Intellidyne HW+ Setup

[Gary in NJ]

I have an older boiler that is 3x oversized for my heat load and Dana suggested that I install a heat purging boiler economizer control on my aquastat to help with short cycling and gain some efficiency from the system. I purchased an Intellidyne 3250 HW+. Installing the controller took all of 10 minutes. It's as simple has connecting the unit to the hot and common for power, and then removing the wire in the aquastst that controls the burner and jumping to the controller. It took me as long to type this as it did to perform.

I do have a few questions regarding set-up.

Currently my aquastst is set for 187F. I'm quite sure I had it set to 180F, but I did have a service performed last winter and my guess is that the tech "up'd" the setting. Sure enough, the boiler shut down right at 187 (confirmed with the temperature gauge and an infer-red) and the temperature continued to climb to about 195. From an efficiency stand point I assume that I'd want the boiler to run hot (it's a WM Gold P-WGO-4 Series 3 and is safe to run to 210F). If I set the HLOLIM at 140F that would give me 55 degrees of purge to circulate before the HW+ releases the boiler to fire. I'm I thinking about this correctly?

Regarding Pre-Purge, my first check of the system was when the boiler had sat idle without firing for a few hours. The water temperature in the boiler was 140F. After the call for heat it took about 110 seconds for the circulator to engage and the boiler fired about 10 seconds after that. Was my pre-purge period 110 seconds, 10 seconds, or 120 seconds? I did a second test with the boiler still at 170 degrees. I cranked up the DHW to force a call. The circulator engaged about 60 seconds later and three minutes later I gave up waiting for the boiler to kick on as there was plenty off hot water in the system too meet the demand - the boiler never kicked on. So what exactly is pre-purge? What is the best test to determine the correct setting? Why the 50 second difference between the first and second test?

Regarding the DHW sensor, my hot water is set to deliver 140F. The directions for the DHW sensor say to install the sensor on the out flow pipe, which I did. The directions state....

"This parameter is used by the controller to set the low-limit temperature for the domestic hot water. When the domestic water temperature goes below this setting, “HEATING/LOLIM” will be displayed, and the controller will no longer attempt to achieve any savings and return control to the operating-control. To change this setting, plug the sensor into the appropriate jack to increase or decrease the value. The indicated value will be what is currently set in the controller (default = 120˚F / 49˚C). The range of adjustment is between 90˚F/32˚C and 180˚F/82˚C. Remove the sensor when the desired value is reached."

I ran my hot water at the sink for 5 minutes and confirmed that it was at 140F with the I/R. I then went to the outflow pipe and measured just 107F where the pipe leaves the tank. My guess is that the actual water tank is much lower in the enclosure, so by the time it exits the enclosure some heat has dissipated. So what would be the proper DLOLIM?

Thanks for any help.

 

[Gary in NJ]

I think I can answer my pre-purge question - my system doesn't have a pre or post purge feature. The ten second period I was describing above is simply the Honeywell R7184U checking that the igniter is firing and a flame is present.

I am confused as to why it takes so long for the circulator to start pumping after the call has been made to the aquastat.

 

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[Dana]

From an efficiency stand point I assume that I'd want the boiler to run hot (it's a WM Gold P-WGO-4 Series 3 and is safe to run to 210F). If I set the HLOLIM at 140F that would give me 55 degrees of purge to circulate before the HW+ releases the boiler to fire. I'm I thinking about this correctly?

The raw combustion efficiency is a bit higher and the standby & distribution losses are lower at low temperature. You're making the trade-off between those factors and the extreme losses of short-cycling. Having 55F of temperature headroom to slew through guarantees fewer ignition cycles and longer burns, which is what the goal is. So raising the high-limit to the max gives you the greatest temperature swing, longest burn time.

Regarding Pre-Purge, my first check of the system was when the boiler had sat idle without firing for a few hours. The water temperature in the boiler was 140F. After the call for heat it took about 110 seconds for the circulator to engage and the boiler fired about 10 seconds after that. Was my pre-purge period 110 seconds, 10 seconds, or 120 seconds? I did a second test with the boiler still at 170 degrees. I cranked up the DHW to force a call. The circulator engaged about 60 seconds later and three minutes later I gave up waiting for the boiler to kick on as there was plenty off hot water in the system too meet the demand - the boiler never kicked on. So what exactly is pre-purge? What is the best test to determine the correct setting? Why the 50 second difference between the first and second test?

