Help with boiler-radiator system

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  #41  
Old 12-01-12, 11:19 AM
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OK, for the period mentioned, 10/24 through 11/26, you had 690 degree days.

Let's see... with oil systems we calculate a constant called the " K factor " which is

Degree Days per Gallon.

I need to get this into 'like terms' so the number makes sense.

1 gallon of fuel oil = 140,000 BTU

1.027 Million BTU per MCF X 20.3 MCF = 20848100 BTU

1.027 Million BTU per MCF X 18 MCF = 18486000 BTU

That's equivalent to 20848100 / 140000 = 149 gallons of fuel oil

That's equivalent to 18486000 / 140000 = 132 gallons of fuel oil

690 / 149 = 4.36

690 / 132 = 5.22

Oh... that's not good at all. IF my numbers are ciphered rightly.

A little better... still not great, but again, take my cipherin' with a grain of salt! I lernt most of my math from Jethro Clampett

In fact, that's pretty pee poor.

Remember though that these numbers are skewed by your cooking and water heating use.

Even so, what percentage of that use is cooking and HW ? probably very small...

Do you have a summer time bill handy?

For a 'fair to middlin' usage, that number should be at LEAST TWICE what you are getting...

My home was running around 8-9 degree days per gallon with my old boiler. New boiler is a bit higher than that, but not enough data yet to quote.

I do feel as though keeping that control scheme is costing you some money... it's NEVER a good idea to let a boiler 'free run' and keep itself warm 24/7 as yours does. Any advantage that the ODR is providing is being heavily offset by the fact that the boiler is staying warm all the time... firing up when not even needed. Like keeping your car idling in the driveway on the chance that you might need to go to the store in the afternoon.

So, let's get an idea of your summer usage and massage the numbers a bit and see just how bad it really is.
 

Last edited by NJT; 12-01-12 at 05:13 PM.
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  #42  
Old 12-01-12, 04:09 PM
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Whoa!!

Shouldn't surprise me I guess.....I don't think theres much insulation in the house.

Summer usage is negligible, just 2 or 3 MCF. Yep, you have the correct airport.
 
  #43  
Old 12-01-12, 05:02 PM
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So let's recalc for 18 MCF then and see what we get... edits above in previous post.
 
  #44  
Old 12-01-12, 05:13 PM
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Bottom line is that you are probably spending more on fuel than you ought.

Let me ask a couple more questions about your system...

How are each of the individual radiators fed by the system?

Is there a single pipe leading around the basement that BOTH the supply and return from the rads are tied into? And if this is the case, can you tell if either or both ends are connected by what is called a 'venturi' tee? If you can take and post a pic of how the rads are connected we should be able to tell by looking.

Or, are there TWO pipes going around, one supply and one return, each with one end of each rad connected to it? (I'm hoping that this is what you have)

Because you have TRVs at each rad, I know that it is not a 'series' piping arrangement. If it was, when one TRV closed off, you wouldn't get heat from ANY of the rads in the loop.
 
  #45  
Old 12-01-12, 05:16 PM
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Yep, I see.....I got 5.22 also, so I guess 'ol Jethro could add after all!

What sort of control would provide better efficiency?
 
  #46  
Old 12-01-12, 05:20 PM
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Let's do a little more cipherin' and then talk about what you can possibly do.

Gonna work backwards. Let's go with a constant of 8.

690 / 8 = 86 gallons of oil equivalent. (which is a little more than I've burned in the same time frame)

[note: if I could save that amount on fuel oil, it would be about $170! not trifling money!]

86 * 140000 = 12040000 BTU total

12040000 / 1027000 = 11.72 MCF

Now cipher what yer bill would have been based on 12 MCF.

This will give what you MIGHT be able to save if you ran the boiler as a cold start.

maybe... in theory anyway...
 
