Indirect DHW causing hot water zone to heat

vr608

Hello folks, been a lurker on this board for many months, awesome, awesome site.

I recently moved into a new (to me) Maplewood, NJ house with a one pipe steam system. My WMC PEG-50 boiler was recently replaced due to the typical rotting between sections as part of a home energy efficiency improvement project. Along with the new boiler (Peerless 63-03, 308 sqft), I got a new Bradford indirect DHW, and also eliminated a smaller hot water boiler which served about 30ft of baseboard in my family room and kitchen by creating a zone.

Despite my (small) issues with the near boiler piping (which I will document in a separate post), the system seems to be running fine since installation last week. However, yesterday I noticed some unforeseen behavior which I reported to my contractor; it would appear that whenever the DHW calls for heat, my hot water zone will also heat up. There is a circulator for each zone and it doesn't appear that they both activate when the DHW calls for heat, but somehow, when the DHW circulator is on, water will flow into the hot water zone.

Someone will be coming by to check it out this weekend, but I wanted to post the question here in case there is something I should look for or ask about. Thanks in advance.

4Johnpipe

Sounds like migration. They may need to add flow check valves to the circulators or somewhere else in line. Pictures of the piping may help. Another issue you may experience as the weather warms is stray heating in the rest of the home.

vr608

Thanks for the quick response. Yes, I think from the diagrams that I saw on the Help Site, flow check valves might be needed. Below are some photos of the two zones, hopefully they help a bit. The pic on the right shows the circulator that serves the hot water zone, and you can just make out the one for the DHW behind the boiler.

BostonSteamer

Is there an aquastat installed on the line going to the DWH to control the boiler? Or does the boiler kick on every time there is a call for hot water and run until the DWH tank aquastat is satisfied?

4Johnpipe

It looks like someone shut off the space heating zone return valve. Did that stop the stray heat?

vr608

BostonSteamer said:

Is there an aquastat installed on the line going to the DWH to control the boiler? Or does the boiler kick on every time there is a call for hot water and run until the DWH tank aquastat is satisfied?

Yes, the boiler turns on whenever the aquastat on the DWH (mounted directly on DWH, see first photo) calls for heat. There is a separate aquastat for the hot water zone that has not been triggered for the last few days due to the more moderate temperatures.

4Johnpipe said:

It looks like someone shut off the space heating zone return valve. Did that stop the stray heat?

No, the handle has not been touched, and the stray heat has remained.

vr608

Added a couple photos; first is the circulator for the DWH (behind the boiler) and second shows the piping for the DWH and return for the hot water zone. The copper pipe in the foreground of the first photo is the supply for the hot water zone, while the lower one is supply to the DWH.

vr608

Installer came out and determined that circulator was mounted ahead of the check valve (there are two installed, the one in question is in first post, second photo), so water was circulating in the opposite direction. I'll post another update once they have had a chance to correct it. Thanks guys!

vr608

FYI, the earlier root cause was incorrect. The problem was that the zone bypass (to cool the boiler water destined to the hot water zone) was teed ahead of the check valve, which was causing unwanted flow (you can just make it out in the second photo I posted). It has now been corrected and everything works normally.

4Johnpipe

I knew it was a check valve (flow check)...glad it was corrected!

vr608

Hey folks, been lurking again over the past few months, and its good to see activity has picked up on the site now that heating season has started again.

Unfortunately, my problem has returned. FYI, I incorrectly described the problem in my last update; the zone bypass actually never had a check valve controlling it, so one was added and that ultimately solved my heating issue (for a while it seems).

In principle, I think the piping for this implementation is correct based on Dan's diagram, but I'm wondering if its possible for a flow control valve (Bell & Gossett Hydrotrol) to fail so quickly in this application?

vr608

FYI, updated photo included that indicates location of check valve. The valve is on the return line coming back from my baseboard heating system. To recap, it would appear that whenever the circulator for the DHW turns on, I am getting flow into my baseboard zone. The only way to stop it is by shutting off the ball valve directly beneath it (blue handle at very bottom of photo).

hot_rod

I know a little bit about that foo-control valve. If you turn the knob all the way it forces open that check inside. Check and be sure it it not forced open. It is a very tight sealing dependable valve.

