second zone getting heat when other zone or dhw call happens

Mcmonster508

prior to yesterday this had never happened, it worked independently from each other.
now whenever there is a call for heat from the first floor or the direct hot water the water also goes through to the second floor(zone 2)
as far as I can tell the grundfos is not running.
nothing has changed other than getting a service done a week ago
any answer or insight would be appriciated

Jolly Bodger

Sounds like your system is zoned with individual pumps and not zone valves? Grundfoss 15-58 by chance? Sounds like the check valve is stuck open. Do your pumps have ISO Flanges?

Mcmonster508

> @Jolly Bodger said:
> Sounds like your system is zoned with individual pumps and not zone valves? Grundfoss 15-58 by chance? Sounds like the check valve is stuck open. Do your pumps have ISO Flanges?


They do have iso flanges and I believe they are 15-58’s
Those are the pumps in the picture

Jolly Bodger

Those are 15-58. They have a check valve in the discharge. Zone 2's valve is probably stuck open. I have seen some ISO flanges are to close to the check valve and if the ISO valve is closed with the pump running it can damage the stem of the check valve. The pump will need to be isolated and removed to inspect.

Mcmonster508

> @Jolly Bodger said:
> Those are 15-58. They have a check valve in the discharge. Zone 2's valve is probably stuck open. I have seen some ISO flanges are to close to the check valve and if the ISO valve is closed with the pump running it can damage the stem of the check valve. The pump will need to be isolated and removed to inspect.

Is there anything else that it could be? AFAIK the iso valve wasn’t turned recently that could cause the issue. Is there anything I could do without removing to test if it’s stuck open or close it?

Jolly Bodger

I don't see any other device to control the flow of hot water through zone 2 when off. It's a very nicely built system. It is most likely the built in check in the pump. It's does not have to be damaged to get stuck open. Dirt, debris, corrosion. With the ISO Flanges you have it is very easy to isolate and pull out the pump. Get a 5/8" and 11/16" box end wrench and have at it. Get this part and just change it out while you are in there. https://www.supplyhouse.com/Grundfos-596630-Check-Valve-Kit-for-UPS-FC-SuperBrute-UP15-UPS15

Mcmonster508

> @Jolly Bodger said:
> I don't see any other device to control the flow of hot water through zone 2 when off. It's a very nicely built system. It is most likely the built in check in the pump. It's does not have to be damaged to get stuck open. Dirt, debris, corrosion. With the ISO Flanges you have it is very easy to isolate and pull out the pump. Get a 5/8" and 11/16" box end wrench and have at it. Get this part and just change it out while you are in there. https://www.supplyhouse.com/Grundfos-596630-Check-Valve-Kit-for-UPS-FC-SuperBrute-UP15-UPS15

Out of curiosity, could this check valve malfunctioning cause a system to short cycle?

HVACNUT

> @Mcmonster508 said:
>
> Out of curiosity, could this check valve malfunctioning cause a system to short cycle?

No but does the boiler have an internal hydraulic separator and primary pump?

Mcmonster508

> @HVACNUT said:
> > @Mcmonster508 said:
> >
> > Out of curiosity, could this check valve malfunctioning cause a system to short cycle?
>
> No but does the boiler have an internal hydraulic separator and primary pump?
>
>
This is the boiler, im not 100% sure it has either of those

hot_rod

That boiler has a circ inside, and it looks like you have zone circulators also, I'll bet the installation manual shows primary secondary piping or a hydraulic separator.

When a heat call is on the boiler circulator may be pushing into the off zones, with it piped like that.

Jolly Bodger

@Mcmonster508 @hot_rod the boiler does have a pump and internal primary/secondary piping. The system looks like it is piped per manufacturer's diagram.
Mcmonster508, you said this had not happened before? Then something has changed. We should ask what could have changed. Has the piping changed? Have valves been opened or closed that were not before? Has a component failed? Maybe the check valve in the zone 2 pump.

hot_rod

Jolly Bodger said:

@Mcmonster508 @hot_rod the boiler does have a pump and internal primary/secondary piping. The system looks like it is piped per manufacturer's diagram.
Mcmonster508, you said this had not happened before? Then something has changed. We should ask what could have changed. Has the piping changed? Have valves been opened or closed that were not before? Has a component failed? Maybe the check valve in the zone 2 pump.

I see. Looks like it has a valve also so it can be configured for internal P/S, or direct piping?

What position is that #13 valve in?

Mcmonster508

> @hot_rod said:
> (Quote)
> I see. Looks like it has a valve also so it can be configured for internal P/S, or direct piping?
>
> What position is that #13 valve in?
I’m at work currently but I’ll look when I get home.
The only thing that changed was a service was done a week prior but the pushing to the second zone happened 5 days later.

I kinda wanna take a video to explain the short cycling that happening. Because I’m starting to suspect that if it is the check valve that’s stuck open it’s been malfunctioning for a while because the short cycling is sporadic and with the second zone being open it won’t stop short cycling when the first zone calls for heat at all.

Mcmonster508

> @hot_rod said:
> (Quote)
> I see. Looks like it has a valve also so it can be configured for internal P/S, or direct piping?
>
> What position is that #13 valve in?

I meant to also say I’ll check it when I get home. I’ll take a picture when I’m home.

HVACNUT

As for the short cycling, is outdoor reset enabled?
Having a second zone always open will actually combat short cycling.
What's the heat loss of the home compared to the boilers lowest firing rate?

Mcmonster508

> @HVACNUT said:
> As for the short cycling, is outdoor reset enabled?
> Having a second zone always open will actually combat short cycling.
> What's the heat loss of the home compared to the boilers lowest firing rate?

It takes 3 hours to get the temp up 3° when it’s circulating two zones with only one on so I try to run both zones at the same time,
Where would I find the outdoor reset?

Mcmonster508

> @hot_rod said:
> (Quote)
> I see. Looks like it has a valve also so it can be configured for internal P/S, or direct piping?
>
> What position is that #13 valve in?

This is what the valve position is in

Mcmonster508

Just in case anyone might have insight this is the video of it doing what it’s doing.

https://youtu.be/4AJBl5WqH4I

hot_rod

Make sure it is piped per the manufacturers diagram. The #13 valve needs to be in the correct position depending on the boiler piping.

I can't see enough of then piping, I don't think it is primary secondary? A sketch may help.

rick in Alaska

You can tell it the pump check valve is stuck open by turning on the heat for the first floor, and holding on to the pipe to the second floor and see if it gets hot. It should not get hot unless the check valve is stuck open.
Rick

Mcmonster508

> @hot_rod said:
> Make sure it is piped per the manufacturers diagram. The #13 valve needs to be in the correct position depending on the boiler piping.
>
> I can't see enough of then piping, I don't think it is primary secondary? A sketch may help.

> @rick in Alaska said:
> You can tell it the pump check valve is stuck open by turning on the heat for the first floor, and holding on to the pipe to the second floor and see if it gets hot. It should not get hot unless the check valve is stuck open.
> Rick


So I did a little experiment today, I turned the isolation valve under the second zone to the t position to cut off water from fully circulating through the entire house to see if the cycling issue in having stops, and it did, as a control I turned off the thermostat and opened the iso valve and called for heat again it started to short cycle again, so I again cut off the circulation, low and behold no short cycle.

Needless to say as long as it doesn’t take an idiot to replace that check valve. I’ll
Be putting a new one in this week and see what happens.

Any insight is appreciated.

Mcmonster508

This valve

hot_rod

The check mark in the center of the motor indicates the pump has a check valve. IF someone removed it there is a sticker in the box that should be applied indicating check removed.

Usually something is stuck preventing the check from closing "bubble free"

You may damage or destroy it if you try to remove it, it has tabs intended to lock it in place. Don't remove it unless it is damaged.

Somewhere along production they changed to a larger size check.

Turn off both valves, turn off power, relieve pressure and remove 4 bolts. Try not to damage ring gaskets.