  #47  
Old 12-01-12, 05:21 PM
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There are two pipes... each rad is fed by the supply and then feeds into the return line. That is except for the final rad in the supply loop...that one leads right into the return, and there's a bypass pipe connecting the supply and return under this rad so it doesn't stop circulation when that rad's valve is closed.
 
  #48  
Old 12-01-12, 05:25 PM
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K factor of 8 would take my $149 bill to about $88!
 
  #49  
Old 12-01-12, 05:28 PM
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there's a bypass pipe connecting the supply and return under this rad so it doesn't stop circulation when that rad's valve is closed.
Hmmmm... I think the logic for that bypass might be a little different...

I believe that valve is there so that your pump isn't deadheaded when ALL the TRV valves close.

Is it by any chance a 'differential bypass valve' ? Does it have a number scale or a pointer on it? Or is it just a normal hand wheel valve or perhaps a ball valve?

Thing is, if the logic were as you say, then that should apply when ANY rad closes, implying that EACH rad should have a bypass valve.

Since your system is set up for constant circulation, you would only need the bypass when ALL the rads were closed.
 
  #50  
Old 12-01-12, 05:34 PM
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K factor of 8 would take my $149 bill to about $88!
That would be some sweet savings if achievable, wouldn't it?

So, let's think about the possibilities then.

The SIMPLEST thing would be to replace the HT with the newer model. $350 or so.

Now, how to get away from the 'warm start' condition...

You could, as mentioned earlier, install a SINGLE thermostat in a room that you feel represents the 'average' temperature of the home.

Turn open the TRVs on the rads in that room to a HIGHER setting than you set this new thermostat to and allow the new thermostat to control the temperature in that room.

New thermostat would wire to the 'summer/winter' inputs on the HT.

When new thermostat is satisfied, system shuts down and waits.

Let's run this through our heads and try to think of downsides...

OK, if the 'outlying' rooms lose heat at a faster rate than the 'average' room, they will end up being colder than normal. That's not good... but, it might not happen... or it might...
 
  #51  
Old 12-01-12, 05:48 PM
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...I'm with you.... so it seems like if an outlying room (upstairs is the best example....big room, entire second floor, single rad) loses heat at a faster rate I could adjust the TRV in the central room lower. This would have the boiler work a bit longer to heat the central room (with the t-stat), before shutting down. Maybe between the t-stat and the TRV's I could find a sweet-spot?
 
  #52  
Old 12-01-12, 05:57 PM
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And yeah, you're right about the bypass...it would apply to the instance where EVERY TRV was closed. The bypass itself is nothing more that black pipe with 90 degree elbows and a couple junctions connecting it to the supply and return.
 
  #53  
Old 12-01-12, 06:20 PM
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Maybe between the t-stat and the TRV's I could find a sweet-spot?
Maybe... it would take a whole lot of tweaking and twiddling though, and might well change as the seasons get colder and warmer again.

For the record, I DO see a few problems with this first approach.

The bypass itself is nothing more that black pipe with 90 degree elbows and a couple junctions connecting it to the supply and return.
No valve?
 
  #54  
Old 12-01-12, 06:27 PM
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Another approach... let's toss this around a bit:

What if:

You installed a t'stat upstairs in the 'great room', and ALSO one downstairs and wire them in PARALLEL to the summer/winter switch on the HT... ?

Set the TRVs in the downstairs room with the t'stat just a couple degrees higher than the t'stat.

Same with the upstairs room.

What would that do for us?

Well, if the upstairs did get much colder than the down, it could still call for heat.

If the down thermostat was satisfied, when the up room called for heat, the down room would overshoot by only the amount that the TRVs in that room were set ABOVE the thermostat...

I would think that you would want the down thermostat in the room with what you feel is the highest heat loss area, that way the other downstairs rooms could be regulated still with their TRVs because the down thermostat would call for heat more often than the other rooms.

Now there is another 'downside' to this...

