 wall is insulated at r15 and one wall has probably nothing or very little, and only has 1 8ft fin. So I need to address that wall after my upstairs and basement.

And that room as with all the others have  no possibility of adding any more. So I have been looking at the Smith HE2 dual element fins. To replace a few rooms.

So I am trying and making changes to meet in the middle of cost of change, vs energy saved or not spent..

But I am at my wits end and will leave it at that.

Jamie Hall

You could also reduce the water flow rate to the first floor, if you had balancing valves to do that. You probably don't.

With regard to the Slant/Fin data for the baseboards -- what they don't quote is the delta T from one end to the other of the baseboard. All they are giving you is the inlet temperature. At intermediate flow rates, the delta T will also be an intermediate value -- and the output is actually at the average temperature of the element. Not, I admit, the most helpful tables in the world in that regard... I might add that the table is actually slightly misleading in that regard, since in a long baseboard the delta T will be more and the average temperature, therefore, less -- and the output less, averaged per foot.

HomerJSmith

Please, don't be at your wits end. You can't be functional thinking and emotional at the same time.

why if you look at the slant-fins btu specs they only State values for 1 and 4 gpm?

Because all tubing has a maximum flow rate before pipe erosion and noise occurs. With 3/4" copper tube it is about 6 GPM and 4 GPM is a safe flow. At less than 1GPM, in a 65' run of fin-tube baseboard, you run out of heat energy before you even can heat baseboard down the line.

ChrisJ

HomerJSmith said:

Please, don't be at your wits end. You can't be functional thinking and emotional at the same time.

why if you look at the slant-fins btu specs they only State values for 1 and 4 gpm?

Because all tubing has a maximum flow rate before pipe erosion and noise occurs. With 3/4" copper tube it is about 6 GPM and 4 GPM is a safe flow. At less than 1GPM, in a 65' run of fin-tube baseboard, you run out of heat energy before you even can heat baseboard down the line.

That's true.
That's another reason I was astonished when so many said a 1/2" copper water service would be fine for a place with two bathrooms

hot_rod

Anybody that tells you the water is moving too fast to give off heat, probably should not be in the Hydronics business, or giving advice on heat transfer.

The hotter a heat emitter of any type the more heat to transfers, true or false?

Also the higher the average water temperature across any of your fin tubes the higher the output, true or false?

Increasing either the flow rate or the supply temperature to the fin will increase the output, true or false?

Here is how that works in picture form🥴

The limiting factor to how much you can flow has to do with velocity, speed of the fluid,

If you do not hear water rushing through your pipes, you are flowing below 5 feet per second. That is a high number for water over 140F in copper pipe on a constant basis.

Additional proof of faster flow = higher heat transfer is the fin tube output sheet you mentioned. 4 gom(faster flow) moves more heat then 1 gpm (slower flow) true or false?

Your problem is not one of excessive flow rate, unless the laws of thermodynamics have been changed?

Although I suspect politicians may attempt to change those laws also🤓

hot_rod

Ecobee on sale!
I use the remote sensor in my basement 
I enable it when we have guests downstairs to keep the basement at a desired temperature.

And yes the upstairs does overshoot since it is a single thermostat for the entire home and a non zoned forced air system.

The sensor is wireless .

 I bought refurbished Ecobees directly from Ecobee, same warranty as new and saves a few more bucks!

TerrS

@hot_rod So I am giving up, until I add some insulation to my upstairs and basement. hopefully that changes the dynamics of the upstairs temperature, adding in the basement helps a few places I already know are colder in the kitchen and dining room.

But to answer. Sometimes people will say something and emphasize it, like its a problem, when in reality its not. Then add in my inexperience, only exasperates the issue.

Yes I agree, the hotter the emitter, the more btus produced/given off, not to say my pump isnt oversized but probably not causing issues, but something to think about for the next boiler.

This weekend, after amazon delivers my clamp-on heat gauge, I will test my supply and return temperatures on each zone. I will report back here...

Yes, i only slightly hear the water when the pump first kicks on, then its pretty quiet.

JakeCK

Insulate the house, and If it's still cold upstairs block off some of the fin tubes downstairs and be done with it until you decide to move.

I'm done, that's all I got to say.

🤕🧱

HomerJSmith

Au Contraire, TerrS. who says.

Yes I agree, the hotter the emitter, the more btus produced/given off.

Not necessarily. If the environment is 120 degs and the emitter is 120 degs there will be no transfer of btus. There must be a temperature differential for heat energy to flow and the rate of flow depends upon how wide that differential is. Heat energy flows to cold regardless of direction. But I know what you mean.

ChrisJ

HomerJSmith said:

Au Contraire, TerrS. who says.

Yes I agree, the hotter the emitter, the more btus produced/given off.

Not necessarily. If the environment is 120 degs and the emitter is 120 degs there will be no transfer of btus. There must be a temperature differential for heat energy to flow and the rate of flow depends upon how wide that differential is. Heat energy flows to cold regardless of direction. But I know what you mean.

Specifically in the OP's case, I think it's very safe to assume the indoor air temperature will never be 180F.

hot_rod

HomerJSmith said:

Au Contraire, TerrS. who says.

Yes I agree, the hotter the emitter, the more btus produced/given off.

Not necessarily. If the environment is 120 degs and the emitter is 120 degs there will be no transfer of btus. There must be a temperature differential for heat energy to flow and the rate of flow depends upon how wide that differential is. Heat energy flows to cold regardless of direction. But I know what you mean.

I suppose it wouldn’t be considered a heat emitter under those conditions, more like a wall decoration

Lance

Plan to first design a system to do this very thing and design it. Decide to build or not. To patch this with unknown results, try either rezone the system with each zone with its own control, or remove the excess heat by fan to the level needing it. I once had a client who used fireplaces to save money. The boiler did not run, it was toasty inside, but the pipes froze in the basement. Cost him two weeks of my labor to find and repair all the leaks in the building. I assure you he, rethought his true cost of a way to save money. You can also try a Honeywell tech's control advice, turn circulator on for constant operation. His control was the 120V pump switch. Outcome for you is unknown. You are now an experimental scientist. Good luck.

UKN

It's actually a very simple solution, get yourself an Ecobee thermostat with at least 2 remote sensors. Put the remote sensors in same room away from the open fire heat radiations. The Ecobee thermostat will take the average sensing form these remote sensors and keep the heater system adjust accordingly. The sensor can also be shielded by walls or doors and will work perfectly. Our living room and dining rooms adjoins using an Ecobee thermostat with two remote sensors, one in the dining room and the other at the opposite end of the living room away from the open fire. It works just great. With a two story 4 bedrooms two baths, we have an Ecobee in each room controlling our hydronic heating system just perfectly. Each Ecobee thermostat has at least 1 remote sensor with each thermostat also being a "sensor". System works great with being able to keep the no-occupied rooms at lower temperature.

Dan Nibbelink

Two Thoughts: First: if you want a second thermostat for the second floor you also need controls so that only the second floor received that heat.
Second: I suspect that you are using more fuel when using the fireplace than if you didn't because of all the heat from the first floor that is going up the chimney.
Bottom line: Simplest solution to get the second story warmer: quit using the fireplace!

TerrS

So as of now, I will know more Saturday as it will be finally cold enough in turn on my boiler.  I will be investigating supply and return pipe temperatures, and will make sure were each of my 4 pipes heat.

Then I will probably go with the ecobee solution so the upstairs can call for heat. But I think there was another solution to have 2 thermostats do an average which would work for this year.

Next fall look at zone valves, smaller pump 10gpm instead of 17gpm and 2 thermostats and a smaller boiler.

Lastly and I have heard the gambit of vent-free fireplaces, but mine has been in use for 20 years. It's cleaned and tested and 2 CO2 monitors. So none of my energy is wasted up the chimney except 25% of the boiler. Since my boiler is only 75%- 1990 technology efficient.

Jamie Hall

Vent-free gas fireplaces put the exhaust in the heated space. Very efficient. Not very good for any human occup0ants (many jurisdictions flat out prohibit them at least in sleeping areas), worse for pets, and lethal for plants. Low level CO (NOt CO2 -- that's a different stuff) monitors are available, but the big box inexpensive monitors will not warn you of chronic low exposure, which is also bad news.

Averaging two thermostats together won't help getting one space warmer and the other cooler. You need to get your system balanced or if you want one area cooler and one warmer, and controlled, you need to zone it.

pecmsg

TerrS said:

Lastly and I have heard the gambit of vent-free fireplaces, but mine has been in use for 20 years. It's cleaned and tested and 2 CO2 monitors. So none of my energy is wasted up the chimney except 25% of the boiler. Since my boiler is only 75%- 1990 technology efficient.

Big box store CO detectors are virtually worthless. 70 PPM has to be exceeded for up to 3 hours before it will alarm. That’s why I preach against them. 

The Defender Low Level will alert at 30 PPM much lower level and earlier warning of potential danger!

pecmsg

TerrS said:

Then I will probably go with the ecobee solution so the upstairs can call for heat. But I think there was another solution to have 2 thermostats do an average which would work for this year.

Next fall look at zone valves, smaller pump 10gpm instead of 17gpm and 2 thermostats and a smaller boiler.

I’ll save you the cost of a t-stat. 

Just turn the 1 st floor stat all the way up. Wait upstairs and when it’s comfortable go down stairs and see what the t-stat is reading b

ChrisJ

pecmsg said:

TerrS said:

Lastly and I have heard the gambit of vent-free fireplaces, but mine has been in use for 20 years. It's cleaned and tested and 2 CO2 monitors. So none of my energy is wasted up the chimney except 25% of the boiler. Since my boiler is only 75%- 1990 technology efficient.