I'm not sure why there is a delay on the circulator on call for heat. I'd have to understand the whole control scheme to figure that out. The default pre-purge setting on the Intellicon is 0 seconds, but the time from the call for heat for until the burner fires is the actual pre-purge time, and it can be set by following the instructions starting at about 2:40 in this video.

The pre-purge time is a delay to allow any interlocks from automatic flue dampers etc to settle, but I believe the circulator should be running during that time. Time 0:00 on the pre-purge should be when the call for heat starts, and for most oil-burners with just a barometric flue damper a zero pre-purge time is appropriate, since the burner would fire right away if it were at the low-limit.

IIRC all WM boilers an Energy Star label all have an electrically operated flue damper that takes several seconds to fully open, but there should be an interlock in the controls that suppresses firing until the open flue is proven by (I believe) a small switch in the flue damper unit. If the contacts or relay power to/from the damper are getting flaky or intermittent it may explain odd delays. When operating with the Intellicon in place damper may or may not open as soon as there is a call for heat, whether the burner eventually fires or not. Some boilers will normally delay the firing for several seconds after an initial call for heat (don't know about this one), and if that's how yours operates add that time into the pre-purge if you need/want better accuracy on the accumulated savings reported. But a pre-purge time north of 100 seconds would be rare if everything else was working properly.

When the boiler's temperature drops the programmed low limit temp during a call for heat with the circulator running it will fire up, which would explain why the burner fired 10 seconds after the circulator started when the boiler had been idling at 140F, and why it didn't fire at all on the second pass when it was idling at 170F and satisfied the call for heat before reaching 140F. ( Congratulations- you avoided an entire burn cycle AND it parked the boiler at a lower temperature, for lower standby loss! )

Regarding the DHW sensor, my hot water is set to deliver 140F. The directions for the DHW sensor say to install the sensor on the out flow pipe, which I did. The directions state....

"This parameter is used by the controller to set the low-limit temperature for the domestic hot water. When the domestic water temperature goes below this setting, “HEATING/LOLIM” will be displayed, and the controller will no longer attempt to achieve any savings and return control to the operating-control. To change this setting, plug the sensor into the appropriate jack to increase or decrease the value. The indicated value will be what is currently set in the controller (default = 120˚F / 49˚C). The range of adjustment is between 90˚F/32˚C and 180˚F/82˚C. Remove the sensor when the desired value is reached."

I ran my hot water at the sink for 5 minutes and confirmed that it was at 140F with the I/R. I then went to the outflow pipe and measured just 107F where the pipe leaves the tank. My guess is that the actual water tank is much lower in the enclosure, so by the time it exits the enclosure some heat has dissipated. So what would be the proper DLOLIM?

Thanks for any help.

The sensor needs to be insulated and as close to the tank as possible, with 100% of the pipe between the sensor & tank insulated. If the water in the tank is really 140F and you're measuring 107F something isn't right. There's no way it's dropping 33F in just a few inches of pipe. If you're taking the temperature measurement with an IR thermometer on bare copper pipe it will read dramatically lower than reality due to the very low IR emissivity of copper. A spot of spray-paint (any non-metallic color) on the pipe where you're taking the IR measurement would give you a more accurate read. This is an issue with aluminum and bright galvanized ducts & plumbing too.

The DLOLIM should be set a 5-10 degrees lower than the tank's aquastat setting. The sensor tells the controller to not suppress firing even if if the boiler temp hasn't yet dropped to the heating low limit yet so that the hot water service is maximized. With the heating low limit set to 140F and the indirect's aquastat also set to 140F you may have issues with getting enough hot water. It's hard to heat a tank of water to 140F with 145F water being pulled from the boiler through the heat exchanger, but you can still get good heat transfer from 145F heating water in the indirect if the tank's storage temp is set to 120F.

More recent code fore new installations usually requires hot water that goes to sinks & bathing to be tempered to 120F or lower with a tempering valve or thermostatic mixing valve. (It's still code-legal to send hotter water to dishwashers and washing machines, but not to sinks and showers.) If there is a tempering valve the sensor needs to be on the tank's outflow, not the tempering valve's outflow pipe.

 

[Gary in NJ]

Dana,

You were correct, the I/R was not reading the copper pipe correctly. The DHW sensor is spot on show 140+ on the output. I set the DLOLIM at 130F and the HLOLIM at 145F. For now I'm keeping the pre-purge @ 000 seconds.

