Please Criticize My DHW Setup For Combi-Boiler

gotgas

We have a 1" main feed from street. The combi-boiler requires 3/4" supply for DHW and another 1/2" supply for the boiler auto feeder. The 1/2" that ends at the valve is that line.

The 3/4" pex pipe going up in the middle is the domestic cold water supply. The Pipe coming horizontal out of the water heater then turning vertical on the right in the DHW.

The DHW supply goes through the Taco 4900 prior to going into the water heater. The camera was canted, but all these lines are generally plumb and level, excepting the cold water supply which bends.

What can I do better? Do you see any glaring problems, or even small issues?

SuperTech

No primary secondary piping for the space heating? Are you sure that boiler can be piped direct? That looks like a cheap Navien (I don't recommend them personally), they are usually best done with the manufacturers manifold kit to make things easy.

Teemok

The taco 4900 and that hydronic expansion tank doesn't belong on the domestic water piping side of things at all.

gotgas

Teemok said:

The taco 4900 and that hydronic expansion tank doesn't belong on the domestic water piping side of things at all.

I have a spirovent and larger expansion tank for the Heat side. This particular hot water heater calls for an expansion tank and air separator between the water inlet and the boiler. I have seen that on one other Combi boiler.

This is an "Exalt Ideal" combi with the same setup. Expansion between the city water and dhw:

I had never seen that before this but the Rheem calls for that as well.

gotgas

SuperTech said:

No primary secondary piping for the space heating? Are you sure that boiler can be piped direct? That looks like a cheap Navien (I don't recommend them personally), they are usually best done with the manufacturers manifold kit to make things easy.

I'm not sure if I'm understanding you correctly, but I think when you call out the space heating you are talking about the heating side of the combi boiler. Is that correct? If so I have not done any of that piping yet.

This is a Rheem 199k combi. It is what the MEP called for. That unit calls for this style of service valve on both dhw and heat side. Heat will go into a manifold when that part is piped

Is this style of service valve typical? It seemed pretty typical to me but I have never used them before.

Teemok

What particular "HOT water heater"? That unit looks like a boiler that also heats cold water on demand. A combi boiler as they are called. If you read the writing on the side of that tank you will find it is for closed loop hydronic use only. The need for an expansion tank on the DHW side of a combi unit would be related to the existence of a recirulation loop and or a storage tank. I like them on the hot side but it's a preference. If there is a need for one it should be rated for open loop use. A filter or strainer might be called for on the DHW inlet piping but I've never seen a hydronic air separator called for. At first glance I don't see that the brass in that Taco 4900 is lead-free. If it happens to be rated for DHW then it won't hurt anything but it's not meant for that job at all.

gotgas

Teemok said:

What particular "HOT water heater"?

I apologize if my terminology is incorrect and causing confusion. I mean the DHW side of the combi boiler.

Teemok said:

The need for an expansion tank on the DHW side of a combi unit would be related to the existence of a recirulation loop and or a storage tank.

Rheem calls for one if there is a back flow preventer. You can find that on page 32 of their installation manual linked below.
Rheem Manual

It says, "If a back flow preventer or a no return valve is used, a thermal
expansion tank must be installed on the cold water supply between the appliance and valve."

The city requires a back flow preventer after the meter, so I installed the expansion tank.

Regarding the Taco 4900, I understand what you are saying. Do you think it is a problem to have it on the DHW? I could remove it and replace with air scoop and hy-vent? I really hate to do that if it is not necessary, but would like to do it right. Appreciate you looking at this.

EdTheHeaterMan

No matter how right or wrong any of the pipes are connected, this will never work if you don't plug it in!!! DAH!

EdTheHeaterMan

Seriously, you have the wrong tank for DHW.
You need something like this: https://www.supplyhouse.com/Amtrol-140735-THERM-X-SPAN-T-5-Expansion-Tank-2-Gallon-Volume?_br_psugg_q=thermal+expansion+tank

Teemok

There is no need for an air separator on the inlet of the DHW. No vent belongs there. I strongly advise you to remove the 4900. If you have kids, leaving it in constitutes willful child endangerment. You might have been looking at the hydronic diagram concerning the 4900 vent placement. The hydronic side piping is a bit harder and is often done first. The flue and gas piping is kinda critical to do well.

EdTheHeaterMan

I think you may be in over your head. You may want to get some professional help for this project. There is 4 pages of WARNINGS, DANGERS, and CAUTIONS at the beginning of these instructions. Some of them are very specific. Like this one above.

Your statements herein indicate that you are not familiar with this equipment. If I were your insurance company, I would deny your claim for damages based on this fact.

But I am not your insurance provider so let me say this. You have interpreted the information, in the instructions, incorrectly. The Cold Water inlet does not require the air separator. There is no indication on this piping diagram that you need one, and there are no words in the manual that indicate that you need one.

