Cycles Per Hour - WEIL McLAIN cga-4 pidn

marcel_20

Hello. I could use some thoughts on the below problem. HVAC is not my area, and the manual was basically a foreign language to me.

We purchased a house in fall 2019. The WEIL McLAIN cga-4 pidn is new, installed 2018. (https://www.weil-mclain.com/products/cga-gas-boiler-series-2).

There are two zones. The majority of the house, zone 1, is on a Nest. Zone 2 is the kitchen floor on a Honeywell thermostat (one of the round ones). At this time, both thermostats are set to 65 degrees. Zone 1 is at 65 degrees and the radiators are cool. Zone 2 is at 72 degrees; the kitchen floor is very warm.

I've been monitoring the boiler and have noticed two things:

• It cycles on often, multiple times an hour, despite the house being at, or above, the set temps on both thermostats.
• The boiler is keeping a temp range of 165-145 degrees. At 145 it turn on, and at 165 it turns off.

My question is basically: Is this normal / working as designed? The amount of times the boiler turns on despite the house being at fine temps seems excessive. Zone 2 being overly warm is also odd to me.

Please let me know your thoughts, and feel free to ask for clarifying information. I appreciate it!

Jamie Hall

Doesn't sound as though it's working quite the way it's intended. You say the kitchen floor is warm? Is this in floor radiant heat? Or radiators? Baseboards?

You may have more than one problem. Nests can sometimes do very odd things with hot water or steam heat...

Much more information needed...

marcel_20

Hello. Thanks for the prompt reply.

Zone 2, the kitchen floor, is radiant heat under a wood floor.

Jamie Hall

That's what I suspected you meant. What is needed then is how the flow through that radiant floor is pumped and controlled. What does the round thermostat control?

marcel_20

The Nest controls zone 1 (the house except the kitchen floor). The round Honeywell thermostat controls zone 2, the kitchen floor.

There are two pumps, one for zone 1 and another for zone 2.

At any point if pictures are helpful, just let me know.

Jamie Hall

So far so good -- and yes, pictures of the pumps and valves and the way they are piped together will be helpful.

But for the moment... when you turn the zone 2 thermostat off (turn it way down low) does the zone 2 pump stop? And does the piping from and to that zone get cool?

HVACNUT

The Honeywell CT87K isn't a thermostat to be used with radiant heat. There will be wild swings in temperature.

The Tekmar 521 is probably the simplest route but it needs to be 24v powered.

Can you check behind the thermostat to see if there's two sets of thermostat wires? Maybe there is a floor sensor not (can't) being used with the CT87K.

marcel_20

A pic tour:

Direct System View:


Angle System View:


Zone 1 Pump (I think. Can anyone confirm this is a pump?)


Zone 2 Pump (this is warm at time of photo)


Digital Read Out:


Analog Read Out:


At the time I took these pics zone 1 is at 69 degrees and zone 2 is at 72 degrees.

When I turn down the zone 2 thermostat nothing changes. Pipes stay warm, pattern as described in my original post continues to happen (system maintains 145-165 degrees) despite the house being at, or above, the set thermostat temp.

marcel_20

Also, unclear if there is a third wire available (power), behind the wall. If there is, it's not visible based on the current hole for the wires.

EdTheHeaterMan

Here is a history of your heating system. The original system looked something like this:


Gravity system with 2 supply risers A1 & A2 depending on the boiler manufacturer the pipes may have been front and back
and 2 return risers B1 and B2. Notice there is no circulator pump. Eventually, that boiler was replaced with a new one. Both supply pipes A1 & A2 were connected with smaller pipes, but this design needs a circulator pump to move the needed heat. Both the return pipes B1 & B2 were also connected because the 1950's boiler only has one supply opening and one return opening.

Your current boiler is the third (at least) boiler because the copper pipes indicate a new generation of piping. Not the best design, but it works.

Now when the new boiler was installed the kitchen floor heat was added. You need 2 temperatures to properly heat the space. Low temperature for the Floor heat and high temperature for the radiators.

here is the design used for that process.

The radiant floor loop is a lower temperature because some of the unheated return water is added at the Three-Way MIXing Valve and some of the high-temperature water is added at the MIXing valve. so you get a MIX of water that yields a lower temperature. You want this so the floor does not get too hot to walk on.

