Hydrostat 3250-Plus ... a simple, intelligent solution needed.

MikeAmann

I have a head-scratcher for you guys............
From the instruction manual:
At initial start up, with the Economy Feature active, the control establishes a 145°F target temperature. If the heating demand is high, the target will increase over time to satisfy the heat load.

Thermal Targeting technology analyzes thermostat activity and continually evaluates how much heat the house requires. When it is very cold outside, the heat demand is high and the Fuel Smart HydroStat will raise the boiler’s Target temperature to provide needed heat to the home. When the outside temperature is milder, the heat demand is lower. During these periods, the Fuel Smart HydroStat will lower the boiler’s Target temperature – saving fuel – while continuing to provide comfort to the house.

While this method probably works great for 99% of users, I have a unique situation where I need a way for the house to heat quickly, and then have the ECONOMY programming take over. I do have the outdoor reset with WWSD connected and enabled. And it is currently set at a 2.50 reset ratio to target 180 F boiler water.

RESET RATIO
The Fuel Smart HydroStat control’s Outdoor Reset feature uses a reset ratio method to control the boiler temperature. The reset ratio determines how much the boiler temperature is adjusted for changes in outdoor temperature. A reset ratio of 2.0 means that for each 1 degree increase in outdoor temperature, the boiler temperature will decrease 2 degrees. Conversely, for each 1 degree drop in outdoor temperature, the boiler temperature will increase 2 degrees. The control adds 10 degrees to the calculated reset temperature and provides a 20 degree differential for burner operation. So, if the control calculates a reset temperature of 150°F, it will set a target temperature of 160°F. It will then allow the burner to fire up to 160°F and draw down to 140°F before re-firing. This operation will maintain the desired average temperature of 150°F. You can check the
current target temperature at any time, by pressing the Test/Settings button in 4 short intervals.

THERMAL BOOST
To insure that the heating system always satisfies a call for heat, the Fuel Smart HydroStat control is equipped with a thermal boost feature. If the thermostat is not satisfied thirty minutes after the boiler reaches the reset temperature, the control will boost the reset temperature by 10 degrees. It will continue to boost at 30 minute intervals until the call is satisfied. Once the call is satisfied, the control reverts to normal operation, utilizing the
calculated reset temperature.

When I am not at the house, the hallway thermostat is set to 55 F. When I get there at night, I raise it to 65 F. But the Hydrostat then sets a target temperature of 145 and in time will keep raising that target up to the temp needed to satisfy the thermostat. But it takes over 3 hours to get there! I need a way of sending my HI Limit (205) water circulating through the pipes to get the house up to temperature faster. My ancient "dumb" controls (Honeywell R8182D with an Intellidyne HW+ economizer) worked this way, and did the job well.

The plumbing is as simple as it gets - the heating side (hydronic baseboards) is 1 loop with it's own circulator - no zones or valves. The IWH has it's own circulator.

Is there a simple way to accomplish this? Here is my thought:
When the IWH calls for heat, through ZC ZR the burner gets fired up to the HI Limit. Could I wire a NO contact of a timer relay to ZC ZR and set the timer for 1 hour? The boiler temp would then run off of the HI Limit during this time, getting the house to 65 F a lot faster.

STEVEusaPA

Mike, any other hobbies besides this aquastat?

MikeAmann

Thanks Steve.
Good thing I wasn't drinking something when I read this, or it would have shot out of my nose!

EBEBRATT-Ed

I don't see any reason why that would not work. The boiler would the idle along adjusting it's temp base on ODA etc. until you wind up the timer

I suppose it could be something as simple as a wind up timer like you use for a bath fan. Set it for an hour the boiler comes out of set back timer opens and it goes back to normal operation

HVACNUT

Get a WiFi thermostat and crank it up 3 hours before arrival. 
Economy is a compromise. 
10° is a lot to make up in a short period of time when it's cold outside. 

Jamie Hall

Which makes me wonder a little... what was the matter with the ancient dumb controls that you were obliged to scrap them for this?

pecmsg

55° to 65° is asking a lot of any adaptive recovery.

Manually raising the t-stat when you get home is the wrong way to use adaptive recovery. Program it.

How old is this install? It could take 30 - 60 days for the controls to gather all the data needed. It's trying to learn at X° outside it will take Y° water to meet demand.

MikeAmann

Jamie Hall said:

Which makes me wonder a little... what was the matter with the ancient dumb controls that you were obliged to scrap them for this?

I was getting short-cycling with my ancient control. Plus I was finding that the built-in fixed LO Limit differential was no longer accurate. And then I started doing the research on the new controls and found them to finally be light-years ahead of what I was trying to accomplish with wiring, timers, relays, add-ons, etc. Thanks SuperTech and STEVEusaPA! And the wiring is much simpler now!

