Triangle Tube Delta Elite Model HMF-30 Combination Heater

[CaLeeHal]

HELP!  A month or so ago my combination heater started periodically acting up. Every once in a while it would decide not to turn the burner on then eventually would start clicking - slowly at first then rapidly then finally the burner would kick in, the clicking would continue for a few seconds then back to normal operation for a few days. Figured problem was electrical, husband thought sounded like relay going so checked out elec diagram & replaced burner relay. (The clicking sounded to me like it came from box behind reset button - relays are on either side so figured maybe the sound just transfered to box?) No fix, so called heating guy, he came said I replaced wrong relay, needed to be circulator relay, he'd "seen this before". So, $300 and 2 new relays later, worked for 2 weeks and now is periodically not turning on again.  We're not using the heat now, just for hot water, so circulating relay should have nothing to do with it. At least now if I go down & press the reset button the burner immediatly comes on though I do hear it click a few times after it comes on (before the new relays the reset button acomplished nothing). Anyway, if ,after reading my novel, you can help me i'd appreciate it muchly.   Cara

[hvacdrd]

Is the burner oil(Beckett) or natural gas(Carlin)?

[CaLeeHal]

it's oil -- Riello. but the burner is not problem. Is furnace reset button not burner reset button that restarts it. triangle tube seems to think its the control thermostat (aquastat?)

[hvacdrd]

Since you are not using the space heating we can rule out the R2 relay and focus on the remaining circuits. The primary thermosat (right side-180F maximum) also is not in use for domestic water heating however it should be set higher than the secondary thermostat (left side-140F maximum). The auto reset high limit is preset at 194 and the manual reset limit is preset at 205.

Here is what you should see on a call for domestic hot water...

1-2   120VAC (after on/off switch and manual reset limit)

5-7   0VAC - low water cutoff

7-11   0VAC - secondary tstat closed for domestic demand -

11-14   0VAC - auto reset limit

14-6   24VAC - R1 relay coil

Look for fluctuating voltages on start up at any of these points. I would focus on the secondary thermostat. Observe the temp temp/pressure gauge and dial down the secondary control to see if it shuts off the burner once the temp is above 120F or so.

[CaLeeHal]

both thermostats are set correctly. when hot water is used & burner comes on primary temp gets up to 200 deg. both relays are new so leaves secondary thermostat - correct?

[CaLeeHal]

also auto reset limit must not be working - i think most times it shuts off before the manual reset limit trips but think that a couple times it didn't ( I did have the secondary t-stat set slightly higher for a while) and tripped manual reset limit - cause pressing manual reset got it going again.

[hvacdrd]

As long as you are not using the heating circuit at this time the temp should only be at the secondary setting -130-140F 

Disconnect the jumper from terminal 9 to 10 (this eliminates the primary thermostat altogether) - run the domestic water and watch the temp. As it gets to 120 or so turn it down and see if it shuts down.

If not disconnect the blue wire to terminal 11 that goes to the secondary tstat. If this shuts down the burner - it is confirmed that you need a new secondary tstat

part# PGRKIT21

[CaLeeHal]

will try this tomorrow. got a source for the thermostat kit?

[hvacdrd]

This is all I can come up with, TriangleTube - looks like there is a representative on Long Island - I'll keep looking for an online source

[CaLeeHal]

Checked out tstat like you suggested - it shut off burner but only when it was turned WAY down (into the blue area) even when primary temp read 160.  (Could turn burner on/off by moving tstat back and forth small amount) Pulled bulb out of dry well to see if it was hot - was luke warm but definately not 160. shut unit off & ran hot water to see how hot it was - barely warm. Usually when hot water not in use unit's primary temp stays around 140 when set like triangle tube recomends, so got to thinking & came up with a theory - tell me if this sounds plausible. When a lot of hot water is run out and domestic tank fills with cold water (well water so it's pretty cold) it signals unit to turn on burner & heat water but since the primary heating tank was already at 140 (and the heat can only transfer from there to the inner tank so fast) when the burner comes on it heats the primary tank even further so primary temp goes up either until the domestic reaches it's goal (when domestic is at 140 primary is at about 200) or until the reset limit shuts it off. Since the auto reset limit isn't working - it goes past 194 so it can't be working - sometimes the manual reset limit shuts it off. This only happens when I use a lot of hot water like last night when I ran the dishwasher after my husband took a shower. Had hot water for the dishwasher but reset limit was tripped and temp had dropped by this am.