I still don't know why it takes 120 seconds for my circulator to kick in. Could this be a setting on the aquastat? I can't find anything in the Honeywell documentation that describes a circulator delay. As soon as the circulator engages the HW+ goes from "Standby" to "Econmizer" mode so it's all communicating correctly.

 

[Dana]

I guess the real test will be during the heating season when you can time the burns, and count how many burns are missed. In an ideal world the minimum burn time would be 10+ minutes, but you don't have enough thermal mass or zone radiation to hit that.

You might look through the boiler manual to see if they spec a smaller nozzle size and down-size with a smaller nozzle at the next tune-up, which would help. Usually down-firing by a large amount will give up a percent or two in maximum achievable combustion efficiency, but if it increases the minimum burn time on zone calls from 3 minutes to 4-5 minutes it'll still be a net savings.

I'm not sure how low you can really go- the WGO-4-RD (reduced input) has a DOE output of 123K to the WGO-4's 145K (a 1.00 gph nozzle instead of 1.20 gph) and a higher AFUE. It's the same boiler underneath, but with a smaller nozzle and an electric flue damper, so whatever nozzle they spec for the -RD would be a safe start, extending the burn times by about 18%, and (if tuned properly) a 2% improvement in raw combustion efficiency. The combination could add up to a 3-5% reduction in fuel use compared to keeping with the nozzle specified for the WGO-4. The nozzle part numbers that can be used would be specific to the burner unit (Carlin, Riello, & Beckett burners have all been shipped with this boiler).

It also looks like some burner specs define a pre-purge time. eg: In Table 1 the Carlin manual calls out a 10 second pre-purge & 10 second post-purge on the primary burner controls for their model 60200-02.

I'm not sure adding the electric flue damper to make it look exactly like the -4RD would be cost effective, but the damper might be worth at least considering, since you seem competent to perform a DIY installation (which seems like you might be.) The smaller nozzle is essentially free, since it's normally replaced every few years anyway, but the damper, not so much. Whether the damper ever "pays off" as a retrofit is a bit harder to tell.

 

[Gary in NJ]

Well the temperatures in the house finally got cold enough for me to turn on the heat. I was excited to see how my HW+ would work. The results are...disappointing. Either I have a set up issue or the unit is defective.

For the first three cycles I observed, when the Aquastat called for heat, rather then going into Economizer mode, the HW+ indicated "HEAT LO/LIM". So I put the unit back into Program Mode and confirmed that I had a low limit set for 145 degrees (which it was).

After repowering the HW+ the boiler cycled to its high temperature. The zones were still calling for heat and I observed the temperature drop from 194 to 178 when I heard the aquastat "click" requesting that the boiler fire and the HW+ went into Economizer Mode. But when the temperature reached 176 the HW+ released the call and the boiler fired. Average Savings 1.9%

Even though I have the the Heat Temperature set to 145 the HW+ consistently released the boiler at 176. After 30 hours my savings have "climbed" to 2.0%.

Any ideas or thoughts?

 

[Gary in NJ]

So I reset the HW+ to its default configuration, including the timers. I then turned the thermostat upstairs (which was set to 62) to 68 - this way I knew I could observe a few cycles.

Cycle 1: It took 90 seconds for the initial call at the thermostat for the zone valve to open. This is a function of the Taco ZVC404-4 - it just takes that long for the valve to completely open (as shown on the LED indicator). Once the valve completely opens the circulator is engaged. I observed the temperature drop from 191 degrees to around 178 degrees and the HW+ entered Economizer Mode. At exactly 145 degrees the HW+ released the boiler and it began to fire about 24 seconds later (12 seconds of nothing and 12 seconds of pre-fire running). In that 24 seconds the temperature continued to drop to 138 and it took a good 45 seconds before the boiler began heating the water...at which time the temperature was 134 degrees. The LO /LIM indication was shown. A = 3%

The boiler stopped its burn at 181 degrees and it continued to climb to 207. A=12.3% and climbing.

Cycle 2: It took quite some time for the temperature to begin to drop. During this time the savings number was climbing (I thought it would increase in Economizer Mode, but it actually drops in that mode). At around 180 degrees the HW+ went into economizer mode with A showing 15.3%. At about 170 degrees the HW+ released the boiler. Once again it took 24 seconds from the release for the boiler to fire. This time the burn continued until the temperature was 187. By the time the boiler finished it's burn it had run 4 minutes. A = 22.9%

Cycle 3: Looked like cycle 2.

