Troubleshooting My Propane Fired Radiant Heating System

[teejk]

It wrong to use an air temperature thermostat sensor to control a radiant floor heating system.

Sense the floor temperature. There is a learning curve to getting the floor temp right in order to be comfortable.
Think about it, when it's "cold", more heat is drawn from the radiant system. When it is "warm", less heat is removed.

SENSE THE FLOOR TEMP!

I've got radiant floor in two areas of the house, Floor temp thermostatic control works wonderfully. What a delight to put your feet on a warm floor regardless of the room temp. ;-)

Just to be clear...modern boilers now incorporate an outdoor sensor that determines whether the boiler is running full bore or somewhere less than that (what they call modulation). I understand it is some gov't mandate. Latest advice I got was as soon as the inspector signs off, disconnect that sensor in a way to trick the computer into thinking it is still there.

 

[dadster4]

Is the boiler controller capable of providing 180° water to the priority DHW loop and another temperature to the loops when the DHW loop is satisfied? Does the DHW loop have it's own circulator? Does the outdoor reset (lowers boiler water temp with an increase in outdoor temperature) only act upon the boiler when NOT in DHW mode?
Sorry for all the questions, but they are necessary to understand what the solution may be for a fix.

 

[sriddle1]

HillStreet,

Read thru your posting and was amazed at the 1863 and 3300 cycles, I too believe it is excessive. I built an ICF Home in 2013, the Walk-out Basement & 1st Floor footprints are 1,735 for a total of 3,470 sq.ft. The basement slab is 5 thick poured over the following: Stego Wrap 15-mil (over crushed stone) + Corning Formular 400 XPS + NIBCO 1/2 Barrier-Pex stapled to XPS then topped with Welded Wire Mesh laying directly on top. For my 1st floor I ran SlantFin Fine-line 30 connected by 1/2" WIRSBO UPONOR PEX. Like you I have (3) Zones, the Basement split into two (in-slab Pex) and the Main Floor (Slant Fins).

I also have a Modulating Boiler - Lochinvar KBN081 (80,000 Btu) but I went with a separate RHEEM RTGH-95DVP on demand water heater. My Boiler has the capability of setting up (3) Setpoint Temperatures, one for each zone. The Slab Zones are setpoint to 140 and the Slant Fin is feed 180. When I was designing the house I hired an HVAC "Expert" to perform a Load Analysis which pointed to a Boiler rating of 46,000 Btu Hr. I downloaded Slant Fin's simple calculating tool where each room is assessed and that tool indicated I needed a higher rated boiler in the 65,000 range so I settled on the Lochnivar 80K, over engineering but glad I did.

QUESTION: Just for the heck of it, have you gone thru a simple analysis to see if your Boiler was properly rated based on your Hot Water and Heating needs, assuming max demand on all of them. I only ask because I'm not familiar with BTU requirements for the Under Floor PEX snapped into the heat shields. I've been in homes where the same PEX approach was used, the sub flooring was 3/4 Plywood + 3/4 T&G Oak Flooring on-top, the heat hardly penetrated and it used allot of energy. Also you can't use the typical multi-colored carpet pads, they trap the heat so you need a dense pad that is designed for radiant heat. These issues really affect the efficiency of what I call between floor truss heating. I would hope there's a way to add those adjustments when deriving the proper BTUs needed to drive everything.

Next I have a TACO controller for the (2) Basement Zones and an overriding relay internal to the boiler that keeps the 1st floor as the top priority when more than one thermostat is calling. QUESTION: Do you have a similar controller or relays that prioritize which zone gets fed, and was it set-up properly. You have to be careful with overloading a Modular Boiler's throughput because it can seemingly run forever where multiple zones are not satisfied all at once. Old style cast-iron boilers can handle real loads but eat lots of energy too.

Lastly, reading your posting there is a simple solution if you want to relocate a Thermostat's location without worrying about wiring, I had to use this solution because I didn't run the right # of wires from a thermostat down to my Forced Air A/C (ooooppppsss). Purchased a Honeywell FocusPro TH6320R Wireless Thermostat that connects (wireless) to an interface unit you can install close to your boiler. Just some thoughts to share, not sure if it helps.

 

[teejk]

Is the boiler controller capable of providing 180° water to the priority DHW loop and another temperature to the loops when the DHW loop is satisfied? Does the DHW loop have it's own circulator? Does the outdoor reset (lowers boiler water temp with an increase in outdoor temperature) only act upon the boiler when NOT in DHW mode?
Sorry for all the questions, but they are necessary to understand what the solution may be for a fix.

Hi Dadster...I looked up the OP's boiler specs and they amazingly look much like my Weil McLain (condensing, modulating, outdoor sensor, etc.)! The OP is probably experiencing what happens when a computer takes over for what used to be a pretty simple system.

 

[HillStreet]

Dadster4,

Thanks for the questions. DHW has its own circulator. The boiler digital display shows a max 180 degrees wether it is supplying the DHW or heat loops. Mixing valves adjust the DHW coming out of the tank, as well as feeding the heat loops through the manifolds. I can only reset the outdoor temperature sensor, I don't think I can adjust the temp.

