Very Old (circa ~1950) Hydronic Boiler System: Any worthwhile low-cost upgrades?


  #1  
Old 08-14-10, 12:03 AM
J
Member
Thread Starter
Join Date: May 2007
Location: USA
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
Very Old (circa ~1950) Hydronic Boiler System: Any worthwhile low-cost upgrades?

Let me preface this by saying that my current system is only heating a small (approx 1000s.f.), single story , stucco walled, slab-floored, 1950 home in the SF Bay Area (with generally mild winters, it is very rare that we ever reach freezing temperatures). The original American Standard boiler is still in place, and until about 3 years ago it used the original B&G pump (now using a Grundfos 15-58). I have no way of knowing the exact layout, but the pipes are copper, embedded in the concrete slab.
I have lived in this house since 1992, so I have a pretty good “history” of using this system: it initially took a few years to get used to the unique heating characteristics of this “high thermal mass” setup. At first, I just left the boiler alone, and it was clearly set to run fairly high temperatures for a system of this type, as I constantly had problems of overshooting the target temperature – subsequently the system would not have to run at all for the next 18-24+ hours, then a repeat of the overshoot. Once I learned a bit more, I have learned to adapt: the water temperature is run lower, and I now use a programmable thermostat setup in the opposite way from most people: it is set to “bump-up” the temperature a couple of degrees during the roughly 2AM to 8AM period, then set back to a slightly lower temperature during the day. This works surprisingly well for our climate here, but I’d like to see what I can do to improve efficiency.
Now for the shocker to all of the experts here: the system uses a gas water-heater style control valve mounted to the point where there would normally be the aquastat. Yes, this uses a standing pilot setup, just like a water heater, and the only high/low cutoff device is this gas control that literally is of the same type used on water heaters. The thermostat is wired to a simple switching relay (Honeywell RA889A) that directly starts the circulator pump every time there is a call for heat. Obviously, when first started up, there is a significant temperature drop (Delta T) when the hot water starts running through this cold concrete slab, but naturally this gradually lowers as the system runs for a period of time.
I have the possibility of adapting this to a more conventional aquastat and electronic ignition/intermittent pilot (Honeywell S8610U and VR8304M) at no cost to me (a next door neighbor had their complete boiler swapped out for a newer mod-con style a year ago - $13,000!!- I grabbed the old boiler and saved the installer from have to haul away this 200lb. beast). What this would also allow me to do would be to update to an outdoor reset control –something along the lines of a Tekmar 256. This would allow the system to essentially completely shut down during the generally mild daytime conditions we experience here, as well as run in a more effective manner when called for ( it has some ability to adapt the water temperature to demand level).
Would anyone care to comment on the validity of my proposed solution, or, better still, care to guess what kind of gain in efficiency I might achieve?
 
  #2  
Old 08-14-10, 07:45 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 19,710
Upvotes: 0
Received 8 Upvotes on 6 Posts
A lot to dig into here...

The first thing I want to mention, and you aren't going to like this, is that systems of this type where the copper is bedded in concrete often develop leaks in the piping due to the concrete 'eating' away at the copper. Usually takes like 40-50 years... sorry to have to tell you this but you should be aware of the possibilities, as this may affect your decisions.

: the system uses a gas water-heater style control valve mounted to the point where there would normally be the aquastat. Yes, this uses a standing pilot setup, just like a water heater, and the only high/low cutoff device is this gas control that literally is of the same type used on water heaters
I don't understand this... pictures might help... you can set up a free account at a photo hosting site like Image hosting, free photo sharing & video sharing at Photobucket and upload your pics there. Come back here and drop a link to the album for us to view.

There is another consideration to make... and you can learn more about it by searching this forum for "flue gas condensation" or Google the term.

Basically, a conventional boiler will condense the water out of the flue gases when those gases contact any surface that is under around 135°F. That's the generally accepted 'dew point' of a gas fired system flue gas. This condensate isn't only water, there are acidic components that will slowly eat away at anything it comes in contact with... cast iron, galvanized flue pipe, masonry and clay chimney components, etc...

In a system such as yours, it is almost guaranteed that the water coming back to the boiler is going to be below 135°F for extended periods of time. And this spells condensation.

