Boiler bypass???

Lawrosa

OK so I have an old Hydrotherm HC 85. I have two zones with zone valves. 68ft element on one zone and 20 ft on the other. Next yr I am going to take 8 ft I added off the first zone and put it on the second zone. This is a length of baseboard I have heating my crawl. I am also going to add an additional 8 ft in the crawl on the second zone.

So after it should be 60ft first floor zone, and 36ft 2nd floor zone. ( 16ft of the second floor zone being in the crawl at each end. This heats the floors nicely and reduces the 1st floor t stat cycles.)

OK so after I do that mod I was reading about a boiler bypass whick I dont have.The boiler is a 180F running on and off. Although its 26yrs old and works fine I probably should not touch it right? I am not that concerned with fuel savings because my whole gas bill for the yr is about $1000 bucks. Boiler, HWH, stove, Dryer. I am more concerned now with temp comfort levels. Usually its hot in the home after t stat kicks off then cold waiting for the t stat to kick on.

Also I notice the temp gauge when the cold slugs from a zone opening hit the boiler. It takes three or 4 passes of the water in the loop to stablize and start raising the temp in the boiler. So if the boiler was at 160F and the upstairs zone opened that cold slug will drop the boiler to say 120F. Then up and down two or three times as the water passes and temp rises back up. Now mind you I am oversized for my heat loss so the boiler heats fairly quickly.

Heat loss is 35,000 btu. Boiler HC 85 hydrotherm.

So I was tinkering with piping a boiler bypass. This will also set me up for my next cast iron boiler if this one goes down the road that will only hold say 1.5 gal of water. I believe this current boiler holds about 4-5 gallons but cant be sure. I have not done the calculation but I believe all my baseboard holds as much or more then what the boiler holds. And if and when I get a new boiler the ratio will be different and hence I believe a boiler bypass would be needed anyway.

So I am looking for info on the benefits. Where to put all the temp gauges, and how to tune it. There is not really any info except for diagrams how to pipe. Am I off here on my thinking? I was looking at also a way to do an outdoor reset but I dont want to spend money on controls and such. I read a boiler bypass is the pooor mans ODR. And I am poor...LOL

So Is there any literature out there and specifics for modifying an older boiler for savings and comfort. I also was thinking with the boiler bypass to lower the aquastat to 160F for fuel saving? Would I need to adjust the bypass configuartion as the temps change? I understand as far as I know you leave the valve open on the bypass at all times and restrict the flow through the boiler. How to adjust the temps and where to put the gauges.



Ok sorry to ramble. I guess you get the idea of my thinking. I know someone will say $1000 a year gas bill, and 26 yrs old boiler..".Leave well enough alone."

Funny as a kid I had a poster that said that " Leave well enough alone" and showed a bulldozer getting ready to plow over two pointed rocks in the ground. Those two pointed rocks were the ears of a giant monster under the ground as the poster portrayed.

Thanks

Mike NJ

nicholas bonham-carter

boiler books

for excellent boiler books go to the shop here.--nbc

Tim McElwain

You really do not

want to lower the operating temperature to that boiler to 160 degrees. With a temperature differential of 20 degrees that would give you a return temp of 140 degrees which is the beginning of the condensing mode. That being a cast iron boiler it would not handle that very well.



I am answering this quickly and should probably re read your posting which rambles a little bit.

Lawrosa

I know I ramble!!!...LOL

OK so basically I am asking how can I pipe this boiler for  more comfortable temps in the home and or some fuel savings?



I want to use the one circ and not add any due to electric usage.

I want better constant temps in the home instead of the swings I get. Constant circulation? Remember though two zone valves.

A boiler bypass seemed like my best option but I want to read more about them and how well they work but cant find much info except for piping diagrams.

Mike

Mike Kusiak_2

Boiler maintaining temperature?

Why are you maintaining a constant 180F in the boiler when you are not also using it for domestic hot water?  You would gain a lot of efficiency and comfort by running it as a cold start system. This means that instead of constantly maintaining a 180F water temperature, the boiler fires and the circulator runs only when there is a call for heat from one of the zones. Since you don't keep the system constantly at 180 F there is less standby loss, and in warmer weather, cooler water will circulate through the radiation, reducing the tendency to overheat. Cold start operation is really a sort of

"poor mans reset" and can work surprisingly well if set up properly.



I don't see what the bypass will get you in your case. Bypasses are typically used with high mass systems with huge cast iron radiators, to prevent the return of too low temperature water to the boiler. Your baseboards are low mass and should not present a low return temp problem. It will certainly not gain you any efficiency.



What type of thermostat do you have and was it set up correctly as to anticipation or cycles per hour. You may be able to reduce the overshoot  and wide swings in room temperature by adjusting it.

Lawrosa

Cold start it is.

"it as a cold start system"



It is cold start. Sorry my post is confusing.



"anticipation or cycles per hour. "

Dont have none of that.

I have a regular t stat programable to change temps but never use the program function. Set for 67 most the time and at night and 71 or so when the wife comes home.



Mike NJ

furnacefigher15

Cycles per hour or differential

That digital thermostat has one or the other.



What temperatures does the thermostat turn on and off at?

Paul48

Cast Iron?

I'd do some research on mod/con boilers for your next boiler. For comfort and efficiency you won't find a better solution.

Lawrosa

Differential..

Oh I have that set at 1 degree which is the lowest it goes. It goes 1-9. Unless I am not using it right.



Mike

Lawrosa

Mod con?

I'd do some research on mod/con boilers for your next boiler. For comfort and efficiency you won't find a better solution.



Not worth the money and will actually cost more to run.



If I replace it will be the smallest weil mclain GGA 25 @ 37000 btu. Standing pilot, A draft. Less crude to go wrong, and will save me much more money.



Mike

Gordy

Mod/Con cost more to run??

Huh? How do you figure that. Do you know how a Modulating condensing boiler works.  You will save 30% for starters replacing that 25 year old Behemoth. Yes they do cost more,

furnacefigher15

you are using right.

A 1 degree differential is about right. But If you feel cold, you may want to turn up the t-stat.



Could be out of calibration meaning actual temp is 68 but says 69. Some thermostats have a display offset feature to correct that when that happens.