Combi Boiler piping/water flow issue

SuperTech

I really need some advice from the community regarding a service call I was on recently. Despite my clever screen name I don't have all the answers.
I was sent to a new customer who has an NTI propane fired mod con Combi boiler, model Ti150. Customer was complaining about no heat in one of the three hydro air zones. When I arrived he had everything shut off. When I turned the boiler and the three hydros on I found that only one zone was heating normally despite the fact that all the circulator pumps we're running.

This is where it gets wierd. When I test each zone individually they work fine and with two calling one will work better than the other but they will both heat up.

I called tech support and the @$$hole I got on the phone said "if the boiler is heating the water normally and there's no error codes there's nothing I can do to help you". After another hour of trying to figure it out I called back and got someone else on the phone who was more helpful. After I described the issue and the piping on the unit he told me that it wasn't piped correctly. He said zone one is pulling all the heat off the boiler.

My experience with mod cons is limited and I want to make sure this is really the problem. I'll post a picture, maybe one of you guys can explain it to me. Two of the three circs are Taco 007, the other is the Grundfos 3 speed equivalent. All three hydros are in the basement not far from each other

SuperTech

It doesn't look like the picture posted. Let me try again....

SuperTech

Hopefully it will work this time

Paul48

I can't follow that piping, at all. I have to admit, that is the first time I've not been able to figure one out. Is the manual packet in-opened? It looks like the planning was done, one fitting at a time. I can't see primary/secondary there, and that would lead to circs in series, and uneven flow distribution. But I couldn't bet on anything. Can you build it for us, in simple diagrams? Maybe someone else is better at puzzles.

Canucker

Your Grundfos pump looks like it is upside down, hard to tell. Can you get any pictures from the expansion tank side of the system piping? Stand back a little, so we can see where it connects. Like @Paul48 says, it's a little hard to follow

SuperTech

Heading back to this house now. The boiler is now going off on fault code ER4, which appears to be an open limit. Possibly caused by bad water flow. I'll take some more pictures and report back.

Any and all advice and recommendations are greatly appreciated!

HomerJSmith

Never admit you don't have all the answers except to you local priest in the confessional.

The Grundfos pump IS mounted upside down instead of horizontally. What happened between mounting the Tacos and the Grundfos? Oh! I get it, it's the color. The pump flanges are all oriented the same except for the Grundfos. Hmmm. I'm sure there is a hidden message there, all I have to do is discern it.

" I found that only one zone was heating normally despite the fact that all the circulator pumps we're running." Is it possible that one pump is pumping against another, one circulator grabbing all the supply? No heat, no flow. There is something to say about flow indicators. And...why is all the common piping 3/4", I see this over and over again.

Which pump is zone 1, zone 2, zone 3, etc? Might help to know and it would certainly help to know what the flow direction of each pump is.

Good grief, I'm sorry, I had to quit looking at the piping, I'm getting a headache. THIS IS NO WAY TO PLUMB A MOD/COM. Looking at this, I'm beginning to feel pretty good about the shabby work that I do.

When did this problem start? It's hard to believe it didn't start at commissioning.

hot_rod

A hand drawing might be better to figure out the piping.

Looks like a boiler loop and those zone circs all taken off on a pair of tees at the bottom.

i'd guess a mixing valve for a slab radiant zone?

bob eck

Form what I just saw on the NTI web site this Combi Boiler has a water tube heat exchanger.
Also most Combi Boiler have a built in primary pump.
This boiler needs to be piped P/S
Is it piped P/S I cant tell looking at that photo.
If you turn off two of the three zones and the one running heats up and you do this with all three zones I would say it is not piped correctly.
Is this a new installation?
You might have to repipe the boiler from start.


Search Caleffi Technical Magazine click on that and look for Idronics book number 15 Seaparation In Hydronics Systems

SuperTech

Well I didn't get back to this house. One of my coworkers did. The mixing valve is for domestic hot water. The Grundfos pump is pumping in the same direction as the two Taco pumps. The boiler was originally installed ten years ago to provide on demand DHW and provide heat for two hydro air systems. Five years ago a third hydro air unit was installed and the Grundfos pump was added for that system. Not sure if the same company did the work.

The whole thing is a mess and I feel bad for the homeowner. It seems like every time I go out on a service call for a mod con the problem is either a failed model specific part that needs to be ordered or just a terrible installation like this. At least when a customer has a traditional cast iron boiler I know I can fix just about anything with my truck stock. Reliability is superior than efficiency.

