radiant heating problem

broke

 Hi guys i have been fighting this problem for 3 years now and ready to give up, I have a 2800 sq house with in slab radiant heat 3 zones. Two zones have 4 loops and each loop is 300 feet the third loop is 3 loops also 300 feet per loop. All pipe in the slab is 1/2 pex for a total of 3300 feet total. My boiler is a weil mclain ultra 230 with a water ingection system that I had add last winter.The problem that I have is my propane consuption is high. I burn 9 gallons of every night no matter what the temp is out side 50 deg or 20 deg until it gets way colder then it goes up. I had to put heaters in the kids rooms and I  turned 2 zones off  other than livingroom and  still burns 9 gal per night .

kcopp

I presume...

that you did the installation? What did you do for insulation? That would be in the walls , the ceiling and most important the slab.... that is in the floor and on the perimeter? kpc

broke

radiant floor problems

 I had a heating contractor do it. He used reflectex bubble insulation under slab.The house is sips panel 6and1/2 wall solid styroform the windows are pella pro-line we spent alot of money to make the house the most efficient place we could. I should probably add that he installed the boiler backwards to begin with,took hin 3 months to figure that out.

kcopp

bummer...

reflectix (in my opinion) in junk. it really does not insulate at all. maybe r-1 value. There was actually "lawsuit" about false advertisement.... any perimeter foam?  maybe put down some more/ any. All your energy is going down and out. ...Here is a blog for some more info.

http://www.healthyheating.com/Page%2055/Page_55_o_bldg_sys.htm

Jean-David Beyer

Whistling in the dark...

I am just a homeowner, so keep that in mind. I have a W-M Ultra 3 80,000 BTU/hr unit with outdoor reset connected. I am in New Jersey with a design day of 14F. My house is quite well insulated and I do not notice any drafts or leaks (but that does not mean there are no drafts or leaks, since that has never been tested). It has Marvin double-glazed windows with Low-E optical coating and argon gas in between.



My house is about 1100 square feet (cape cod) with radiant heat down stairs (750 square feet) and baseboard upstairs (400 square feet). The radiant heat is 1/2 inch copper tubing in concrete slab. I have no idea if it was insulated underneath or around the perimeter. Sometimes I think so, bot sometimes I do not. Sometimes the snow, if it is very heavy, goes right up to the house, but if it is not heavy, it is melted away from the house 8 to 12 inches.



The coldest month I went through was last January when I burned 120 therms of natural gas. For 31 days, or 3.87 therms per day. Your house is about 2.5x mine in floor area. Scaling up, that would be about 10 therms per day for you. At about 1 therm per gallon for propane, you would use 9.85 gallons per day if everything is comparable (a doubtful assumption, but the best I have to go on). That seems to indicate you are using about the right amount of gas, but watch out for the assumptions.



If you do a heat loss calculation, you could see if your boiler is the right size. If it is too large, it will not modulate down to low temperatures in warm months, and that will waste you money.



Is your outdoor reset adjusted correctly?

Is your boiler properly sized (so it can modulate low enough)?

With a W-M Ultra, why do you need a water-injection system (I assume you mean injection mixing)? Why not adjust the reset curve(s) on the controller to give the water temperature(s) you need?



Other readings.

October 2009  20 therms

Novenber        25 therms

December        60 therms

January 2010  120 therms

February 2010 110 therms



March              65 therms

April                 30 therms

July                    4 therms



I put July in there because I use an indirect fired hot water heater, and I did no house heating that month.

              

broke

radiant heating problem

Thanks for the site I have been reading things on the internet to try and figure this out. I have spent alot of time looking into the cause of this system not working correctly is there any chance that the boiler is so oversized that it can't run any more efficient ? I hope if not,  I need to cut my losses now.

broke

JDB

 Thanks for reading  post, that 9 gal per day is with one zone on I have electric heaters put in rooms . When i turn other zones on the gal per day only go up alittle bit. We had a different contractor install the injection system to see if that would help. The first contractor had a lp meter installed out side to see how many gallons per day we used. I used to read meter everymorning.

broke

radiant heating problem

No heat calc. was done on house the installer used 35 btus per sq foot as a rule to figure boiler size. I looked at this math and I get 98000 btus for whole house.I should mention that I have a iderect fired water heater for domestic. The problem I have is the boiler can only modulate 20% down from 230 btu. Where do all the other btus go if they cant get into the 10 gal per min. water heading to the one zone I have on do they go out the exhaught

Jean-David Beyer

Is there any chance that the boiler is so oversized

I think there is a good chance that your boiler is oversized.



Watch out for this assumption I am going to make: if your heat loss scales up from mine in direct proportion to your floor area, then your heat loss would be around 75,000 BTU/hour. There is no substitute from calculating this; it must be done. If your contractor goofed enough to install your boiler backwards (I assume you meant hooking the supply and return backwards), it is quite possible that he figured your heat loss incorrectly, if he did it at all. Remember that I am not a professional here. I would say a W-M Ultra 80 would just be enough, and if you do not trust me (you should not trust me), you might go up to their 105 model. Not the Ultra 230. (Unless you are doing some serious snow melting you did not tell us about.)

Jean-David Beyer

Where do all the other btus go

First of all, you boiler should be able to modulate down from 230,000 BTU/hr (input)  down to 46,000 BTU/hour (input). But you should need that only on the design day, that might happen only once a year. But if it is warmer than design day, where I figured (roughly) you needed 75,000 BTU/hr, your boiler might modulate down to there. And my figure assumes all your zones are on, and for me that is rarely the case, so you would want the boiler to modulate down even further.



What happens if it cannot? It modulates down as far as it can. Then the boiler cycles on and off so it is producing the average heat you need. But constantly cycling the boiler on and off lowers its efficiency. In addition to that, it wears it out more quickly. And the hotter it runs, the less condensing you get, and if you get maximum condensing, you could be saving 10% of your gas bill. Chances you will not get maximum condensing, but you might as well get the odds in your favor. So some of the BTUs will go up the chimney from all that rapid cycling, and some will go up the chimney from lost opportunity of condensing.

Gordy

Domestic hot water

 What is your typical hot water usage per day? You mentioned you have an indirect WH.  Do you have large GPM shower heads, Large tubs, Lots a Laundry, House full of teens showering multible times per day? Sometimes Domestic hot water loads can be more than a heat load on a dwelling. I only ask this because your LP usage seems consistent daily.



Your boiler at its present size can only modulate down to 46,000 btus at low fire. Probably more than half your heatload at design temps. IF your load calcs out to 35 btus a sf which I doubt. What you got now is a bang bang boiler You may be hurting yourself by shutting down zones. Your boiler at present size is still churning out 46000 btus to heat what zones you have on and your not at design temps yet. Couple that with using electric heaters.  Sounds like you may have piping issues possibly also. Pics are worth a thousand words here.



As far as slab insulation I highly doubt with the time of year, and your loads at present its the culprit....yet.





Just a Homeowner stoking the think tank.



Gordy

broke

radiant heating problem

Thanks again for looking at my posts. How did you figure out the the modulation down to 46000 btu I thought the boiler only modulates 20% from the 230000 to 187000 btu.

Gordy

5 to 1 turn down ratio

Each step down in modulation is 20%.  Your control pad should tell you what modulation rate the boiler is running at when firing.



Gordy

broke

Gordy

In the summer months i use less tha one gal per day. sorry I don't understand the 5to1 tur down ratio

Gordy

how are zones heating

When all zones are running is everything heating properly.....are you comfortable?  Did you shut zones down to save fuel?

Gordy

broke

problems

If I have a 5 to 1 turndown ratio I would get 100% off of 230,000 I still have 115,000 btus to heat a 1 zone.I dont get the turn down ratio.

Gordy

turn down ratios

230000

184000

138000

92000

46000



These are the firing (input) rates for each step down in Modulation for the 230

broke

problems

Yes I shut zones down to save fuel but the boiler only uses a little bit more fuel to heat the other zones.The house is very comfortable also the boiler only fires once a day for about 3 hours until it gets really cold I live in MT. I am curios about the boiler size a friend of mine told me he is heating 2800 sq feet with an ultra 105.I dont understand why mine is so large same guy did both instals

Gordy

The key

If your boiler is sized correctly for  the load which its not. It will modulate to the load in real time. Via temp sensors, and outdoor reset.

So if its design day it would be firing at 230000 btus. Shoulder season 46000 btus, and the whole range in between that. 



Usually when there is a call for domestic hot water it will go to high fire.



Gordy

Gordy

Comfort

Is good at least we now know the emitter end is doing its job.  As for your boiler size You should approach the installer if he did the other job with a smaller boiler as you stated. Unless your domestic load is high. sounds like a thumb in to me.



Gordy

Mark Eatherton

Got insulation??

If not, got shallow ground water?



Also. got fire side combustion analysis?



ME

Gordy

As for the friend

 Would his house be similar in construction to yours?  This is all fiddle faddle until you get an actual heatloss calculation done. If you really want to know where you stand with this ordeal.



Gordy

broke

gordy

This is very interesting how can I tell if the boiler is modulating down the boiler is about 3 years old . I can watch the fan speed and that is it is there something else that I can look at.I can set the fan parameter to 1500 and not let hit high fire. I have done this many times to see if that helps it doesnt change anything. I also have changed the boiler targets down to110 deg to see if that does anything . You have me curios if the boilers modlating down very far.

Gordy

You got help

Now the Guru is here! And yes what ME said. Possible heat sink!



Gordy

broke

Gordy

 I feel the house construction isnt very close I think my sips panel house should be more efficient. I hope .

broke

problems

I hope not the ground water is apox. 15 feet . How can you tell if you have a heat sink.

Gordy

Soil

Type of soil?

Ironman

My Thoughts Too, Mark

Ground water leaching the heat out of the slab. I would check the delta T on the slab's zone. If it's high, and the gpm is also high from the injection, that might be the culprit.



One other thought: has anyone done a recent pressure test on the gas lines to see if they are holding? Particularly the underground lines.



Again, pics. of your piping and controls would be helpful.

broke

problems

Black dirt under that coble rock. The house sits 20 inches out of the gound on the lostend higher end 30 inch out under the house I have  with a 48inch wall on footings.

broke

problems

I dont think the ground water could be the problem I didnt have the master bath done yet and I dug down under the tub to get to the drain when we hooked it up we dug 12 inches apro. below slab to get to it. Also I do have a good delta tee I have checked the returns many nights looking at the boiler the deta tee is close to 20 apart after 20 to30 min. Last week I fired the boiler for the first this year  the I checked return temp  as fast as I could and it was 70 deg I hit the thermastat  and checked quick.

Ironman

Also

What about the possibility of a broken line in the slab and fresh water feeding into the boiler continuously? Does the system hold pressure if you close the fill valve?

broke

problems

Boiler does hold pressure. Cant hear any water coming in on the system valve as for propane leak contractor had propane company come twice to check.

Ironman

Try...

Turning off the zone to the slab. If your gas usage drops, then you'll know it's the culprit.

broke

problems

All three zones are in the slab. I have turned the others off and checked each one. The two 1200 foot  zones use about the same fuel as the smaller 900 foot zone. How can I tell if the boiler is modlating down other than fan speed.

Ironman

Listening to the Fan...

Is the simplest way. But lowering the firing rate is not going to make that much difference. This is not the main issue you have.



You stated earlier that your boiler comes on for 3 hours at a time and yet according to your contractor's guesstimate of 30btu. per square foot, your load would be 84kbtu at design temp. It shouldn't take that long to satisfy a heat call unless you're setting your stats way back at night. This indicates the boilers probably firing high for most of that 3 hours. 200kbtu x 3 hours = 600k / 92k per gal of propane = 6.52 gal. of propane.



Lowering the firing rate will only make the process take longer; it won't reduce the fuel consumption.



You need to get the numbers I stated earlier: the delta T of the loop and the gpm. That will give the info needed to determine exactly how many btus per hour are being put into that zone, and thus how much propane it's taking.



Given the info that you've provided, I don't think there's much wrong with your boiler other than it's oversized. The issue is: where is the heat going?

Gordy

Foundation insulated?

If you have 20 to 30 inches of foundation wall out of the ground, and its not insulated get it done!



While bubble foil insulation is a farce, even if its an r -1 thats 100% better than an r -0 or nothing



What are you using for floor coverings through out the house?



Do you have alot of glazing in your home?





Your burnin about 11btus a sf on average for a 24 hour period high for sip construction.



Do you set back?



Are t stats controlled by air temp or slab sensor?



What are the supply temps to your loops?



Are flow meters installed on the loop manifolds?  If so what are they set at GPM ?

 

Is boiler piped primary secondary or using a low loss header?





Gordy

Jean-David Beyer

Modulation in W-M Ultra boilers

I have an Ultra-3, which has a very nice controller. As far as I can tell, anything that can be adjusted can be done from the front panel of the unit, and furthermore, it tells you in plain english what is going on. No confusing codes. My guess is that you have an Ultra-2. The Ultra 2 has a "simpler" but more confusing control board.



For example, The Ultra 3 has a little bar that shows the current modulation level.

It has adjustements so you can set the reset curve (essentially a straight line, but you can move the end points, and change the slope) to anything you want. You can also set the minimum and maximum combustion rates (You should not go below 20% and the default upper limit is 94%), and the hysteresis around the desired temperature (+ | - 5% is default).



So for me, it is trivial to see the turndown. It does not seem to turn down in 20% steps. If it is in steps (may well be), they are finer than 20%. It is just that 20% is the lower limit (unless you raise it. I do not know what happens if you try to go below 20%, because they say not to).



I would guess you need more heat per square foot than I do here in New Jersey. What is your design day temperature? Here in my part of N.J., it is +14F. According to my chart, for Montana, it varies between -7F and -17F depending on where you are. -7F in Kalispell, -17 in Butte, -16 in Helena.

Jean-David Beyer

What are the supply temps to your loops?

Yes. For my radiant zone, my supply temperature is 75F until it gets to 55F outside. From there it slopes up until it is 0F outside, when the supply is 120F. Since design day around here is +14F, it should not go over about 109F. And the return water temperature should be less than the supply. The lower the return temperature, the more efficiently the boiler will operate.



As a rule-of-thumb, for natural gas, return temperatures over 130F will not condense and your efficiency will be less than about 87%. If your return temperatures are about 90F, the efficiency can be about 96%. If your are snow melting and your return temperatures are a bit under 70F, you might get 98% These are read off a graph of what you can expect, and are not for any particular boiler. I do not know if they apply to propane, and they are different for fuel oil.

broke

Hi Gordy and Jdb and Ironman thanks for the post this morning

The thermastats only look at air temp. The foundation is isulated inside with 2 inch blue board down 2 feet.I dont touch thermastats once I start heating season no set backs.I have turned supply temps down from 120 all the way down to 95 the returns always look good.You stated that a sips house losses about 11 btus sqf  if my zone is 990 sqf how many btus do I need to supply the floor.No flow meters on loops.    The weird thing is the boiler only fires once a day unless its really really cold out but it still burns the same fuel warm or cold until it gets really cold .Mobody I have talked to can believe this and I agree it seems impossible but I read the meter every morning. I have two thoughts on this 1 the bioler can only modulate down to 46000 btus and I dont need that many to supply the zone. 2nd the slab is not able work right because of the bubble rap I hope its the first.   Broke

Jean-David Beyer

I have turned supply temps down from 120 all the way down to 95

I though you said you had a W-M Ultra that I assumed was a Series 2 model.

Do you not have it running with outdoor reset? I know the Series 3 come with all the stuff you need for outdoor reset, and I think the Series 2 does as well.



I wonder two things.



First: Did your contractor who plumbed your boiler in backwards also hook the supply and return temperature sensors incorrectly (i.e., not reversed) as well? Did he not bother to hook it up at all?



Second: when you say you set supply temperature to 90F, that is an unsatisfactory description. For my Series 3 model, you set the entire reset curve. Mine runs between 75F and 120F depending on the outside temperature. So for my house and heat loss, mine runs at 90F only when the outside temperature is 37F outside. When it is 70F outside, the water would be 75F (if the thermostat called for heat, which it normally would not). When it is 20F outside, the water would be 104F. Your mileage would be different, but I hope you get the idea.



I am also concerned about that injection mixing valve. Have you removed it? I think it could only complicate understanding the system and how it is working. Just set the boiler to supply the water in the necessary temperature range (by setting the reset curve appropriately). I would infer that you would have to run the boiler hotter than necessary in order to have sufficient temperature difference across the injection mixing setup to work properly. And I can think of no good reason to run the boiler any hotter than necessary. But remember I am not a professional.



"The weird thing is the boiler only fires once a day unless its really

really cold out but it still burns the same fuel warm or cold until it

gets really cold ." I cannot believe you are lying about this, but it is difficult to believe. I could believe you boiler runs only once a day, but that just means your reset curve is not perfectly adjusted. By perfectly adjusted, I only mean that it is set to deliver just enough heat to keep the house at the desired indoor temperature irrespective of the outdoor temperature, and therefore that the circulator runs continuously. I do not believe this is possible, but I have mine set so it is pretty close to that when it is very cold out. It would run 18 hours or so during the day. Right now, it is about 50F out and the system has run only 6 hours and 20 minutes since midnight. Now 8:39 PM. In fact, it has run only 107 hours 17 minutes since September 1. Most of those days it has not run at all (except a few minutes a day for the indirect.



It is true that the boiler can modulate down only to  46,000 BTU/hour. But if less is required, it does not dump all the rest up the chimney. It would just go into start-stop mode and rapidly cycle. Inefficient and causing excess wear. But the gas consumption should go down. I would not know which of the two problems you suggest is preferable. If the boiler is seriously oversized, which I expect is the case, would you be prepared to replace it with a smaller one? It would be difficult to eat the cost. OTOH, I am not sure about the bubble wrap being the problem. I thought you said the pex tubing is in the slab. If the bubble wrap is above your slab, that would be a problem difficult to fix. I have visions of getting in the demo people with compressed air jack hammers to remove your slab and putting in one correctly. Seems even worse than replacing the boiler.



I believe at some point  you should get a real pro in there to study your system. Someone who really understands mod|con boilers. I doubt the guy who did your system is the pro you need.

Ironman

A Mis-conception?

I may be wrong, but it appears that you have a mis-conception about boiler modulation. Just because the boiler won't turn down as low as we would like to see does not mean that the "extra" btus are being wasted out the flue pipe. You are still getting most of that heat into the system.



Example: Your boiler input @ 100% is 230k btu. At 95% efficiency your output would be: 218.5k btus. 230k x .95 = 218.5. This means that 218.5k btus are going into your piping. If you were firing @ 20% modulation the equation would be: 46k x .95 = 43.7 btus output. 43.7k btus would go into your piping



The advantage of modulation is to match the firing rate to the load and thus keep the boiler condensing longer which in turn increases efficiency. Over-firing lowers the efficiency slightly (not more than 8-10%, if that much).



The over-sizing of your boiler is not the main cause of your excessive fuel usage.



If you'll do a simple test, I'll show you where all the heat is going:

1. Lock the boiler into a fixed firing rate - any percentage you like, 100% or 50% or 20%.it does not matter. Just as long as we know what the rate is.

2. Accurately measure the supply and return water temps from the system at the boiler. Do this with all zones calling and then with each zone separately.

3. Record the temp difference (delta T) each time and post them with the firing rate or email them to me. I'll then be able to tell you where your heat is going.



This is the only scientific method to do this. You can't keep taking shots and hope by chance to hit the problem.