I do know that when the boiler comes on, wether heat loop or DHW, I watch the temp rise to 180 degrees, then it begins to fall from there with the circulators running. The display also shows the return temperature, which seems to be just below the max temperature, say about 160 degrees.

 

[HillStreet]

Thanks sriddle1,

The plumber allegedly did the heat loss with his supplier. I also did a heat loss a couple of months ago, plugging in all the factors. The house floors are 3/4 inch Advantech and 3/4 inch oak hardwood with tile in the bathrooms. Mixing valves are set at 110 degrees but that can be increased (my reading says it should be ok). The 3/4 inch hardwood over Advantech is actually ok to use according to my reading. Some area rugs but that seems ok.

I do think the issue was the t-stat arrangement I mentioned in my initial post. I will check it once this current cold snap is over because the coal stove is keeping us warm with zero propane. I will adjust temps and balance the system once I go back to propane.

I built this same house by the same methods years ago, but this house is 100 sf bigger. That house had a Baxi-Luna boiler with separate controls for heat loop and DHW. Two zones with circulators and that was it. That boiler ran for 15 minutes or so every few hours. I think I burned 400 gallons of propane all year, and burned a small wood stove on weekends mostly as I traveled during the week.

I also had a house with a 3section Weil McLain with slant fin 30. No trouble at all. I really regret trying to be "neighborly". He has caused me too much money, too much aggravation, and the little bastard never even said thank you.

 

[HillStreet]

Hi Dadster...I looked up the OP's boiler specs and they amazingly look much like my Weil McLain (condensing, modulating, outdoor sensor, etc.)! The OP is probably experiencing what happens when a computer takes over for what used to be a pretty simple system.

That is a fact. All I want to do is circulate water under my floor to efficiently heat the house. This "spaceship" I have downstairs is junk as far as I'm concerned.

I do have a Taco 4 place controller with DHW on priority. DHW shows 47 hours since new. I don't think that I can select different temperatures for the heat and domestic loops.

 

[dadster4]

I found a good manual to help change some operating parameters Table Of Contents - Alpine ALPB Installation, Operating And Service Instructions [Page 4]. Read through it a few times to get familiar with the terminology and how to adjust some settings, especially pages 83 on up. Some pictures or a drawing of the piping layout would help also. A few comments:
If the primary loop supply and return are separate or tied together at the end of the run would make a big difference how the system operated. The supply to each heating manifold should tee off the SUPPLY of the primary loop, into the zone pump, into the manifold, through the loops, back to the return manifold, into a closely-spaced tee (3" from the first tee in the SUPPLY of the primary loop). I don't know why a mixing valve is installed at the manifold, so follow the suggestions below before any physical changes to the system.
You are able to have different temps for DHW and heating loops. I am almost sure the heating loop temps should be lowered to maybe 150° vs 180° where they are set now. If your mixing valves are set to 110°, they have no way to reach this temp without cooler water available, set them to 140° (which is fine for under-floor heating). Condensing boilers are the most efficient when the return water temps are near the acceptable minimum (near 130°)...your controller will let you know when operating at this range.
The DHW loop should remain at 180°
The boiler may be over firing also. The controller has settings to change the maximum BTU output for heating and DHW, I wouldn't change these yet, but may be necessary to match output to required heat load for the house.
The regulator should probably be checked to verify that the input pressure to the boiler gas valve is correct.
All these changes can be set back to where you started if you keep a record of everything you do. It's usually best to try this before ripping things apart and repiping the system!
It's a lot to digest...and if it doesn't work "It's not my fault, I am only 58". :laughing:

 

[1stDeuce]

I'm busy learning about radiant floor heating as I prep to build a house this spring... We're planning to just do the basement floor at present, and we'll heat upstairs with wood or pellet stove. We won't be able to close off the basement from the upstairs, so I'm planning to use a floor temp sensor or two in the basement, rather than traditional thermostats.

From what I've read, the only real issue I see with your setup is that you're running a zoned system where you shouldn't be... Your "solution" is how it should have been set up from the beginning, since you don't want to close doors. Zones generally either need to be really large, or more or less sealed to work well. Your problem may be compounded by thermostats that don't quite agree on the temperature, biasing the bedroom zone to run all the time because it thought the temp was a few degrees cooler...

Bottom line: I don't think a zone setup is going to work well if you're not going to close doors to separate the zones.

I think also you keep saying "plumber" when you mean HVAC guy?? A plumber is generally NOT a HVAC expert, but is good at ensuring poo flows downhill, and the hot is on the left, cold on the right... If you hired a Plumber to install your heating system, you may be at least partially responsible for your troubles...

I'm 43, and I usually find that when I have problems, it usually IS my fault...

 

[dadster4]

1stDuece,
You can get by using a hot water heater for your basement floor to avoid the expense of a condensing boiler...but not the most efficient by any means. If I were to build my home from scratch I would have a condensing boiler provide all heat and DHW, bath floor warming, garage floor warming, guest house heat and hot water, hot tub, dog house, chicken coop...well you get the idea :thumbsup: