radiant heat loss because of pex placement?

Gordan

Yeah...

On this one, the boiler temp sensor is tapped directly into the top of the heat exchanger jacket, off to the side. Inadequate flow (due to either underpumping or blockage on the water side of things) could conceivably create a hot spot near the sensor, causing it to read much higher than the actual supply coming out of the water. At least that's my mind's eye's view...

panman

re-groundfos

Gordan, i am sure the water temp was 170, because the light was bouncing back and forth from water temp to gas temp. The gas temp went much higher, sometimes in the mid to high 200's. I do not have an outdoor temp on the boiler. The light on that setting never lights up and when i go into the function mode, nothing comes up on the screen plus there is nothing outside anywhere on my house to indicate there is a sensor hooked up. Thanks-peter

Gordan

I was going to ask you about the gas reading...

I didn't want to muddy the waters. If that reading is in the 200s, then basically the boiler is giving it its all and simply unable to keep up. According to the manual, the Ti200 gas input display goes from 40 (meaning lowest input) to 240 (meaning highest input - 200,000 BTU/hr.)



One thing I would still like to be able to explain is why it's saying it's making 170 degree water when all other indications point to much lower.



If the boiler is truly on full tilt all the time, and still not able to keep up, then you're probably wasting your money heating the soil under the house, in which case you'd be better off spending the money that you'd have put into ripping up the carpet and etching the concrete, on some radiators or baseboard instead. But still do that test that I asked you to do above, with increasing the flow. Use your hand to confirm, too, but carefully... the difference between what 125 F feels like and what 170 F feels like is pretty startling.

Zman

Isolate the boiler

Let's find out what is up with the boiler.Turn off the mixing blocks and see if the boiler will come to temp.Both on its own gauge and with your measurement tool. If the boiler won't come up let's figure it out. Is the pump correct? Is the piping correct? Sensor error? Call tech support if needed but get the boiler working.There is no point in messing with mixing blocks until you know that you are are giving them enough heat.

If the boiler is in fact a 200,000 btu, There is no way that a small radiant slab is dragging it down 40+ degrees. The mixing block would have to be pumping over 10 gpm through a few 1/2" tubes.

I see the sequence as

Get the boiler working at a high temp (170 or more)

Get the lower level mixing block putting out a higher temp (150)

Balance the boiler and mixing block for optimal efficiency

panman

re-groundfos

Gordan, my circulator is a groundfos 15-58 with a 1'' pipe. I put the circulator on high and both the boiler out and the return went up 5 degrees. The funny thing is that it is 20 degrees outside and my basement zones were satisfied this morning. I will have to get a tech in and find out why the temp of boiler is not the same as outlet. Thanks a bunch

panman

re-isolate boiler

Zman, Like i told Gordan- the circulator is a 15-58 with 1'' pipe. I agree with you that i need to find out why the boiler is saying 170 and the outlet is only reading 125 and mixing block inlet pipes 90-100. I need to get a tech into look at the boile. I do have some great info to help them along. Thanks Zman-Peter

Gordan

UPS 15-58

So... that circulator is "smaller" than what your boiler install manual recommends. It would not be able to flow anywhere near the recommended minimum of 8 gpm through the boiler and the piping on medium speed, probably only half of what it's flowing on high speed. The result is that, when the boiler is firing at or near full tilt, there could be big differences in water temperature at different spots in the heat exchanger. (For instance, where the sensor is located.) This could explain the difference in sensed vs. actual water temperature. The ability of the heat exchanger to transfer heat from the flame to the water would also be severely compromised, which could explain high flue temperatures. Did you take new measurements once you kicked the circ to high speed? What temperature was the boiler showing, versus the temperature of the boiler supply pipe? What was the flue temperature?



