Weil Mclain Ultra 155 - Supply greater than return by 58 °F

Mohamed

Hello...I am running a Weil Mclain Ultra 155 and have a problem I need help with. For a while I was getting shut downs for the boiler heating up too quickly for the domestic hot water. Now I get shut downs for supply greater than return by 58 degree. Flushed out the system. I have tried everything! I changed flow rates. I told it the domestic water is a radiant heat zone. Two plumbers plus many phone calls and problem persists. The only thing I see is that my plumber installed 1" copper for the loop to the boilermate and it requires 1 1/4". I don't know if that's problematic. Any help would be greatly appreciated. Every time my family showers it shuts down and it's been really frustrating.

Ironman

That’s caused by insufficient flow. It could be air bound; a bad or undersized circulator; or, as you mentioned, undersized piping. Or, any combination of these.

Without being on site to be able to evaluate the system, the best that I can recommend is that you call a COMPETENT hydronic contractor. The average plumber or HVAC tech is clueless about hydronics.

Try the contractor locator above. If you don’t see one near, post your locale and someone on here may have a recommendation.

JUGHNE

Did it ever work well?

Can you lower the high temp that the boiler supplies for the DHW mode?

Zman

Do the pipes feel like there is a 58 degree difference? Does the console tell you the temps it is reading?
You may have a bad sensor.

HVACNUT

That's reading the temperature difference on the block sensors, not the system manifold sensors. 
Is the boiler circulator running?
Are the other circulators running? Could be just recirculating at the boiler. 
Could be air in the boiler. 
Could be a dirty HX.
When was the last time it was opened and cleaned?
How is the inhibitor level?

Mohamed

My location is Madison, NJ 07940.

Mohamed

I switched the circulator pump with one I knew was working and nothing changed.

Mohamed

It does send heat to other zones and only **** down for the DHW zone.

Mohamed

The only way it is sort of working now is because I set the hot water zone as a radiant zone and now it doesn't overheat but it takes too long to heat the water.

Mohamed

I will lower high temp that boiler supplies to 170. It was 190. The problem is it usually heats up too quickly and shuts down.

Zman

How do the pipes feel?

Jamie Hall

As @Steamhead said -- the fundamental problem is insufficient flow. The question is what is causing that and without being on-site one would be guessing.

There are several good folks who might service your area -- two I can think of right off are @EzzyT or @clammy , but i know there are others whom I have forgotten at the moment.

TonyPipes

Mohamed said:

The only way it is sort of working now is because I set the hot water zone as a radiant zone and now it doesn't overheat but it takes too long to heat the water.

What is the number on the motor on the side of the red grunfus circulator pump? If it's a  standard circ set to high its A the wrong circulator and it's failing so it was barely able to move enough water and those pumps suck. They always fail. 

Mohamed

Mohamed

Mohamed

The circulator is set to high.

I swapped it with another one from a heat zone and nothing changed so I swapped it back.

Mohamed

I lowered the temp on the DHW zone to 160 and it seemed to work for a couple weeks. But now it's going into error again many times a day. So today I lowered the temp to 150 and the flow rate to 70%. I'm just guessing.

Mohamed

The pipes feel warm / hot.

Mohamed

It has not been opened and cleaned. The last guy here ran something through it to clean it and flushed it out.

Then I was supposed to add the inhibitor but I haven't yet.

How can you tell the inhibitor level?

Mohamed

Zman....how do I know if I have a bad sensor? This makes sense.

Zman

If you have an electric meter you can check the ohms and compare it to the specs in the manual.
You could estimate with your hands or measure the pipe temp and see if they make sense. Sensors are not that expensive, you could always just swap them out.
If you want to get someone's attention, @Mohamed does the trick.

HVACNUT

The heat cycle is fine and only locks out on a DHW demand?
Have you purged the loop after you replaced the circulator, twice?

Not exactly "closely spaced Tee's" on the space heat side either.

Mohamed

Hi again. This thing is worse than ever. I need a pro. Need recommendations for someone who really knows Ultra 155 that can come to Morris County, NJ. I had two plumbers come and it's still no good.

Jamie Hall

Try @EzzyT or @clammy

Tom_133

Heat exchanger is probably plugged due to Onix tubing.