poor performing indirect

[Deleted User]

300,000 btuH input, times 82 % efficiency (.82) equals 246,000 net btuh.

246,000 btuH divided by 8.33 divided by 100 (140 - 40) equals 295. Thats the hourly output potential of the heat source. Provided you have enough heat exchanger and flow, you should be able to transfer it.

295 divded by 60 minutes in an hour = 4.9 GPM of 100 degree rise water.

Assuming that all of your critical parameters are in order, this is approximatley what you should be able to get out of the equipment. If you aren't. or IF you are exceeding the flow rate capability of the system, somethin' else is out of whack. Turning up the operating temperature is the LAST thing I would do, but that's just me. It's the FIRST thing most people do.

Look at input, output, flow rates and temperatures. Somethings out of whack. You've got 337 first hour gallons, and 4 GPM after that. Somethin' ain't jivin'. Or jukin' for that fact...

ME

able1

I just installed 2 super stor ssu 60s on a job they will produce around 7 minutes of hot water before running out I have never had a issue with any other indirect in the past .I have 2 buderus g215-4 piped primary secondary with a MBX control to stage the boilers .customer complaint of no hot water after 7 minutes so we went to job and performed test and it did run out in 7 minutes sensor mounted at about half way in tank moved sensor to bottom of tank in cold water inlet so the minute water is run it calls for heat boiler is temp is usaly at around 140 degrees because it is providing heat for the rest of the house once domestic calls it will fire to limit of 180 degrees and if it needs to the other boiler will fire we installed a 5 gallon a minute flow restictor on cold water feed to heater and this only made it last another 3 minutes I have a taco 0010 with about 18 feet total of 1inch fosta pex with a total of 3 elbows primary loop is 2 inch steel water temp entering heater is 58 degrees boiler loop reaches 180 and Iam only getting a fifteen degree differental between supply and return if flow through coil was not enough wouldnt I be getting a much cooler return also I called tech service wich told me it might be getting to much flow though the coil so we throttled down supply side of circ and that did not help at all I thought you couldnt have to much flow through the coil were it woulndt give off heat to surrounding water any help greatly appreciated

hot_rod

10 minutes worth at 5 gpm?

so you are running 50 gallons out? Starting at 140F and running down to what temperature? How cold is the incoming water?

hot rod

steve_38

interesting

when i bought my house 7 yrs ago the existing boiler was only about 10yrs old Slant fin L-30 3 section cast iron wet base... i didn't like the plumbing or the wiring. so i went in there with a sawsall and re-plumb an re-wired. i set the coil up with a thermostatic mixing valve and also plumbed it to back flush it, and also installed a 30 gallon aquabuster. I can run hot water all day long and never run out. i've always stayed away from indirects never liked them. lol that's another story though. oh i also removed the beckett burner and put a Riello F5 on and now not only do i never run out of hot water but i don't think i'll ever have to vac my boiler, although i abviously inspect it every year... by the way good luck with those Indirects

Maine Ken

Are the tanks piped in seriesor in parrallel??? Any pictures of your piping arrangement? What are you using for anti-scald? What temp are the aquastats set too?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

able1

58 degree incoming water and temp of water after 7 minutes cool to touch under 100.thanks again

able1

one tank does the master bath and pool bath and the other tank does the kids baths and office bath there are 2 adults and 2 children tanks are not tied together

able1

tank is set a 125 with sensor in the bottom the temp will go up to 140 temp at the faucet straight hot 127 untill it runs out there is nothing mixing with the hot no cross connection or backfeeding through a valve as far as a mixing valve we havent installed one yet but will probably install a honneywell thermostatic and maintain 140 in the tank seems like I am getting very little heat transfer with no water running tank will re heat in about 10 to 12 minutes from around 65 degrees wich it reads at tank sensor on boiler control also there is no antifreeze in system just h20

[Deleted User]

Tank Math...

Due to internal tank mixing, it is virtually impossible to get more than 80% of any given tanks stored volume out in the form of good pure hot water. That said, 60 gallons time .8 = 48 gallons. 48 gallons divided by 5 GPM flow rate equals around 7 minutes.

Sounds to me that you are getting EXACTLY what the tanks are rated for...