Is the pipe 1" all the way around? It looks from the pictures like it's smaller near the boiler, but that might just be a trick of the eye.

panman

re- UPS 15-58

Gordan, there is 1'' pipe out of the boiler and out of the circulator then goes to 3/4'' at the T's before going to the mixing blocks, i will double check measurments of pipe on the entire system tonight and heat on the boiler when circulator on high. Thanks so much for your continuing input. Your knowledge is much appreciated-Peter

panman

re-ups 15-58

Gordan, i have some good news and bad news. Bad news 1st. I took the serial # and model number off the boiler and it is a Ti150 NOT the 200. Good news is that when i turned the pump to high, the boiler temp dropped to around 140-150 and my basement mixing block went to a steady 135 degrees and the both zones down stairs were met in a matter of few hours!!!! YAY. FINALLY the root of the problem.i did not have the temp gun with me. I will eventually change the circulator to the 26-64 that the book recomends for the 150 but for now that is a great improvement. Gordan, if i ever have a problem with 1 or both of the mixing blocks, is the ti 150 boiler capable setting a DHW temp and radiant water temp so i can illiminate the blocks and straight pipe it???????? Gordan i think your work here is done!! I have learned alot about my boiler and the parimeters thanks to you and a few others. Thanks Peter

Gordan

Phew...

Finally we're getting somewhere! :-) See how getting some data helps us quickly pinpoint where the problem may lie?

 

What was the outdoor temperature last night? If it wasn't as cold as it gets, you could still have problems keeping up when temperatures dip further down. If you can get your hands on the thermometer again, you should take a fresh set of measurements (the full set of 16) and post them here so we can see what's going on now.

 

To answer one of your questions, the boiler can do what you're asking but you need to get, and install, an outdoor sensor for it. Judging by the manual, you COULD use the sensor from one of the RMB-1s as they seem compatible. Or you could just buy this: http://bostonheatingsupply.com/81027-1.aspx



You can reuse the wiring that's currently going out to the RMB-1 outdoor sensors and mount this in the place of one of them. Then you would set the outdoor curve using a combination of HI and RES settings on the boiler.



If this were mine to redo, I'd combine the upstairs and downstairs circuit to one. Then I'd put in a Grundfos Alpha, which is a much more efficient circulator than the ones you've got, to circulate water through all the zones. It can detect zone valves opening and closing and adjust its flow accordingly. You may not need a different circulator on the boiler circuit; measurements will tell. What you DO need is for a qualified guy to come in on an annual basis and check everything over, clean the heat exchanger, perform combustion analysis, and adjust anything that needs to be adjusted.

panman

question

Gordan,Got a question. I now have 2 taco mixing blocks, 1 for 2 zones down stairs and 1 for the 2 zones upstairs. In the future rather than pay $1000 to replace one of them, you recomemded replacing them both with 1 grundfos alpha  to do all 4 zone on 1 circuit.(1) will the grundfos pump a constant 140 degree water no matter how many zones are calling?(2) Can it push the water as fast as the 2 mixing blocks when needed to fulfill demand on all 4 zones? (3) Do i still need the head circulator or can i put it in the place of it? Thanks for any info. P.s. System has been meeting the supply down stairs unless it goes down to 0. Much better than before. Thanks-Peter

Zman

Yes

I believe Gordon's recommendation is "spot on". Yes the grundfos alpha can easily handle the load. It may take a bit of trial and error to get it dialed in.

panman

re-yes

Zman, thanks for the input. I was looking for some info as to my questions. You answered the load question, can you elaborate on the other 2. Thanks -Peter

Zman

The rest of the answer

The boiler can be set up to manage the outdoor reset.The actual output temperature of the boiler will be what is calculated for the heating load just as the mixing blocks are doing now. The (secondary) heating loop with the alpha circulator will tie into the main boiler loop using closely spaced tees or another "hydrolic separating" method, similar to the way the mixing blocks are now.. You will still need your primary boiler circulator. I am not sure whether the primary boiler pump needs to be upsized. It sounds like it is smaller than spec, but is working.That boiler is designed for more of a high head circulator.The safe move would be to replace it.This approach should allow the boiler to run more efficiently and reduce your pumps from 5 to 2, saving quite a bit of electricity

panman

re-rest of answer

Zman, Thanks for such a quick response. Makes sense now. Just looking ahead to better the system. Can my boiler be set pump out 140-150 degree water to the 1-4 zones with out all the outdoor re-set and goolash, another words when thermostate calls for heat, the zone has 140 degree water going through it until zone is satisfied? Just wondering. Thanks a bunch-Peter

