Couple of quesitons on a gravity hot water system

Northbear

First, I have been reading many of the posts here and want to thank you all for sharing your knowledge!



 Before my questions, a brief explanation of my heating system.  It is a gravity hot water system from sometime in the 1920's, with the larger pipes and cast iron radiators that come with it.  The boiler is the original coal boiler which was converted to a natural gas burner sometime long ago (1950's or 60's?).<span>*</span>  The system is basically untouched with exception to the burner conversion.<span>**</span>  I am sure it is not particularly efficient, but the worst gas bill in the winter is about $300 here in Minnesota so it could be worse. Anyways, two questions:



<strong><span style="font-size:16pt"> 1) Thermostat / Comfort issues</span></strong>

My wife would mention she was cold even when the thermostat said it was at temp (67-68 deg F.).  I ended up moving a digital thermometer around the house and yes the thermostat was sometimes higher then the thermometer by up to 4 deg.  I then came to the realization (after 10 years there!) that the thermostat was on a wall behind which  was the chimney!  Probably not a good idea! I have now temporally moved the thermostat to a different location and it seems to work better (more even heating, temp on thermostat still a bit higher (maybe 1 deg), but more stable).  But this new location is not very good from a aesthetic standpoint.  <strong>



So:  Is there a good thermostat for a gravity hot water system with a remote sensor so I can put the thermostat back on the original wall but have it set the temperature from a remote location?  Or are they going to cost an arm and a leg and I should just move the thermostat to the better location and hope to get used to the ugliness?<span>***  </span></strong>





<strong> <span style="font-size:16pt">2) TRV vs  Standard Valves</span></strong>

I found this winter that one of my radiator valves is stuck shut.  The knob turns but does not actually open or close the valve.  Same situation on a different radiator except it is stuck open (been that way for years).  I am looking at replacing these

and potentially the rest of the valves (total of 8 more) next summer.  I am not currently planning on upgrading the boiler<span>**** </span>, but was wondering: <strong>



Would be better  to just replace the valves or replace standard vales or with TRV's?</strong>



I am thinking of just replacing them all with regular valves because 1)  it doesn't seem like TRV's are really recommended for gravity systems and 2) availability of the 1-1/2" (or 2'?) TRV fittings I would need for the larger radiators. 



<span style="font-size:16pt"><strong>3) Simple upgrades?</strong></span>

Any simple things I should do to increase efficiency /  longevity?  Install a makeup air intake (OK maybe that isn't so simple), cleaning anything, or any maintenance  I should be doing on the boiler? I mostly ignore it unless there is a problem (ie expansion tank getting waterlogged)



Sorry for the long post. Any advice would be greatly appreciated!



Thanks!





<span>

asides:

</span><span><strong>*</strong>I always thinks it is entertaining to open the door to the boiler and see the fireball this burner produces.  No small, nicely burning blue flames for this boiler!</span><span>

</span><span><strong>** </strong>OK not completely true as I slightly moved one radiator due to a remodel project and a second radiator I added back in (it had been removed but they kept the radiator in the Garage! Yeah!).  Both of these were completed with no issues.</span><span>

</span><span><strong>***</strong> Just FYI, my older LUX digital thermostat (LX8000?) can be programmed for 7 day a week with 4  different temp settings each day, but we currently have it set to the same settings everyday and only set it back a couple degrees at night for comfort for sleeping.  Also it is set with a </span><span>a "Swing" setting of 1 which equals +/- .25 deg for those who care.</span><span>

</span><span><strong>****</strong> Not that I wouldn't want to, but 1) it still works fine 2) when I purchased the home the inspector told me that a boiler designed for coal and now burning natural would basically last "forever"  3) I like the simplicity of the system 4)  have not done a complete analysis of this but based on initial looking at things the payback period would be many, many, years.  </span>

nicholas bonham-carter

things to do

the most effective thing to do would be to buy a copy of the book on old systems here at the shop. it deals specifically with your sort of system.

as far as thermostats go, the honeywell visionpro would be a good choice as it can be used with a wired remote sensor. even more convenient would be the prestige which has wireless sensors.

of course the boiler will last a long time, but is probably not as efficient at getting the btu's where you need them, because it is unpumped, and needs a higher loop temperature to get the thermosyphon moving. a pumped system could be equipped with an outdoor reset to vary the loop temperature to suit the heating load. --nbc

Jamie Hall

Takes some thought...

but I think that I'd be very wary of using TRVs on a gravity system.  Not because they wouldn't work, but because the response time would be very slow indeed (takes time to get that circulation going) -- and then they would overshoot because of the mass of those lovely big radiators.



nbc's suggestion of a wireless thermostat would fix that aesthetic problem, and the Prestige can be programmed for hot water gravity.



And you've got the setback nailed -- same thing as steam; takes a long time to get warm, and a long time to cool down, so big setbacks are a pain.



Of course you can convert it and get more efficiency.  But -- would you save enough to pay off the conversion?  I have me doubts...

Northbear

Thanks for the reply

Thanks for the replies!



nicholas bonham-carter - Do you have a specific book you would recommend reading?



Jamie Hall - Thanks for your thoughts on the TRV's and a conversion.  Sounds like my thoughts were similar to yours which is good to hear from someone with more experience then myself!



I looked at my thermostat again and it is the LX9000.  I did a bit more testing last night with a very accurate thermometer and did determine that the thermostat was reading 1 deg too high.  Fortunately, I am able to calibrate the thermostat and did so this morning, so it should now read the correct temperature. 



http://www.luxproducts.com/support/TX9000a_ENG_Manual.pdf



The thermostats you mention seem fairly expensive with no other advantages from my current setup (that I can see) other then remote sensor and so I will probably see if I can get used to new thermostat location and make it permanent.  



