Troubleshooting My Propane Fired Radiant Heating System

[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.