DZoro

Looks like the grunfos was added at a later date. Poorly but not during the original install. At the taco boiler pump to the left is a brass tee, the drop on that tee does it go down into another tee and back into the boiler? Maybe?? I believe back then that is how they did some of there piping. But yes I agree no planning there just keep going until kindof dun..... Which zone is the issue?

clammy

How about shutting the ball valve on the bottom of the loop that runs between the secondary loops ,system side .Looks like with that valve open and that u may not be pulling through the tees instead just by passing between your system supply and return give closing that ball valve a shot also chk the speed o that 3 speed pump peace and good luck clammy

Paul48

If I bought a house, and it had that mess, I'd dope it out, and re-build it on a board to fit in the space. Then at an appropriate time, I'd perform some sawzall surgery, mount the new board and make my connections.

SuperTech

Well I didn't get back to this house. One of my coworkers did. The mixing valve is for domestic hot water. The Grundfos pump is pumping in the same direction as the two Taco pumps. The boiler was originally installed ten years ago to provide on demand DHW and provide heat for two hydro air systems. Five years ago a third hydro air unit was installed and the Grundfos pump was added for th

DZoro

Agree with Clammy, That bottom pipe was cut out and re-added. But looks like it should have never been there. That's your easy water route, turn the valve off and see what happens. But with all that piping we may not be seeing everything

DZoro

Three speed pump should have, but does it still have the flow check in it?

SuperTech

I found out that the flue temperature limit switch was stuck open with the boiler shut down and cold. This was the issue that made the customer call us originally. But he said that the zone 3 always took longer than the other two zones. Zone 3 is the zone with the Grundfos pump. He said it worked fine after that zone was added to the boiler and the issue he's having now he's never had before. Zone two is the pump in the middle and zone one is the top zone.
When I tested each zone individually I could feel the supply pipes heat up and then the returns shortly after, so it seems like the water is circulating in the right direction. I'm sure it wouldn't do that if the Grundfos pump was backwards.

Can anybody recommend a good resource for learning the finer points about mod con/primary secondary piping? A book or website perhaps. I want to become an expert for the few mod con customers I have.

kcopp

https://heatinghelp.com/store/detail/primary-secondary-pumping-made-easy

HomerJSmith

Yes, I'm happy to recommend Caleffi Idronic Series of booklets that you can download off the Caleffi web site. I just received the newest one. I use a lot of Caleffi products. They may be a little more cost wise, but the quality is unsurpassed and the innovations are top notch.

Tom_133

took awhile but I figured out the piping arrangement. You can close the bottom ball valve. More than likely thats pulling back return water and cooling the grundfos zone. That will help. The good part is the piping isn't the worst Ive seen. It could be a lot better, the closely spaced tees are a little too far apart. Just shut the valve and see what happens.

HomerJSmith

Closely spaced tee's are for hydrolic separation between parts of a heating system to prevent interaction between the system parts. It is usually used on primary/secondary systems.

I don't see a primary/secondary system in the photo.

Which tee's are you talking about. I'm still having trouble following the layout.

SuperTech

***Upate***"

My coworker ordered a couple of parts for this boiler and being the nice guy that I am I volunteered to go there today, on a Saturday.

Since the first time I was there I have read every thread about NTI Trinity boilers on this forum as well as HVAC talk. One of the many things I learned is these Giannoni boilers are very sensitive to water flow issues and piping.

So I wasn't shocked when I returned and found that at some point some genius replaced the primary pump with a Taco 007. I remember reading online that this should be a 0011!

The piping is far from perfect but this likely explains why I was having trouble getting all three zones to heat at once.

SuperTech

I forgot to mention that while I was there I completely cleaned the fire side of the heat exchanger as well as the condensate drainage system. Naturally I performed a combustion test right after.
Inlet gas pressure, CO and CO2 were all within the manufacturers specifications. But two things bothered me. First of all the stack temperature peaked at 175 degrees! This is likely a result of poor piping and the undersized primary pump. New pump will be installed this week. The second issue I've never seen or heard of before. The refractory disk inside the boiler is dark brown. Possible result of overheating? I'll attach a picture

Tom_133

Have never seen that before, you did a nice job cleaning the Hx!! That could be from someone in the past cleaning the Hx with the refractory disc still in. Getting it covered in overspray.

Good catch on the pump. Yeah a Grundfos 26-99 would also work. That is a tight Hx needs big pump to flow.

@HomerJSmith yeah its primary secondary the tees are there if you look closely, they are hiding behind the mixing valve. That boiler requires it.

kcopp

I have seen the refractory in that type of HX be partially stained but not the whole thing. I would prob replace it at some point. It indeed could have gotten wet.