Zman

Yes

Your boiler can produce the same heating curves your blocks presently do. You might decide you need 150 on the coldest day and 100 on the warmest. Your boiler will start condensing and approaching peak efficiency if you can return water that is cooler than about 130 degrees. It is not a big deal if you don't condense on the coldest day, but ideally your boiler curve will allow condensation on your "typical" heating day.Check out this Ashrea presentation and you will see what I mean www.pugetsoundashrae.org/PDF.../AshraeCondensingtechnology.ppt

Harvey Ramer

Don't mean to cut in here Gordan

If the outdoor sensor says it's 20 when it's actually 5 ; it's entirely possible that the wrong type of wire was used. If it's installed with anything other than a sheilded thermistor cable that may be the problem. A regular thermostat wire would get resistance (especially on a longer run) across the wire itself causing erroneous readings. Also an unsheilded cable is suseptable to interference from other electrcal wires and such.



Just my 2cents



Never mind, finished reading the post and it's already been mentoned.

Gordan

Outdoor reset is better

Peter, it's not just a matter of efficiency, but also of comfort. If you've got nothing but a thermostat controlling a high-mass emitter such as the slab, you can expect a lot of under- and over-shooting of the temperature in those zones. By the time the thermostat falls below its setpoint, the slab will have cooled enough that it will take a while for it to warm up to the point where it's once again meeting the setpoint, and by the time that happens (and the thermostat cuts the flow to that zone) the slab will have warmed enough that it will continue to release heat long after the zone is satisfied. It's possible that a very intelligent thermostat (with a PID control, for instance) could anticipate and prevent the temperature variation, but you'd be far better off with near-constant circulation and outdoor reset (where the large mass is kept at or near the optimal temperature so that it keeps up with heat loss.)

panman

re-outside of the system

Thanks Gorden, the system is doing much better. The downstairs is meeting the heating need and shutting off alot more than before i got on to this website. Thanks for your help. My wife and i are still mulling the fact of removing the carpet and tiling in the near future. Thanks so much-Peter

panman

heat loss calculation ?

Can anyone figure out the heat loss in water temp and heat loss in propane gallons with my carpet and pad being an R-value of 3 over concrete and heating 1300 sqft. I am just wondering how much of a heat gian i would have if i pulled the carpet and layed tile. The home is WELL  insulated. Thanks - Peter

PeterNH

a few numbers

Hello Panman,

I can't get any accurate figures with the sand.

I also believe, there is not enough insualtion underneath everything.

Furthmore, i can''t offer any thoughts about propane usage, without knowing hours of operation, design temp, heatloss etc.



Now having said all that here's what i can offer:

A 4 inch slab, without sand and with 2" of extruded insulation

with 1/2 inch pex spaced 12 inches apart and a R2.5 carpet will tranfer about 10 btu's per square foot, with 100 degree water.

The same set-up with 100 degree water and 1/2 tile with a R value of .4 will transfer about 23 btu's per sq ft.

Put another way, it would take 147 degree water to transfer the same 23 btu's wit R2.5 carpet.

Obviusly the numbers get worse with R3 and probably worse yet with the sand factor.



Peter

panman

re-a few numbers

PeterNH, thank you for your input. You gave me valuable info. I am sure you read some of my posts and see why i am strongly considering losing the carpet. some of the info i got from websites said it would take 40 degree more water temp to get the same results as just tile on the concrete. You nailed it pretty well !!!!!!! My guess is that i would notice a considerable difference. Thanks again. PeterME.

PeterNH

insulation?

 

Hello Peter ME,

Are you sure there is 2" of extruded polystyrene insulation??

Do you know if the perimiter of the slab is insulated? HDow so? The perimiter insulation is critical.

Beware.

Based on the numbers i see, it looks like a reduction in water temp from 150 to 100 degrees, will only save 2-4000 btu's. But the sand is hard o figure.

Not very much savings, but it is dependent upon how the perimiter is insulated.

Any idea?