Your family is USED TO being able to RAISE the temp in some rooms. Let's say the kids want the bedroom a little warmer. It could happen that it won't happen. If the room with the thermostat is now at temp, and the boiler and pump are OFF, raising the TRV won't increase that room temp until the next time either of the thermostat rooms call for heat.

Another possibility... the upstairs room with the minimal radiation and probable higher heat loss would 'drive' the system. It could well turn out that you could get by with just ONE thermostat in that upstairs room. It also might turn out that the thermostat upstairs would be calling for heat MOST of the time and adding it might not save all that much... it would depend on just how often it DID call for heat.
 
  #55  
Old 12-01-12, 06:33 PM
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Ya know, your system is probably providing a VERY comfortable and even temperature in every room. But it was designed when fuel was cheap. It's actually kind of a luxury... but one that you are paying for! (as with most luxuries!)
 
  #56  
Old 12-01-12, 06:58 PM
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Yeah, we definitely enjoy nice even, on-demand heat. The room by room flexibility of the TRV's is great. But, yeah I see what you're saying with the downside....even when the rad's (TRV's) aren't flowing much water through the individual rads, the water flowing through the entire system is always at temp.

Let me just think out loud regarding the dual t-stat setup, and see if I have this right.....

- The control will still set the water temp based on the outdoor temp and the control settings.
- The water will still flow through the individual rads based on the TRV setting.
- Two t-stats installed in parallel...one upstairs and one in the room downstairs that loses heat quickest.
- In these t-stat rooms set TRV's full open so the t-stat can function and control the temp.
- When EITHER of those t-stats close the system is activated and brought to temp.
- When BOTH of the t-stats are satisfied the system shuts down. (what is min. water temp when this happens anyway?)

So with this dual t-stat setup I wouldn't need the 55* outdoor temp cut off either, would I?

Also, seems like if I wanted at any point for this setup to perform like my current system, all I'd have to do is turn both t-stats to max, right?
 
  #57  
Old 12-01-12, 07:21 PM
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IDK trrop I read some of this thread and would it be just plain simple to open all rads, make cold start with t stat and be done?????

If he is uninsulated cape @ $141 for the month I guess aint bad.

I am insulated OK ( 1050 sq ft cape ) and I used 83 ccf this month or 88.90 therms from oct 22-nov 26. I am ready to complain to the gas company...LOL. Geez $108 bucks...

Using more then last month. Ugggg.

To the OP capes are bad...LOL.

Oh x .071 btu content whatever that means....

Just throwing this out there for comparison.
 
  #58  
Old 12-01-12, 07:26 PM
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- The control will still set the water temp based on the outdoor temp and the control settings.
Yes.

- The water will still flow through the individual rads based on the TRV setting.
Yes, but only when one of the t'stats is calling for heat and the pump is running.

- Two t-stats installed in parallel...one upstairs and one in the room downstairs that loses heat quickest.
Yes. OR - possibly just one in the upstairs room if it is determined that placing it there will be sufficient to 'drive' the entire system. If that is the single highest heat loss room, it will call for heat more often than in any other room, and the other rooms can simply 'piggy back' those heat calls.

BUT, if the heat loss in that room is high enough that the thermosat calls almost all the time ANYWAY, you are back in the same boat as without the thermostat. All things to consider!

- In these t-stat rooms set TRV's full open so the t-stat can function and control the temp.
NO. You would set those TRVs just a degree or two HIGHER than the t'stat in that room so that if one room was satisfied, and the OTHER t'stat called, that room would not go into crazy overshoot temperature mode. The PITA here is that if you change the t'stat temp for whatever reason, you also need to change the TRV setting.

- When EITHER of those t-stats close the system is activated and brought to temp.
Yes.

- When BOTH of the t-stats are satisfied the system shuts down. (what is min. water temp when this happens anyway?)
Yes, temperature is whatever the control has calculated.

So with this dual t-stat setup I wouldn't need the 55* outdoor temp cut off either, would I?
You could and would keep that. In the ODR world of Tekmar, they call this Warm Weather Shut Down ( WWSD ), but usually not set as low as 55░... typically 65░, but open to individual interpretation, your choice!

