Troubleshooting My Propane Fired Radiant Heating System

[Raspy]

You're looking at the whole problem in the opposite way I am and am making some assumptions that have not been shown with a schematic.

As I understand it, HillStreet said the delivery temp was controlled by the tempering valves at 110 degrees. That means they are mixing return water from the floor loops with hot boiler water to deliver a temp lower than the boiler setpoint. And it means the mixing valves do have an affect. We just haven't seen how they are actually piped in.

Arguing that the return temp determines condensation misses the point. If the boiler is cycling, and we know it is, and if it's set at a higher temp, which we know it is, then the inlet and outlet are close to the same unless there is a severely incorrect flow rate. So close that the boiler has to cycle. They can easily both be above the condensing point or both below it. If the outlet is below it we know the inlet temp is to, but not the other way around. This is especially true with the underfloor delivery system as compared to an in-slab system. With in-floor systems the boiler can be overloaded for some time and have a large differential. Since this is a condensing boiler, we want it to condense as much as possible. But we still don't know how the DHW system is tied in, so we can't necessarily just turn it down. If we can adjust the CH different than the DHW we can turn it down. Just too many unknowns here to make a lot of assumptions.

He has already said that the house heats with 110 degree water, so that is close to the minimum it should run at. 130 or 140 would be a more practical temp, possibly, but apparently the mixing valves are only allowing 110. Since we don't know exactly how his delivery is arranged, or his lifestyle, we can't say that slow even heat is the best either. Often, it's not.

If you have a slow even heating system, one that circulates constantly, or almost constantly, then the outdoor reset begins to make more sense. But if you have a tempering valve controlled delivery, the outdoor reset is somewhat defeated. When heating rooms that are not constantly used, such as spare bedrooms, or even the master bedroom in most cases, slow even heating is a disadvantage. It's better suited to living rooms where retired folks might spend the majority of their time and want a constant temp all the time. Faster recovery works better where you want to sleep in a cool room but get up to a warm floor. That's where the setback thermostat gives better control than delivery temp.

Too bad we can't see a schematic or know more about what is actually going on.

 

[dadster4]

"As I understand it, HillStreet said the delivery temp was controlled by the tempering valves at 110 degrees. That means they are mixing return water from the floor loops with hot boiler water to deliver a temp lower than the boiler setpoint." The mixing valves have 180 degree supply and 160 degree return to mix- there is no way 110 degree water is supplied to the loops.
"But we still don't know how the DHW system is tied in, so we can't necessarily just turn it down. If we can adjust the CH different than the DHW we can turn it down." The DHW is a separate loop off the primary supply loop with it's own circulator pump, the boiler will ramp up to 180 degrees to heat the DHW on a call for heat from the DHW aquastat, and when satisfied, will revert back to the supply temp chosen for the radiant heat.

 

[HillStreet]

Cooler return water is still the best method to provide condensing conditions in the heat exchanger (that's why it is so bad for a standard boiler to have low return temps), the supply temp will be whatever the boiler is set for.
The outdoor reset control will adjust the boiler supply temp downward from the setpoint but not increase it above the setpoint. It will not affect boiler temp below 0 degrees outdoor temp, and only modulate it down slightly with large increases in outdoor temps.
Water temp in his system was never lower than 160 degrees, so the mixing valves had no effect when set to 110 degrees. The goal is to have a supply temp just high enough to provide proper heating of the space (140ish), a return temp low enough so that the mixing valves have cooler water to mix with the supply (120ish), and a mixed supply temp at the manifold to provide a slow even heat to the loops (130ish).
I wanted Hillstreet to try these changes first to get closer to a good running condition, I still think the boiler control settings should be changed to lower the output of the burner, but making these changes will familiarize him with how to operate the controller...Let's see how it goes today!

Well, I just made the changes to the boiler controller. No problem at all, pretty easy to follow the menus, you get the knack quickly.

Central heat = 140, DHW = 170, outdoor sensor is DISABLED, and the mixing valves are set to approximately 140. (I say approximately because range is 70 to 180). Should the mixing valves be lower?

The house today is 80 with the sun and coal stove adjusted to minimum. The boiler I would expect will come on sometime Saturday night. I will watch it closely and let you know. I have to say thanks to everyone who chimed in, this has been a good learning experience for me. I know I could not put up with all of the run hours and cycles, it was really bugging me. I think we are getting to the bottom of it now.

