Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Plumbing => Topic started by: kayakerski on November 01, 2013, 05:35:42 AM
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Good morning everyone. Yesterday I bought 2 Honeywell GT162 temp guages that I want to install soon. They are 1/2" NPT thread and the probe (for lack of a better term) is 2.5". I plan on installing them into 3/4" black iron T fittings.
Does it matter how far the probe protrudes into the 3/4" line? I don't want to restrict flow.
Thanks,
Gregg
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You should get long neck tees that are specifically desgned for temp probes, they keep the probe in the well without restricting flow and with only 3/4 inch lines you don't want to restrict flow.
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Thanks!
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Were you able to find the long neck tees
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No but between the T and a reducer I was able to make it work.
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Well, did it help.
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Well I'm glad I have them installed but I'm still not happy with my system. Last night the boiler ran for about 25 minutes and the return temp gauge got down to 110f. It seems like this happens once or twice a day. Other than that my delta t is about 20-30f (I hope that term means the change in temp between supply and return). I don't know if there is any way to fix those low return temps. It seems like it happens when the boiler has been dormant for awhile and there is a call for heat and my oil boiler fills with cool radiator water. I know I did alot better last year when daytime temps were below about 20f.
I guess I really need to get that aquastat in order to keep my boiler from coming on. On an additional note, I was reading up on the Honeywell 6006c-1018 aquastat and the say a minimum pipe dia of 1" is needed for accurate temp reading on a strap on aquastat. I only have 3/4". I would think it will still be ok for what I'm trying to do? I will just have to adjust it up or down a little in order to have it turn the oil burner on when owb supply line temps get down to 160. Hopefully it's just that and the smaller pipe does not make irratic readings.
Has anyone ever used a strap on aqustat on 3/4" iron?
Gregg
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The 3/4 inch iron is more than likely a big part of the problem if it is what you are running int othe oil boiler, think about it your heat zones are as well 3/4 inch, when they call for heat, they are dumping as much cool water back into the oil boiler as is coming from the wood boiler especially if your heat zones have cast iron rads and have been sitting dormant most of the day and are at ambiant temps, some of those rads will hold 30 or 40 gallons of water.
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Hmm, I see. Actually my supply lines going from my oil boiler to the radiators are acually much larger than 3/4". I think 1.25-1.5" copper going out of the boiler but there are several 2" iron lines running around in my basement. The lines going to the radiators seem to be 3/4" though. Thats alot of water! 5 cast iron radiators and 3-4 baseboard units that dont seem to work well (I probably should try to fix them but we run a wood stove in that area anyway so I really dont want to run them). Thats all on the first floor. Upstairs there are 4 more cast iron radiators.
There is probably alot more going on here than I'll be able to fix without redoing EVERYTHING. I'm still saving alot of money now so I guess I can live with the issues I have as long as I'm not hurting anything.
Gregg
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Yes that is a lot of water, you will need to either limit the return temps to the boiler with a mixing valve or severely increase water flow from the wood boiler, maybe both.
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Ah, more to ponder slim.
I'll look into both of those options and have more questions I'm sure.
The pumps you suggested (bumblebee or alpha) seem like cost effective options for increasing flow. I wonder how much that will help though since it seems like when there is a call for heat, ALOT more water comes back to the oil boiler than the 5-10 gallons it probable holds. I assume that's where a mixing valve comes in?
Gregg
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Yes, exactly, there is a lot of cold water up there in those rads, you may need to limit the amount of it coming back at one time with a mixing valve.
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Ok, I think I understand the theory behind the mixing valve because I have a thermostatic mixing valve installed in my owb supply line as per central boiler.
I believe that one makes it so owb supply water less than 150f goes back to the owb for reheating in order to protect the boiler from low return temps. Is that also mixing supply water with my return water from the oil boiler that is below 150f? If so then that low temp return water that I'm worried about should be ok, right?
Anyway, where would i install a mixing valve? In the return line to my oil boiler I assume. If thats the case, where would it send water that is below the set temp?
Gregg
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Is your boiler able to maintain temperature or is it dropping low there too?
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Good question RSI that will certainly show the 3/4 inch is not large enough volume to work the wood boiler to it's capacity
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Oil boiler maintains 160 even when return is at 120
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Which boiler RSI? The owb seems to maintain. Even when the return is at 120 the owb is at 170-185.
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That shows you that you are not moving enough water through the 3/4 inch black iron, your stove can make the heat but your piping can't deliver it.
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Ah well the 1" pex definitely has to stay. Not much I can do about that unfortunately.
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Do you think the 3/4 inch black iron is the issue or is it the pex too? The only reason I'm asking is because I thought I just read somewhere that 1" pex holds a lot less water per foot than 1" black iron. It seems like 3/4" iron would hold a similar amount of water as 1" pex. Whether it flows as well is another story I guess. I'm sure the brass pex barbed couplers limit things as well.
I'm not questioning you so much as trying satisfy my own curiosity. Reqardless, its obvious that the flow is limited I guess.