Your neighbor that purchased the mod/con (Modulating CONDENSING) boiler did the best thing he could do... because those are DESIGNED to condense... proper materials, provision to remove the condensate, etc.

I think that your proposed changes may actually make the situation worse... by forcing the water to be cooler yet.

The best solution might be to have some re-piping done, and go to what they call 'primary/secondary' piping. This would allow the water in the SYSTEM to run cooler as required, but the BOILER to run at the temperature it was designed for, i.e. not in the condensing range for extended time periods.

Let's see some pics and go from there...
 
  #3  
Old 08-15-10, 08:46 PM
T
Member
Join Date: Jul 2009
Location: Toronto
Posts: 1,043
Upvotes: 0
Received 0 Upvotes on 0 Posts
ODR will really help the overshoot, and may lessen the thermal stress on your slab.
Listen to NJ, be careful how you pipe the system.
I would recommend the tekmar 356 that will give you variable speed injection into the system loop. It will give you boiler protection as well, by monitoring the return water temp.

Pics would be nice, see this beast.
 
  #4  
Old 08-16-10, 10:25 PM
J
Member
Thread Starter
Join Date: May 2007
Location: USA
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
Sorry for the delay, but here are the photos:
Old_Boiler_Corte_Madera

As for the first comment about the copper deteriorating, it is definitely a worry; but I have to say that it has been for many years, but so far, no leaks (system holds pressure for many days/weeks with cold water supply line closed off –this of course was tested in summer with system completely off, or with circulator only running and no heating). I have even found some contrary opinions that seem to indicate that copper in concrete systems (like mine) may not be the problem that others would make it out to be. For examples, see this site:
Tubing Comparison
and
Tubing Degradation

I have been doing some reading on the subject of flue gas condensation, and in fact was already aware of its dangers, but oddly enough, I don’t see significant evidence of it occurring in my boiler. Shouldn’t I see some white scale, or massive rust/flaking problems on the inside surfaces of the boiler? For that matter, how is it possible that this unit has survived this long (60 years!!)? I’m not saying it is not happening; it’s just odd that I can’t see signs of it.
In any case, I am aware it would be advantageous to run the boiler at a higher temperature, and use some means of controlling the flow of return water from the slab to moderate the thermal shock potential and condensing problems. Please elaborate on the various ways of achieving this, both technology wise (with controllers), and plumbing/pumping wise. I have just started looking into the Tekmar 356, but have had long to study the means of integrating this into my system. I get the impression I would need to go to the (also suggested) split primary/secondary loops, as simply wiring it to my existing single loop pump would not do the job (or would it?).
I look forward to learning more from all of your suggestions.
 
  #5  
Old 08-17-10, 04:11 AM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
Copper in concrete eventually fails. It's just chemistry (Cu, H2O, CaCO3, etc.). Usually it's around 40-60 years. Some go longer, some go shorter.

Maybe you don't have a significant condensation problem. Your operation cycle description sounds like you probably should, but who knows. But an important consideration is the age of the boiler. Boilers of that vintage were built like tanks. Massive hunks of iron with really thick heat exchanger walls. They could go many years before showing overt signs of condensation damage. Today's cast iron boilers have a lot less mass. They would not fare so well in an operating situation as you describe.

On mixing/protection approaches, check out

tekmar Essays

Is the CSST (corrugated stainless steel tubing) gas line required by seismic code out there? Is it well-bonded to the grounding system of the house? Here in the east, its use is much debated and separately addressed in codes because if not properly grounded it can fail catastrophically during nearby lightning strikes.
 
  #6  
Old 08-18-10, 11:03 PM
J
Member
Thread Starter
Join Date: May 2007
Location: USA
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
First; many, many thanks to forum member Xiphias for suggesting the Tekmar essays: they are outstanding, and should be required reading for anyone interested in radiant heating. I would say that they answered 80% of the questions I had, but naturally I’m back here hoping that one of you will be able to answer the few that were not.