So it appears that it is working. My expectation is that it would always allow economizer mode to run down to 145 degrees. But the software must review the rate of temperature drop and the differential from the high temperature and calculate the most efficient duration of economizer mode and then release to boiler (heat mode).

I'm thinking I should add 24 seconds of PRE-PURGE to keep the boiler from going below 145 degrees.

 

[Dana]

I too would expect it to always purge down to the programmed low-limit EXCEPT when serving the indirect. The manual is a bit terse on this, but that's how I've always interpreted it.

It's not clear how the boiler's temp continues to climb when the burner isn't firing, unless perhaps there isn't sufficient thermal contact with the sensor to the sensor well(?).

The 24 second pre-purge sounds like that's what the burner's internal timer is set up for. Setting up the Intellicon for a 24 second pre-purge will more accurately reflect the economizer's performance.

 

[Gary in NJ]

I think the difference in the temperature is due to the fact that the aquastat is submerged in the boiler while the temperature sensor is as close to the boiler as possible on the output and requires the pipe to fully conduct the heat.

I added 24 seconds of purge. A Savings currently at 29.1%

 

[WJcandee]

So I am thinking about installing the HW+ on an older cast-iron oil boiler that has a domestic hot water coil in it that we don't use and is closed off. Everything is super-simple in our setup; no zone valves to open or close, and the circulator and boiler fire together immediately on a call for heat.

Query: Do I disable (or set very low) the LOLIM on the Aquastat if it is not so set already? What would be a good DIFF to use on the HILIM on the Aquastat? Current HILIM on the Aquastat is 180 degrees.

Once I have done that, if I read things correctly, all I have to do is use the factory settings on the 3250 HW+, correct?

One wiring peculiarity is that we have a setup where the firing of the heating boiler is inhibited whenever the separate Bock hot water heater kicks on; I don't know if that is going to complicate my installation, the dealer who installed that feature years ago is long out of business. It was done because a simultaneous pull of oil from the tank by both units regularly caused one or the other to shut down from insufficient fuel; this was the most-straightforward solution which has served us well from an operational perspective.

 

[Dana]

With the HW+ you bypass most of the aquastat controls, setting the aquastat's high-limit to it's maximum then program the low-limit into the HW+ and let it figure out the differential from there.

Read the installation instructions. Check out some of the HW+ setup & programming videos.

Not all cast iron boilers are the same. The safe low-limit depends on the fuel type, and sometimes the chimney/liner details.

 

[WJcandee]

Thanks, Dana! I had actually read and re-read the instructions several times in an attempt to have my questions answered, which is why I came here next.

I didn't see anywhere in the instructions to put the aquastat on its maximum, which would seem to be unsafe given that there are circumstances when the HW+ cuts out. Maybe you mean that you set the max safe temperature on the aquastat (which is lower than the control itself can be set)?

The low limit part of the written instructions was a little confusing, hence my questions. I think some of the advice I have seen about disabling the low limit where there is no hot water coil (and or turning the whole thing off in the summer) may be extreme, and lead to other issues. Taking that advice out of the picture, and assuming a low limit of 140-145 would be fine for the boiler, then the instructions make more sense.

 

[Dana]

In most locations codes require thermostatic mixing valve or tempering valve between the tankless coil (or any other water heater) and the hot water distribution plumbing to limit the domestic hot water temperture, in which case there is no boiler temperature that would create a scald risk. If you don't already have one, install one.

The higher the high limit is set, the greater range the HW+ has to work with, which lengthens the burn time average, and lowers the numbers of burns per year, all of which makes it more efficient.

The HW+ only "cuts out", when it detects the domestic hot water temp dropping.

Firing an oil boiler below 140F can cause excessive flue condensation or even condensation on the heat exchanger plates, which is corrosive. Some oil boilers are cold-start tolerant, but even those should have a low-limit of at least 140F.

 

[WJcandee]

We are talking past each other a little. Probably a result of me not being sufficiently-clear, as your advice on these forums is legendary and super-detailed and reliable.

