Boiler protection strategy for gas fired boiler

Turse22

Hello,
I had a boiler installed last fall by a plumber that I was happy with. It is a Burnham esc gas fired boiler. It is feeding old gravity cast iron radiators. After install I noticed that it takes forever (over 20 minutes)to reach 130 degree return temp, sometimes the call for heat ends before it reaches it. I am
concerned. The plumber did primary secondary which heats very even. He said it will be fine and this protects boiler but I disagree. Should I be concerned for flue gas condensation ruining new boiler? Everything I read here says yes.
I am thinking about adding an ESBE 140 degree
valve to bring boiler temp up. I attached the spot I think it needs to be. Any opinions would be great .

hot_rod

looks like a primary secondary, perhaps a tekmar control for the boiler pump would be easier.
http://www.tekmarcontrols.com/solutions/browsesolutions/radiant/33-support/glossary/89-boiler-protection.html

Turse22

Thanks for the comment. The link you attached is kinda vague. It shows use of a mixing device. Which is what the esbe valve is. Can you be a little more specific ? How does boiler loop pump get controlled? Or specific tekmar device i should consider?

JohnNY

Yeah, you've got full flow out to the system in that setup. Do like @hot_rod said...or something. I'd like to see a 4-way mixing valve there.

Turse22

So you agree its not right. Thanks. I know it may be asking alot but If anyone can advise a pipe arrangement diagram with part model numbers it would help me tremendously.

Zman

I don't think the tekmar can prevent condensation without a mixing valve or injection mixing.
I like the original plan with the ESBE it will work and is super simple.

clammy

Install the esbe valve and be done original installer should have installed it in my eye from the get go no if and or but’s ,on another note your tees are from the looks of it to far apart and there should have been at least 10 pipe diameters of straight pipe before and after your p/s tees.mkae sure you install a throttling valve on the by pass and be sure to use the proper valve ( globe valve ) ball and gate valves are not what should be used to throttle flow old school .i find it funny that so many believe that no by pass or return protection is requires when ps a gravity conversions until there Utilities increase and call for service and are told they need a new boiler due to prolonged low temp corrosion . Some can’t even follow a simple drawing very sad or just plan lazy and don’t care or chalk it up no experience extremely sad to say the least .i just looked at one that was piped wrong on return protection and now looks like a rust bucket and a budget oil for the year close to 5 grand ,I just shake my head and say why didn’t u let me straighten it out 10 years ago I told u so but oil co says it great running like a top .put in the thermic valve be sure to find a new installer service provider ,if they didn’t get that right what else did they screw up? I hope they flushed your system well and I’m not surprised they did not install any y strainer or dirt separator which would have been wise .Peace and good luck clammy

mikeg2015

Take temperature reading on the boiler in & out and secondary in & out. I’ll bet it’s just overpumped on the boiler side or both sides. Probably sized correctly (shocker) but again, overpumped so delta T is low and supply temp in mild weather never gets above 130.

Did he install 3 speed pumps? Or single speed pumps? We always put in 3 speed pumps for that reason on ALL boiler installs.

In mild weather delta T on secondary will be around 6-8F. When Boiler water is up to 180F, 20F. Pump should be adjusted to match this for best economy.

hot_rod

Basically with some high mass, high volume systems you need a way to "thermally" disconnect the load from the boiler.

The only true, and appropriate way to accomplish that is have a valve or device respond to a temperature reading at the boiler return. Bypass piping, bypass pumping, flow balance alone cannot always accomplish that, it MUST have a temperature sensing ability and response mechanism.

A super simple way that Viessmann used on cast boilers was an aqua stat the turned off the boiler circulator when it sensed low return. They actually had a triple well with operating, high limit and return sensors all in one place. Effective, but it was a bang/ bang control, potentially a lot of off on cycles of that circulator. That would be a simple add on, a strap on aqua stat controlling the boiler circulator.

The best way I feel it to be able to gradually adjust the flow, like slipping the clutch in your truck when starting with a heavy load

Thermostatic valves are ideal, simple, non electric devices. they cost a small amount of pumping power, would not be an issue in your system.

4 way valves can work but they need to be motorized and responding to that return temperature again.

Pulse a zone valve is another bang/ bang option.

All things considered the return temperature specific high Cv valves are my suggestion.

At Caleffi we build a valve or pump valve specifically for return protection, which sell by the thousands in Europe where pellet and wood fired boilers are very common in rural areas.

If you feel you need the return protection, maybe chose the method based on the cost and amount of piping change required.

Turse22

Finally got around to adding The 140 degree Esbe valve In the red spot in above picture . Boiler loop now runs at steady 140 to 160 and gets there rather quickly. Did not adversely affect heat to cast iron radiators at all. Thanks for the advice. Next is to fix the air scoop and bleed I believe located on wrong side of circulator. He placed it on the output side of pump In the secondary loop. I believe that is why I never quite get all of the air out . I think it should be on suction side. Agree?

SuperTech

Yes, the circulator should be pumping away from the expansion tank and air separator. 

Solid_Fuel_Man

When you pump away from the ex tank, and have air elimination at the hottest point...air literally jumps out the vent! 

Mr. Boyle knew what he saw,  and pumping away is taking advantage of his law. Thermodynamic law always wins!

motoguy128

I’ve seen 49 year old cast iron atmospheric boilers that are 49 years old connected to gravity hot water systems that probably spend 1/3 of their livers under 140F. I’ve never heard or seen condensation in those boilers. I think the high approach temp of the heat exchanger prevents it.

When these boilers are only 3/4 full of water operating as a steam boiler, they are 82% efficient with 210F return water. With hot water trim, full, they are 83% at 180F and 160F return water. I’m doubting that they get above 87%, with all the excess secondary air and condense with water Temps even at 70F.

Making observation in my own home, my stack temps don’t appear dramatically lower when making DHW in the summer with 150F out 130F return with boiler overfilled, vs. steaming at normal water level. Biggest difference is standby losses with lower water temps.

Solid_Fuel_Man

Honestly, I cannot fathom why anyone with gas would mess with all the return protection etc, just get a condensing boiler. Low return temps are then your friend, and you save gas too! 

The Steam Whisperer

I'm with motoguy on this one. I used to use return temperature protection until I tried bypass piping. With the typical cast iron boiler you will be slowing the water flow into the boiler allowing it to mix with hotter water in the boiler, increasing the temperature of the castings near the return connection. In addition, and this is the concept used for the condensing cast iron boilers, is that once the boiler shuts off, the castings heat soak, and dry off any condensation that has taken place near the return. It's really important that the pump be shut off at the end of the heat cycle, otherwise this heat soak doesn't occur and he will get alot of corrosion. It's interesting to check on the older boilers with cast iron atmospheric burners that typically run at 20 to 30% excess air and they don't have problems with condensation, yet everyone is up in arms if you don't put return protection on new boilers that usually run 50% excess air on the atmospheric lanced steel burners.