Boiler temp vs storage temp

[hartkem]

I'm starting my second year heating with my Eko 40 and 500 gallons of pressurized storage. I have noticed that I can't get my storage close to the boilers max temp of 195 degrees. Now and then the boiler will idle at 195 degrees but the tank only shows 177 degrees top and bottom. I'm using an Azel technologies thermometer on the storage tank with the sensor inside a thermowell. The Azel has a min /max function that shows a max temp of 187 degrees. I have personally only seen 181. It would be nice to see a consistent 190 or higher to get more usable heat from the storage tank. Is it unrealistic to expect the storage tank to get as hot as the boiler?

Thanks in advance

 

[maple1]

I can drive my storage to 195/190 top & bottom fairly easily if I want to - have to be pretty darn careful on the last bits of loading though. Given your relatively small storage vs. boiler output, you should be able to get more than 177. Not sure what the issue could be though.

What do you have for charging storage (loading unit?). Wonder if you've got too much flow - and if you could slow it down it might move more heat out and get better stratification/less tank mixing? Although more flow should move more heat. More info on your storage setup?

 

[woodsmaster]

I can get my storage to 190 / 195 top to bottom pretty easy if I wish. I don' t usually push it that high if it averages 185 i'm happy. I try not to let the boiler idle rather then to get every last degree.

 

[hartkem]

I have a Danfoss valve and a taco 0011 for a pump. 1 1/4 Thermopex 150' to house with storage in the basement. I bought the pre insulated 490 gallon tank from new horizons. The boiler water enters the tank on the top left side and exits the bottom left. I do notice that when the pump is running the bottom temp sensor which is on the copper pipe that exits the boiler can get as much as 10 degrees hotter than the top temp sensor which is in a thermowell in the center of the tank. This only happens when the tank is heat saturated. When the pump shuts off then the tank stratifies much better.

 

[Nofossil]

.....the bottom temp sensor which is on the copper pipe that exits the boiler ......

Assume you meant 'tank' rather than 'boiler' in this statement?

I'd be curious about the temp in and out of the boiler and in and out of storage during storage charging. If storage is the only heat load, I'd expect something like this:

• Boiler out is ~ equal to storage in
• Boiler in (actually, Danfoss cold in) is ~ equal to storage out
• Storage out is cooler than storage center
• Temp rise through boiler is about 20 degrees

It's really useful to have at least three temp sensors in storage - top third, middle third, and bottom third. Wells are ideal, but three sensors taped to the side of the tank can work pretty well. It's helpful to be able to see the temperature difference between top and bottom.

I'm very suspicious if storage outlet (at the bottom of storage) is warmer than the middle of storage. In a pressurized tank I'd think that would be pretty near impossible unless there are internal baffles or something that promotes a straight top-to-bottom flow path with minimal mixing during charging.

 

[hobbyheater]

I have noticed that I can't get my storage close to the boilers max temp of 195 degrees Is it unrealistic to expect the storage tank to get as hot as the boiler?

Had a similar problem . Its realistic to expect the top of storage to match the boiler max temp without idling .
My problem turned out to be flow related .Not enough flow due to undersized piping 1" instead of 1 1/4 . I opted for a bigger circulator .
In my setup the storage bottom temp is about 15 to 20 degrees less than the top when the fire goes out , I believe with larger piping and slower flow rate this number would have been closer top / bottom .
But the nature of the Jetstream with the heat exchanger sitting on top of its 1,400 lbs burn chamber , the bottom storage temp can be raised another 5 to 15 degrees after the fire is out .

 

[hartkem]

No fossil your correct I did mean tank. I personally think I'm over pumping with the 011 but i don't have anything to swap in unless I purchase a new pump. This setup heats the house fine but I know I could sneeze out more time between firings if I could get storage hotter. I have an infrared temp gun but i'm skeptical of surface temps being accurate. I do remember a thread about Eko boiler temp sensors reading hotter than actual water temp depending on placement of the temp sensor. I'm already running 11/4 thermopex which I'm told is similar to 1 1/2 pex since its measured ID. It is a lot larger than the 1" thermopex. I'll try to get some temp readings and post them

 

[maple1]

Yes, more temp readings would definitely help.

Almost sounds like the hot supply water is entering the top of storage, then proceeding directly down to the return outlet. Like a narrow stream inside the tank from inlet to outlet. I'm not familiar with your tank, but you did say inlet & outlet on the same side? Surely there are internal baffles or the like to prevent that from happening?

When charging storage from cold, you should see some big differences in temps between top & bottom of storage. Actually what you should see is the bottom staying the same cold temp for quite a while while the top temp steadily goes up. Then after the top hits your boiler-out temp, or close to it, the bottom temp will start to rise - there should be an invisible horizontal line or layer inside your tank that separates the hot from the cold, and that line/layer will fall when charging, and rise when drawing. More or less, kinda fuzzy-like.

 

[BoiledOver]

I'm starting my second year heating with my Eko 40 and 500 gallons of pressurized storage. I have noticed that I can't get my storage close to the boilers max temp of 195 degrees.

This sounds very familiar. It might be a good idea to get a known to be accurate measuring device to verify the tempratures in in your storage.

My experience with the Azel thermistor readings is; they show a lesser reading than actual.
Also, in my experience with an Eko 25; the controller shows a slightly higher than actual temperature and there seems to be quite a lag in time of reading changes.

