PEX vs Copper - Boiler to Indirect

rsc92

I am having an indirect (Burnham Alliance) installed and was wondering if the plumber should be using copper or PEX between the boiler and the new indirect tank. Does it matter?

Please help. Unit is being installed today.

Thanks!

jonny88

Copper One inch preferably I would advise a heel tee before he drops into tank and put a caleffi air vent on top.

rsc92

Thank you.

Anything else I should look out for? It's a 70 gallon indirect paired with a Burnham PVG6.

Do I need to be concerned with the sizing of the circulator?

I'm sure it will be fine, he has been in business a long time and comes highly recommended. I just want to be well informed.

Again thanks for your feedback!

rsc92

Install is complete. He used 3/4 copper. The fittings on the indirect were 3/4 so he said there would be little to no benefit of using 1".

Thanks for the help.

icesailor

rsc92 said:

Install is complete. He used 3/4 copper. The fittings on the indirect were 3/4 so he said there would be little to no benefit of using 1".

Thanks for the help.

He's wrong about that.

Look at the ratings in the I/O manual. 1" reduced at the coil provides more flow.

kcopp

It probably would have been good to ask these questions when he was bidding the job. , not the morning of an install. 70 gallons is a lot of hot water. The recovery time will be a bit longer but unless you have a substantial demand ( ie fill a whirlpool and then need to take a few showers soon after) you will more than likely be fine.

rsc92

You are correct. Should have thought to ask these questions sooner. I checked the I/O Manual. Specs are based on 3/4"

Bob Bona_4

Ouch. Let me guess, something like a Taco 007 pump driving (not that the 007 isn't a fine pump) or zone valves?

It's a constipated loop. Would not accept.

rsc92

Indirect has its own circulator. its 18 degrees outside and house temperature is totally fine and 4 showers in a row (2 of which were simultaneous). all good. Maybe it would have been better with 1" supplying the indirect, but clearly this is working just fine. Cold tank (fresh fill) got to temperature in under 20 mins.

Curious though, if the coil in the tank is 3/4, that would be a bottleneck if 1" was used on the supply and return. Not really sure how flow would be enhanced by using the larger supply and return pipe. I am open to an education....

bob eck

The manufactures come up with a installation manual for a reason.
I would say it will work most of the time but using the wrong size supply and return piping and or the wrong circulator pump is this causing the home owner to use more energy to make his / her domestic hot water and costing them more money in the long run?

rsc92

I guess I am not convinced that the supply and return are the incorrect size. The indirect supply and return fittings are 3/4, so I don't understand the benefit of plumbing 1" to the indirect to only have to downsize to 3/4 anyway. Plus the spec sheet on the owners manual lists 3/4 for my model. The next model up is specd at 1".

SWEI

Pipe sizing depends on the boiler's output rating and also on the indirect's HX capacity. Charts provided in the indirect manuals are based on the indirect's maximum capacity -- it's up to the installer to know enough to make the correct sizing decision. In residential applications where the boiler is properly sized to the heating load, that will be the limiting factor.

What size is the boiler?

rsc92

The hx on the indirect is 3/4. Boiler is 130k output. Min btu for indirect is 120k. Circ for indirect is on priority

SWEI

There is really no minimum BTU for an indirect. What did the heat loss calculation say? You'd need a 40˚F ΔT to make 3/4" pipe work at a reasonable velocity.

SWEI

I'll bet the boiler is way oversized.

SWEI

3/4" pipe would probably have been the correct choice for a properly sized boiler.

rsc92

Boiler is not oversized. It runs 2 fan coils and 5 radiant zones. The radiant zones cover approx 1000 square feet of floor area. The indirect is a Burnham Alliance Stone Lined tank. Not the cheapest indirect by any means.

Thanks for all the input

jonny88

I actually inherited a 50 gallon Alliance.I have a grundfoss 26/99 and 1 inch copper.But to be quite honest as Hatterasguy has stated it is about the surface area of coil.Unfortunatly for me the 3/4 coil cant take heat away quick enough causing boiler to cycle a lot more.Cant see why they would not make a 1inch coil maybe Vaughn/Burnham were to cheap in this instance.I will be changing mine when I can .

Bob Bona_4

A 120k boiler wants to jam it's full on output to an indirect. With 3/4" piping....40k...maybe..maybe 50k at best is going to make it. Cue in short cycling, slow recovery, excessive pump on times, if that zone is prioritized, heat is going to be needlessly delayed. Not the ideal situation that doesn't have to be.

rsc92

Bob Bona - isn't the real problem the diameter of the coil in the indirect? Not the size of the copper to and from the indirect?

With that said, Burnham has been manufacturing the 70 gallon alliance for years - if it were truly an issue, I would have come across it in my earlier (pre-purchase) research. In fact, the Burnhsm Allance line receives very good feedback.

To your earliier point of a "constipated loop" - the flow would be little changed if the indirect was fed with 3/4", 1" or larger. Ultimately the flow is dictated by narrowest pipe, which in this case cannot be changed because it is the 3/4 coil inside the indirect. This is basic physics. All a larger supply and return line would accomplish is higher pressure and more turbulent flow inside the coil. It would have a minimal impact on gpm

jonny88

Burnham doesnt make the indirect.Vaughn makes it.You pay an extra 200 for the burnham sticker.

rsc92

Hatterasguy said:

rsc92 said:

To your earliier point of a "constipated loop" - the flow would be little changed if the indirect was fed with 3/4", 1" or larger. Ultimately the flow is dictated by narrowest pipe, which in this case cannot be changed because it is the 3/4 coil inside the indirect. This is basic physics. All a larger supply and return line would accomplish is higher pressure and more turbulent flow inside the coil. It would have a minimal impact on gpm

This is correct.