I should have emphasized better that for decades we have had a separate oil-fired hot water heater (Bock 50 gal); that the tankless coil in this boiler is closed off and not used. When I said "dangerous", I wasn't talking about scald risk. I was talking about, for example, the boiler and circulators shutting off at, say, 200 degrees and the residual heat in the cast iron proceeding to raise the boiler water temperature past where the relief valve lets go (i.e. boiling the heating water).

I do get your point about giving the maximum range to the controls, and I understand from other reading that cast-iron radiators like ones in our house (no finned baseboard here) conduct heat best at higher temperatures, which would also militate in favor of setting the aquastat hi limit above 180 degrees, Intellidyne control or not, so I will see what my furnace guy thinks is safe.

I appreciate the advice not to go below 140 on the low limit. That's where it is now, and I calculate that we're burning a gallon a day in the summer over and above what the separate Bock heater is using. At our average price of $2.50/gal, it just seemed like that $75/month would be better in my pocket than in the oil company's, but if that is penny-wise and pound-foolish, then it is just an unavoidable expense and I won't give it another thought. (On the other hand, the boiler is at least pre-1955 in vintage, so at some point it probably needs to be replaced; remarkable that it still runs like a champ, albeit not likely very-efficiently.)

Thank you again. Being able to reach out to a definitive source like yourself is so helpful, particularly in light of the advice on so many other sites that clearly misapprehends how an aquastat even works.

 

[Gary in NJ]

I thought I'd give a mid-winter update of my experience with the Intellidyne HW+

Between November 1st and January 15th I saw 168.5 hours of "Econimizer" time and 389.1 hours of "Run" time. In that time I've consumed about 470 gallons of fuel. I'm a bit OCD, and as a result I keep a daily log of temperatures at my house and the reading on the HW+. I record the low daily temperature and the high daily temperature. I plot the average daily temperature against the HW+ run time. This allows me to compare the fuel used with the HW+ to a previous winter where I tracked average weekly temperature to fuel consumed.

For example, the week of January 6, 2014 we had a weekly average temperature of just 19 degrees. In that week I consumed 13 gallons of fuel per day. So far this winter I have had a few daily averages of 19-20 degrees. On those days the heat ran anywhere from 7.2 hours per day to 9.1 hours per day. Sticking the tank every 10 days allows me a measurement of actual gallons used and it appears to be 1.2 gallons for each hour of run time. So on those cold days I burned 8.5 to 10 gallons of fuel. This shows me that I am saving 23% in real fuel usage. This tracks well with the HW+ reading.

I have to say that the HW+ works. At $2.50 a gallon I've already paid for the HW+ and have saved real money. Some observations:

- Even though I have the LOLIM set at 145 degrees, it never runs down that low. The HW+ usually releases the boiler around 156-161 degrees. The release is based on the rate that the water temperature is dropping. On a warm day, if I don't get a heat or hot water call, my boiler will sit idle all day allowing the boiler to drop well below the 145 LOLIM.
- One of the reasons I installed the HW+ was due to short cycling - my boiler is 3x oversized rather than the usual 1.5 to 2x. Prior to using the HW+ my "long" runs were just about 4 minutes. With the HW+ a long run is now 6 to 8 minutes. An improvement, but not ideal. I can still get boiler runs that are just a few seconds. If a heat call ends my aquastat shuts down the boiler. So if the boiler just started because it was released at 160 degrees, yet the heat calls ends 10 seconds later (because prior to that the water was circulating), I get a 10 second run.
- I went through 3 HW+ units to get one that worked. The first unit was defective and I received a full refund. The second unit was used (even though it was sold as "New in the box") and it too was returned. I would have kept that unit but it was a very early production unit (number 380 I think) and it lacked the digital readout. So back it went. My third unit has worked well, but it is an early unit that uses the digital readout, and as a result the interface isn't as "slick" as the late production units.

 

[Dana]

Sorry to hear about having to cycle through a couple of them before finding the right one, but glad to hear that it's now fully up and running, doing the right thing, and delivering a double-digit percentage fuel savings!

It's true that no economizer control can guarantee a minimum burn time- there will be the oddly timed cycles, but the average burn time goes up and the total numbers of burns (and the average boiler temp) goes down, both of which lowers fuel use.

Many or even most new oil-fired boilers come already fitted with smarter controls, and eventually the market for retrofit economizer controls will go away, but there are MANY oil fired boilers currently in service that could benefit from this type of retrofit.