For example, I now understand that my old (non-condensing) boiler should operate at a minimum of 135-140F to avoid flue-gas condensation and the associated corrosion problems. I also see how separating/isolating the rest of the system and using some form of mixing control would help as well, certainly in terms of evening out the temperature fluctuations and avoiding overshoot. However, it would appear that one of the preferred methods of doing this would require three pumps: one for a boiler loop, one for the (variable speed) injection loop, and finally the traditional system circulation loop pump. Is it really necessary to have the boiler loop itself a pumped/constantly circulating loop, or does this only circulate when the boiler fires? Perhaps I should be asking “Why is this loop pumped at all”? , but I suppose it allows faster control feedback via the thermistor/boiler temp sensor. My next question is in regards to the pump/circulator for the main system loop: does this one also have to be “on” continuously (24/7, at least during the heating season). These continuous additional electrical costs could potentially wipe out any savings I might see on the heating fuel (natural gas) side, right? Also, and this is a larger concern; since I am dealing with a non-condensing boiler, having to always run it (again, during the heating season), at a minimum operating temperature of about 140F (presumably even during the generally mild daytime” standby” periods), would also seem to counter any realized gains in efficiency otherwise. Yes, I may have a boiler operating in a theoretically better manner from the standpoint of longevity, but it is 60 years old as it is, and if the energy cost savings don’t make up for the initial outlay (probably $300 for the controller, and another $200-$300 minimum in pumps and associated plumbing) it is hard to justify the cost. My goal here was to save on the ongoing energy costs, as I already have a reasonable system setup from the standpoint of comfort.

Would anyone care to comment on these points, and perhaps shed some more light on some of the questions I brought up?
 
  #7  
Old 08-19-10, 04:54 AM
T
Member
Join Date: Jul 2009
Location: Toronto
Posts: 1,043
Upvotes: 0
Received 0 Upvotes on 0 Posts
your loop pump would be controlled by the Tekmar boiler control (any above 356), or in the case of a 356 perhaps a Taco SR501 to allow the thermostat to control the pump.

The variable speed inj pump is controlled by the Tekmar mixing control.

The Boiler loop pump would be controlled by the Tekmar (if above 356) or can be controlled by the boiler controls, if any.
It can also be run in a parrallel configuration with the system loop pump.

The Tekmar control would look after the boiler TT.

That should be it.

Size your pumps right for the best use of electricity
 
  #8  
Old 08-19-10, 05:38 AM
J
Member
Join Date: Mar 2006
Location: USA
Posts: 197
Upvotes: 0
Received 0 Upvotes on 0 Posts
I'm no expert, but I'm wrestling with the same issues right now. It does seem there are three choices when using ODR:

1) Simple loop - this is cheapest from the point of pumps and plumbing, but the controller must keep the temp above 140, so your efficiency gain is limited, especially in a milder climate (the longevity of the boiler is _not_ theoretical - if you let the water remain below 140 consistently, you will spend more on replacing boilers than you will ever save by using ODR).

2) Mixed system using primary-secondary loops - more circulators and more plumbing means higher install cost, but can protect the boiler while allowing the system temp to get lower. Seems to be an especially good option with high thermal mass heat emitters like you have. I am considering this option with the Tekmar 422 controller, as I want multiple zones on a TN4 bus, but you can also use a cheaper non-TN4 controller for this.

3) Mod-con boiler - simpler plumbing than option 2 as you can safely let the water temp come way down, and this is probably the most efficient option out there. Mod-con boilers are expensive (although $15k is absurd, unless the whole system was gutted - the boiler itself should be around $2500, plus install costs), this will likely cost the most of the 3 options, but federal and possibly state/utility rebates may help with costs. Any boiler with better than 90% AFUE is eligible for the federal rebate of 30% of cost (including install, I believe), provided it's installed in 2010 (check with your tax professional to make sure you are eligible before relying on the credit). I am currently considering this option with a Tekmar 420 controller, but, again, if you forego TN4 there are cheaper controllers. For that matter, most of the mod-cons out there have built-in controllers that can provide ODR, and if you only have 1 zone this may be adequate, saving you money on the controller.

As to saving money - here in NY I estimated that any major system upgrade (options 2 or 3) would require at least 5-7 years to pay back in fuel savings. In the milder SF climate, I suspect you'll be closer to 10, so this is definitely a project with long-term benefits, not immediate payback.
 