Thanks again and any other advice is welcome!

LarryC

Why did nobody suggest a combustion analysis?

As a homeowner and an avid reader of the Wall, I am suprised that nobody has suggested getting a qualified burner technician in there to perform an annual inspection, cleaning, and combustion check.



I assume that the furnace has a relatively low efficiency and is loosing alot of its heat up the chimney.  Would this type of furnace benefit with the addition of some sort of baffles to increase the amount of heat transfered to the water?  How about installing a liner in the chimney to allow downfiring the gas burner (if that is possible).



I assume an ODR is not economically feasible because the gravity system automatically does that by its nature and the gas bill is already pretty low.

Northbear

Thanks again!

Just a quick note of thanks again for the responses and one more follow up question



How would I go about finding a "qualified burner technician".  Would this be the gas company or maybe someone else?  I am in the Minneapolis /  St Paul area and so if anyone has a specific recommendation (if that is allowed on this forum) that would be great!



Thanks again!

furnacefigher15

You may have to call around

And ask specifically about combustion analysis, using a digital combustion analyzer, or if they are old fashioned, an Orsat gauge.



Preferably the digital analyzer. Anyone that does combustion testing on a regular basis will have a digital combustion analyzer.



If the company acts weird, or is vague about there procedure, call someone else.



Also this is not a 5 minute job. The Tech should be there on a boiler that has been untouched since the 50's for at least 2 to 4 hours if not 1 full day or more.

Mike Kusiak_2

Finding someone qualified

It may be difficult to find someone familiar with a 1950's gas conversion burner. Most current techs probably weren't even born yet when that burner was installed.



My advice would be to find the brand and model number of the burner and post it in the "gas heating" section of the Wall. Tim McElwain is the master of all things gas, and has many years experience with older conversion burners. He may be able to find data and instructions for your burner, which could be very helpful to a qualified tech otherwise unfamiliar with your unit.

icesailor

Improving Comfort:

Without some considering me an asshat, I would consider this. Because I have done this and was extremely surprised at how well it worked. Or at least a variation of what you have.

Your gravity system when designed and installed, depended on coal as a solid fuel to heat the water. If you haven't had a circulator installed to pump the system, it depends on the flow of warm water to heat the structure. The thermostat is only to turn the burner on. The high limit shuts it off. The heat loss to the outside controls the system temperature. What you really need is to pump the system with outdoor reset. That way, all the radiators will get to the same temperature. Regardless where they are and how well they flow. Your wife will be more comfortable because it eliminates the hot spots from hot radiators.

If its already pumped, put a 4 way mixer like a Taco I series valve with outdoor reset. You can keep the boiler hotter or whatever and the system at whatever temperature the controller decides. It really makes a comfortable house.

bob eck

gas boiler

i have a old system like yours but there was a oil fired cast iron Weil Mclain boiler in with one circulator. I took that boiler out two years ago and went with a Triangle Tube (www.triangletube.com) PE110 condensing gas boiler. oil vs nat gas I am saving about $1500+ per year on my heat and domestic hot water costs. when going from old gas boiler to condensing boiler you should be able to lower your energy costs but not as much as going from oil to nat gas. I would put new radiator valves on and install a condensing gas boiler that works off a outdoor reset control. you could look at taking out the large pipes and use a radiant manifold and run 1/2" viega fostapex pipe direct to each radiator. the radiators close to the thermostat you can reduce the flow so when there is a call for heat the system would run just a little longer and all other radiators should be nice and warm. If installing a radiant manifold and running 1/2" direct to each radiator you could get rid of all radiator valves and balance each radiator at the manifold.

Northbear

responces...

furnacefigher15 and Mike Kusiak,



Thanks for the advice on the combustion analyzer.  I will take a look a the model number on the side and see if I can dig up more information.  Also, could you explain what the Tech would be doing for several hours?  I don't know much (anything) about a combustion analysis, but the burner is fairly simple and I just don't see that there is that many parts to adjust that it would take that long. 





icesailor

Thanks for the suggestion.  Looks similar to the Q and A at

http://www.heatinghelp.com/article/332/Gravity-Hot-Water-Heating/72/Gravity-Hot-Water-Heating-FAQ



Q: How about if I just install a circulator on that old boiler and forget about the flow-control valve?

A: This will help lower the fuel bills by moving the hot water to the

radiators more quickly, while not stopping the residual heat from moving

into the radiators. You'll have to fiddle with the thermostat's heat

anticipator, though, to keep the system from overriding. Also, you may

need more than one circulator if there's more than one set of supply and

return lines.



Bob eck,

I like the idea of a full boiler conversion but I would be afraid my payback period would be many, many years.  I should really have a firm quote but based on my gas bills even if I cut the bills in half it would be a while.

furnacefigher15

Most of the time

will be taken, just to clean the boiler. If the boiler is cast iron, then the castings may need to be cleaned of the fire side. The fire box itself will also need a cleaning, and that may involve burner removal. If the boiler has hand holes, or clean out caps to get access to the water side, it would be good to wash out the inside of the boiler.



The combustion testing itself on a single stage burner is generally not too tricky. As part of the combustion testing, a draft test should be done, and if draft in the boiler is excessive, then the addition of draft controls may aid in significant reduction of heat wasted to the chimney.



Also the gas meter should be clocked to be sure the burner is firing the right amount of fuel.



A combustion test requires the sampling of the flue gasses before any dilution air. The device is similar to what the EPA uses on older cars at emmisions testing centers.



I would not recommend adding a pump to the existing boiler. The boiler was not intended to have that kind of flow.



However, something to keep in mind for the future, if you do replace the boiler, and add a pump. If you have a multi story home, there may be restrictor plates in one of the radiator valves on each of the upper floor radiators, which will require removal in a pumped system.