 

[dadster4]

Try the mixing valves at 130, you want them set lower than the supply temp. The real test is to see what return temp you get back to the boiler, less than 130 would be good- lower even better. Good Luck :thumbsup:

 

[teejk]

Try the mixing valves at 130, you want them set lower than the supply temp. The real test is to see what return temp you get back to the boiler, less than 130 would be good- lower even better. Good Luck :thumbsup:

Glad I don't have mixing valves! I do have a few manifolds (Rehau) though, all with their own supply/return temp gauges and flow control valves for each loop. The computer on the Weil McLain would say 160F supply for under-floor radiant. Return is up to me I think so it amounts to goofing with the manifolds to maintain what my installer says should be a 15F "T Delta" (his son says it should be 20F and I think that is probably closer to the truth with modern boilers but probably not a big deal either way).

 

[HillStreet]

Try the mixing valves at 130, you want them set lower than the supply temp. The real test is to see what return temp you get back to the boiler, less than 130 would be good- lower even better. Good Luck :thumbsup:

When the system starts up again I will read the mixing valve temps at the manifolds and adjust more accurately.

Now, assuming for the sake of argument that all loops are equal in length. I think that I have each manifold loop flowing at maximum rate. It is a Uponor manifold, and I have the adjusters screwed out to where the sight glass has the least amount of stem showing.

 

[Rustyiron]

FWIW, the design temp of my radiant system is 112*, tempered down from the boiler (mixing valve) with return water & then supplied to the manifold(s).

 

[Raspy]

"As I understand it, HillStreet said the delivery temp was controlled by the tempering valves at 110 degrees. That means they are mixing return water from the floor loops with hot boiler water to deliver a temp lower than the boiler setpoint." The mixing valves have 180 degree supply and 160 degree return to mix- there is no way 110 degree water is supplied to the loops.
"But we still don't know how the DHW system is tied in, so we can't necessarily just turn it down. If we can adjust the CH different than the DHW we can turn it down." The DHW is a separate loop off the primary supply loop with it's own circulator pump, the boiler will ramp up to 180 degrees to heat the DHW on a call for heat from the DHW aquastat, and when satisfied, will revert back to the supply temp chosen for the radiant heat.

We still don't know how the mixing valves are plumbed. So they could very well be delivering 110 to the system by recirculating the floor loop and only adding a little boiler water as needed. I've done this many times with a lower delivery temp than the boiler high limit or boiler return temp. We don't have the schematic so we can't say for sure what is going on.

We also don't know the DHW storage or HX plan, so again, can't really come to any solid conclusions. There is more than one way to do this. You're right on your explanation about the boiler in a general sense, but I wasn't wondering about how the boiler works. I'm wondering how the storage works to determine if the boiler should be programmed in a normal DHW/CW heating mode with priority or if we can make it better. There are a number of ways to manage DHW.

It's better to have experience and be curious, than it is to be absolute with limited knowledge or argue about something we don't know.

 

[sailfast]

dadster4,

I will certainly reference the manual. I'm retired and it's winter, what the heck, need something to do. I will keep excellent notes so I'll not get lost.

The supply and return pipes are connected at the end where supply turns into return. There is a quick turn valve in the end, set at about 1/2 open. The supply loop and return loop tees off to the mixing valve, then the mix goes to the circulator, that goes to the manifold.

I will lower the heating setting in the boiler to 150 degrees, and I will set the mixing valve to 140 degrees. The "controller" you refer to I assume is integrated into the boiler. I have a Taco 4 position electrical box where the t-stats, outdoor sensor, DHW sensor, and circulators all connect but that is just electrical connections. I will read the boiler manual.

The regulator was checked by the propane company. One guy here several hours while the plumber adjusted the vent stacks (some harmonic imbalance that had to be corrected. Plumber did offer that it "was not my fault".

I do appreciate all the effort from you guys, it is a big help to me. I am able to comprehend these things but do need input from you folks. I really don't know what the run time should be but know if it runs 80% of the hours when the sun is down it is way too much.

Seems to me you are in way over your head. I recommend that you contact a local HVAC professional experienced and licensed in radiant heat. Otherwise you will likely never get this truly done right. That is what I would do.

 

[sailfast]

Thank you Raspy. I am going to read the manual for resetting these parameters. I guess I will make the changes while the coal stove is running so in case I screw it up I will have

 

[HillStreet]

Hey Folks,

The continuing saga ........continues. Sailfast, I will continue with my efforts. No way am I in over my head, it will get done just fine.

Woke up at 0430 and the house was 89. I figured it was the coal stove putting out that heat and the outside temp rose to 35. A little while later I was working in the basement, and I saw that zone 4 (DHW) was lit up. I thought no problem, I just got out of the shower and it is refilling/heating the storage tank. Half an hour later, it's still running.

Here is what I noticed. Boiler display said central heat was on (still 88 upstairs, t-stat set 68). Boiler circulator was on, system circulator was on, and DHW circulator was on. The loop manifolds were warm, mix valve temperature was 130. However, the circulators at the manifolds were quiet.

I did a number of temp changes to no avail. I disconnected the outside temp sensor. This started out with boiler set temp at 140, and it supplied the mixer valves at 130 dead nuts. To fix it, I rewired the circulators back to original, then changed temps back to original. My next step is to leave everything wired as is, and adjust the temps again. If that holds, I have to look at the zone rewiring again.

Here's what the display read at one random point. (Remember, CH, System, and DHW circulators running)

CIRCULATOR STATUS/CYCLES
System circulator. ON
Boiler circulator. ON
DHW. ON

HEAT DEMAND
CH. ON
DHW. OFF
AUX HEAT. OFF
FROST PROTECTION. OFF

BOILER
SUPPLY. 140
SET POINT 140
RETURN. 134
RATE. 23%
PRIORITY. CH
STATUS. RUNNING
STACK. 145

 

[teejk]

Hey Folks,

The continuing saga ........continues. Sailfast, I will continue with my efforts. No way am I in over my head, it will get done just fine.

I think it is very important that you know how this stuff works so keep at it! You know for a fact that if it needs service it will always be on a Sunday...I'll check my Weil McLain (sounds like the identical boiler) manual to see what they say about DHW.

 

[Raspy]

HillStreet,

It sounds like your DHW circulator is able to push water through the manifolds with the manifold (central heat) pumps off. Since you were not calling for heat and the manifolds were warm and the house continued to get hotter, that must be happening.

I'm not sure, but I think you adjusted the tempering valves up from 110 to 130. If so, return the setting to 110 and see if you stop the overheating under the same conditions.

I don't think your system is plumbed properly, but we have no schematic to look at. Normally, I'd want a pump for the heating loop and a separate circuit with it's own pump for the DHW circuit. Each of these circuits would have a check valve to prevent flow from the other circuit. This check valve is often built into the pump.

If the zone controller that manages the system also manages the DHW, the DHW should be set on the priority zone with the priority switch on. In my systems with a zone controller, the DHW sensor or aquastat is connected directly to the boiler and the boiler prioritizes. In that case, the zone controller just manages the various CH zones. It allows the heating pumps to be off when DHW is on and it allows a different high limit for each function.

If the boiler manages the DHW/CW priority it can also adjust the high limit for the particular mode. This is better because then you can have a sensible temperature for heating the house and a higher temp to give you fast hot water recovery. It also helps with managing the heat by not having unexpected high temps at the loops. And it eliminates the need for tempering valves.

Part of your problem is managing the various temps., but I think you also have flows from the DHW circuit to the heating loops. That may have been masked before, but is showing up now with the tempering valve settings.

From your earlier description, it sounds like the installer knew something wasn't right. We haven'y pinpointed it yet, but there must be a design problem. You're getting closer to solving it.

 

[HillStreet]

Hey Everybody,

The boiler situation is fixed, and the radiant system is operating just fine. After exhausting everything I learned from the manual, I called the factory (US Boiler Company) in Pennsylvania. I spoke with Ron in the Tech Support Dept and he was terrific, patient, and very knowledgeable.

I really studied the system, boiler, circulating pumps, and all of the plumbing and wiring. The one situation I could not remedy is getting the pumps to run when they are commanded, not when something else initiated it.

