TT Smart 80 & Prestige Solo 110 Summer Gas Usage

JustinS

Hi



I have a Triangle Tube Smart 80 water heater that is connected to a TT Prestige Solo 110 boiler... DWH is set to 140 DEGF with a 6 DEGF differential on the boiler... we also have a recirculating loop... and I believe that there is an anti-scalding mixing valve, as there's a T between the heater output and input that is DHW...



Right now, none of the DHW pipes are insulated and we're seeing DWH calls to the boiler approximately ever 4 hrs, give or take...



I don't really know if this frequency is OK but I feel that my natural gas usage may be a little high... this is my 1st summer in my new house so the only point of comparison I have is my old apartment where we used 14 CCF compared to 42 CCF in approximately the same time period...



Now, my house uses natural gas for cooktop and clothes dryer so I would expect there to be some increase but given that it's just my wife and I, wouldn't you expect less of a difference? Particularly, since my boiler and water heater are supposed to be so efficient?



Any thoughts? Thanks!

Gordy

insulate

Pipes, and boiler does domestic on high fire so its not going to be 93% efficient at that temperature output. But is way more efficient than a tank style water heater. Maybe widen differential to 10*.

JustinS

Recirc System Lowering Tank Temp?

Something I am wondering... If the tank is storing at at 140 and the mixing valve brings it down to 120 or so, doesn't my recirculating system lower my tank's efficiency by dumping this colder water back into the tank?



I ask because the SMART is supposed to have only 1 degf/hr loss (though, not clear what ambient temp that's at) and my tank seems to be losing more than that...

Charlie from wmass

you are loosing heat

through your hot water pipes and recirculating lines. If you insulate them it will reduce the heat loss. Also the use of an aquastat instead of a timer to control the recirculation pump will reduce heat loss as once the return water reaches 100 degrees fahrenheit the pump stops moving the water until it cools again.

JustinS

Right...

but aren't I losing more heat by the fact that I am taking 140degf water out of the tank, mixing it down to ~120degf and then re-introducing it to the tank?



I realize that there is loss due to the un-insulated pipes but what about the above loss?

Gordy

Aqua stat

As Charlie mentioned.



How big is your recirc pump you only need a little bump.



Bringing cooler water back to the tank is the nature of recirc. You should not be introducing a lot of lower temp water into the tank. You need to get your lines insulated is most of the problem. And an aqua stat.

Zman

Mixing

Your mixing valve is not bringing in cold water and reinjecting it in the tank. I couldn't because it would have to somehow displace the hot water. What it does is, circulates the 120 water and then mixes in 140 as needed.

As mentioned, insulating the line would be the best first step.

I like a combination of time and aquastat control on recircs.

Over sized and over used recirc pumps can also cause pipe failure.

Pictures are always nice.

Carl

JustinS

Taco 006-4B w/ Aquastat L6006C

The recirc pump is a Taco 006-4B - 1/40 HP, I think?



It's controlled by an aquastat attached to its discharge pipe which is set to 110degf with a 5degf differential...

Charlie from wmass

The water moving

is simply water drawn from the tank pushed back into the tank. Think of the old clothes line set ups with the pulley. No "new water" is introduced. you are simply warming the water that cooled in the hot water distribution piping. The point of the recirculating pump is to prevent dumping the heated water into the drain and replacing it in the tank with cold water until it displaces the cooled water that was in the hot water pipes with hot water to your given faucet of choice. It is better to warm 70 degree water to 140 then 42-50 degree water to 140. This is why the insulation is important as the change in temperature will be slowed, meaning less cycles per day to keep the water warm out to the faucets. You are using a little fuel to save a lot of fuel.

Charlie from wmass

dryer usage

I would look at that for savings also. They use a lot of fuel. did your apartment use gas for the dryer and hot water? Did you have to pay for that gas for both units? Does your boiler have a warm weather shut down set to below the current low temps you had for the given month? Was the boiler calibrated with proper testing equipment within the last year?

JustinS

No

Only the DHW was gas in the apartment... the dryer was electric...



I believe that the boiler has a warm weather shutdown but don't think it's configured - thermostats are off so I don't think it matters?



Boiler was just installed 8 months ago so I believe it was calibrated at that time....

JustinS

Understood

but I guess I was getting caught up on the fact that the mixing valve is intentionally cooling the water to 120F and then ultimately putting that back into the tank when the pipe surface drops below 110F...



Though, I guess since the pump only runs for a short time, I'm not continuously taking 140F and then putting 120F back in...

Charlie from wmass

when I was 6

I believed in the Easter bunny. Many boilers are not calibrated. Check to see if yours was by the installing contractor . Dryers use lots of gas.

