Indirect water heater timer

Stapler

I need a 7-day programmable timer to block calls for heat from my indirect triangle tube water heater during the day and night when we aren't using it. It's amazing that although manufacturers say there is only a 1/2 degree temperature drop per hour in these heaters, it is still calling for heat every 30 minutes or so. I guess I could take out the current thermostat and put in an aquastat with a wider temperature range, but I thought a timer would be better if I could find one that operates on 24v ac. Thanks in advance.

STEVEusaPA

tell me more.....

about your other controls.  What's controlling the boiler, the DHW call, do you have setback features, unoccupied modes, etc., or are your current controls expandable? 

Jean-David Beyer

calling for heat every 30 minutes or so

Something is the matter. I have a W-M indirect that as far as I can tell is the same as a Triangle Tube one. I do not know if the heat loss is exactly 1/2 degree per hour, but it is very low. Obviously the loss depends on the temperature you are trying to maintain in the tank and the environmental temperature. As far as I can tell, mine heats 2 or 3 times a day, but my heat demands are low: 1 shower per day, two loads of laundry a week (but use only cold or warm water, never hot), one or two loads in the diswasher per week.



One possibility is that you have continually running hot water somewhere (a leak), but that seems not very likely because that would be a lot of water.



I have my cold water supply and hot water delivery pipes insulated because they get fairly hot when no water is running. But here, too, that does not strike me as a likely source of temperature loss evey half hour.



Could the circulator from the boiler be running when the boiler is not firing? This would pump heat out of the outer tank and waste it in your boiler and elsewhere. I am not sure it is a likely problem either, but is easy to check.



In W-M's instruction, they want a flow check in the heating loop. If missing, the heat could get out  without the circulator running.



You do not have a water recirculation system running, do you? That could be unintentionally heating your building.

Stapler

Parts

I have only TACO SR506 6 with Priority zoned to 4 room thermostats heated by a Monitor gas boiler. The indirect is on the 5th zone, with no-priority. The indirect heater has swing check valves on the return and heat supply, hopefully, limiting the migration of heat out of the tank. The only other unusual aspect of the install, is that I have a solar hot water tank in front of the indirect, to preheat pottable water supplied to the tank.

There may be a need to put a check valve on the supply here, too, so that heat won't migrate out into the cold water supply. although I can't imagine that much heat would escape in 30 to 40 minutes. It certainly is not warm to the touch more than 3 or 4 inches past the cold water inlet and I have never seen an indirect with a check valve on the pottable water supply pipe.

STEVEusaPA

oilman19008@yahoo.com

I agree with JDB that something is definately 'up'.  My Smart 60 only calls when I use alot of hot water, or if it sat awhile, when i start using hot water,and if no hot water is used, it may only come on once all day.  I hope you have flow checks instead of swing checks, but thats a whole different thread.  Is it possible to show a diagram or photos of the piping to/from the solar storage tank? I'm curious as to the interaction between the two, specifically the piping & controls.  Yes flow checks are used on the potable side, especially with a DHW return line/pump.  My initial thought is it could be the aquastat, and I would start there, checking it with a meter.  Following up with what JDB asked, do you know if your DHW pump is running at all?  You said the priority switch is off, but can/did you confirm it with an electic meter.  Is this a recent problem, or did you notice it recently?  Also, any dripping of a hot water faucet or leak would hurt you too.  If possible, see if your water meter is spinning (little red arrow on mine), or check the gallons, then check in a half hour (with no water usuage) to see if there are any change.

Mark Eatherton

One pipe heat loss...

Imagine this in your minds eye. Hot water rising up the core of the pipe, adn cold water settling down the outside of the pipe and into the tank. It's referred to as one pipe thermosiphon, and it is for real.



How do you over come it?



Heat trap (at least 24" of drop immediately after tanks hot water outlet before rising upwards to the distribution system.



A spring loaded check valve installed on the hot water outlet pipe could work as well.



Lastly, good ol' pipe insulation installed on as much pipe as possible.



ME

mark schofield

aquastat high limit ?

Could the high limit on the aquastat be set lower than the "on" setting for the DHW tank/circulator?

Stapler

@ mark schofield

The thermostat on the Triangle Tube doesn't have a high and low limit. That's part of the problem. But I'm still interested in a digital timer for an indirect tank that would work like a room T-stat and shut off calls for heat even if the temps fall below what is set on the indirect. That way you could shut off the indirect at night, for vacations, etc.

meplumber

Check the insertion depth on the probe.

On the Triangle Tube/Weil Mclain Tanks, stratification has always been an issue.  Check that the insertion depth is not too deep.  Also, which mark do you have the contained aquastat set on.



I agree with JDB.  I have quite a few of these tanks out there and while I cannot vouch for the 1/2 deg per hour.  The standby loss is pretty low.  Every 30 minutes means something else is going on.

Jean-David Beyer

That's part of the problem.

I am not a professional. But I disagree. The fact that the indirect does not have a high limit and a low limit is not part of the problem. I do not know what is, but that is not it. And I think putting in a timer is a waste of time and would, at best, hide the symptoms of whatever the problem is without actually solving it.



Either the aquastat in the indirect is defective (limits way too close together), or something else. Another possibility is that there is no silicone grease in the well and that the aquastat is measuring the air temperature in there instead of the water temperature in the tank. I do not know if there is supposed to be silicone grease in there or not. I looked in the installation manual for the W-M version and it is silent on that point. It also does not say how far in the aquastat should be inserted.



On my W-M indirect, they say the hot and cold domestic pipes should have a 12-inch drop on entry and exit from the indirect. Since my cold water comes direct from the floor, and the hot water goes to the house at floor level, I have about 5 foot drop for this. Even so, I found it helpful to insulate those pipes because they get hot even when there is no demand for hot water. I have not measured how much the cycle time has increased because of the insulation, but it theory it makes a difference.

mark schofield

backwards piping

A few years ago my solar storage tank began to leak. I was having trouble with the new tank (external heat exchanger) until I noticed that had piped it backwards. Just a thought.

hot_rod

could be

the ncheck valve(s) on the solar are allowing the energy to go back out through the collector at night and taking some of the heat from the indirect with it?  Is there a recirc pump on the DHW?  If so how is it piped to the tanks?



What about a 3 way thermostatic valve on either tank?



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