I started when there was zero demand for heat and domestic hot water. I ran DHW to initiate a call for that. The boiler and control panel responded by starting the boiler, the boiler pump, the DHW pump, and the System pump. I wanted the DHW pump and boiler pump to run, but not the system pump. I would do this repeatedly, and make changes to the system parameters with the boiler controller. At every evolution, the system pump kept running, which sent hot water through the main loop up to the manifolds. The pumps on the manifolds did not run until thermostats called for heat.

The zone 4 light went on, telling me that DHW was active, and the priority switch was enabled. The boiler control display showed Central Heat was active, and made no mention of DHW. I sat there, keeping logs, checking pumps and temps and could not figure it out. On a subsequent try, I noticed the temps at the manifolds were 120 degrees as I set them. Then the zone 4 light would go out, and the boiler would shut off. Humph. Did it again, and finally realized it was one hour from start to shut down. Did it again to prove it and yes it shut off after one hour. I knew about the one hour priority wait time for Central Heat to wait for DHW. I could not correlate that to my situation though, because I tried every single combination on the boiler controller.

Next morning I called the factory, and Ron found the problem in the first 4 minutes. My plumber used a TACO switching relay 504. It controls the t-stats for central heat, but it would not work for the DHW, despite the priority switch on zone 4, where the DHW was connected. Ron told me to remove the DHW t-stat from the TACO switching relay, and connect it to the boiler terminal strip on the boiler. Same with the pump for DHW.

I did that, and it works fine now. Not only that, but the pump settings in the boiler software now actually work on the choices I was selecting this whole ordeal. Priority for DHW is chosen by the boiler software, not a switch on the switching relay. The boiler factory wiring is really mostly done for the installer, if the installer knows how to read a diagram.

I set DHW to 170, and central heat to 140, with the mixing valves at 120. In weather similar to this, the boiler would run 7 to 11 hours after the sun went down. Last night it ran one hour about 4am today. It will get cold later this week so we'll know how it performs.

I know, this is long, too windy. Thanks to all of you who responded and supported my cause. I do appreciate it.

 

[CalG]

Hey Everybody,

The boiler situation is fixed, and the radiant system is operating just fine. After exhausting everything I learned from the manual, I called the factory (US Boiler Company) in Pennsylvania. I spoke with Ron in the Tech Support Dept and he was terrific, patient, and very knowledgeable.

I know, this is long, too windy. Thanks to all of you who responded and supported my cause. I do appreciate it.

WeeHaaaa! An improper relay!

Thanks for the follow on.

Now, aren't you one smart fellow! ;-)))) (At least you have a strong working knowledge of the heating system you have.)

 

[dadster4]

Glad you are up and running, it's good to know the supplier has a knowledgeable staff to help in situations like this...say hey to your neighbor for all of us:laughing:

 

[Raspy]

Hillstreet,
Glad you got it figured out. Yes, the boiler is the only place the decision can be made between DHW and CH. That is not a heating control priority, its a function priority that must switch pumps and high limits.
Good job.

 

[HillStreet]

WeeHaaaa! An improper relay!

Thanks for the follow on.

Now, aren't you one smart fellow! ;-)))) (At least you have a strong working knowledge of the heating system you have.)

i

Yeah, I know the system pretty well now. It was actually a good project for me as I don't work and am home most of the time. All the while I did the boiler thing, I also puttered in the basement.

 

[HillStreet]

Glad you are up and running, it's good to know the supplier has a knowledgeable staff to help in situations like this...say hey to your neighbor for all of us:laughing:

Yes, the factory guy seemed to know right away what it was--- he asked the questions that led him to the conclusion. My neighbor, what a piece of work. You know, whenever I think of him saying "It's not my fault, I'm only 27" I am actually repulsed. Not the bad job, gimme money, had to shutdown mentally for two weeks, not the money. It is just the spoiled brat, no consequences, greedy attitude. Awful. Funny thing is, I recommend the carpenter crew for jobs all the time, and he gets a lot of them. I non-recommended my neighbor all the time, even if I invite myself into the conversation.

 

[HillStreet]

So NOW you tell me! Thanks Raspy, it took me a while but finally got there. I knew where the connection points were for the pump and t-stat were on the boiler, but I was thinking an alternate was to do it with the relay. Not so. Anyway, should also save propane money because CH temp is 140 vice 180, and the floor loops are 120 vice 110.