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The Wall


Joined on January 19, 2012

Last Post on September 1, 2014

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@ July 1, 2014 8:36 PM in New gas boiler sizing

We don't talk pricing here but I am curious how you came up with a budget.
The cost of getting a system installed is a combination of cost of materials and the contractors labor and profit/overhead. It will vary from region to region depending on local economies.
How in the world did you come up with a budget without a single bid or a system design?
Just because you want something to cost a certain amount does not mean it will. Try going to your local restaurant and telling them you want the lobster diner for $5.

I would suggest you find a reputable contractor and have them design and price a few options. Some will let you pay for the design and credit it back if they get the job. This approach would allow you to get apples to apples price comparisons.


@ June 30, 2014 10:57 PM in TT Smart 80 & Prestige Solo 110 Summer Gas Usage

I have never messed with the post purge setting. I would concerned that it would create a delay between the DHW and heat cycles.The logic in the controller may overide.

You could observe how long it takes to equalize the DHW storage with the Boiler temp and set it for that amount of time.

I think your thinking about the recirc aquastat being effected  buy the tank is correct.



@ June 30, 2014 7:18 AM in TT Smart 80 & Prestige Solo 110 Summer Gas Usage

If you need higher than 120 then so be it. I would play with the lower numbers and see how you like it. 120 is not a magic number for dishwasher sanitation.

The DHW timeout setting is not the same as post purge. It is designed to prevent the house from getting cold in the event of a very long DHW cycle. It will make the boiler switch back to heating mode after a set amount of time.


@ June 30, 2014 1:29 AM in TT Smart 80 & Prestige Solo 110 Summer Gas Usage

Attached is a presentation that should clear up the condensing question.

My point about the electric water heater is that if you multiply the wattage of the heater coil by 3.412 you will get the Btu output. Most heaters are around 5kw. I say this because people who install regular electric water heaters on there jobs love to make a big deal about oversizing  boilers for the DHW load when they do indirect jobs. It just does not make sense.

Back to your setup. You have a boiler with 110K/btu input. derated  for efficiency it will put out between 90 and 100 k/btu. At 18% firing, it will be putting out 18% of that number.

By the nature of  heat exchanges the return temp can never be lower that the tank temp. By turning down some settings, you should be able to keep the return boiler temps under 130.

Your indirect has a great deal of surface area relative to the boiler size. This means you do not need a 46 degree add. I would set the the add to about 20 degrees and the tank temp to 120. I would leave the on/off differentials alone. The anti-legenella should be turned on and the DHW timeout I usually set to 90 minutes. If you have a variable speed circulator on the DHW turn it to low.

Keep in mind all this is chasing approx 5% in efficiency.

By turning down these settings you may run the risk of the DHW cycle taking too long and short changing the heat load. Keep an eye on this.


Rad Pad

@ June 30, 2014 12:57 AM in Help with radiant floor in shop

I came up with similar numbers using Siggys software.
The 008 is clearly not big enough. You also need to figure in the other piping components. It is likely you will end up with a 26-99 grundfos.
Have you read Idronics 10?

Hot Rod,
Is the Rad pad app out yet?


@ June 29, 2014 5:27 PM in Water Tank Temperature After Shower

The well is in the center of the tank. You can raise and lower the sensor a good distance within the well. Just pop the cover and carefully pull the wire.

you are correct

@ June 29, 2014 5:24 PM in TT Smart 80 & Prestige Solo 110 Summer Gas Usage

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.

Smart tank

@ June 29, 2014 4:37 PM in Water Tank Temperature After Shower

The smart tank has a tendency to run uneven temps. I think the high mass of water in the jacket and the heating from the outside has a lot to do with it. I have noticed big fluctuations in may own tank.
As stated moving the sensor may help.


@ June 29, 2014 12:22 PM in need electrical help

My posts where directed to the OP "jimmyc"
The confusion has come from someone introducing a new system.
The Wall works much better when people don't do that.


@ June 29, 2014 9:00 AM in need electrical help

Some boilers provide a 24v terminal for external safeties, which is normally jumpered.. In that case 24 volt external safeties make a lot of sense.
Wiring them in series with the t-stats will "work", I think it makes for difficult troubleshooting down the road,
I have seen too may jobs where someone has accidentally bipassed the boilers onboard safeties while trying to add externals. Even if the original installer gets it right, you don't want to encourage the next guy troubleshooting the system to mess with it.

Unless the manufacture gives you a clean way to install 24volt, I would go with 120 volt.

About right

@ June 29, 2014 8:49 AM in TT Smart 80 & Prestige Solo 110 Summer Gas Usage

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.



@ June 29, 2014 8:19 AM in Pilot goes out when trying to turn on..

I agree with steamhead that this seems like a bad DYI repair. Wall heaters have been responsible for quite a few CO poisonings.

The one thing that would be worth checking before calling a pro would be to make sure the vent has not been blocked by a critters nest.


@ June 28, 2014 10:15 AM in TT Smart 80 & Prestige Solo 110 Summer Gas Usage

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

No idea...

@ June 28, 2014 10:04 AM in Need to replace big old galvanized pipe with pex

I still have no idea how you existing system is piped and honestly cannot make a suggestion.
It sounds like you have a gravity system that has been converted and has had some baseboards added. How did they pipe it?
If you are changing the main distribution piping , the way it is piped is far more important than the size of the pipe.
If you post a piping drawing, you will get better advise.
Otherwise, more guessing....


@ June 28, 2014 9:45 AM in need electrical help

A agree that in most cases 120 volt is the best choice.
Unless the boiler manufacture provides terminals for external safeties, you are rewireing the boiler. The potential to make a mistake that either voids the warrantee or creates an unsafe operating condition is high.


@ June 26, 2014 8:19 AM in need electrical help

Unless you are installing external safety devices, the boiler is pre wired to handle all that.
Anytime the connection from R to G is made, the boiler will fire.
For the one zone system the t-stat can be wired to R and G.
For 2 zones, I would use a taco zvc403-4


@ June 26, 2014 7:50 AM in need electrical help

Zone valves? Single circ?
I think the taco control relays really clean up and simplify the low voltage side.


@ June 26, 2014 7:27 AM in Wood with mod/con. Piping help please

Here is a good read on the subject.

The points I would be most aware of is the need for a buffer tank and if the boiler is going to be in the house, a good thermal bypass loop.

You cannot just shut off a wood boiler the potential for overheating is huge.

The expansion tank location in the manual is incorrect.



@ June 24, 2014 10:06 PM in Need to replace big old galvanized pipe with pex

I agree with jstar, you have to do the math.
How is the piping being run? Is this a reverse return system?
Take your time and do this right. There are far too many folks using rules of thumb and guessing.

Flow rate

@ June 24, 2014 9:57 PM in Initial target Flow Rate calculations

First off, you do not need 2fps with a continuos pex loop. It will easily purge air at 1/2 that.

I do think you will have trouble balancing a system as out of balance as yours will flow rate alone.i also think you are likely to have air issues at .1 gpm.

Is it possible to put trvs on in the areas that are over radiated.


@ June 24, 2014 6:38 AM in how prevalent is this?

You realize this article is 25 years old?
Much has been learned since....


@ June 21, 2014 12:39 AM in Hot water first floor, luke warm water second floor

Air would make sense if you had hot water after waiting for it.
Diagnose the problem, don't just guess.
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