  #9  
Old 08-19-10, 03:39 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
IMHO, throwing a 600-1000 at a 60-year old boiler in a quest for efficiency and fuel savings is totally misplaced. The total system efficiency of your system is probably abysmal. The combustion efficiency cannot be very good. Those old boilers have huge passageways and a large portion of the heat goes right up the chimney. The slab is small, holds a lot of heat, and you have a pretty light heating climate (although I'm guessing the building is not particularly well-insulated and the building envelope not particularly tight, so relative heat loss may actually be somewhat high). So the boiler cycles a lot, which is not efficient.

If you plan on being in the house a long time, then ~$1000 on upgrading the existing system makes little sense. If you plan on being in the house a short time, it makes even less sense.

For long-term occupancy, think new heat source. For short-term occupancy, do nothing. And regardless, look into what you can do to improve the building envelope by reducing heat loss with insulation and air sealing. A $1000 investment in that will pay back in short order.

But you have a real dinosaur of a boiler, so let's talk options.

Modcons are not the best solution for everything. But a small, high-mass, one-zone radiant slab in a mild climate is a very good application for a small modcon or similar heat source. The smallest you can get, based on a heat loss calculation and estimate of slab output at various water temperatures. This is not hard to do yourself using on-line resources and a book from the library (John Siegenthaler's Modern Hydronic Heating).

You could do something like the Triangle Tube 60. That could also do an indirect water heater if the water heater is properly sized and controlled.

Or go new wave and try something like the HTP Pioneer:
Pioneer Heating Appliance - Heat Transfer Products

It is entirely possible that with a small modcon you could cut your gas bill more than in half.

Also possible you could meet the load with a high-efficiency domestic water heater, so long as it's rated for use as a space heating appliance. There are a few out there.
 
  #10  
Old 08-19-10, 04:44 PM
T
Member
Join Date: Jul 2009
Location: Toronto
Posts: 1,043
Upvotes: 0
Received 0 Upvotes on 0 Posts
Been to the HTP factory and training on those boilers / hot water tanks.
Interesting product, has a ton of possibilities
 
  #11  
Old 08-22-10, 09:19 PM
J
Member
Thread Starter
Join Date: May 2007
Location: USA
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
Again, many thanks for all of the suggestions. I know that my best option for the long term (lower heating costs and best system life), would be to install a small mod-con boiler as suggested. I like the specs of the Triangle Tube 60, and its price is not outrageous. I was also impressed with the design of the HTP Pioneer, but could not easily find any pricing info to compare. However, given that my yearly total gas usage only averages between 600 and 700 Therms (about $700 to $900 per year), and even in the non-heating months my average monthly usage (mostly for the gas water heater) is 13 to 19 Therms per month, really my true annual “Household Heating” cost is only 400 to 500 Therms, or about $500 to $600 dollars. Realistically, I think I might save (at best) 35-40% by moving to a new 95% AFUE new boiler, or about $200 per year. So my payback period is easily 10+ years, probably more like 15 years. Kind of hard to justify with money tight right now.
However, I still have a few questions in regards to the option of trying out something along the lines of the Tekmar 356, if I could pick one up cheap on EBay for example. If I have this straight, the boiler loop pump and the main system circulator pump could be setup to come on simultaneously (controlled by the thermostat demand): is this right? Or, should the boiler loop pump come on every time the boiler fires? I have no problem with the mixing pump, it makes complete sense that it is variably controlled by the Tekmar 356, I’m just having a hard time “wrapping my head around” when exactly the boiler loop should be running. I also question whether I would save any fuel at all, since my boiler would presumably need to always keep water at at least 135-140, even during the normally mild daytime temperatures around here. I suppose this is not too much more than I have it set to now (125-135F). I’m not sure why so many of you seem to think my boiler must be short cycling: the way I see it, it generally needs to fire starting during the night (around 2AM, when my programmable thermostat “bumps up” the temperature) and continues to run for anywhere from an hour to maybe 3 or more hours continuously. This does not sound like a short cycle to me. At this point, the house is warm enough to “carry through” for the rest of the day, and I insure this by having the setback point of the thermostat lower the (called for) temperature a couple of degrees during the daytime hours. Other than that period, the only times my boiler fires are perhaps a couple of times a day when the differential cases it to kick on in order to maintain about 130F before shutting off again.
Still weighing my options, and still learning……..
 