Mad Dog_2

I agree..you're dabbling in Heat, Fuel & Domestic Hot water...Ya gotta know when you aren't qualified. I'll wire boilers and controls all day, wire outlets, but I STAY OUT OF THE PANEL...Mad Dog 🐕 

gotgas

EdTheHeaterMan said:

I think you may be in over your head.

I am definitely in over my head. We have a propane and oil company that is going to come in and do all the gas piping and then fire the boiler and do the testing. They want us to have the plumbing part done before they come. They do HVAC installs, but do not have space in the schedule for us. They are going to look it all over and verify everything before they fire it.

We had one person lined up but he decided to retire. We had another but he was hired by someone else full-time and cannot come. We have cold weather coming and live in a small area without a lot of choices, so I am stuck at this point. I am trying to get a friend to come over from another state who is a master plumber, also HVAC and gas licensed.

I understand what you are saying about the expansion tank and the air separator and will change that.

This is not the position we hoped to be in, but it is for now. I am hoping to get some pro help asap. Not sure when that will be.

I appreciate the advice on this and the warnings.

Mad Dog_2

You're on the right track now.  You can feel good about that.  Mad Dog 🐕 

Teemok

Necessity is a hard task master. Beware hydronics design and problem solving is sometimes like the law or art. Put three good lawyers or artists in a room with something debatable and they will argue till they drop. Lots of plumbers say they know what's up but it's like 2-3 out of 10 that are really worth their salt, depending on where you are. Finding someone who knows what they are doing is worth it, even if they are just advising and checking it over. I've done it for a few and it does work out in the end but it's rarely efficient with time or materials and the quality is not what I'm proud to be mixed up with. Communication of the many details can be frustrating. It can be done well by a novice with learning, care and time. I hope it goes well.

hot_rod

any device on potable water needs to be low lead. Not Mot all hydronic components are

gotgas

hot_rod said:

any device on potable water needs to be low lead. Not Mot all hydronic components are

Yes, pulling it out. Everything else on the DHW side is lead free. I confirmed when ordering and before installing. Purchased most of this through Pexuniverse or Supplyhouse. They are pretty good at marking this. I don't know why I did not think about that component. Thanks for the input.

gotgas

Teemok said:

Necessity is a hard task master. Beware hydronics design and problem solving is sometimes like the law or art. Put three good lawyers or artists in a room with something debatable and they will argue till they drop. Lots of plumbers say they know what's up but it's like 2-3 out of 10 that are really worth their salt, depending on where you are. Finding someone who knows what they are doing is worth it, even if they are just advising and checking it over. I've done it for a few and it does work out in the end but it's rarely efficient with time or materials and the quality is not what I'm proud to be mixed up with. Communication of the many details can be frustrating. It can be done well by a novice with learning, care and time. I hope it goes well.

Thank for the advice and well wishes. We are trying to get this right in a tough situation.

hot_rod

All questions are welcomed here.
We can do best by looking over a design or concept before you start buying and installing.
But we also get plenty of after the fact challenges and questions.

gotgas

If I can get this done without burning anything down or blowing anything up, I will invite you all over for ribs.

ncalhvac

The boiler autofeeder is pressure regulated down to 12psi, it's 1/2 line can reduce tee off of the 3/4 cold supply, which is where the expansion could go, but the expansion tank is not necessary because you already have a pressure relief valve on the service valve.

Mustangman

There seemed to be some confusion or weather you need thermal expansion tank on a tankless or not. It wasn't in our code book so I asked the codes department what they want. To me, there is no water storage like a tank so there is very little to expand. Add in the fact that when you are done drawing hot water, the unit shuts down. You don't have to deal with the expansion of a 40 gallon tank until it gets to temperature. The codes inspector agreed with not needing an expansion tank. FYI Im sure someone already brought this up but the grey tank in the pic is NOT a thermal expansion tank made for house HW expansion. The one you have is a #30 extrol for heating systems. You need an ST series for domestic water. You can pitch the air seperator too. Good luck
Steve

hot_rod

Code requirements vary a bit from area to area. IPC seems to be less stringent than UPC.
Also there are different versions of the codebook, they get updated every few years.
And the AHJ can add addendums.

We are seeing more and more tankless heaters with small tanks inside them for some storage a few gallons maybe.
No harm in adding a small expansion device.

A pressure gauge with a "lazy hand" would tell you if you are getting a pressure increase from thermal expansion.

Some of the isolation valve kits have a tap to add an expansion device.

gotgas

https://forum.heatinghelp.com/discussion/comment/1798305#Comment_1798305

The boiler in use calls for an expansion tank prior to the DHW intake and also on the heat side. Everything in that picture was pulled out. Here is the result:

gotgas

gotgas

Click on the pictures. No idea why they are all wonky like that. I realize the condensate is vertical and should be horizontal. Codes enforcement said, "Nah, it's fine."

WMno57

please delete.