A 1" line feeding a 3/4" coil would give slightly more flow (because of the reduced headloss between the boiler and the indirect).

I would guess you'd see an additional 15% or so.

For a dramatic flow change, the indirect needs the 1" coil.

Don't believe all the glowing reviews...............a 3/4" coil in a 70 gallon unit is just plain stupid.

So what we are talking about is a slightly slower recovery versus a larger coil/supply/return. In the end the stone lined tank was the best choice for our water conditions. Tank is well built and has very little heat loss.

SWEI

The actual ΔT seen by the boiler will start out high if there is a big DHW draw and taper off as the tank comes up to temperature, which will work out fine for a typical residential or light commercial user.

What circulator did they end up installing? I'm a tad concerned about fluid velocity in that loop.

rsc92

He used a Taco 007-F5-7IFC. 1/25 hp. 3,250 rpm. Good or no good?

SWEI

Couldn't find head loss numbers from Burnham, but Vaughn was nice enough to post them on their site.

Looks like about 5.5 GPM, which is just fine for 3/4" pipe.

rsc92

SWEI said:

Couldn't find head loss numbers from Burnham, but Vaughn was nice enough to post them on their site.

Looks like about 5.5 GPM, which is just fine for 3/4" pipe.

So with the 3/4 supply and return, the circulator he used is ok?

Do you think I should go back to him and ask to Re-pipe to 1"? Will I even notice a difference in performance?

SWEI

As long as you're getting the hot water you need, I wouldn't mess with it.

jonny88

out of curiousity what temp is the indirect set for and did you put a mixing valve on unit.I agree with you that it is a very durable unit just wish they would increase the size of their coil.From a cold start how long did it take to satisfy?

rsc92

jonny88 said:

out of curiousity what temp is the indirect set for and did you put a mixing valve on unit.I agree with you that it is a very durable unit just wish they would increase the size of their coil.From a cold start how long did it take to satisfy?

That is a good question. When he installed it yesterday, he told me it got to temperature in about 20 minutes. I just did a test. I filled the whirlpool tub using only hot water. Capacity is around 70 gallons. By the time it was full, the water entering the tub from the spout was around 90 to 95 degrees. From the moment i shut the water off on the tub until the indirect was satisfied was 22 minutes. So clearly he exaggerated.

It is much colder today, not sure that really has an impact though - around 15 degrees outside.

The indirect is set at 137 degrees plus or minus. There is no mixing valve. I will be adding one.

How does that recovery time sound to you??

I may do another experiment and run the HW until its cold and time the recovery. What is a normal, acceptable recovery time?

In truth, the tub experiment is beyond anything we would usually do in regular practice. The tub water temperature once it was full was well over 100 degrees - too hot to use.

Again, thanks for the input. Much appreciated.

Tinman

I used the Alliance years ago. The last 10 years or so strictly the Triangle Tube. My only complaint about those is how dang heavy the bigger ones are.

SWEI

Those SMART 120's are a real bear. Took four football players to schlep one of them into a 1949 concrete basement.

rsc92

Just did phase 1 of the experiment. Ran 3 showers simultaneously at 90 degrees each (one of which has no water saver). They sustained for about 16 minutes before dropping to 85 degrees.

Next phase was to run hot water in whirlpool tub until it cooled. Ran for a heck of a long time and seems to stabilize at 82 degrees. Recovery took 27 minutes to get indirect back up to 137 degrees from presumably around 82 degrees.

Acceptable performance or NO??

rsc92

I just got off the phone with Tech Support at Vaughn. He said that a 1" supply and return would make little to no difference in the overall performance.

I told him about the results of my unscientific test and he said the results were good and along the lines of what he would expect in the field (real life??)

I inquired about a stronger circulator - at present there is a 007 running the DHW zone and was curious if jumping to a 0010 or even an 0011 would make a difference. He did not think changing the circulator would materially impact the performance. Anyone care to voice an opinion?

FWIW the actual draw from running the 3 showers was about 10.5 gallons per minute (again based on my very unscientific bucket test).

At the end of the day, the new Alliance performs better than the 75 gallon Rheem PV it replaced ever did. I installed the Rheem 16 years ago, before we had a boiler and while it served us well, it could never keep up with that draw.

Thanks to everyone for the input!

rsc92

Hatterasguy said:

Well, if tech support at Vaughn said it, it has to be true. They, of course, know much more than anyone on here.................

Well...... They should know more about their own product, but we all know that is not always the case. Either way, the gentleman I spoke with seemed very knowledgeable.

rsc92

I said he seemed knowledgeable, not that he was knowledgeable. Plus, his reasoning made sense.

With respect to your girlfriend's debacle, very unfortunate, but entirely preventable had she telephoned the embassy herself to get the proper information.

icesailor

Amazing the information you can get from the phone.

No disrespect for the problem.

If you have an issue to be resolved, and you ask three persons their opinion and all three agree, its a good chance that the answer is right. If you get three different opinions, you will have to figure out which one is the closest to your problem.

In My Experience.

Zman

It sounds like you have plentiful hot water. As long as the boiler is not short cycling, I don't think you have a problem.
Adding 20' or so of 1" to a 3/4" coil is not going to make much difference.

rsc92

11 feet of pipe in total. There are 8 elbows.

Boiler does not seem to be short cycling.

Now if I could figure out how to stop the whistling noise the boiler makes, I'd really be happy. Have had several techs and a Burnham rep all to no avail. Out of warranty so Burnham won't do anything. Definitely an air leak somewhere- noise starts as soon as fan turns on. It's not the exhaust vent either. Even disconnected it still whistles. Changed fan and gasket- did not help. Burnham PVG6

Well said Icesailor.

I meant no disrespect Hatterasguy

Thanks to all for the input.