  #12  
Old 08-28-10, 07:40 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
First let's question the data and assumptions, then get on to the primary/secondary.

13-19 therms/mo for what kind of DHW load? (i.e., how many people, shower fixture gpm, dishwasher, other hot water uses, etc.) That kind of use should cover 3-4 people if you have a decently performing indirect water heater or gas-fired water heater.

If you're using 400-500 therms/year to heat 1000 sq feet in SF Bay, then either or both your building envelope stinks and/or your boiler stinks. Badly. Your area has about 2500-2800 heating degree days/year. As a point of comparison, a 2000 sq ft house around these parts (5600-6000 HDD/yr) with decent weatherization and boiler will use about 750 therms/yr.

You: 1000 sf, 450 therms, 2650 HDD = 0.00017 therms/HDD/sf
Reference: 2000 sf, 750 therms and 5800 HDD = 0.000065 therms/HDD/sf

In other words, you're using 2.6 times the energy of a house that's twice as big and experiences a climate that's more than twice as cold. That's a big difference....

Cutting your fuel bill a lot more than your estimated 30-40% is very likely. But you need to first address the heat loss of the building.

For your boiler to run continuously for hours at a stretch, you have one or more of a ridiculously high heat loss, a hugely inefficient boiler, or a lot of water leaking out of your system. Any idea what happens to the boiler pressure if you turn off the feed water?

And no, continuous firing >10-15 minutes is not short cycling.

In your situation, I would not even consider adding a control and piping. Put that money into the building envelope (insulation and air sealing). It is truly the best bang for the energy saving buck.

Then, when you've got the heat loss down and the boiler really does start to short cycle and rot, then get a modcon or other small, appropriate heating appliance.

For the p/s. The boiler loop pump runs whenever the boiler is firing and in the case of the 356 whenever there is a BOIL DEMAND. If you get fancy (maybe beyond the 356, I forget), you can also tell it to circulate until some other condition (e.g., purge) is met.

The distribution system pump will run as long as the room thermostat calls for heat.
 
  #13  
Old 08-28-10, 11:31 PM
J
Member
Thread Starter
Join Date: May 2007
Location: USA
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks again to member xiphias for reviving this thread, I thought it had died a slow death due to lack of interest.

I’m glad to hear that at least my energy use for DHW is about on par with where it should be: that 13-19 Therms per (non-heating season) month is for three people (who like long showers), as well as some cooking use (stovetop and oven are also natural gas). One less thing to worry about……

Now on to some of the points you brought up regarding heating and building envelope losses: yes, I’m sure my home is not as “weather-tight” as modern construction would allow, but frankly, I’m surprised to hear it might be as bad as you say. I have made some attempts at improving the situation with more weather-stripping around doors and windows, more attic insulation, and changing out about half the windows (all of the bedroom windows) for modern double-pane glass, but the returns have been so small as to be unnoticeable on my yearly gas consumption. Obviously this has been disappointing (to say the least), so I have not made much effort to continue along those lines. I am not interested in opening up the walls to add insulation (there is currently none), and I am sure there is no insulation (nor vapor barrier) under the slab, so these are some of the limitations I am working with.

That being said, I do appreciate the comparison numbers for (heating use) Therms per year; seeing the total gas usage only 1.5 times my own for a far larger home in a far colder climate was an eye opener. Clearly, there is room for improvement.

In one of my previous posts, I mentioned that have checked for leakage in the boiler/system loop by turning off the makeup supply water, and checking for pressure loss. This has been done in the summer (with the boiler is completely off), and I could not detect any loss of pressure for several days. Should I do any other tests, or be checking for even longer periods?

So, this leaves my ancient boiler as the primary target for upgrades. As I also previously mentioned, my neighbor changed her old (identical to mine) boiler out for a newer unit for the outrageous sum of about $12-13,000 a couple of years ago. I recently had the opportunity to ask to see what unit was installed, assuming I would find something along the lines of the Triangle Tube 60, or similar, but to my surprise it was the Takagi T-KJr tankless water heater. I did some quick web shopping, and this appears to be about a $600-$700 unit, which makes her installation price even more shocking than I had previously believed. Any thoughts on using this unit (or something similar), for my application? She has never really studied the efficiency compared to her old boiler, so I am unable to learn anything useful there. If not this unit, are there any other tankless water heaters that are rated for (radiant) home heating use – from what I have seen, this appears to be a relatively rare feature among these units. As much as I would love to move up to a Lochinvar Knight or a Triangle Tube boiler, there is a huge difference in up-front costs compared to one of these Takagi units; as long as I can reasonably expect some significant gain in efficiency, that could be a worthwhile tradeoff.

