Correct installation of the expansion vessel in the DHW installation

Question

Is this diagram correct?
I have a similar system, only behind the water meter there is a reducer set at 4 Bars, which indicates 6 Bar while the water is heating.
I do not have an expansion vessel, so I am asking if it can be installed this way?

stanislaw1954 · Answer

It is natural, when the water is heated, its volume increases, and since there is no outlet, the pressure increases. There can only be one correction: between the valve on the cold water inlet to the boiler and the tee for the safety group, a check valve should be installed so that the water does not flow back from the boiler to the entire domestic installation, but only discharges its excess in the aforementioned safety group.

alienone · Answer

A few more questions
1.supply of the safety group with what minimum cross-section
2. Does the location of the vessel bottom - top in relation to the bolier have any significance?
3. vessel with initial pressure with what parameters

stanislaw1954 · Answer

1- even 1/2 is enough, because it only releases pressure. 2-there is no, and it makes sense to return, as in the picture. 3-approx. 1.5 bar is enough.

alienone · Answer

I do not understand on the return, that is, not on the cold water supply

stanislaw1954 · Answer

This postage was unintentional. Of course, on the cold water supply. Include a check valve.

alienone · Answer

Thank you for the clarification, this week I will want to rebuild. After the modernization I will let you know.
I do not really understand the dependence of the pressure from the network, e.g. 4Bar and the expansion vessel, e.g. 1.5 Bar or 4 Bar, which one to choose?

stanislaw1954 · Answer

Since you always have 4 bars in the network (I do not take into account the increase caused by water heating), 4 bars in the expansion tank is too much. Search the internet, but I assume 1.5-2 bar is enough.

ls_77 · Answer

DHW expansion vessels are factory filled with ~ 3.5-4bar.
Those with a filling pressure of ~ 1.5 bar are most often for CO and are not suitable for DHW!
Look for hot water vessels.

If you have ~ 4 bar at the input from the mains, then as much as at the input I would set in the vessel.

DiGital_Butcher · Answer

Exactly as a colleague writes, you need a DHW vessel (preferably buy a reflex DD) and the pre-pressure in the vessel is 4 bar at home, set 3.5-3.7 on the reducer and you'll be fine. If you set a lower pressure in the vessel than you have in the installation, you will fill it with water immediately after unscrewing the valve, and the point is that the vessel will expand the excess pressure that increases when water is heated.

emigrant · Answer

Correct installation of an expansion vessel for DHW is a flow vessel and its gross capacity is calculated taking into account several variables. As the installation has a pressure reducer, the initial pressure in the vessel should be set by 0.2 bar lower than the pressure downstream of the reducer. In your case, the precharge pressure in the vessel should be set to 3.8 bar. To work properly, the vessel must always be partially filled with water. Must be visible for installation. Enter how many liters you have a boiler, I will tell you what capacity you should buy an expansion vessel. Remember about a good branded check valve that should be installed in front of the expansion vessel.

alienone · Answer

I have 80 liters of Boljer. Tomorrow's assembling the chip. I was a bit surprised by the white Flamco expansion vessel, the manufacturer recommends installation with the valve facing down, so I have to change the safety group as in the photo with the appropriate diameter for the vessel. I think it will be correct.

emigrant · Answer

Remember that Flamco Airfix A and Airfix D are flow-through vessels and must not be installed as a non-flow vessel. In general, non-flow vessels for domestic hot water should not be installed ...
With the parameters you have and the pre-pressure setting of 3.8 bar, you should have a vessel with a gross capacity of 8.6 liters, i.e. the closest you can buy is a 12-liter vessel. The redundancy of the vessel does not matter.

BTW, this safety group in this photo doesn't meet any drinking water requirements. There, only rust will be produced from the inside, and it is not known what else. If you want, some safety groups are entirely brass, not steel, painted with paint. Apart from the fact that in this photo there is a non-flow vessel attached. In fact, it is not known for what purposes the water from this installation is in the photo.

alienone · Answer

This is Airfix R, so I can not mount it as in the photo?
I have a safety group Diamond Brass CWU 6Bar. The photo I put in is borrowed from the network
Replace the 12 liter tank with the blue Diamond too and supply it directly from the tee keeping the valve facing down, okay?

emigrant · Answer

The photo rather shows how not to do. Airfix R is a non-flow vessel and you can install it as in the photo ... BTW, the R series is probably a slightly different application than DHW ... Even there is no PZH approval like the A and D series. Water can smell a bit of EPDM rubber from this R vessel I see they used a diaphragm pouch as it is in the non-flowing blue Reflex Refix DE.

alienone · Answer

I edited the above post, will it be okay if I mount the vessel with Diamond?

emigrant · Answer

No, it won't be okay. Return this Airfix R and simply buy the flow-through Refix DD and a Flowjet for it. Connect the cold water supply by flowing through the vessel (tee) to the boiler. Google Refix DD (green or white) and Flowjet google. No security groups are needed. The ZB 6 bar should be as close to the boiler as possible, the maximum distance from the boiler 100 cm (at least this is what SYR recommends for its membrane ZB). Preferably right next to the boiler connection. Not installed in some safety groups ...

That it wasn't. If you install a non-flow vessel, it will work properly as it should. Only for DHW in homes, such dishes should not be installed. Such a vessel can be the habitat and multiplication of legionella. It's really just about sanitation. Because whether it will be a flow-through vessel or a non-flow vessel, both will work properly and fulfill their function. There is always fresh water in the diaphragm at the flow-through vessel ...

alienone · Answer

Now I have a problem. Today I bought accessories, they don't have them in my shop
Reflex Refix DE.

The purchase of the group was made to facilitate the assembly and to have an overview of the pressure. Currently, I have a safety valve directly on the bolt head and 5 liters of water is dripping a week

emigrant · Answer

Water is dripping because you don't have an expansion vessel. Due to the fact that each connection should have an anti-pollution check valve, the internal installation is made in a closed system. Therefore, an expansion vessel is required. The ZB 6 bar itself is a total last resort and is supposed to work only in an emergency, e.g. if the diaphragm has broken, or the thermostat in the heater has broken down and heats the water until it boils.

Install a thermo-pressure gauge on the hot water outlet of the boiler. I have one installed in the range up to 10 bar and 120 degrees Celsius. You can view pressure and temperature.

alienone · Answer

Tomorrow I will try to replace the vessel and recharge it according to the manufacturer's instructions

emigrant · Answer

What capacity did you buy the vessel with that you intend to replace? I understand you will replace non-flow ones with non-flow ones?

alienone · Answer

I bought 8 liters but from what you wrote earlier it should be 12 liters. this is the diagram and is it a flow vessel or not?

emigrant · Answer

An 8 liter vessel would even be fine for a 100 liter boiler, but not with this downstream pressure setting. If you want to use a pressure of 4 bar downstream of the regulator, the initial pressure in the vessel should be 3.8 bar. The 8 liter container is too small.

I do not see the diagram exactly, because the photo is too small. Flow-through vessels on the Polish market, you probably have only 3. From Flamco Airfix A and D and REFLEX Refix DD. I guess that's it. I don't know the others.

alienone · Answer

I should mount the flow-through how to recognize it

emigrant · Answer

After all, I wrote like ... Eh ... From the company REFLEX, the flow units are marked as Refix DD, they are green or white. Blue Refix DE are non-flow vessels. From Flamco it is white with the designation Airfix A (not full flow) or Airfix D (full flow). I don't know the others.
Don't think that you give a tee to the non-flow underneath and make it automagically flow-through.

alienone · Answer

It was a boyish boy right away. I understood a lot, thank you for your help. greetings

emigrant · Answer

I think you already know what you will do and what you will buy is your business. Good luck.

alienone · Answer

I simplified it to such a solution. They don't have flow-through vessels in the store,
cold water supply - check valve - triangle with 12 l vessel - 6Bar safety valve - 80 L bolster plus PEX 20 connection

It'll be all right ?

emigrant · Answer

The diagram is correct for a non-flow vessel. Remember that the ZB should be in a vertical position (they are not through). Pass-through are the so-called combined with the non-return valve, but you cannot use it in this situation as shown in the diagram, because you will cut off the expansion vessel from the boiler. Also remember that the vessel is not mounted spicy. It must be on the so-called quick-release coupler, so that the vessel can be disconnected from the system at any time, e.g. to periodically check the initial pressure. The initial pressure is checked with the vessel disconnected from the system. No closing of valves and no depressurization of the boiler through the hot water tap.

alienone · Answer

You deserve a good bottle

[Solved] Correct installation of the expansion vessel in the DHW installation

Post #1

Post #2

Post #3

Post #4

Post #5

Post #6

Post #7

Post #8

Post #9

Post #10

Post #11

Post #12

Post #13

Post #14

Post #15

Post #16

Post #17

Post #18

Post #19

Post #20

Post #21

Post #22

Post #23

Post #24

Post #25

Post #26

Post #27

Post #28

Post #29

Post #30

Topic summary