How do I properly set the bypass????

[Victorious1_1]

I've got a new boiler (NYThermal Legacy 150) on my hot water heating system in my home. It's a one pipe system that has a 1" pipe circulating around the basement feeding off to the baseboards in the house. The 1" pipe begins and terminates from the boiler through 1 1/4" pipes and the bypass is also 1 1/4" with a ball valve in the middle. I also have a tankless DHW coil in this boiler. The bypass feeds into the suction side of the circulating pump which is on the return line at the boiler.

I have been running this boiler with the bypass fully closed but I have read here that it should be fully open.

How do I properly set the bypass valve on my system and verify that it is working correctly?

Vic

[KField]

Your bypass is not piped correctly if it is on the suction side of the circulator and your circulator is on the return side of the boiler. What a bypass is intended to do is 'bypass' some of the water around the boiler. In your case, it will recirculate boiler water back through the boiler. You would be better off leaving the bypass closed than opening it at all. Or install a circulator in the bypass and then you can throttle the bypass valve. As it is now, you do not have a bypass. Maybe your installer would correct it for you if it is new. It is his mistake after all.

Ken

[Victorious1_1]

Thanks Ken.

According to the manufacturer of this unit, the bypass is plumbed this way to make certain that return water to the boiler is always at or above 120 degrees farenheit so that condensate will not collect inside the boiler.

Do you think it's possible that the manufacturer is misinforming me or are they trying to bypass the home heating to prolong the life of their boiler? After all, they did say that the warranty would be voided if the boiler showed signs of condensate damage to the boiler due to return temp being too low.

Ken, if I post a link to a picture of this setup would you have a look at it to determine if it is correct and tell me what should be done to correct any problems if it's plumbed wrong?

Vic

[KField]

What Weil McLain does in boiler that cannot tolerate a low return water temp is to use a mix valve but I am not in favor of that either because they do not support parts for that valve for as long as the boiler lasts. A second pump might be overkill since you don't have a large water volume. If the reason the manufacturer specs the bypass the way you have it, then you definitely don't want to change it. You will probably find that it will onle need to be open about 5 % or slightly more. Don't open it too far or you will have a boiler off on high limit and radiators that are not hot enough. Sorry for sounding off like I knew it all because the reason for your bypass is valid and I did not see it.

Ken

[Victorious1_1]

Thanks for getting back to me on this Ken.

You are so accurate 99.99% of the time that I really worried that I had a problem here, but, I feel confident in your last reply and will only open the bypass a maximum of 5% if needed to keep the return temp up.

You would think that if the manufacturer felt that return water temp was so critical that they would have installed or recommended an aquastat on the return line to shut off or cycle the circulator if the return temp was too low.

Is this something I should consider doing on my own or should I just let it be? It seems to work fine presently, but, I am having a professional come to give it an annual inspection this Friday.

Do they check the return temps/adjust bypasses and combustion mixture when they do these inspections?

Vic

[KField]

I am not familiar with your particular boiler but I know that long durations of return water below 110 can cause scale on the fireside of the boiler. I believe you said that you had 1" copper and if you have finned baseboard radiation, you don't have much to worry about. The manufacturers don't want to price themselves out of the game by providing all the accessories you MAY need. They instead make the recommendations, hoping that an installer will read and heed their info. A reverse aquastat would not do the trick because the cold water is already in the boiler by the time the aquastat stops the pump. The best way to adjust your type of bypass would be to start the boiler with a cold house and hold your hand on the return pipe right at the boiler and open the bypass a tiny bit at a time until you can just keep a hold of it with your whole hand. That would be less than 130 degrees (approximately). If it is 130 or above, you will have a hard time grasping the pipe with your whole hand and holding on. I know that sounds crude but without an infrared thermometer or a digital temp thermocouple, it will suffice. If you leave the bypass as far closed as possible, all the rest of the pumps power will be sent to the radiators and not be wasted running water around the boiler.

Ken

[Victorious1_1]

Thanks Ken, as always, your answer is clear and extremely helpful. I'll check the performance of that bypass using the method you stated.

Vic