So in my case the truth was somewhere in the middle. A buddy came over with a thermocouple that he claimed to be accurate within 1/10 of a degree F (I wouldn't know the truth in that statement but accepted it).

The results compared with the Azel reading at top of storage 177 was thermocoupled at 189.
The result compared with the RK-2001U controller at 194 was thermocoupled at 190. The thermocouple was placed on the boiler output, whereas the controllers thermistor is several inches away on the flat top surface.

Your system and devices may well be different, but these are my results when troubleshooting the same concern you mentioned.

 

[hartkem]

This sounds very familiar. It might be a good idea to get a known to be accurate measuring device to verify the tempratures in in your storage.

My experience with the Azel thermistor readings is; they show a lesser reading than actual.
Also, in my experience with an Eko 25; the controller shows a slightly higher than actual temperature and there seems to be quite a lag in time of reading changes.

So in my case the truth was somewhere in the middle. A buddy came over with a thermocouple that he claimed to be accurate within 1/10 of a degree F (I wouldn't know the truth in that statement but accepted it).

The results compared with the Azel reading at top of storage 177 was thermocoupled at 189.
The result compared with the RK-2001U controller at 194 was thermocoupled at 190. The thermocouple was placed on the boiler output, whereas the controllers thermistor is several inches away on the flat top surface.

Your system and devices may well be different, but these are my results when troubleshooting the same concern you mentioned.

I actually have the azel temp sensor probe and a johnson controls a419 in the top of the tank about one foot apart. They read 177 and 181 so I know the tank is somwhere in that range. What really gets me is why my return temp is almost always higher than the top of the tank when the primary pump is running. I think the issue is related to what maple1 suggested with my inlet and outlet being on the same side. There are no baffels in the tank and I think my 0011 pump is way to big with my 140' of 1 1/4 thermopoex. I just ordered a taco 0015 three speed pump which im going to try. It was only 80 bucks and if it doesn't work out I have an alternative use for it.

 

[BoilerMan]

Where in the world did you get a 3speed 0015 for 80 smackers????? That is a GREAT DEAL!

TS

 

[hartkem]

Where in the world did you get a 3speed 0015 for 80 smackers????? That is a GREAT DEAL!

TS

Pex supply.com
http://www.pexsupply.com/Taco-0015-...t-Iron-Circulator-Integral-Flow-Check-1-20-HP

 

[BoilerMan]

Oh ok, it's a 00R, I was thinking a 0015 was not the 00R equivelant.

TS

 

[huffdawg]

I have the same problem with my eko 4o and 1000 gal storage. The hottest I have had my storage temp is 187. and thats if I let it short cycle for a while near the end of a burn.. My controller is set at 195. My boiler out temp reads 187. I think if I raise the sensor on top of the boiler a couple mm off the tank top I could get the temps a little higher.

 

[maple1]

I had to go away this weekend. Left home Friday afternoon, threw a half load in to finish off my charging on the way out the door. Texted the kid that evening to check in, storage was 205 top & 185 bottom. Ooops - well, I guess you won't have to fire for a bit. That's about the highest I've seen my storage driven to. It's nice in a way to have a boiler that is incapable of cycling - but ya gotta be careful on the reloading.

 

[hartkem]

I wish I could get my storage that high. I was able to verify that the EKO temp sensor is accurate. I borrowed a Fluke thermocouple for my multimeter and both were within 1-2 degrees. Temps around here in missouri are back in the low 60s through the day and its not supposed to get cold again for over a week so it's going to be awhile before I can get you guys some readings off my tank.

 

[TimfromPittsburgh]

This thread is interesting, also very relevant for me. After operating my Tarm 502 with no storage for 15 years, I finally brought online 200 gallon of unpressurized storage last week. My upper temp. limit for the tank is dictated by the tank liner at 180 F. I have two heat exchanger coils, one toward the top of the tank and the other near the bottom of the tank plummed in parallel. My thinking behind parallel verses series connection was that parallel connection would produce a more even heating of the tank and therefore more BTUs stored. The storage tank is treated line a heating zone. Whenever the boiler outlet temperature is > 160 F hot water flows through the storage tank coils until the temperature at the top of the tank reaches 180 F. The first time I charged the tank When the temperature at the top of the tank reached 180 F, the bottom of the tank was 158 F which surprised me. On the next tank charging cycle I shut off flow to the top heat exchanger coil but the result was nearly the same (when the top of the tank reached 180 F the water temperature at the bottom of the tank was 162 F). So, it seems that water heated at the bottom of the tank rapidly rises toward the top of the tank and is replaced by cooler water. I also noted that when the heat storage had discharged to 140 F at the top of the tank, the temperature at the bottom of the tank was nearly the same (138 F in my case)

In another thread on stratification, Nofossil had pointed out that the cooler water at the bottom of the tank is necessary to load the boiler and I can see that now.

I am already seeing the benefits of storage, in that I can operate the boiler through a complete burn cycle at higher flue temperature without the boiler idling. No smoke from the chimney and no smoke pouring out into the basement like always happened when I opened the feed door while the boiler was idling. With our current weather pattern of cold nights (near 32 F) and warm days with temperatures in the 50s, I build a fire in the morning to charge the storage, and again in the evening. Now that I see that storage works, I am going to build a second 200 gallon tank.