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The reduced flow all the way around is limiting the flow but take a look at the end of a pieceof 3/4 inch black iron and a piece of 1 inch pex, I would start with either a high head circ or change out the 3/4 inch black iron.
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i think 3/4 black iron would hold about 2.3 gallons per 100 feet and 1 inch pex would hold about 3.03 gallons per 100 feet
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Thank you, where did you get that info.
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Unless you have a lot of 90s in the black iron it shouldn't be much worse than 1" pex. It is usually over 3/4" inside and 1" pex is only 7/8"
It sounds like it is just the large volume of cold water that is the problem. Is there any way you can modify the return pipes from the radiators? If you can do that, putting a zone valve in it with a small bypass around the zone valve would keep it from dumping all the cold water in so fast. A strap on aquastat could be used to open the zone valve once the returns are hot.
Another option that would probably be kind of complicated would be to get some type of a pulse controller so the pumps just run for a few seconds on and off till the cold water is all flushed into the system.
Probably the easiest is if you have an unused supply port on the boiler, run a pipe from it to the existing return port and put a tee onto it for the existing return and another pump (probably taco 007). Then put a strap on aquastat on the return pipe that turns on the new pump and have it come on whenever the return water is under 150 or 160. If you use large enough pipe you can easily get 2-3 times the GPM that is returning from the house. So if you are getting 6gpm from the house at 110° and 12 gpm from the new loop at 180° you will have return into the boiler about 155° to 160°.
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i just googled each type of pipe so i am reposting it
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Thanks Willie. I'll have to look at the printout I have at work. I could have sworn that 1" apex was a liitle over 3 gal per 100' and 1" iron was well over 4. Maybe I miss read.
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I forgot to mention in the last post that I just pulled the GPM numbers out of the air. If you are currently way under 6gpm you may be able to correct the low return by getting rid of some restriction but if you are currently close to the 6GPM you will need around 18-20 GPM and you will never get that.
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you are likley right i quoted a little over three for 1 inch pex and the black iron was only for 3/4 1 inch black iron would be 4.1
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How much 3/4" iron pipe is there in the system and is it sch 40 or 80?
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How much 3/4" iron pipe is there in the system and is it sch 40 or 80?
you think they would use expensive schedule 80 in a house boiler application (low pressure)
but on that same note (restriction) i would almost bet if they are old cast iron rads that the pipes (and/or) the rads have a lot of scale in them and might be reduced a whole dang bunch?
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Unless you have a lot of 90s in the black iron it shouldn't be much worse than 1" pex. It is usually over 3/4" inside and 1" pex is only 7/8"
It sounds like it is just the large volume of cold water that is the problem. Is there any way you can modify the return pipes from the radiators? If you can do that, putting a zone valve in it with a small bypass around the zone valve would keep it from dumping all the cold water in so fast. A strap on aquastat could be used to open the zone valve once the returns are hot.
Another option that would probably be kind of complicated would be to get some type of a pulse controller so the pumps just run for a few seconds on and off till the cold water is all flushed into the system.
Probably the easiest is if you have an unused supply port on the boiler, run a pipe from it to the existing return port and put a tee onto it for the existing return and another pump (probably taco 007). Then put a strap on aquastat on the return pipe that turns on the new pump and have it come on whenever the return water is under 150 or 160. If you use large enough pipe you can easily get 2-3 times the GPM that is returning from the house. So if you are getting 6gpm from the house at 110° and 12 gpm from the new loop at 180° you will have return into the boiler about 155° to 160°.
Wow! I have alot to think about here. This is all starting to get frustating. I guess I should look at increasing flow in other ways first?
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How much 3/4" iron pipe is there in the system and is it sch 40 or 80?
The iron pipe from the owb to oil boiler is schedule 40 and there isnt much of it. Mainly a few fitting to get in an out of the owb and a few more to get into the oil boiler(I do have a 12" & 4" nipple on the supply though.
Also, the ports where the supply and returns enter both boilers are 3/4", if that matters. The owb has some unused 1-1/4" ports on it but the only other ports on the oil boiler are the 1-1/2" supply and return ports that feed the radiators.
Gregg
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How much 3/4" iron pipe is there in the system and is it sch 40 or 80?
you think they would use expensive schedule 80 in a house boiler application (low pressure)
but on that same note (restriction) i would almost bet if they are old cast iron rads that the pipes (and/or) the rads have a lot of scale in them and might be reduced a whole dang bunch?
Some of my radiator supply lines may even be 1/2" but I'll need to check again.
How do you tell if pipe is schedule 80? Are the fittings thicker?
Gregg
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My untrained mind thinks its the large amount of cold water dumping at once that causes the problems, but then again increased hot water supply should help clear it faster.
As I've said before, when its real cold out everything runs great and the oil burner doesn't come on for days. I guess that's because the water doesn't get time to cool in the radiators.
Gregg
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Yes that is what I would expect, again the oil burner can be controlled by the strap on aquastat that I suggested.
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Yes that is what I would expect, again the oil burner can be controlled by the strap on aquastat that I suggested.
Yup, thanks slim. That project is in the works in the next few weeks.
Gregg