Counterflow system problems

Dan C.

I have been working on a system for about two heating seasons now trying to correct problems they are having. The problems are spitting vents, banging, and uneven heating and according to the homeowner these were new issues. The first thing we did was re-pipe the boiler, add main vents, skim the boiler and clean/flush the boiler. The biggest problem with the system which we did not correct is every radiator is fed with 1" and all but two should be 1 1/4". The reasons why we did not correct this problem are 1- The cost, 2- Most of the feeds are buried in the foundation where they go up to the radiators and would require chipping away at an old fieldstone foundation, and 3- Because it has worked in the past. I have Gorton #4s on every radiator because if we put anything bigger the radiators will spit. I installed a vaporstat and we have tried many different operating pressures. I think right now I have it cutting out at 12 oz. The vents are no longer spitting but the boiler is short cycling pretty badly and it is taking very long (too long) for the radiators to heat up. When we put bigger vents on the radiators they spit. I have not tried bigger main vents because they heat up fast. The only thing left I can think of to do is to replace all of the run outs and size them properly which is going to be difficult and expensive. Is there anything else that can be done? I can't think of anything. The EDR calculation is 374. The boiler is an IN6 which has a rating of 450 and is the closest size without going under. We have two counterflow mains. The front main is 10' 2 1/2", 10' 2", and 6' 1 1/2" and gas 1 Gorton #1. The back main is 5' 2 1/2, 10' 2" and 5' 1 1/2" and also has one Gorton # 1.

Dan C.

Ironman

I'm curios: why is there a Hartford loop on a counter flow system?

Dan C.

I normally don't put one. Not sure why I did here but I don't think that is a problem. I've seen many counterflow systems with it. I know it's not necessary but as far as I know it doesn't hurt anything.

Jamie Hall

Take the homeowner's these are new issues with a grain of salt -- they may be. They may not be...

Those runouts are small. They probably can be made to work, but you will want to check the pitch on them very very carefully -- more is better. In fact, much more will be much better! Then I would be inclined to try slower vents (!) on the radiators -- particularly if there are radiators that heat significantly faster than others -- if that didn't help. Then double check the pitch on all the mains. Every little bit will help.

When in the cycle does the short cycling occur? If it's after the mains are hot and at least some of the radiators are getting pretty warm, it suggests that the boiler really is bigger than it needs to be. Is there any possibility of down-firing it?

Dan C.

The vents are already downsized. Every radiator has a Gorton number 4. The short cycling starts after the mains get hot but before the radiators get hot. I am assuming this is because the radiator vents are so small. Not sure about downfiring. I have not done a combistion test. If I can downfire I don't think it will be enough to make a difference. As far as boiler sizing, the next boiler down would be too small. I usually do the edr calc and put in the boiler that is closest without going under. I have never had any short cycling issue. I did not install the boiler originally but it seems to be the closest one for this application.

Dan C.

The column on the right is what I've always used. Is this wrong?

Fred

Dan C. said:

The column on the right is what I've always used. Is this wrong?

That is the right column but steam boilers have another 33% piping and pick-up factor built in that is not reflected in that number.

Bio

As said before two stage gas valve will be a good start, putting hoffman 40s on radiators will also help as they're between G4 & G5, and use G4 on radiators the are overheating, i will try to set the thermostat at 3CPH as well, may be even 4CPH, is going to cycle anyways but not as fast as using the vaporstat, it's worth the shot, also make sure sight glass has a 1/2" bounce, more than that it may just be oils in the water that is causing wet steam

Steamhead

Check the shutoff valves on those radiators. They should be wide open. There are some valves that don't open wide enough for steam, even when open "all the way". Or, the disk that holds the washer can come off and block the seat opening. Either can cause water to back up in the radiators and make them spit.

Fred

Are all the radiators pitched correctly?

Danny Scully

Also test the Vaporstat, and keep skimming! Maybe try a wand cleaning.

jumper

Spitting from condensate draining too slowly? Cold radiators and short cycling because steam can't get to rads? Is air impeding circulation? Time to visit the vacuum threads?

Ironman

An obvious question: has the pigtail been checked? If not, you could be building up more pressure than you think.

Dan C.

Water line is steady. Valves are all open all the way but I have not taken them apart. Radiators are all pitched correctly. Pigtail has been cleaned and it is cutting out at the setting it's at. To do the two stage gas valve do I need to add another vaporstat or can I use the one that is already there? Where can I find a wiring diagram?

Dan C.

Also if the boiler is oversized why would it take so long to heat the radiators after the mains heat up so fast?

Fred

If it worked before, as they say, ask them to think long and hard about what has changed between the time it worked and the time these problems started. Something isn't the way it was???

Charlie from wmass

Can you with a combustion analyzer turn down the manifold pressure to reduce the fire rate. Be very careful that your combustion number stay clean.

Charlie from wmass

I actually have one that I'm working on that is having similar issues. If I Find a silver bullet I'll let you know what it was.

Dan C.

I am going to try that. Usually with gas I find that you can't go down much without throwing off all of the numbers.