Help! Domestic Water Too Hot!

I have a problem with the water being too hot in the winter only. I've searched this site, and my problem appears to be similar to Harry12's problem.
I've got an oil fired furnace and three zones for baseboard heat (all controlled by Taco 571-2 valves). These three zones are for specific areas upstairs, and there is no apparent zone valve for the domestic water (possible problem, but I've read on this site that I shouldn't have zone valves for domestic? Did I read that correct?).

Anyway, what I believe is happening is that when the upstairs zone thermostat calls for heat, the zone valve opens, the furnace fires, and the pump circulates. The remaining zones don't get warm because their respective zone valve is closed. Since the holding tank doesn't have this zone valve, every time an upstairs zone calls for heat, hot water also circulates through the holding tank.


I've had my furnace guys to the house several times, but every time they just lower the thermostat on the holding tank and tell me that the water from the furnace goes through a coil in the holding tank and doesn’t mix. Their fixes never work, and on warm days, we don't have hot enough water. I believe that even if the water doesn't mix, it is still being headed by this coil loop of hot water every time the zone upstairs calls for it.

So, can I, or should I put another 571-2 valve in the domestic water heat loop somewhere to close off the loop when the thermostat in the holding tank isn't calling for hot water?

Thanks in advance for any thoughts. I can try and post pics if I didn't explain this enough (which I'm quite sure that I just managed to really confuse everyone)

Tom

 

They may have lowered the temperature too low so that on warmer days the tank does not make enough hot water. The overheating proble is more than likley ghost flow when other zones are running.

Please post some pictures.

 

And besides pics, some addit'l info regarding the various components...mfr's? m/n's?
But once the pics are posted we could give you feedback as to info on what else would be helpful

Considering that apparently you do not have a zone valve for the DHW loop...do you have a mixing valve somewhere there?

 

From what I can tell, the hot water leaves the furnace (when any thermostat trips), goes to the expansion tank, and then to the zone that accepts flow (only the zone with open valve due to thermostat - and the domestic water because it doesn't have a valve). the water then enters the top portion of the holding tank, heats the water in there, and returns to the furnace at the bottem. This happens, and I assume that the water just flows past the circulator pump on the lower leg even if it's not pumping.

 

sorry for those huge pics, I didn't think they would be that big. Well, you might be able to see some of the mf info. If you need anything else, let me know. Next time, i'll just put the link and not the image.

 

great pics! nice looking system too!

Yup your indirect water heater does not have a zone valve...and don't need it! that green Taco circulator is your zoning.

There are two ways to zone: with zone valves OR with circulators.

Please let me know the setpoint of the Aquastat on the water heater. it's a honeywell. Please let me also know the model number of it...for example: L4006XXXX or whatever that might be (all nine characters if possible)

Turn the dial of that aquastat first up (to a higher setting) then down (to a lower setting) and let me know if and WHEN that green circulator turned ON and OFF (on the way up? T=?...on the way down? T=?)

 

is what rbeck said... and you correctly diagnosed the problem also when you said that you had flow in the water heater when the zones were running, but...

you don't need a zone valve, you need a FLOW CHECK valve installed on the water heater zone.

I'm disappointed that your so-called 'professional' technicians couldn't diagnose that and suggest a remedy.

 

I can't tell how all the plumbing ties together up top, but I've heard gravity feed is a problem with hydronic systems.

Try some stuff before dropping a couple bills on a zone valve.

Disconnect power to domestic circulator and/or shut off aquastat during severly cold wether.

Does the hot water heater stay hot?

Aquastat could be messed up too.

 

Is the Taco circ on the DHW an IFC model? If not, swapping one in would be your installer's easiest method for correcting his errors.

 

Is the indirect on a "priority" zone? If not, you may be getting simultaneous flow through the space heating as well as the indirect. Nothing would prevent the indirect circ from running at the same time the zones are running.

Check the model on the green Taco box on the boiler, and see if it's wired like this:

http://www.taco-hvac.com/uploads/Fil...ry/102-089.pdf

or this:

http://www.taco-hvac.com/uploads/Fil...ry/102-090.pdf

If it's not on priority (or even if it is), then Who's suggestion to replace the existing indirect circ with an IFC model would be the simplest solution. This would be a likely candidate:

http://www.taco-hvac.com/en/products...nt_category=53

 

I agree with Xiphias, but I also see the possibility of single pipe gravity ghost flow on the
supply side of the indirect DHW. I'd suggest a heat trap (copper piping going down over 12" to stop gravity flow) or a gravity flow check on that leg as well. I assume the supply piping is just above the circulator on the DHW return?

Pete

 

The Aquastat is currently set at 100 deg, but as I said before, the water can easily get 140 plus. The number stamped on the top is L4006A 2114 (and a 2 on its side).

Turning the dial up, the pump engages at between 120 and 125 (furnace comes on too - I believe the pump is running because voltage in the wires then present and not present when the furnace turns off/dial turned down-pump runs so smooth I can't be sure by just feeling the pump!) Anyway, the pump and furnace turn off immediately after you turn back the dial the other way.

The circ pump is a Taco 007-F5. I don't see IFC anywhere on the pump. As for the wiring of the zone being primary, the green Taco box on the furnace is a Taco SR 501, 1 Zone Switching Relay. The diagram on the inside cover is 102-081, but it appears that it can only be wired one way (and surprisingly, it appears that it was done right!!)

As for how the feed is plumbed, I'll post another pic below. The Feed water is at the very bottom of the tank. The water from the boiler leaves the expansion tank horizontally (by the back wall), and then turns down and enters the tank at the upper most port (no heat trap).
http://i252.photobucket.com/albums/h...2/IMG_0284.jpg
http://i252.photobucket.com/albums/h...2/IMG_0283.jpg

 

Now we can see the supply. There is nothing to stop flow. Who stated change circ for one with built in flow check. (IFC). Aquastat seems to be off a little. Verify the sensing bulb is all the way in the well. You will have to put something small enough to go all the way back in the well. Lay it on the sensing bulb and make a mark on the capillary tube. Re-insert the control and the maek should be at the well opening.