I figured I'd start a new thread for this.
I have a Burnham boiler, Model # XG2000, Ser. # 01004737. After repiping some of the venturi piping to the BB, (yes, the mono-flow tees are correctly installed) I refilled the system, started the boiler, and went around bleeding the BB, but I could never get enough hot water to circulate thru the whole system. The boiler is equipped with a Taco Thermostatic Bypass Valve. Quoted from the Owners Manual: "....provides a mechanical operating type temperature thermostat that will permit flow thru a by-pass around the boiler while preventing return water from circulating thru boiler until thermostat senses a temperature of 160 degrees F. This minimizes condensation within the boiler flues. The thermostat reduces flow thru the by-pass as the temperature of the water leaving the boiler increases above 160 degrees F and is fully open at 180 degrees F. Thus, system supply water temperature modulates with heating load demand."
Here's a couple of pics: http://www.flickr.com/photos/steve22l/

I can't seem to get hot water to all the baseboards. I've bled the system several times, for more than several minutes per baseboard. I can get very hot water for a short time and then lukewarm water after. All the time, the thermostat is calling for heat.
I suspect the by-pass valve is the culprit.
Anyone ever have a similiar problem with a by-pass valve? Or maybe some ideas on how to replace the by-pass with something else? Burnham says it is no longer available. i wonder if the thermostatic element inside the valve is available?

 

You can't have the bypass closed or you will never have full flow through the monoflow loop. That will make baseboards heat unevenly. Open the bypass and let the boiler come up to temperature and see if that corrects the problem. It is better for the water to flow fast enough that the whole loop gets the same approximate water temperature.

Ken

 

I've had it open and also closed.....same results. Also had it halfway closed/open......same same

 

Did you also purge the main loop? If so, you have done everyhting that you should have. Once you get water at a bleeder, don't bother taking out any more. The air will either be there or it won't. It just prolongs the job when you take out water. All you really want is air. You could remove the element altogether from the mixer and preset the bypass valve to recirc some water. Just be careful you don't set it too far closed or you will get the condensation inside the boiler on a cold start and that is what you don't want.

Ken

 

the boiler is 20 yrs. old...... or more. Do you think condensation on a cast iron boiler is all that bad?

Yes, I did purge the main loop, starting at the BB closest to the boiler, and working my way around.

I really wish I could remove the by-pass valve, re-pipe it with black pipe and set an aquastat somehow in it.

Any other thoughts are much appreciated, Ken.

Thanks

 

Condensation will drip on the burners and create havoc with anything it gets wet. If you took out the element inside the mixer, it just becomes a tee and then the valve that is closed in your pictures will be your adjustment. When it is full open most of the returning water will bypass the boiler and when it is closed, all water will go through the boiler.

What I meant about purging was closing the ball valve by the circulator and putting a hose on the drain valve above it. That would guarantee you that the main was full. You probably did the same thing by venting baseboards though.

See if you can get the mixer apart and go from there.

Ken

 

ok, I understand your answer. The system was purged and being a venturi system, I also bled all the BB. I just got off the phone with Taco, the maker of the valve. There are no replacement parts. He suggested a different valve, but offered no suggestion as to what kind or who could supply it. I like your suggestion about just turning it into a tee, tho.

Do you have any recommendations on a different by-pass valve or do you think I should just do as you suggest and turn it into a tee?

Thanks, Ken..........your replies are very much appreciated.

 

There would be nothing wrong at all with just regulating the amount of bypass with the ball valve. I think the challenge may be disassembling the mixer. They are not tapered threads, they are machine threads with a face to face fit and they can be hard to open up. You should be fine after getting it apart. You may need to put some sealer on the faces to reseal but that should solve the problem you initially had.

Ken

 

Thanks for the heads up on the machine threads. I'm having the homeowner soak it several times with PB Blaster and I will disassemble it tomorrow.
Thanks for the replies and your advice. It is much appreciated.

Steve

 

I have one of these XG-2000 boilers and have had a problem with the thermostat. The symtoms I saw where that I only got luke warm water out of it. No initial hot water like you indicate. When I first had this problem I just pulled out the thermostat and ran the boiler that way for a couple of years. I did not notice any problems from condensation without it. The difference between the Xg-2000 and the next lower effeciency modle Burnam sold at the time was bascally this valve.
I eventually found another thermostat but that one has now failed too so I am back to taking it out for this heating season. The XG2000 is basically beyond its useful life since there are quite a few parts that are no longer available. You may as well go ahead and get what ever you can out of it.

I suggest you get a 2" socket to take the cover off this valve since it will be on there very tight if you have never removed it and there isn't much to grip on.