Anyway it's very well possible you will end up using more LP, not less.

By removing the carpet,  more heat will transfer into the room. The room temp will go way up to comfort levels, and it very well may cost more gas to achieve it.



Peter NH

Zman

high numbers

A do not believe the 50 degree numbers are correct. I use "radiant precision" as a reference on this kind of stuff. The 2" insulation is going to provide a good protection against downward heat loss. The lack of perimeter insulation will have some impact, less it is below the frost layer. With good downside insulation the heat is not lost, It just takes more time to get there. I would estimate a 10 degree water diff. It would take considerable brain damage to guestimate the energy savings, A SWAG would be a couple of percent of the total heating bill. I don't believe that from a cost savings point of view the tile is worth it.

PeterNH

Yes

Hello ZMAN,

I agree overall. There might be some savings from lower temps to by getting into condensing mode, but there will also be more usage via keeping the room temps at 72 vs 65 on cold days.

I think adding basebaord and or fan coils would be better than tearing up the whole floor. ugh.

The 47 degree number comes from Siggy's - Hyrdronics Design Stiudio.

Take it or leave it.

As far as the heat loss goes, yes, the perimeter insulation is a big factor.

If there isn't any, it make a big difference, and yes,  the deeper inthe ground the less it matters.



Peter

Zman

R?

Peter,

I was thinking you were comparing carpet and pad at R 1.4 to2.0 depending on type, to tile at .3. My personal experience in setting up reset curves has led me to think it is in the 10 degree range. I realize there is a serious SWAG factor. As a rule, I don't argue with Siggy!

panman

re-insulation

PeterNH, Thanks for the reply. 3 1/2 sides of the finished basement sit into a hill, well below frost level and are insulated. Not alot of heat loss on the perimeters. You lost me on using more propane to heat the area without rug as apposed to with the carpet and pad??? i would think trapping the heat under the r-3 rug would put less heat into the air which means the furnace would have to run ATLEAST longer to heat the same area without the r-3 carpet??? Just trying to justify pulling the carpetand pad. Thanks- Peter

PeterNH

heat

Hi Pete,

I'm prettty sure i read somewhere in this thread, that the radiant spaces can't heat above 65 degrees when it gets real cold out.

Correct?

Let's forget about condensing for a moment.

The heat under the slab..has a big blanket in the form of a carpet and pad over it.

This is keeping the heat from getting into the house on the colder days.

If you remove the blanket, more heat will be able to get into the house.

Thus on the all the colder - coldest days, the radiant zones will now easily maintain the 72 degree thermostat setting.

Doing so will require more LP gas energy than what heppens now, being that the heat is kept in the blanket and not coming out of the boiler.

There will be some savings from lower water temps to the outside, but being  way down deep and well insulated, it won't be that much, the only other saving will come from the boiler possibly spending more time in condensing mode. Maybe.

Overall, i'm guessing it's a wash, ie not much savings, but yes, more comfort.

Certainly adding in the cost of tiling the floor it may never pay.



That's my opinion, sorry that's not what you want to hear, but i can't see any massive savings, if any at all.



Peter

NH

panman

re-heat

Hey PeterNH, thanks for the reply. I do understand the logic behind the sarpet keeping my slab warmer as of now with the carpet but want to make sure i understand your reply.

Without the carpet i can get roughly 13 more btu's per square foot with same water temp.

My room would heat up quicker and demand would be met sooner causing my furnace to shut of sooner.

The slab would be cooler so when the room called for heat it would have to run longer to heat the slab to get the heat into the room, this is where it washes out!!

My question is could the carpet be causing the heat to go back down to the least resistance material (SAND) and when the carpet is gone, the heat would be generated into the room more than can be figured on paper. I ask this because the majority of the room is in the ground and well insulated and i feel the the time to heat the slab in between demands without the carpet heat sink effect would be more efficiant than what i have now. Just a thought. I am sure my wife and i at some point will tile, stain, ect. the floor and than the speculation will be over. The youngest goes to college this fall and i am fairly handy, so maybe i will tile it myself and see what happens. Thanks for the info. Peter