The higher temperature water is still available for the rest of the system.

Now your problem may be a result of a control failure. If the wire from the Honeywell thermostat has a nail or staple in it, the circuit may be completed without the thermostat. the thermostat may be broken in the closed position. The control the thermostat connects to may have a bad contact inside. Any of these reasons could cause the circulator motor to operate continuously. The thermostat may be satisfied and the electric circuit open... but the pump is still operating from another failure. The Maroon color Grundfos pump is very quiet. You need a stethoscope to listen for the pump operation in some cases

Without an onsite inspection to review the actual wiring, this is impossible for anyone to diagnose over the phone or internet.

One final note about the boiler piping, although the design could be better there is one thing that I noticed. The installer did understand that the large water volume of the radiator system could cause a different problem. To overcome this problem there is a bypass piped into the main. It is illustrated here :
the blue pipe added is the bypass and that valve should be adjusted to maintain a 130° minimum return water temperature within the first 5 minutes of burner operation (give or take). If the return water is below 130° for a long period of the burner operation time, the boiler may experience premature failure. That means the boiler may fail in 10 years or less instead of the normal 30+ life expectancy of a cast-iron boiler.

That completes today's history lesson.

If you can find a good residential boiler man in your area, he will be able to make the needed repairs to solve your cycling problem. Since Radiant floor heat takes hours to change temperatures my guess is the pump for the floor heat is always on for some reason. The floor temperature in the kitchen is comfortable and possibly overheating the room. The surrounding space is siphoning off the overheating from the kitchen and you are not realizing the system is malfunctioning. But that is only a guess at this point. You need a good technician to check it out. Not everybody in the trade is qualified to find this problem. You need someone with experience. Try the Find a Contractor page on this site. if unsuccessful here, go to your local plumbing and heating house and talk to the manager. He will know which of his customers is most qualified to handle your situation.

marcel_20

Thanks! I just made a call to the folks who installed it and they are saying similar things, mostly about the thermostat...they speculate that there is something in the wire / connection / whatever that is closing the loop to call for heat.

I'm going to head into the basement and see what I can see.

As for the red pump, it is super quiet, but I can feel it running when I put my hand on it. I'll see if it turns off.

marcel_20

> @EdTheHeaterMan said:
> Your current boiler is the third (at least) boiler because the copper pipes indicate a new generation of piping. Not the best design, but it works.
>

Thanks so much! I have someone coming out Tuesday and will give you all an update.

Wondering if you would say more about the design. I've had two very general comments about it. I've highlighted what was pointed out as not great design in these pics. Do you see more design problems?

One problem is that there is no offset to the junction. The other is an old leaky part that should have likly been replaced when the new system was installed.

EdTheHeaterMan

This gets a little more technical. The water feed line has a pressure reducer set at 12 psi from the factory. If no adjustment has been made then it is still set there. It is connected to a pipe just before the inlet of the circulator pump. The point of no pressure change also known as the expansion tank or air cushion tank is connected on the outlet side of the circulator pump. This causes the pressure to fall on the inlet side of the pump whenever the pump operates.


In a close examination, I find your plumber did not install an auto-feed or pressure reducer.

But if he did or you decide to add one later... think about this... when the pump operates the pressure on one side of the pump is higher and the other side is lower.

If the pump is pushing against the expansion tank (The point of no pressure change) then the outlet pressure can't get higher... that means inlet must get lower. Now if the inlet gets lower than 12 psi, the pressures reducing valve will add pressure to get the inlet pressure back up to 12 psi.

This mistake happens a lot by plumbers that were never educated or instructed in this particular scenario. Since the pressure relief valve is set at 30 psi and usually the additional water in the system only adds 3 to 6 psi to the system there is hardly ever a problem. It is just poor design and may cause a problem in a system larger than yours. The thing is... when it is a problem, the installer does not know why, because "this is the way I always do it and I never had a problem before ?!?" could be the response of the installer

Back to your problem. Have you discovered if the radiant floor zone pump is operating full time? OR is it cycling off when the thermostat for that pump is below the set point?

marcel_20

Answer: Zone valve for zone 2 was malfunctioning and stuck open.

Jamie Hall

marcel_20 said:

Answer: Zone valve for zone 2 was malfunctioning and stuck open.

Thank you! That will do it...