Also, seems like if I wanted at any point for this setup to perform like my current system, all I'd have to do is turn both t-stats to max, right?
Yes. Or disconnect them from the control and place the jumper bar back on the terminals of the control.
 
  #59  
Old 12-01-12, 07:36 PM
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I like it...

You mind giving me your recommendation on the equipment thenů.?

- The HWE-SS control.
- A programmable t-stat to use as an advanced setback timer. (which model would you go with?)
- Two t-stats. (simple here, right? Temp only?)
 
  #60  
Old 12-01-12, 07:40 PM
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Oh, or do I not do the setback if I install the 2 t-stats?

Does it make sense to still have setback and morning boost with the 2 t-stat setup?
 
  #61  
Old 12-01-12, 07:42 PM
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IF you decided to go with the 256:

Run constant circulation as you do now, but would need to wire the pump to a wall switch so that you can shut it off in the summer.

JUMPER the 'heat demand' on the 256. This would give you essentially the same thing as you have now with the HT.

Variations on a theme:

Add a thermostat (or two) and wire to the 256 thermostat terminals, and add a relay to operate the pump from the thermostat calls.

This would give you essentially the same thing that you would have if you added the thermostats to your HT setup.
 
  #62  
Old 12-01-12, 07:51 PM
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- The HWE-SS control.
Yes, if you stayed with HT, that would be the model.

- A programmable t-stat to use as an advanced setback timer. (which model would you go with?)
El cheapo... something like this:

5-2 Day Programmable Thermostat with Backlight-RTH2300B at The Home Depot

You could also get a 5-1-1 if you needed individual SAT/SUN settings.

- Two t-stats. (simple here, right? Temp only?)
Yes, don't even need programmable, that will be taken care of by the setback timer above.

You could get by with the old 'standard' !

Round Mechanical Thermostat Heat Only-CT87K at The Home Depot

By the way, if you do decide to run the wiring for the t'stats, you might be tempted to run a wire from upstairs t'stat to the location of the downstairs t'stat stop there and make the parallel connection, and then continue the wire from the downstairs location to the basement.

I would suggest that you run BOTH wires all the way to the boiler and make the parallel connection THERE. Just in case in the future you might want to do something different, like zone valves or something... or change out the boiler and zone the system...
 
  #63  
Old 12-01-12, 08:01 PM
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Oh, or do I not do the setback if I install the 2 t-stats?

Does it make sense to still have setback and morning boost with the 2 t-stat setup?
I was thinking about this earlier...

Since you have TRVs on all the rads, AND the constant circ, I have to wonder if the setback ever did anything at all in the first place.

I guess it COULD, but it would depend on how finely tuned your 'reset curve' in the control was.

To explain it all, I would have to go into a month long dissertation fillibuster about how ODR works, but let's just suffice to say that if a TRV is set to say 70, that room will attempt to make 70 whether the control is targeting 140 or 155 degree water.

Because you see, the night setback simply adds an 'offset' to the targeted water temperature.

If for a given outdoor temp, the targeted temp is say 155 to meet the heat loss of the home, when the setback timer kicks in, it adds a pre-programmed negative offset to that temperature, let's say 15 degrees lower... 140.

The TRVs know from nothing... they are stupid. If cooler water comes along, they will simply open wider to try and keep the room at their setting, which they may be able to do.
 
  #64  
Old 12-01-12, 08:43 PM
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The setback definitely functioned before the timer went bad. Water temp dipped 20* between 12 mid and 5:30 AM. To your point, the TRV prob opened up to allow as much water to pass during setback period.

If I do the setup with the 2 t-stats then they'll power the whole system on and off as needed, so no need for setback in this case is what I would figure. In fact, a setback would only make it harder for the t-stats to be satisfied. (Unless I set the t-stats back each eve as well)
 
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