bock sidekick too hot

plumbob44

brand new 40 gal sidekick makes water always between 130-140 degrees regardless of aquastat setting. replaced L 4080B with same new control and problem still persists. Anyone else ever had this problem? need solution. seems to me to be design problem, well is very shallow and does not protrude into tank very far. or is it possible that i just got two defective controls?

billtwocase

I would say

no to 2 defective controls. I haven't installed a Bock indirect in years. Not that good of a unit. Is there a anti scald mixer on it? I would put one on. How is it zoned? Slow acting zone valves will overshoot taking too long to close. Also boiler temps?

plumbob44

too hot

it is zoned with honeywell zv. it closes immediately when aquastat clicks, babysat this unit all day, it seems that desired temp is over shot due to improper reading from aquastat. brand new boiler, zv's, and indirect

billtwocase

I would

certainly have a rep step in. Is this an issue when water is flowing thru the domestic side, or did it also overshoot the first recovery cycle when you filled it? If it is when it is in use, I would check the temp drop on the outlet. If this thing is looking to recover almost as soon as you run a faucet, may be a dip tube problem? With the tank sitting unused, does the aquastat at any time agree with the water temp in the tank?

lchmb

once

had one come through that had a damaged well. I couldnt tell pushing the bulb in but it stopped short causing an over heat problem. I would also put a mixing valve on the tank. That way your protected no matter what the tank does..

billtwocase

I also see

That the tank piping specifies the boiler supply be piped into the top, and out the bottom? That seems a bit bass ackwards. The top of that tank will heat first, and is where the hottest water is anyway. By the time the control senses the temp increase towards the bottom, it is practically steam. It just doesn't look, or seem right to me

zacmobile

in & out

As far as I know indirect tanks are always in on the top & out on the bottom. Heat exchangers are always piped so there is a counterflow configuration for maximum heat transfer, think of an indirect as a big heat exchanger: heating water travelling down & domestic water travelling up.



The aquastat well looks like it's in a fine spot, the hot water will migrate to the top of the tank then stack up until it gets down to the aquastat which will de-energize the zone valve: stratification...

billtwocase

not always

There are some that feed and return all top, and some that feed and return all bottom. Amtrol, Bradford White to name a couple. An external by-pass would be a plus on these tanks to even them out. I have never seen hot water migrate down unless you show it the way, or help it out. These tanks do neither. The hottest water will always be on top, and that is what will be coming out of the faucets. 

billtwocase

I will add

not totally disagreeing Zack, so no offense intended, JMHO. I've been down this road with the earlier generations of Bock indirects. They need some tweaking 

kcopp

Honeywell 4080b...

aquastat is really a junky control. I would upgrade to a HW 4006 or  the TPI control... http://www.vaughncorp.com/html/tstats.html

bill_105

Same thought

Five years ago I installed a Saint Fin indirect (By HTP,at the time). The water would not go above 120 at the relief valve, even when the dial was maxed out. I went to a (mostly) controls supplier and was told that 4080 was an OEM part and was not available over the counter. But the 4006 worked just fine.

After hearing this I guessed that maybe Honeywell makes a budget,bargain basement control for some indirect makers.

Interestingly,Superstor and Lochinvars Squire makes you go by a control separately.

billtwocase

I've had a few

of those controls that were off a few degrees, but i don't think that is what is causing this problem.

Robert_25

Overshoot, stratification

What size boiler are you heating tank with?  Does the boiler quickly reach the high limit during a heat call?  I had a very similar situation with my Bradford White 80 gallon indirect, which has a similar design to your Bock.  Mine uses a L4006 aquastat, and the well is only about 15" off the bottom of the tank.  If you get several short hot water draws, i.e. just enough to trigger a heat call....and the boiler is already at 160 or 180...you quickly satisfy the tank's aquastat, the zone valve closes, then the coil continues to transfer heat into the tank....repeat this a few times and it is easy to see how the tank can stratify and contain some water above the temperature control setpoint. 



The easiest way to control this is install a mixing valve, which would get a good idea regardless.

icesailor

Too Hot Domestic HW:

Bingo, Robert. You win the prize.

If the high limit on the boiler is 180 degrees, and you get a call for hot water in the indirect, you will be getting 180 degree water going into the coil and heating the water around the coil to a higher temperature than the aqua-stat setting. Even if the boiler starts cold, it will usually pass the tank temperature on the way to the high limit.. You need a mixer to solve the problem.

If you set the high limit on the boiler to 130 or 140 degrees while it is still warm out, and the problem improves, it will show that the problem is caused by excessively high boiler water temperature.

I use a 50 gallon water heater with a tank-less in the boiler. I have my limit stops set so I just turn the valve to the hot water stop. In the winter, when the heat comes on from the clock thermostat at 4:00 AM, the zone is on high limit and I can tell that the domestic water is hotter when I am in the shower at 4:30 AM. If I take a shower at 10:00 AM when the heat is off and the boiler is running on the operating/low limit control (140 degrees), the hottest water in the shower is not as hot. Nice, but not as hot. If I set the limit stop to a higher level, the water would be hotter.

I've never seen a water heater that didn't do it.

If you want more hot water, raise the tank temperature and install a mixer. Mix the hot water at the heater, not at the valve.

billtwocase

my recommendation

was an anti-scald mixer, and yes short draws drive the tank temp up, but is this an overshot with no draws?

plumbob44

all good

sugestions, but why i think this is a control/well/diptube problem is because;

1) control turned all the way down

2) open hot water supply @ 2 faucets

3) wait for domestic hw temp to  drop below 120 ( desired target temp)

4) go to basment, close domestic hw side valve on heater, wait for aquastat to open and close zv, open domestic hw valve, run upstairs, check water temp and it is always between 130 -140 degrees

i repeated this process 5 maybe 6 times, there is no time for stratification or any other variable. control on indirect simply does not sense water temp in tank. i've installed hundreds of indirct heaters, from many different manufacturers, never had any trouble with one.... until now.



installing mixing valve is an obvious solution, but i've never needed to before and don't think that a malfunctioning product should be remedied with another. this is a brand new SK40

icesailor

All Good. No, Bad:

You just described a heater not working properly. You are used to seeing it that way.

If you set the aqua-stat to 120 degrees, it shouldn't be overshooting to 130 to 140 degrees. Massachusetts says 125 degrees, depending on who you ask. With a zone valve on an indirect, it slows the action too far down. Before I started using mixers, I would have to set that aqua-stat to 120 degrees and lower, and just before I get inspected, run the tank temperature so it wasn't over 125 degrees at the inspection. Or else it would fail.

If you use a 40 gallon indirect, install a mixer at the tank, set the mixer at 125 degrees, and set the Augusts at 140, the tank will deliver what a 60 gallon indirect will provide. With less water.

Honeywell AMX 101 mixers rule. They come as a direct mount on water heaters, have flow checks, and a recirc, line port available.

billtwocase

I agree plumbob

I think it is a warranty issue, or poor design as I said earlier. Do whatever you feel is going to give you and the customer piece of mind, and good luck. Let us know what becomes of this.