In addition to the stored capacity, there is the recovery capacity of the tanks. That's the net raw btuH output of the fire power on hand. You can generally figure that out by taking the net output of the boiler, and dividing it by the GPM flow times the poundage of that flow and the delta T of the water. That number, combined with the stored output capacity (48 gallons in your case) will give you an approximate first hour output. After that, for continued draw, you only get the boilers output capacity per hour because the storage factor has already been exhausted.

Another part of tank math has to do with hydronic heat source coil differential. Contrary to popular belief, with storage tanks and other heat exchanger devices, the lower the delta T across the heat exchanger, the higher the exchange efficiency, assuming you have a place to dump the incoming btu's. It's the "average" differential that counts. In other words, if water is entering at 180 degrees F and exiting at 175, your average coil temperature is 177.5 Whereas if you have a 20 degree differential (180-160) then your average coil temperature is only 170 degrees F. Higher and hotter is better.

But what REALLY drives the b.t.u. bus on these devices is the tank water to coil temperature differential. In order to quickly and efficiently transfer a LOT of heat from the heat source to the "load" or storage tank, the coil needs to be completely immersed in a large pool of relatively cool water. Hence, the aquastat 1/2 way up the wall of the tank. You can leave the sensor well in the bottom, however, you can expect to get higher temperatures of discharge from the potable outlet of the tank due to stratification, and you can expect the boiler to short cycle when it is trying to rebuild the tank due to a lack of overall differential.

Another thing that is working against you is the lag time of the cast iron boiler in getting up to production temperatures. This has been a problem since, forever... I've seriously considered putting a timer on the TT contacts of the boiler and having it close prior to the typical AM call for DHW so that the boiler is not playing catch up as well... This is more of a problem during the summer than the winter for obviousy reasons..

This problem of capacity is only going to show during large fixed volume dump loads (filling large soaking tubs) or simultaneous calls for DHW (2 or more loads occuring at the same time) If your customer has a code approved shower head installed, at 2.5 GPM, roughly 80% of the flow through the head is hot water (unless custoemr is part lobster...) so your shower head load is only actually only 2 GPM. So, 48 gallons divided by 2 GPM flow rate equals 24 minutes of good hot showering time. And that does NOT include the recovery capacity of the fire power connected!

So, your options are,

1. Increase the size of the storage tanks to handle large dump loads.

2. Increase the storage tank temperatures significantly and mix down (not suggested).

3. Decrease the load to match the capacity connected (no friggin' 20 GPM Rain Forest shower heads).

NOw, you have all the answers, whats your customers problem?

BTW, if they have a 20 GPM shower head, in my environmental opinion, they are unconscienable...

ME

able1

Thanks for the info Mark I realize the fact the tank should of used its stored volume the thing I dont understand is adomestic coil can produce around 3 to 5 gpm I would think the coil in the indirect should be able to produce this when the tank specs say it will produce around 200 the first hour and the boilers are capable of 300 thousand btus and the point of the boilers getting up to temp they climb pretty fast as they start out around 140 do you think i should turn the boiler limit up to 200 thanks again.

GW

hot water

The ratings seem to be normal if you want to take a stop watch, trickle out the water, and after an hour you should have your 200 gallons of hot water. You're expecting the water heater to do an hour's work in 5 minutes; aint happening. We had this problem once; we went back and added a mixing valve and cranked up the aquastat to its highest setting... problem solved. If people need that much hot water, energy considerations should be thrown out with the bath water.

Did you discuss with the HO how long they needed this high flow? That's how much capacity you need, the gallons x the minutes with GPM as the factor (not sure if I said that correctly, but you get the idea)

Gary

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Wayco Wayne_2

Why not

pipe the tanks in series and put an anti scald on the last tank where the water is leaving? WW

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Steve A_2

able 1

If the coil on the superstore is a double wall design like you would use in a glycol system the Heat transfer rate is poor, 1/2 the ratings of the standard single wall. Sounds like your only using 1/2 of your available input.

hot_rod

Also the id of that 1\" pex

is hampering flow a bit. At .862 I" pex looks more like 3/4 m .811. Plus you have the insert fitting restriction.

hot rod

Dhivscjl

Verygczs good Sitesplf!

http://www.fagichrobluepill.com/site1/ [url=http://www.fagicbkhbluepill.com/site2/]site2[/url] site3 site4 [url="http://www.fagicvfbbluepill.com/site5/"]site5[/url] [LINK http://www.fagicfcybluepill.com/site6/]site6[/LINK] wgufl