It sure sounds like it is "forced open".

vr608

Yep, it sure sounds that way. As I mentioned there is a ball valve directly beneath the check valve that will stop the flow manually, and was installed to isolate the DHW loop from the baseboard loop.

Yesterday I did a quick test; when the DHW called for heat, I closed the ball valve and kept feeling the pipes above and below it. As expected, the area above it where the check valve is located stayed cold, as well as the pipe leading away from the check valve (baseboard return copper piping).

As soon as I opened the ball valve, the check valve and return pipe got hot, leading me to believe the check valve must be stuck open. The heated water began to travel up the return pipe into the baseboard zone and eventually made it back down to the supply line (basically in reverse of the design). This leads me to believe that the check valve must be stuck open.

Also, after reviewing Dan's diagram again, I think my contractor missed adding a check valve on the supply line, which I think if it had been included would have masked this problem, at least for a while. Here's a question though; at the beginning of the supply line there is a Taco 005 circulator which is pointed in the UP direction. When off, shouldn't it prevent water from flowing in the opposite direction? Do circulators have a built in check valve?

vr608

FYI, so I asked my contractor about the missing check valve and he said that the 005 has one built in. Can anyone confirm that? Is this standard for most circulators? Also, if that is the case, I wonder why it wouldn't have retarded the reverse circulation in the piping?

vr608

Interesting. Mine doesn't say IFC, it says SF5. I suppose this is the model that doesn't include the check valve?

vr608

Understood. I'll have to have my contractor add a flow control valve on the supply side then, at his cost since this was not properly installed. This in addition to replacing the failed one on the return. That's going to be a fun conversation.

Thanks hat!

vr608

Ha, I sent him a text asking how to tell whether the pump has a check valve or not, and that the 005-IFC one does. His response was to check the flange.

vr608

So after reviewing my earlier photo , it appears that they used a B&G Check-trol rather than the pump that includes a built-in flow control valve. I'll need to confirm its pointed in the right direction though.

vr608

Attached a clearer image of pump and B&G valve.

Hatterasguy said:

He's correct if you pull the pump out from the piping.

But, why bother if you can simply read the data plate!!

Agreed, however, I think i misunderstood an earlier conversation with him regarding the pump model, since I thought the pump installed had the control valve built-in.

I think the setup installed satisfies the requirement on the supply, although I still cannot understand why reverse flow would still be possible due to a failed control valve on the return side. It would appear that both valves need to function in order to stop migration, which does jive with Dan's diagram. Just having trouble understanding why.

vr608

Update on this. The failed flow control valve was replaced (I got to see the old one, it was definitely damaged), but the problem remains, i.e. heat migrating up the return line up into the baseboard zone. One curious thing we noticed is that if the bypass valve is almost fully opened, we don't see the problem. I guess this would make sense, since the heated boiler water finds it easier to flow thru the bypass rather than up the supply.

I think the long term solution is adding a zone valve in place of the FCV, but I'm open to other suggestions at this point.

vr608

Another day, another failed Hydrotrol control valve. This one lasted about a day, so I'm guessing that my DHW pump is either too close or too powerful. I've attached a schematic of the piping since my earlier photos may not easily reveal anything obvious. The valve highlighted in red is my failure point.

I've contacted my installer again, since it appears that we'll need to use a zone valve in place of what is there. If anyone has a recommended 115v zone valve to use in this application, please let me know and I'll pass it along to him. I'd rather not use a transformer if I don't need to.

vr608

So, looks like my installer plans on installing a Taco motorized ball valve, not sure how much different these are than a zone valve? Anyone had any experience with these?

vr608

Still looking for some opinions on this, since a few of the reviews I've read on these motorized ball valves have been less than stellar.

vr608

Update: Taco Sentry zone valve installed and problem appears to be resolved. I'll be sure to update if this continues to be an issue, although it is highly unlikely at this point since the zone valve is normally closed.

@DanHolohan, I wonder if you've run into similar trouble with failed zone valves when implementing this solution? It would appear my case was a bit extreme to have to resort to a zone valve, although it could be that since I have both an indirect DHW and a baseboard zone that perhaps this is a better solution in those instances?