Thanks for answering my questions about the Tekmar controller and P/S pumping arrangement: as you said, this is probably not an area I should be pursuing, so I’d like to focus on what I should be looking for in a boiler (or a tankless water heater functioning as radiant system boiler).
 
  #14  
Old 08-29-10, 06:16 AM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
The economics of windows as energy efficiency upgrades are poor. Windows seldom have payback. They should be replaced for other reasons (e.g., rot, desire to change in window size, style, design, etc.).

No wall insulation is likely what's making the biggest difference. In a one-story building, it might be possible to blow in cellulose or fiberglass through the top plates in the attic. It's also not a big deal to blow into walls through 2-2.5" diameter holes in each stud bay, up near the ceiling. Very simple. Patch, paint, and you'll never notice visually.

In your mild climate, lack of underslab insulation is not a huge big deal. What could really help is to add ~2" of rigid foam around the perimeter of the slab. Edge losses are huge. Simple enough to do, as well.

2.6 times, not 1.5.

Days of no boiler feed without drop in pressure is good. Assuming gauge is trustworthy. Longer periods are better. Rummage around here for posts by NJ Trooper on how to build a simple pressure gauge that can attach to a hose bib (drain) on the boiler piping.

People use all kinds of things as heat sources. Some good, some not. Some rated for it, some not. I don't remember if any of the various Takagi's are rated for space heating.

For any replacement heat source, the thing to do is figure out the heat load of the building and go from there to determine water temperatures, flow rates, temperature drop, etc. You can do a real ASHRAE Manual J heat load calculation yourself, or an energy audit firm can do one, or a heating contractor should. There is some freeware out there to do it, or something like HVAC-Calc does good calcs for a modest fee. There are also firms like comfort-calc.net that will do it via email discussion.

But first! The thing to do is reduce the heat load by weatherization. No point in sizing a heat source only to then reduce the load. Sorry to beat on this so much, but it truly is the most economic way to reduce fuel use. Weatherization is cheap, effective, and lasts forever. Think of it as fuel you buy only once. And you also improve comfort along the way.

The best $200-$300 you can spend on your house is a real energy audit using a blower door and thermal IR imagery. This will show insulation or lack of (and quality of existing installation), and identify more air leaks than you can possibly imagine.

Using those results as a guide, you can make a plan to implement weatherization measures. They come with good fed tax credits (30%). CA probably has good state incentives, too. See dsireusa.org for list of federal, state and utility incentives in your area.

If you really have no wall insulation, it is very likely that you can reduce your heat load by half or more. Now you only need a teeny tiny heat source. Maybe not even a boiler at all. Tankless heater, or water heater rated as a heat source. That will have less up front cost and less energy use over the long term.

The Takagi Jr is described here
Takagi USA - The tankless water heater pioneers. Experience "Endless Hot Water"

It's rated for space heating, but has a max output of around 140,000 BTU/hr. That probably limits the turndown. I see it's 19,500. Even that might be more than you need for most of the heating season. The reason you need to do a load calc is to make sure the flow rates and temperature drops will allow the unit to perform properly. There are issues with making sure it kicks on and stays on when it's supposed to, and fires at the lowest possible rate to meet the load.
 
  #15  
Old 08-29-10, 07:59 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 19,710
Upvotes: 0
Received 8 Upvotes on 6 Posts
Busy day here, so not much time... but wanted to jump in and point out that those very long run cycles are likely due to the thermal 'lag' of the slab heating. During the time when you are set back that slab continues to emit heat... and the home and slab cool very slowly.

Then, when it's cooled off, you kick the t'stats up, and the boiler runs for a LONG time to play catch up, before the t'stats register any change. Once you've stored all that energy in the slab, and the t'stat responds and cuts the boiler off, it's a LONG time off.

