Comments on Design of former Gravity Replacement Boiler Near piping

OldawgBryant

OK, thanks for all the help I've gotten from everyone. I have finished the design and am getting-out the wrenches tape and dope. But before I make a dope mistake, I am looking for comments on the near boiler piping layout. All near piping is 1-1/4" and a lot is threaded. Pumping away and both temp mixing valve & manual boiler protection (see my other post for all the specs on the system) I'm going to calculate the Head loss for this piping also. Flow is around 7.5-8.5 gpm. The goal is to have very limited space but have access to all components and isolate for service and repair in the future. Tying into the existing 1-1/4" & 1-1/2" black pipes of the 1 zone house. The Existing house piping is all black pipe, so the copper is the bridge from new to old. I am wondering how the flow will work at the (2) Tees for the single giant radiator. The house used to heat evenly, so I hope I have not screwed that up. Let me know what people think about the layout.
Thanks!

EdTheHeaterMan

Not the best design. You ARE pumping away from the expansion tank, however you are pumping into the boiler return. When you add the static pressure plus the pressure associates with the pump head, you will make the pressure in the boiler higher. If the circulator is located on the supply side of the boiler, then you will allow the boiler pressure to stay at or near the static fill pressure and add the pump's additional pressure into the system, This will increase the air removal ability of the system.

And what is the purpose of this part (green circle) and why is it located there?...

EdTheHeaterMan

Here is a recommended circulator, expansion tank, and air control system from a Weil Mclain boiler. This shows the Circulator, pumping away from the expansion tank on the boiler supply piping. I took the liberty of adding the bypass for the high volume system in RED on Figure 14 . You can add the dirt mag between the Isolation valve from the system return and the mixing valve on the boiler return

mattmia2

Those drawings are as hard to follow as someone's collection of pictures, but i think the green thing is a thermostatic boiler return temp protection valve.

OldawgBryant

The green is the Thermo mixing valve boiler protection, Caleffi. The directions show pumping away from the valve, hence the pump on the return. Also a hand mixing valve for insurance. I think pumping towards the valve will not work well. The drawing is a confusing looking because it simulates the dry piping that is there, so it does look like a photo... But with better angles to view it than a photo. and drawn to scale.

EricPeterson

@OldawgBryant - as far as the Caleffi valve goes, the important thing for the valve is to pipe it correctly, with the recommendation being that is it installed on the boiler return side. You have done that.
Yes, the diagram in the Caleffi instructions does show the circulator pumping into the boiler return, away from the valve, but I don't know how important that is. I piped mine with the circulator on the supply and pumping toward the valve. Either way on startup there is a tight loop of water flowing through the boiler and the valve, bypassing the system. I don't see what difference it makes as far as the valve is concerned.

You can call Caleffi and speak with a tech if want to get the final word, that's what I did, and they were able to answer my question, which was would the valve work with a single circulator (yes).


Eric

EdTheHeaterMan

@hot_rod works for Caleffi and is on here a lot as you already know. Perhaps he can look at my illustration and see if that is a better idea or if you have the better idea. The reason to pump into a boiler is that many ModCom boilers are designed with primary secondary design and the manufacturer wants the have higher pressure in the boiler to reduce the chance of the water flashing into steam in the tiny passages of those heat exchangers. You show a cast iron boiler, and they do not require the circulator on the return. In fact they recommend using a pumping away on the supply in most cases.

PS. I like you design software renderings. They are very easy to understand when you can provide so many angles of view. Looking thru the floors to the radiators above. Even angles that are impossible to actually take pictures of. Nice Job

hot_rod

the 280 is just a fixed temperature mix valve, nothing else.

When we use a thermostatic on a radiant loop for example, the concern is the pressure drop in the radiant loop being higher than the path back to the boiler, so the valve does not mix properly when pumping at the valve in that application.

With the valve just protecting the flow through a very low, cast iron boiler I would not worry so much about the mixing accuracy, easy enough to try?

Pumping away from the expansion tank is still the more critical detail for easy purging and the dynamic pressure being seen in the distribution..

The exp tank at the pump on the return is an option. Just be sure the pumps additional pressure does not pop the relief.

With a 12 psi fill and a common 007- 15-58 I doubt you would hit 30 psi on the boiler gauge, pumping at the boiler.

A high head circ could be more of a close call.