And thanks for all for the replies on this. And, as usual, you are all correct. And so am I.........
STEVEusaPA, you talk directly with Carlin, so you might find this especially interesting.
I am not saying that this will work for all situations, but it does work for mine.
My idea from above:
When the IWH calls for heat, through ZC ZR the burner gets fired up to the HI Limit. Could I wire a NO contact of a timer relay to ZC ZR and set the timer for 1 hour? The boiler temp would then run off of the HI Limit during this time, getting the house to 65 F a lot faster. Then the control would revert back to it's ECONOMY programming.

I had an extra programmable timer relay and used a small plug-in 12v wall transformer to power it. I connected the N.O. contact to ZC ZR and set the timer for 1 hour. A momentary push-button activates the cycle. The Hydrostat is programmed to fire the burner to the HI Limit (205 F in my case) when using ZC ZR. And this worked perfectly as I watched for the next 2 hours trying to determine if there were any conditions where doing this would cause a problem, or create a safety issue. NONE that I could think of.
I again read through the manual and found this:
NOTE:
• Smart DHW Priority: During a call from an indirect water heater, the control will de-energize the circulator contacts (C1/C2) to heat only the indirect tank ensuring an adequate supply of domestic hot water. The control will re-energize the circulator when the indirect tank is satisfied or if the boiler temperature reaches 170°F. If the indirect call continues for 45 minutes, the control will override the priority function energizing the circulator to provide space heating.

So after 45 minutes of a CFH via ZR, the Hydrostat will ignore that input and go back to what it was doing.
Therefore, I reset the timer to 45 minutes. Outside temp = 32 F. Here is how it cycled:

• Heating circulator is already running.
  
• Activate timer relay.
  
• Burner runs up to 205 F, instead of lower TARGET temperature.
  
• Temp creeps up to 208 F.
  
• Boiler water circulates for 10 minutes until temp gets down to 195 F (HL diff set for 10 degrees).
  
• Burner fires again for 5 minutes until 205 degrees.
  
• Lather, rinse, repeat.
  
• This will continue for 45 minutes until the relay times out. Then the Hydrostat goes back to it's ECONOMY programming (Economy LED turns on and TARGET is now 177 F).
  

Robert_25

Mike, your 1 hr ZR/ZC idea would work - but I am having a hard time seeing why you would want to run a huge setback and part-time HIGH boiler temperature instead of just a steady set point and full outdoor reset?

MikeAmann

Robert, it's just my odd work hours and days off, Dad got dementia and we just got him in a facility the week before Thanksgiving, trying to take care of Mom and get her house back in order and she is being difficult, etc. Basically I am not at the house on a regular basis. My pipes will never freeze, so I can, and have in the past, completely turned the heat off when I knew I wouldn't be there. Now that the boiler is more efficient and reliable, I am leaving the heat on, just at a lower temperature, and increase it when needed.

Cycle times - does anyone thing that I should change the HL differential to 20 degrees?

Robert_25

In that case I would just get a smart thermostat and turn up the heat remotely.

EBEBRATT-Ed

The burner is off for 10 min so I would say it is ok

MikeAmann

Robert_25 said:

In that case I would just get a smart thermostat and turn up the heat remotely.

Old-school Robert.
No smart phone, no apps, no WiFi, no RING doorbells, no relentless ads, no spyware, no tracking, no COVID shots.
I will not spend my life with my head down tapping away all day on a smart phone.
Not a conspiracy theorist, but it's getting really hard to not believe some of it.

Does anyone really want to see another "I can't find the C wire" post?

MikeAmann

Changing the HL differential has no effect when any kind of ECONOMY is in use. That setting only works with economy OFF.

It was 20 F when I got out of work tonight and the boiler was already running off of the HI Limit.

So I will be removing the heat reclaimer connected to the breach and moving the draft damper to that location so that I can install a vent damper where the draft damper was. Is there anything wrong with using the heavier gauge black stove pipe? I bought up a bunch years ago when a store was going out of business. All I need is a 7" tee. I have the rest.



I am just planning ahead right now.

HVACNUT

Why is limit at 205°?
It seems your efforts are contradictory. 

MikeAmann

HVACNUT said:

Why is limit at 205°?
It seems your efforts are contradictory. 

My old control had the high limit set to 200 F, but it's sensor was on the output pipe. That sensor did read accurately and would display 215 F with the creep up in temp after hitting the 200 limit and shutting the burner off. Besides, I read somewhere in the past that 200 degree water has much more heat available than 180 - implying a non-linear relationship, if you know what I mean. I also read that baseboards are more efficient at those higher temperatures. Either way, 200 works well for heating my house when it gets below 32 F outside.

The difference between the old and new controls is that the old controls worked from the top down (run burner to HI Limit and then calculate if a lower temp can satisfy the CFH) and the new control works from the bottom up (slowly keeps raising the water temp if the CFH is not being satisfied within a reasonable amount of time) in calculating the correct water temperature to meet the heat loss load of the house.