RobG

I'm not

I'm not sure you are fully grasping what Charlie and Carl are saying. When you are putting out 120 deg water and bringing back 110 deg, the majority of the 110 deg water bypasses the tank and goes back into the cold side of the mixing valve. As the mixing valve is putting out 120, just a tad of the return water goes into the tank and just a tad of the 140 water leaves the tank into the hot side of the mixing valve to create 120 on the outlet of the mixing valve.



I don't know if I made any sense whatsoever :-) 



Rob

JustinS

Is That

Is that because the mixing valve limits how much hot water is removed from the tank - i.e, just enough to bring the 110F up to 120F? And then the same amount of "colder" water is made up into the tank?

JustinS

:-)

Good call ;-)

JustinS

Calibrating

What specifically does calibrating a boiler involve?



Just so I can sound a little more intelligent when talking to installer ;-)

RobG

Exactly

Exactly, the only time you are putting "cold" water into the tank is when you are using hot water. When circulating it is just displacing enough of the 140 to make the bring the 110 back up to 120.



It's tough to descibe but I think you've got it.

Charlie from wmass

water does not flow through the cold port

unless the pressure is lower on the outlet port of the mixing valve compared to the cold water pressure. If you do not open a faucet cold water can not enter the system. the return water comes back, the hot water goes out. Please just insulate your hot water lines.

RobG

Sure it does

Sure it does, if you have a mixing valve. Have a look at this drawing from a couple of posts back.



I can't get the picture to copy but look at drawing one from hot Rod on the post "recirculation loop" (It should be two posts down in this forum).



Rob

JustinS

How Does This Look

Applied the first insulation - how does it look? Tried to make sure that it's properly sealed along the seam... my thinking is that I would just continue the insulation on the other side of the ball valve to the left (towards boiler) and not worry about the bleed valve to the right?



Also, any recommendations on how to work the insulation around the hardware that attaches the piping to the wall?

RobG

Lools good

That looks just fine. Insulate everything you can get to. Even the drain side, hot goes to cold, that is the reason for the insulation. What is it, another six inches? 



As for the mounting brackets just trim it as best you can. Cut a couple of holes for the wings on the brackets and face the seam toward the wall.

JustinS

OK

OK but how to deal with the mounting hardware? Should I just cut away some of the insulation to allow for it?

RobG

See

See my edit above. You won't get it perfect, but just as close to perfect is good enough.

JustinS

OK

Ok, thank you...



Also, as I did in the picture, I'm intending to wrap the rubber insulation as much around elbows but not sure what to do about Ts



I guess that I could cut into the insulation around the T along the main pipe and then just lay another length for the T itself... alternatively, I guess I could use foam T segments but those don't seem to come in the rubber foam I got here...

JustinS

Suggestions

In this picture, you can see the recirculation pump and its aquastat...



How should I insulate the piping that the aquastat is up against since it covers the front of the pipe? I won't be able to seal the rubber so not sure what to do...

RobG

Insulating

Just trim the foam around what you have to work with. There is no science to it, just do the best that you can and it will be fine. The aquastat has an enclosed bulb so once again just get it as well insulated as you can. As someone said earlier in the thread " you are using a little energy to save allot of energy". In an ideal world whomever built the home should have had the lines insulated prior to closing in the walls. Post some pictures of the rest of the system and we'll see if there are any other modifications that can be done to improve the system efficiency / operation.



Rob

RobG

Insulating

Just trim the foam around what you have to work with. There is no science to it, just do the best that you can and it will be fine. The aquastat has an enclosed bulb so once again just get it as well insulated as you can. As someone said earlier in the thread " you are using a little energy to save allot of energy". In an ideal world whomever built the home should have had the lines insulated prior to closing in the walls. Post some pictures of the rest of the system and we'll see if there are any other modifications that can be done to improve the system efficiency / operation.



Rob

JustinS

Cooling Period

My ambient is approx 70F with storage at 140F...



Prestige Solo 110 heats water to 186F with the tank ultimately getting as high as 148F... The boiler fires when the tank drops to 134F...



With no use, this happens about every 4 hrs... This translates to 3.5F/hr which seems pretty high... Do you have any thoughts on this? I am in the process of insulating the DHW and boiler piping...



We do have a recirculating pump that runs when the pipe exterior drops below 110F and stops when it reaches 115F... There's also a mixing valve that is set to about 120F or so on the tank outlet pipe...



Any thoughts on why the tank is losing so much heat so quickly? It's supposed to be rated at 1F/hr at 120F storage vs 70F ambient...

JustinS

Do they?

My dryer says that it has an input rate of 20K/hr - so if we do 5 loads of laundry per week, that's only 4 therms of gas per month, approx, right?

JustinS

Here's the system

As requested, here's a picture of my system... as you can see, I'm in the middle of insulating - I've pretty much finished the DHW piping around the boiler, still need to do in the ceilings between the I-trusses... worth doing, right?



Thoughts?



Also, on the Aquastat L6006C - I would like to stop it from closing its contact that starts the pump - I see that its setpoint range is 65F to 200F but the dial goes below 65F - can I set it even lower and prevent it from working?



I'm just wondering why I am still losing so much heat from the tank so quickly (3.5F/hr, as noted above)



P.S.



Why is the pic upside down? it's not like that on my computer?

JustinS

Recirc Pump's Mostly Off Now

and I'm in awe...



I got up this morning to check on it since I turned down the Aquastat as far down as it could go (past 65F on the dial)... whereas before, the heating cycle appeared to be about every 4 hrs or so (with no use), the last cycle was almost 8 hrs ago and the temperature in the tank is still 144F...



So by seemingly disabling the pump, I've gone from what appeared to be ~3.5F/hr loss to ~0.5F/hr... this new loss seems a bit low, considering the tank is rated at 1F/hr w/ 50degF differential but I guess it is what it is...



It would seem that the pump is responsible for a significant amount of heat loss to the tank...



Any thoughts?

Zman

Copper

Bare copper is a great conductor. It is just giving up heat to the surrounding air.

Insulate,insulate then insulate some more....

A circ with a combo temp-time control will also help.

Your tank losses are about right

Carl

JustinS

About Right?

Which losses are about right?



I've already put as good rubber insulation as I could find on all of the DHW copper piping - it's about R 3.3 - how can I put more? Working on the PVC now but that doesn't seem as bad as the copper in terms of heat loss...

JustinS

Must Have

Missed a cycle or something yesterday morning because it looks like the cycle is now about every 8 hrs - not sure why it was 144F yesterday AM after running 8 hrs prior... seems odd

Zman

About right

The 0.5 is what I would expect from the water heater with no recirc.

3.5 is not out of the ordinary for an insulated recirc line.It works out to about 1,000 BTU/Hr. With natural gas, that is about 1 cent per hour.



If you post the size and length of  the pipe as well as the average temp around the pipe it can be double checked..



There a good chance that the dial on your indirect tank has been bipassed. The better way to setup that system is to pipass the tank dial and install a  sensor that is read by the boiler. If the boiler shows the DHW temp in the info menu, the dial has been bipassed.



If this was my system, I would set the tank temp on the boiler to 120 then activate the anti legionella feature in the setup menu. this would reduce you tank losses slightly and allow the boiler to condense through more of the DHW cycle.



Carl

JustinS

Don't Understand

The heat capacity of water is ~8.3 BTU/gal-F, right?



Since my tank is 70 gallon capacity, wouldn't the loss work out to be ~2000 BTU/hr (8.3 x 70 x 3.5)?



Also, not sure why I observed a loss of ~0.5F/hr yesterday morning but now it's more like 1.8/hr as the temp is going from 150 to 134 in about 9 hrs or so... not sure why that changed...



As to the length of pipe - I'm not sure how I would be able to determine this since much of the pipe is unaccessible in the walls?



Yes, there is a thermal sensor in the tank that is connected to the boiler...



As to adjusting the tank temperature - what would you use for the temperature of the boiler water? Right now, it's set 46F above storage temperature...

Zman

you are correct

I thought you had a 40 gal tank.



Most recirc lines return water from the farthest point of use. If you estimate the supply and return to that point that is the number you need. How much is and is not insulated?



The TT boiler has tons of hot water adjustments.



If you want long boiler cycles, just change to on/off differentials.



For longer time in the more efficient condensing temps you can lower the tank temp and the 46 degree "add" temp you are referring to.



Because you live in the house, you can make adjustments until the output is unsatisfactory then dial in the sweet spot.



Keep in mind most electric water heaters only use about 16k/btu. You have a lot of room to tweak the settings.

JustinS

Condensing

Don't I have to have the return below 130F in order to operate I condensing mode?



What efficiency am I operating at now? 87%? Or would it be lower since I am heating to 186F?



Is the efficiency separate from the amount of gas being burned? I think so but want to be sure... I know that on e supply temp is up to set point, the boiler firing rate is drastically reduced... I've seen it as low as 18% - is that 18% of my 30k to 110k BTU?



Would I really use less gas running longer? Would the. Oiler be that much more efficient at lower temp?



What do you mean by 16k/but for electric heater?

SWEI

Condensing mode

is actually a misnomer.  As the boiler water return temp drops, efficiency goes up.  As efficiency goes up, condensation increases.  Cold DHW lowers boiler return water temps significantly.

JustinS

Dew Point

I thought that the water vapor in the flue gas couldn't condense unless the return water temperature was less than its dewpoint - which I thought was ~130F...



And isn't the other way around? Efficiency goes up because of the condensation?