I think what I'm trying to say is that the long run times are not entirely because of a high heat loss... yes, if there's no insulation at all in the walls, that's a big factor, and of course must be addressed.
 
  #16  
Old 08-29-10, 02:13 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
True. But it's a 1000 sf slab with no under or perimeter insulation. That's heat loss. Somewhat semantic, but....
 
  #17  
Old 08-29-10, 02:47 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 19,710
Upvotes: 0
Received 8 Upvotes on 6 Posts
Absolutely... not to detract from your excellent advice, because all of it is 100%... whatever the reasons for the long cycles, you still need to insulate.

I know jsb doesn't get much in the way of snow, but to illustrate a point:

The home I growed up in was on a slab with radiant heat, built in very early 50s.

There was no perimeter insulation whatsoever. What it amounted to was a very early 'snow melt' system. There was never any snow accumulation within 2' of the house, unless we had a blizzard... and then, any snow that was piled up against the house melted within a day or two.

There was one nice advantage to this... my brother and I built a 'cold frame' against the back of the house, and we could grow herbs all year long, and start our veggies VERY early...

But, it's a good illustration of exactly how much heat you could be losing into the ground around the home.
 
  #18  
Old 08-29-10, 07:55 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 16,321
Received 39 Upvotes on 31 Posts
The economics of windows as energy efficiency upgrades are poor. Windows seldom have payback. They should be replaced for other reasons (e.g., rot, desire to change in window size, style, design, etc.).
THANK YOU! I've been preaching this fact for years. The spiel by window replacement companies that a homeowner can save gobs of money by decreasing their fuel requirements has got to be one of the biggest scams of the last thirty years. Unless you leave your windows open 24/7/365 or conquered the problems of cleaning by removing the glass it will likely take upwards of FORTY YEARS to recover the cost of window replacement.

NEVER use "energy savings" as a primary excuse to replace windows.
 
  #19  
Old 08-30-10, 03:55 AM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
Trying not to continue thread drift, but...

The Energy-Efficiency Pyramid | GreenBuildingAdvisor.com

This is a useful diagram. It does a great job showing how and where to start to reduce energy use and increase efficiency. It is particularly germane to this thread (and many others in this forum) because it shows how high up the pyramid heating systems are. There's lots of other stuff that has better economics than slapping in a new heat source. And in this particular situation, makes no sense to blow a grand on fancy piping and controls for a dinosaur boiler when that grand could be much better spent on reducing the load of the building.

And notice that windows are the penultimate brick in the pyramid....

In the linked article, I take some exception to arguments against implementing the upper parts of the pyramid, principally because the discussion of cost-effectiveness does not include federal and state tax credits, and utility rebates. It should. Around here, for example, PV is heavily subsidized and simple payback is very often <5 years. And if you sell your energy as renewable energy credits, then you can have a positive cash flow starting in the first year.
 
  #20  
Old 12-02-10, 10:20 PM
M
Member
Join Date: Dec 2010
Location: USA
Posts: 24
Upvotes: 0
Received 0 Upvotes on 0 Posts
I too live in the SF Bay area down in Sunnyvale. I replace my old boiler 9 yrs (or so) ago with a Takagi TK-2 and was happy until Thanksgiving morning. I think it should have had a condensate drain (but it didn't)...

Curious what you went with for your replacement. I've had a couple of different quotes so far and I'm going to be much more involved in what to pick this time.

Mark
 
  #21  
Old 12-02-10, 10:46 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 15,993
Received 85 Upvotes on 77 Posts
I would think that boiler illegal with a well type gas valve. 40,000 btu gas valve for 100,000 btu burners? Carboned up? CO2 issues? I cant believe your all talking about modifying this boiler.

SAFTEY GET RID OF THE THING ITS DANGEROUS. ITS RIGGED AND NOT REALLY FUNNY.

Mike NJ
 
  #22  
Old 12-03-10, 04:06 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 19,710
Upvotes: 0
Received 8 Upvotes on 6 Posts
I think most of us were trying back in August to discourage the poster... but your safety concerns are actually quite well-founded, and we probably should have done more to point out that the gas valve isn't appropriate and probably dangerous to some extent...

But, that is an old post... hopefully the poster has changed his mind.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: