Weil McClain Ultra 80 Programming Questions

JVB

The Weil McClain Ultra 80 user manual presents many details on programming priorities 1-3 but in the opinion of this biologist does not do a very good job of explaining what various parameters mean. My confusion rests with the Max and Min OD reset parameters as they pertain to radiant slab circuit. I have the outdoor sensor that is temperature corrected to read the actual outdoor temp accurately. My Max OD reset is at 70, and Min OD reset is at 0. I don't understand the "heating" curve (I believe figure 100 in the WM manual). Can anyone break this down for a non-heating specialist?

Also, my radiant slab Max is set for 120 degrees F and Min supply is 90. Recently, outdoor temp dropped to around 23 F, the boiler ran continuously-- never reached 68F indoor set temp. I think this may be related to the heating curve defined by the OD reset parameters, but I'm not clear on this. Any insights would be very appreciated. And thanks in advance for your patience.

Jean-David Beyer

W-M Ultra 80 resets.

I assume you have an Ultra-3 UE.



Max supply is the maximum temperature that will be supplied to that load. For my radiant slab zone, I have that set to 120F.

Min Supply is the minimum temperature that will be supplied to that zone. Mine is set to 75F.

Max OD Reset is the temperature at which you will get the Min Supply. In my case, 54F.

Min OD Reset is the temperature at which you will get the Max Supply. In my case, 2F.



In the book, they say the reset curve is curved a little. I do not notice that it differs from a straight line, so if they are right, the difference is very slight.



If outdoors is hotter than Max OD Reset, the output temperature is constant Min Supply.

If outdoors is colder than Min OD Reset, you will get Max Supply.



If outdoors is hotter than WWSD, you will get nothing (except for indirect hot water).



All this assumes the domestic hot water is across the boiler loop, and the heating loads are in the secondary loop, and you have controller set to run the right circulators. Mine are set up with the default circulators for priority 1 (indirect hot water) and priority 2 (my downstairs slab). For Priority 3 (my upstairs baseboard), I run just the boiler circulator, and an auxiliary relay runs the circulator for the upstairs zone. Do you have the System Type for priority 2 (or whatever your radiant zone is) set to RAD SLAB (or whatever form of radiant you have)? Is the thermostat for that zone connected to the priority 2 input terminals? P15-1 and P15-2? Also, do you have the Supply and return sensors attached properly. Some people put them on the primary (boiler) loop by mistake. They should be on the secondary (load) loop. Mine is pretty much like Figure 50 of your manual, but with circulators for the zoning, so no bypass pressure regulator valve is needed. Look where the temperature sensors are attached.



What kind of radiant heating do you have? Mine is radiant heat with 1/2 inch copper tube in a concrete slab. If yours is some other form of radiant, you may need to run hotter water temperatures. In my house, I would put about 102F water into the slab if it were 23F outside, but your mileage would surely differ.

JVB

W-M Ultra 80 3UE Sensors Not Installed

Hi JDB,

Thanks so much for the explanations. Your system settings are helpful to understand the reset programming. Answers to your questions:

Ultra 80 3-UE is my boiler with DHW on priority 1 with Set Temp at 160F and Modulate on differential of 5F. Priority 2 is Radiant Slab with Target Temp at 120F. Pump 1 is for DHW and Pumps 2 and 3 are for Radiant Slab. I do have a Honeywell thermostat (mercury bulb type) on P15-1 and P15-2. Radiant heat pipe diameter is 1 inch (Rummer Home).  

The only accessory "inputs" I have on my system: thermostat; DHW thermocouple; outdoor thermocouple. There are no SUPPLY and RETURN sensors installed. W-M indicates that the sensors come with the boiler, but my installer did not put them in. Am I correct that these are not accessory items that are optional? The boiler does report Supply and Return temperatures, but these must be internal sensors, or perhaps "calculated" values from the heating curve and not actual temps! Is it reasonable to insist that my installer put the sensors in? Can I do this myself?

Thanks again for any guidance you can give me.

Jean-David Beyer

Installer is incompetent, or does not know how to read.

The boiler will run without those sensors, but since W-M supplied them (and you paid for them), he could have no reason not to install them. The internal sensors can measure only the temperatures of the primary loop, whereas what you want to control is the secondary loop temperatures (the water being actually delivered to the load). So your installer does not know how your boiler is designed to work. Incidentally, he also does not know how outdoor reset works as he left your reset settings at the factory defaults. Now you should not use my settings either as they depend on the heat loss of your radiant zone and the type of radiation you have. My installer, my former contractor, did the same thing. Trouble is that running default settings for radiant slab is way too hot in warmer weather. I moved it down to 75F, and that is a little too high, but any lower and the boiler cycles too often in warmer weather.  What you want is for the supply temperature to be just barely hotter than what you need to replace the heat lost to the outside. Ideal might be so that your boiler and circulator to the radiant zone run all the time, but with the thermostat almost satisfied. Mine is set to 69F and it reads that, but it is not quite satisfied on very cold days. On warm days, it is satisfied and the system shuts off. It is probably better for it to shut off some, so you have a margin of safety. On very cold days, it runs about 18 hours a day, but these days (it is 23F at the moment, it runs between 8 and 10 hours.



As far as DHW is concerned, and assuming you have a W-M indirect, the default temperature for that is 190F. Lowering it increases the time to recover, at least in principle. I lowered mine in the hope of getting more condensation and have it at 170F. I picked that because mine required less than 10 minutes to recover. My domestic hot water demand is low because there is only one of me and I am not a teenage girl using long hot showers. During the time it takes to recover the DHW, about half the time is spent getting the boiler water up to 170F, so some condensation does occur, but it probably is not saving me a whole lot of money. I.e., the 170F limit almost does nothing. When I had it at the default 190F, it never got up that high because the domestic water (set at about 125F) recovered before it got that high. Unless they changed things a lot, there is no DHW thermocouple; that is a regular aquastat in the well at the top of the indirect.



The target should normally not be 120F for the radiant zone. That is what you are stuck with if you do not have the sensors attached to the left and right of the closely spaced Ts (or at the output of a low loss header, if that is what you have). It should only be 120F if your outside temperature is below the MinOD Reset. Not having these sensors connected deprives you of the benefit of outdoor reset. It is perfectly reasonable to insist your installer install these sensors, and to do it correctly. I.e., in the secondary loop before any water leaves to go to the actual radiation. They must be installed electrically correctly. If they are reversed, you will get problems because the return sensor should not ever get much warmer than the supply sensor or it will lock out. There is a little wiggle room in there, but I forget how much. By the way, supply means supply to the house, and return means return from the house. Some people mean something else by those terms.



If you are handy, you could install those sensors yourself. You make sure the pipe is clean and you just place them on the pipe and fasten them with a tie-wrap, Do it pretty tightly. If you can slide them along the pipe easily, they are not tight enough.



I do not know what a Rummer Home is, nor how its radiant heating is done. If it is copper (or Pex-Al-Pex) in a concrete slab, using temperatures  of up to 120F is usually appropriate. What is the design day temperature where you live. Here, it is 14F. I just looked it up, and apparently it is some kind of flex tube in a concrete slab.  In Portland Oregon, it is 23 degrees. Your contractor should have calculated the heat loss of your house, but my guess is that he did not. If it is gyp-crete or Pex tubing in the space under the floor, it will be higher. At some point, if your required temperature is over about 130F, you are likely to lose much of the advantage of your condensing boiler because there will be little condensation. With my values, it condenses all the time, but if you cannot get enough heat, that saving may not be important to you.



After you get those sensors installed, it sounds as though your contractor will not be able to set your resets correctly, since he does not understand your system. So you will have to do it. So let me know where you are, so we can find out your design day temperature, and exactly what kind of radiant heat you have, so we can come up with a first guess as to your required reset settings. It took me an entire heating season to do that for mine.



I wish W-M would not sell Ultra boilers to companies that do not know how they work, how to install them, and how to maintain them. My former contractor even said that gas boilers do not require maintenance. That is why his company is no my former contractor.

Jean-David Beyer

Attempt to show my reset curve.

Here is my first attempt to post a .pdf file. It is the reset curve I am currently using for my radiant heat concrete slab on ground. Design day temperature here is 14F. Heat loss for that zone is around 22,500 BTU/hr at 0F outside.



I see it contains both my zones. Upstairs is baseboard; Downstairs is Radiant.

Jean-David Beyer

Another afterthought.

I am concerned that if your target temperature is 120F going into your slab, and it is only 23F outside, that you cannot heat your house to 68F. It would be extremely helpful to know what the supply and return temperatures, as measured in the secondary loop, are. Is the heat loss in the radiant loop so great that your boiler cannot keep up with it and that although the target is 120F that the boiler cannot achieve it? Or is the boiler supplying 120F water and the radiation from the floor is not enough to supply the heat loss.



Hence the need for those two sensors to be installed. And perhaps having the heat loss calculation that your installer should have done. If your house's heat loss is like mine, you have way more boiler capacity than necessary to heat your house, especially if your design day temperature is in the order of 23F. So either your house is way too leaky in terms of heat lost to the outside through conduction through the walls, radiation through the windows, or just plain leaks here and there (around doors, windows. Do you happen to know if your slab is insulated underneath (of some importance) and around its perimeter (of greater importance)? How far down is your water table? I suspect, in my case, that my slab is uninsulated, but fortunately, the water table is at least six feet down (but not much more than that).



You do know, I hope, that the thermal mass of a concrete slab is enormous, right? So if you change your thermostat setting (perhaps with automatic setback) that it can take 4 to 12 hours to recover from it. I have found that it does not make much sense to do setback to my radiant zone. It would if I were to go on vacation for a week or more, expecially since I can program mine to resume normal operation after a specified number of days. So I would have it resume normal temperatures a day before I was to come back.

JVB

Contractor to Install Sensors 01-11-11

JDB,

I spoke to the president of the company that sold and installed my W-M Ultra 80 3UE. I asked him why my supply and return sensors were not installed and why my resets were at default values. He said they install the sensors 99% of the time, an odd response to be certain. He asked me if their programming person evaluated our system after install. I told him 3 staff members from his company evaluated our system prior to state inspections, but their expertise was not defined for us. I asked him if one of those people was the programming specialist. He did not know. Very frustrating. I should never have trusted their expertise, but at some level, what did we pay for? In biological research, you check and double check and never trust someone's expertise as such. I knew better. I should have seen this 7 weeks ago after install.

Company president said he would make it right. The programming specialist will come tomorrow to install the sensors and program the boiler. I will be present and ask about the heat loss study etc. I simply don't trust this installer. I have a call in to W-M to list the issues we have had with the installation. They need to know what's going on here. Stay tuned on this one, and again, I appreciate the information and insights. 

JB

JVB

Sensor Installation 01-14-10

JDB,

Installation was to take place today but contractor did not have any sensors available. Will install on the 14th. I'm in a holding pattern here. Just wanted to keep the thread updated. More to follow.

JB

Jean-David Beyer

Why no sensors available?

They came with your boiler. Did he throw them out? He better charge neither parts nor labor to install them.

JVB

Sensors Installed

Hi JDB,

Correct sensors were finally installed yesterday; long story but contractor initially obtained incorrect sensors, with problem corrected. I do not know where the original sensors that shipped with my boiler are, and neither does the installer. My sense is that they do not install the sensors routinely; they had to check the owner's manual to learn how to properly wire them, which is odd for a routine part.

I've completed my first full 24 hr heating cycle with the sensors in, so not much data to go on. I've noticed, however, that my flue 1 and flue 2 temps are about 10 degrees cooler than they had been prior to sensor installation. I think this puts me in a better temp range for condensation, and this bears out with the "drip rate" on the condensate tube, which is about twice as fast as it had been.

The contractor came up with a series of OD resets that closely match the values I determined empirically. It was output from a computer program that I think may be W-L in origin. I have a lower temp of 80F and a max supply of 120F. We're in the Pacific Northwest, and we often get temps in the 50s during the day in winter, but damp as heck so it feels colder to most. I may push the min supply temp to 90 in a cold snap, but right now the heating curve is perfect.

I need to collect more data to see how the system responds during cooler nights, but as luck would have it we're in a wet and warm weather pattern that is predicted to stay with us for a few more days at least.

I was happy to see, instead of XXs under Diagnostics/Temperatures/supply and return actual values derived from the newly installed sensors! Let me know if what I am seeing makes sense to you. And no charge for sensor installation, parts or labor.

Jean-David Beyer

Good that you have sensors.

I hope they are equivanlent to what W-M supply. If they do not install these sensors routinely, they are incompetent. They come with the boiler, just as the boiler circulator and the pressure relief valve come with the boiler. They are meant to be installed; they are not just packing material. I hate contractors who do not read the installation manual. They must be morons.



If your boiler is running, you should be able to press the square button in the middle of the control panel and it will bring up a screen that shows modulation rate, the temperature the reset is trying to achieve, the supply temperature, and the return temperature. These seem to be updated about once a second. It also displays which thermostats are calling for heat, and which circulators are running. This screen will remain lit for about 5 minutes, and then revert to the default screen. This is easier to get to than the maintenance screens, so you may find it easier to use.