[CaLeeHal]

ok- still not sure about tstat working. I pressed manual reset button so unit came on - temp was about 80 deg. Since both primary & domestic were the same thought it should shut off around 140 (triangle tube says the "m" in "domestic" on the dial is 140) but it kept going... at 160 i turned thermostat down (to "e") and it clicked off, turned it back up to the "m" and it didn't come back on. Turned to "o" and it came on so just turned back down to shut it off. Seems like if i move tstat dial it clicks on and off at right spot but not sure about otherwise.  Maybe the outer tank just heats up faster than the inner one. When just shut off I can turn on/off w tstat but I waited about 15 min then turned tstat all the way up and it doesn't come on. Did it take a bit for the temps in the 2 tanks to eqalize? Don't want to replace tstat if nothing wrong with it. Maybe when the auto reset limit is working it takes care of problem by just resetting it all the time?

[hvacdrd]

I think you are on the right track as far as the temp issue goes, when not using the heating the burner is cycled off on one of two controls. Either when the domestic thermostat reaches its setting 140F or when the primary temp reaches the automatic reset limit 194F - which I think is too close to the manual reset temp. Can you adjust the auto reset limit down 5-10 degrees? This would eliminate the reset condition.  

One other thing to consider is the possibility that the inner tank (domestic) has begun to scale which would reduce the heat transfer rate. The outer tank would need to reach a higher temp to heat the inner tank. Do you have hard water? TriangleTube recommends hardness be maintained below 7 grains

I am still trying to figure out what the initial clicking was all about. I got side tracked trying to figure out which control would be 'bouncing' or making poor contact.

[CaLeeHal]

triangle tube had told me that the auto reset limit is not working properly since the temp is going up to 200 before the tstat shuts it off, so not sure if changing it would do anything.  don't know how hard my water is - was very acidic but just recently put in an acid neutralizing system (in march) Maybe I should just replace the auto reset limit. Could that have been the clicking if it was being tripped and getting stuck trying to reset itself? The unit is only 3 years old, could scale build up that fast? Thanks for being patient & trying to help answer all my questions.

[hvacdrd]

I agree that starting with the automatic reset limit would be best. Try to access the control and see if it has any adjustment to it. Like I mentioned turning it 5-10 degrees lower would solve the tripped reset condition.

As for the scale build up I don't even know how you could tell other than a reduced recovery rate. I just thought I would throw that out there as a possibility, TriangleTube does not even mention a method of de-scaling if need be.

According to the specs on this unit it looks like it should provide plenty of hot water. Scale tends to build up faster when the temperature difference is high. I have seen on demand water heaters plug up to the point that it almost stops water flow. Typically these types use small tubing in which the domestic water is flowing, which is unlike the design of this unit.

One other thought that came to mind was the fact that they do not run the primary loop pump during the domestic only heat cycle. If they did it would keep the outer tank at a more even temperature from top to bottom. It would take a few simple wiring changes.

As for the clicking - looking at the controls in the unit I would suspect the low water cut-out of "bouncing" if any. The primary loop must be above 10psi to make the switch. I'm not saying that is what the problem is, just that it is the most likely device to act this way. Verify the pressure - it should be 12-15 psi normally.

[CaLeeHal]

i'll start w/ checking the auto reset limit. it did eventually stop clicking, now if it trips & i press reset it just starts up again like normal.  I would consider changing it around so the pump came on during the domestic cycle - makes sense that the heat could transfer to the domestic tank faster that way..