water heater stacking

Mike2

We recently changed out a 10 year old centerflue superstor oil fired water heater which developed a leak. We installed a thermaflow centerflue water tank in its place and re-installed the existing burner. Insertion depth and firing rate has been checked and adjusted for new tank. The problem is that we have been stacking water and building temperature to the point of blowing the T&P valve on a regular basis. We never had this issue with the last heater which didn't even have a thermal expansion tank. There has been no change in usage patterns. This is for a single lady with minimal water usge.

What we have done so far:
Installed thermal expansion tank and matched precharge to street pressure, 60psi.

Replaced Honeywell L4103a 1019 with Carlin EZ temp 90000B10S factory control for Thermaflow/Everhot.

Tried installing a venturi tee on cold water supply with the branch side connected to the hot water outlet. This was recommended by thermaflo to pull hot water from the top of the tank back into the bottom. It didn't work, it actually allowed cold water to flow back into the hot supply.

We checked the dip tube, 24" long and repiped the cold water supply to the boiler drain tapping on the bottom of the tank.

Still no luck. I know that a water tank is not rocket science, but I can't see why this tank would stack water to this extent but the old one never did. We have had this customer for many years.

As a side note, Thermaflow has been good to deal with, even willing to have us change out the tank if we want to. I haven't done so yet, not seeing what difference it could make.

Mike2

water heater stacking

We recently changed out a 10 year old centerflue superstor oil fired water heater which developed a leak. We installed a thermaflow centerflue water tank in its place and re-installed the existing burner. Insertion depth and firing rate has been checked and adjusted for new tank. The problem is that we have been stacking water and building temperature to the point of blowing the T&P valve on a regular basis. We never had this issue with the last heater which didn't even have a thermal expansion tank. There has been no change in usage patterns. This is for a single lady with minimal water usge.

What we have done so far:

Installed thermal expansion tank and matched precharge to street pressure, 60psi.

Replaced Honeywell L4103a 1019 with Carlin EZ temp 90000B10S factory control for Thermaflow/Everhot.

Tried installing a venturi tee on cold water supply with the branch side connected to the hot water outlet. This was recommended by thermaflo to pull hot water from the top of the tank back into the bottom. It didn't work, it actually allowed cold water to flow back into the hot supply.

We checked the dip tube, 24" long and repiped the cold water supply to the boiler drain tapping on the bottom of the tank.

Still no luck. I know that a water tank is not rocket science, but I can't see why this tank would stack water to this extent but the old one never did. We have had this customer for many years.

As a side note, Thermaflow has been good to deal with, even willing to have us change out the tank if we want to. I haven't done so yet, not seeing what difference it could make.

Mike2

water heater stacking

We recently changed out a 10 year old centerflue superstor oil fired water heater which developed a leak. We installed a thermaflow centerflue water tank in its place and re-installed the existing burner. Insertion depth and firing rate has been checked and adjusted for new tank. The problem is that we have been stacking water and building temperature to the point of blowing the T&P valve on a regular basis. We never had this issue with the last heater which didn't even have a thermal expansion tank. There has been no change in usage patterns. This is for a single lady with minimal water usge.

What we have done so far:

Installed thermal expansion tank and matched precharge to street pressure, 60psi.

Replaced Honeywell L4103a 1019 with Carlin EZ temp 90000B10S factory control for Thermaflow/Everhot.

Tried installing a venturi tee on cold water supply with the branch side connected to the hot water outlet. This was recommended by thermaflo to pull hot water from the top of the tank back into the bottom. It didn't work, it actually allowed cold water to flow back into the hot supply.

We checked the dip tube, 24" long and repiped the cold water supply to the boiler drain tapping on the bottom of the tank.

Still no luck. I know that a water tank is not rocket science, but I can't see why this tank would stack water to this extent but the old one never did. We have had this customer for many years.

As a side note, Thermaflow has been good to deal with, even willing to have us change out the tank if we want to. I haven't done so yet, not seeing what difference it could make.

[Deleted User]

Missing component in the venturi trick...

You need to install an orifice in the side branch between the hot water return into the cold water inlet venturi. In other words, the venturi tee would be on the cold water inlet with the venturi pointing down. The side branch of this tee would be connected to the hot water outlet tee. In the side branch of this tee (cold water venturi), you need a restrictive orifice. We use a (don't tell Uncle Sam) nickel with a 1/8" hole driled in the center of the nickel. This nickel is held in place with the 3/4" copper pipe inserted into the side branch of the fitting.

However, with that said, it sounds to me like you are over driving the heat exchange process. Any chance of down firing the burner a bit to give stratification a chance to break up before setting off the T part of the T&P valve kicks in?

Other than adding a SMALL circ pump betwixt the gozinta and the gozouta of the tank, can't give you much help...

ME

JACQ

Mike,it is possible that you might have gotten a faulty tank.

Mike2

Mark, thanks for the advice. I'm confused about the placement of the nickle. We used a 3/4 x 1/2 venturi. Would the orifice be located in the 1/2" side branch of the venturi. Thanks again.

Larry Weingarten

Stacking...

...is caused by multiple small draws, causing the burner to fire often and for short periods of time. Is there a way to increase the dead band in your control... or am I off base?

Yours, Larry

Mike2

The Carlin control for this application has an 8 degree fixed differential with a 90 to 130 degree adjustable limit and a 160 degree secondary limit. Our best results have been setting the adjustable limit to 110. We will also try downfiring the unit from .65 to .5 to see if it helps.

[Deleted User]

Mike...

My presumption is 3/4" cold and hot water connections. The nickle will fit quite neatly into the side branch of a 3/4" copper tee. So the Nibco venturi insert fitting would be dropped into the top of the cold water tee, the nickel into the branch of the tee, and the branch connected to another 3/4" tee on the hot water outlet.

If someone is drawing hot water, the venturi will induce flow from the hot into the cold through the side branches of the two tees. Even when someone is not using hot water, the 1/8" orifice allows the hot water to destratify.

Yes, it is a cross connection between the hot and the cold, but during a draw, the venturi and the orifice will keep the cold water from cross charging into the hot, thereby diluting the hot water.

Let me know if you need more clarity and I will whip up a drawing for you.

ME

Nron_13

new HWT

add the expantion tank to the water heater the dip tube may have a built in check valve , and check to see what your static water pressure is before firing the tank
Nron

Edward A. (Ed) Carey_3

Temp or presure

Mike,

I assume you have a T&P that is the usual 150 psi/210F.

Also, I assume that the T&P you are using is rated for the BTU capacity of that water heater. In some cases a standard 100XL may not have the rating of your WH.

Have you actually measured the temp of the water at 210 F when it discharges?

What pressure is in the tank at start up of the burner, and what is the temp when the T&P deploys?

Just want to be very sure that you have a temp problem instead of a pressure problem.


Ed Carey

Direwolf

Stacking

Any luck on the solution to this problem?  I am having the exact same issue