Aquastat reaction time, add Tankless coil back?


Old 04-07-15, 06:38 PM
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Aquastat reaction time, add Tankless coil back?

The background: In November 2013 I re plumbed the whole boiler (peerless WBV-04) and added zones for indirect water heater and father-in-laws room/bathroom. My tankless coil was leaking at gasket (and rusty). Since I was converting to indirect with cold start I replaced it with a blank plate. I bought the Beckett Aquasmart because it had the built in LWCO and heat manager. It was working pretty well but I found that it had A LOT of short cycling and I had some domestic hot water issues when 2 people shower which happens often with 2 teenagers and people getting ready for work. All zones controlled by Taco SR506 with superstor on priority.

The Aquasmart tries to keep low temperature which doesn’t coincide with Indirect needing BTU’s to reheat the water. It takes a while before it actually reaches 180 degrees, usually done with shower by then, or got out due to lack of HW.

This year I turned off the heat manager portion and tried the Intellidyne HW+ (since I already had it). One of the first things that I found with the HW+ was that the output temperature to my zones never reached 180 degrees, 170 was rare, normally 165 but Aquasmart showed 180 and heat soaked to 190+. I bought 3 different thermometers (2 oven remote sensor) and used the Flir thermal camera when I had it. I was getting a pretty consistent 20 degree delta T from output to return. All the thermometers matched the sensor from the Intellicon HW+ and very close to the temp pressure gauge mounted on boiler, all low as compared to Aquasmart Control readout.

What it appears to me is that the 5-6 gallons that used to surround the tankless coil (with cold water flowing through it) now heats up too fast and registers on the aquasmart accordingly to shut down. The water flowing through boiler eventually cools down, evens out and as the temperature drops it does so at a consistent rate that matches all the sensors down until it calls for heat.

I asked a couple plumbers I work with and even called Intellidyne about options (like adding a domestic sensor) with varying answers. Peerless said to contact a hvac/plumbing contractor. Checking through all different things I found that with this cold this year the water coming in to my supply was REAL cold which of course takes more BTU’s and time. The Superstor Aquastat Honeywell 4080 has a 15 degree differential (my old Boilermate had 10 degree). I turned off the Intellicon and left heat manager off. Of course this does nothing to help any fuel savings.

I had to turn the water temp up on the Superstor (I don’t have a tempering valve yet!) AND needed to turn boiler aquasmart to 190+ so I could actually get 180 out to my zones. This is definitely helping for the showers but not the wallet.

I’m not sure what options to try. I’m thinking replace the superstor aquastat with one that has a 10 degree differential so it will react quicker. Crazy thought of adding tankless coil back and piping it to cold supply of superstor. Try a different Aquastat? Wire up the Superstor differently to Aquasmart? Any where to relocate the Aquastat so it’s not sitting in such a large area of water? Would that cause other safety issues? Try different temp settings/diffs? New larger indirect water heater? All I know is I burned some serious oil the past 2.5 months and had domestic water issues. Heat worked fine.

The Intellicon HW+ was showing I was saving a HUGE .5% (just 9.5% shy of the guaranteed savings). The Aquasmart never showed anything except lots of short cycles when you went to history menu.
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Old 04-09-15, 04:20 PM
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How do you have the indirect pipe and wired in? What size pipe and pump?
Old 04-09-15, 07:03 PM
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I have a similar issue running an HW+, only the other way around. My output water temp as read by the HW+ and confirmed with IR gun and another thermometer is 10-15 deg. higher then my aquastat sees. I set the system up looking at output temps from the sensors on the pipes, (HW+) disregarding what the settings on my aquastat are.

If you've got 180 degree water temp flowing out of the boiler and your hot water keeps up, heat should be fine, then you shouldn't be using excessive oil. Try to get the cycle times under control. If your going to use the HW+, turn off the heat manager and economizr on the aquastat. Let the HW+ take control of the system which should give you nice long run times. Adjust the system temps to give you just enough recovery for hot water. If 180 is the magic number, leave it at that.

I still have my coil in place so the HW+ sees my hot water demand (2 sensors) and allows the burner to fire to keep up with my demand. When the system is on a heat call I get much larger temp dif swings and nice long run times. I show almost 30% savings on the HW+. Have you asked Intellidyne if or how you could use the 2nd sensor for DHW on your hot water tank zone?
I think if you have the DHW sensor on the output of the tank and set a minimum temp on the HW+ to say 130 for DHW, it should give full control to the aquastat to fire the burner to give you adequate recovery for hot water. Remember, sensor placement is critical for the HW+ to operate correctly.
Old 04-09-15, 08:52 PM
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rbeck- wiring is Taco SR506, Superstor as priority on zone 6. Bolier piping to/from SS is 1" copper with long turn elbows. Supply / return manifolds are 1 1/2" 5 zone manufactured. 4 x 3/4, 1 x 1". On return to Peerless it adapts down to 1 1/4 (why does Peerless have it that way?)

tomf63- HW+ sensor is 1" up on supply piping and well insulated. When HW+ was on all aquastat extra controls were off. Burner run times definitely increased. HW sensor matches independent remote sensor thermostat also on supply and insulated but 1' further up stream.