OldawgBryant

@hot_rod @EdTheHeaterMan I'm using a TACO 0010 I could move the pump & expansion to the supply, that's why I'm mocking it up dry-fit before actually installing. The drawing is easier to view than a photo

OldawgBryant

It would not be much to swap the expansion & pump to the Supply side

neilc

understand,
it's not moving the circ to the supply side of the boiler(unless the tank and feed is connected direct to the boiler),
it's moving the circ, or tank/feed connection, so that the circ pulls from the tank/feed, aka PONPC, this is pumping away, from the PONPC.

OldawgBryant

OldawgBryant

@neilc Right-O, in the drawings, you can see I can just switch from left to right the pump & Tee for the expand fill (and move the Tee below the pump) correct?

OldawgBryant

It does appear the manufacturer has no prob with pumping to the return for the bypass (probably a 007 TACO)

neilc

OldawgBryant said:

It would not be much to swap the expansion & pump to the Supply side

this sketch works,
the tank, then the circ, then the boiler, then the supply back up to the system,
no need to switch to the supply side of boiler,

EdTheHeaterMan

Can you see this working?
The actual expansion tank location can be lower or off the the side

neilc

does he need to pull from the boiler protection mix valve ?

OldawgBryant

This is from the manual

OldawgBryant

So the question is will I over pressure the boiler with the 010 going on the return?
@EdTheHeaterMan damn good job of rearranging my drawing so fast! (I used SketchUp, by the way, as all of these parts are free online and saves a lot of time.)

OldawgBryant

Just looking at it, I should probably swap the unions and ball valves to isolate the boiler THEN be able to open the union. As I've laid it out, if you crack the union, you have to drain the boiler (that's why I'm doing a dry run on this thing)

neilc

these last diagrams are showing a buffer tank,
not your expansion tank,
different tanks and purposes

OldawgBryant

I should be able to figure the system Head loss now with all the parts. I have Siggy's book with all the formulae. Since all this near piping is 1-1/4" I'm hoping the boiler can take the 0010 going into the return

OldawgBryant

@neilc I thought that tank was a symbol for the "load" of the system...

EdTheHeaterMan

I just like this better. (left) The boiler is kept at the lower (near static fill pressure) and you get the benefits of pumping away.
In the IO manual diagram, (right) there is a higher pressure in the boiler and the air vent fitting at the top of the boiler may be less effective at higher pressure. Just my own opinion, the extra air vent taping on the boiler will work a little better.

hot_rod

Shut off head on the 0010 is around 8’ or 3.4 psi. That should not cause a problem pumping into a boiler

OldawgBryant

@hot_rod do you think, from looking at these, the near boiler piping (all at 1-1/4") will have a substantial head loss for that pump? I can see the Caleffi units (DirtMAg Pro and the 280) have great C numbers, but what do you think about all my other piping around the boiler?

hot_rod

A couple feet maybe, nothing to be concerned about

OldawgBryant

@hot_rod Thank you sir! I go to sleep now with confidence for my work this weekend!

hot_rod

Apparently some boiler manufacturers have large warranty budgets. That that they show un-workable boiler protection @kits” based on variable speed circs

here is the explanation of how it really works with cold return to a boiler. The variable speed circ cannot add heat energy to the bypass loop

So how does  it mix 90 degree degree boiler water to 130F? Warp speed mode maybe🥴

neilc

OldawgBryant said:

@neilc I thought that tank was a symbol for the "load" of the system...

ok, buffer tank, building load, buffer tank and building load , , ,
can we sell you a buffer tank ?

mattmia2

Unless there is really a reason you can't do it, it is best to put the boiler, air separator/expansion tank, circulator since the hottest water holds the least air and lowest pressure water on the suction of the circulator holds the least air. Since the boiler is very low resistance the mixing valve can tap in to that wherever it needs to, the boiler essentially looks like a piece of pipe.

OldawgBryant

@mattmia2 Got it. I was going in that direction, but from everything I've read and seen that mixing valve seems to work best with the calculator pulling from it rather than pushing at it. I could have gone over 100 years with the last system, but the condensation in the last 25 years killed it. It ran about 140 deg, no pressure switch, but i had pressure problems trying to get over 140. The new boiler ain't gonna be built like that old one, so the return water is important to keep hot.

EricPeterson

@OldawgBryant - regardless of where you place the circulator, will be looking forward to a report on how the valve works for you in your setup with the Taco 0010. In particular I will be interested to hear if it's a little noisy at startup when the valve is closed to the system and just looping water through the boiler.

As I mentioned before, in my system, from a cold start it takes about two minutes for the boiler to raise the temperature to 140F so the valve starts to open, during that time I can hear some whining from the circulator. So I am thinking or replacing the 140 element with a 115 or 130.
It's not terrible, but I wonder if it will shorten the life of the circulator (B&G NRF-22).

If there was a variable speed pump that could be configured to run at a lower speed when the water temperature is low, that I would think would work well with the Caleffi valve.

Which element are you planning on using in the Caleffi valve - 140, 130, or 115?

Eric

OldawgBryant

@EricPeterson The one I got came with the 130deg element. There is not much distance to go with it closed, so I hope it gives me no problem. Then again, I'm used to having to oil-up the Red BAron this time of year every year, and that pump was a pig! With radiators it is like having a speaker system in every room for your heating system...

EdTheHeaterMan

neilc said:

OldawgBryant said:

@neilc I thought that tank was a symbol for the "load" of the system...

ok, buffer tank, building load, buffer tank and building load , , ,
can we sell you a buffer tank ?

I get the joke @neilc ...Funny, But some of my attempts at comedy go over some folks heads. They are not expecting levity in the answers to their problems and may take you seriously.

@OldawgBryant ...No buffer tank needed because you have a large volume system. The buffer tank is used for systems with Micro Zones of other situations where short cycling is a problem. Not your situation, not your problem, you don't need a buffer tank

OldawgBryant

@EdTheHeaterMan what? I thought the buffer tank was for your jokes! (just kidding) I am thankful for you and everyone here on the wall as I have learned much in my recent excursion into this project.

mattmia2

EricPeterson said:

If there was a variable speed pump that could be configured to run at a lower speed when the water temperature is low, that I would think would work well with the Caleffi valve.

That's what a delta p circulator does, it tries to maintain the same pressure increase regardless of flow so if there is a only a few zones open or in your case only the bypass open it ramps down speed to produce a reasonable flow in that bypass.

SuperTech

mattmia2 said:

If there was a variable speed pump that could be configured to run at a lower speed when the water temperature is low, that I would think would work well with the Caleffi valve.

That's what a delta p circulator does, it tries to maintain the same pressure increase regardless of flow so if there is a only a few zones open or in your case only the bypass open it ramps down speed to produce a reasonable flow in that bypass.

Taco makes the VT2218 that can vary the speed depending on the temperature of the supply and return. Tekmar makes variable speed pump controls that will work with any PSC wet rotor pump.

hot_rod

I don’t think you will need to go that far on a small circ system like this. I think just a setpoint control function would work to vary the circ speed, no need to measure two temperatures, just the return

Actually all the Resol and other brands of solar controls do exactly that, ramp the pump speed up as the temperature increases at the collector. It’s a simple, fairly inexpensive control with a triac relay as the speed function. A wave chopper basically. They do cause the pump to pulse a bit, noticeable down around 20%

You can set the rise and the step%. For example for every 5degrees of temperature increase it stepsup 10%

PeteA

EdTheHeaterMan said:

I just like this better. (left) The boiler is kept at the lower (near static fill pressure) and you get the benefits of pumping away.
In the IO manual diagram, (right) there is a higher pressure in the boiler and the air vent fitting at the top of the boiler may be less effective at higher pressure. Just my own opinion, the extra air vent taping on the boiler will work a little better.

@EdTheHeaterMan I am going to be installing my 280 valve in the same orientation as the image on the left that you attached so I am hoping for a smooth ramp up of temperature and then a gradual opening of the valve to distribute the water through my radiators. I bought the one with the 130 temp setting so I'll let you know if I get any noise or issues when the system ramps up. I will also attach some photos of my set up for everyone to poke fun at me so get you note pad ready . won't be this weekend probably in the next 2 weeks.

EricPeterson

@EdTheHeaterMan - so pumping towards the valve? 

That’s how mine is piped and it works fine, only thing is some is some whining noise when the valve is closed, which I attribute to high water flow (over 7 FPS) due to the GPM and low head pressure.
What circulator are you using?

Eric