Big box store CO detectors are virtually worthless. 70 PPM has to be exceeded for up to 3 hours before it will alarm. That’s why I preach against them. 

The Defender Low Level will alert at 30 PPM much lower level and earlier warning of potential danger!

I'm fairly certain the design characteristics of CO detectors have absolutely nothing to do with them being sold by a "big box store" in fact they typically come in small boxes.


And I would disagree and say they are far from worthless.

This is a design requirement by UL, no?
And it's intent is to save lives not stop headaches. Similar to how GFCI receptacles work, they are there to stop lethal shocks, not all shocks.

pecmsg

ChrisJ said:

TerrS said:

Lastly and I have heard the gambit of vent-free fireplaces, but mine has been in use for 20 years. It's cleaned and tested and 2 CO2 monitors. So none of my energy is wasted up the chimney except 25% of the boiler. Since my boiler is only 75%- 1990 technology efficient.

Big box store CO detectors are virtually worthless. 70 PPM has to be exceeded for up to 3 hours before it will alarm. That’s why I preach against them. 

The Defender Low Level will alert at 30 PPM much lower level and earlier warning of potential danger!

I'm fairly certain the design characteristics of CO detectors have absolutely nothing to do with them being sold by a "big box store" in fact they typically come in small boxes. And I would disagree and say they are far from worthless.

UL Rated alarms ARE rated to exceed 70 PPM for up to 3 hours before they alarm. Virtually  Worthless!

That’s the minimum for the UL listing. 

My personal CO monitor alerts at 15 PPM. 

OSHA only allows 50 PPM over an 8 hour period. 

pedmec

Some people just can't be helped.

EdTheHeaterMan

As far as I see, no one has actually answered @TerrS's first question.

Dual Thermostats - 1 system Pump/Zone

Yes you can. Here is the diagram.

Now the first floor may get too hot. if it does then shut down the radiators on the first floor. If they are standard baseboard radiators "aluminum fin" as TerrS stated, then close the dampers and 80% of the radiator out put is stopped. If there are valves, then set them to almost closed. If there is no other way, then put duct tape over the opening of the radiator to stop air flow.

OR

We can all chip in and hire a mechanical engineer and redesign the system on paper after careful consideration of the load calculation of the structure before and after there are any efforts to seal up the home, but please allow for combustion air for the boiler and the fireplace with different flues. Then the actual water flow to each radiator can be adjusted by having custom made pipe diameters to allow for the proper flow rate by calculating the water temperature, flow rate and the amount of time it will take to attain perfect room temperature balance with thermally self adjusting orifices within each pipe fitting. This way the Pipes Will Know which thermostat is calling for heat. This way, with a paid mechanical engineer, No One will be

WRONG
WRONG
WRONG

And we can all ignore any mis quoted posts because the engineer can provide a 650 page report with all the necessary spreadsheets, charts, projections, and details based on every possible weather scenario, including the possibility of moving the building to the frozen tundra, or to the hottest desert. We need to be all inclusive these days!

ChrisJ

pecmsg said:

ChrisJ said:

TerrS said:

Lastly and I have heard the gambit of vent-free fireplaces, but mine has been in use for 20 years. It's cleaned and tested and 2 CO2 monitors. So none of my energy is wasted up the chimney except 25% of the boiler. Since my boiler is only 75%- 1990 technology efficient.

Big box store CO detectors are virtually worthless. 70 PPM has to be exceeded for up to 3 hours before it will alarm. That’s why I preach against them. 

The Defender Low Level will alert at 30 PPM much lower level and earlier warning of potential danger!

I'm fairly certain the design characteristics of CO detectors have absolutely nothing to do with them being sold by a "big box store" in fact they typically come in small boxes.


And I would disagree and say they are far from worthless.

UL Rated alarms ARE rated to exceed 70 PPM for up to 3 hours before they alarm. Virtually  Worthless!

That’s the minimum for the UL listing. 

My personal CO monitor alerts at 15 PPM. 

OSHA only allows 50 PPM over an 8 hour period. 

Your personal alarm is expected to be used under certain conditions by a trained operator.

UL listed alarms are to be used by the general public and is intended to save lives under extremely dangerous conditions. nuisance alarms need to be avoided and the product needs to be affordable and reliable long term under a huge variety of conditions.

There's a big difference between them and I honestly feel telling people they're worthless is dangerous on our part.

Typically, if people keep having headaches etc they will investigate why.
They can't do this if they're dead, that's where the code required UL listed alarms come in.

Those are my thoughts anyway.

pedmec

Been there and done that with the engineers. (5) 750 gallon vertical domestic hot water tanks.They draw out the whole building piping for the hot water issue. new $25,000 mixing station. couple of $100,000 for the engineers. I found they never installed a $150 dollar swing check between the heat exchanger and tanks. 25 years they tried finding what was going on. what a waste of money. sometimes you gotta take a step back