Intellidyne said extra sensor would probably not work since it will always read cool as the indirect only shows 140 max normally. If there is a call it will kick in right away. Yours with the coil will show whatever your boiler temp which is higher than that allowing time to show it cooling down. With the coil you are probably still warm start with a low limit. Mine is cold start.

Your description of issues is what I think mine is "missing". You have constant supply of cold water cooling off the 5-6 gallon pot surrounding the aquastat. I have a plastic well with metal tip sitting in it.

Just had a heat call and checked. Aquastat HL is 190, 20 diff, low limit off. Boiler shut off at HL (190), output showed 180 on all external sensors. Aquastat heat soaked to to 201 before dropping down to match all other sensors all the way to 165 when heat call as satisfied and circulators shut off.

I did turn HW+ back on the other day. Showing .6% savings. incoming water temp feels warmer, no shower complaints but everybody is off this week and showering at different times.
Old 04-09-15, 09:33 PM
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It was asked pumps or zone valve? What size pump for SS if so?

Aquastat from SS goes to zone 6 correct? Set on priority? Then zone valve or pump for SS connects to proper terminals on zone 6 right?

Need to know if wiring is correct first..

The HW + is hooked in series with the boiler controls?

What aquastat is on the boiler? model?

The HW + has many settings and they may or may not be set correctly. Especially for hot water.. We dont know what these are...

''IMO your better off with the aqua-smart then the HW +"
Old 04-09-15, 09:56 PM
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It was working pretty well but I found that it had A LOT of short cycling and I had some domestic hot water issues when 2 people shower which happens often with 2 teenagers and people getting ready for work. All zones controlled by Taco SR506 with superstor on priority.
Must have had it wired wrong IMO..

With the aquasmart you run the Indirect t stat to TT of the aquasmart. The circ for indirect goes to c1 c2 of aquasmart.

zc/zr of the aquasmart go to zc/zr of the taco panal. The end switch from the taco is not used.

All other zones are hooked up normally in the taco panel.

Hooking up like that tells the aquasmart that on a call from TT the boil fires HL and will priority the DHW pump at c1/c2.

Set DHWP on TT (see programming section for instructions).
Set C1 on TT (default, see programming section for instructions).
Circulator-on and -off delay will only effect DHW zone.
A call for heat on TT (from the DHW zone) will change boiler set point to the high limit. All
other zones willheat to the reset temperature determined by the HeatManager.
Ensure that the zone panel and AquaSmart are powered from the same service switch.
Old 04-10-15, 10:10 AM
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I had posted more info but it logged me out while typing, missed on retype. All zones are on circulators, Taco 007 IFC. 1st floor (1), second floor (2), Father in laws room (3), Superstor (6 as priority), Basement zone possible future. All T-stats control correct circulators. Isolated end switch is wired to TW and TR on side of aquastat. ZC/ZR jumped as per cold start directions. Same wiring and plumbing setup that worked perfectly for years on my old house with Amtrol boilermate, Weil Mclain WG0-4, Honeywell 8184a. Same as a couple friends also that have cold start (no coil option) Weil McLains with Superstor and honeywell basic HL aquastats. All working well, recover fast, and showing savings correctly

Aquastat is Beckett Aquasmart 7600A (currently set as HL 190, diff 20, LL off, heat manager off). HW+ in series? Wired as schematic with leads in between the B1 from aquastat and Riello power leads. HW settings were set at default but I bumped the low limit to 150 after the conversations with Intellidyne trying to get the domestic to recover quicker. Old house was left at defaults (only adjusted for prepurge delay time).

What I found for the year that I had just the Aquasmart was the numerous short cycles and lack of recovery on domestic. Since it always tried to keep as cool as possible starting at like 130 and bumped in small increments. It would run 2-3 minutes, off 2-3, HM set limit 5 degrees higher, cycle would repeat until it finally went to HL. The constant short cycles just kill to listen to.

I can try wiring as you suggest to see if it changes anything (even though that would $uck since everything is neatly in conduit and BX).

The features on the HW+ that I like are the showing of calculated savings and run times. All the ones at friends were done after years of use and like mine showed correct for savings vs. actual gallons used year to year.

Do you think that any of the wiring changes will change or effect the part that the aquastat shuts at HL but the actual output to zones is 15-20 degrees colder while heating? Once burner is off and water circulates longer then aquastat matches all other sensor readings.

Side note- any recommendations for coil cleaning /descaling liquids. I'd have no issue pulling some stuff to make sure I'm not having heat transfer issues inside SS.
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