HW Cylinder, 22mm feed, 15mm return question?

[Muzz]

Hi,

As mentioned on some of my other posts, i'm planning on replacing my gravity fed cylinder with an unvented or thermal store (depending on whether i pay for a pro or diy myself)

I've got a bosch worcester greenstar 24ri boiler, 2 years old, sealed system, S plan (i think).

My current system is 22mm in the garage until it disapears under the floor, the cylinder connections are 15mm feed and return.

I've found one of the inspection hatches they cut in the floor. The cylinder feed is 22mm until about 1m from the cylinder down to 15mm, but the return looks to be 15mm all the way back to the garage.

I can't rip up my lounge floor yet, but will and I'm sure i'll be able to replace all with 22mm, but hypothetically, is 22mm feed to cylinder and 15m return ok?

I'm probably going to put in about a 180litre cylinder, which will serve 1 bath, 1 shower, 3 basins, 1 sink..

Cheers,

 

[charliechaplinspants]

I think you need to look at and sort out what goes where in your heating system first, then understand the pipework before deciding on the size of cylinder you need to put in. You can`t fit an unvented cylinder yourself.

 

[Muzz]

Not planning on fitting an unvented myself, hence why I am also considering a thermal store as the diy option.

I was just about to edit my post to say that it looks like the return from the cylinder is 15mm until it gets to the garage.

I can see two manifolds in the same inspection hatch connected to 22mm for the feed and return for the heating loop.

In the garage I have two 22mm going in for HW and CH, one 22mm coming back, with a 15mm that then tee's into it.

 

[charliechaplinspants]

If you are keeping the cylinder, then you will be replacing your regular boiler, I would expect to see 22mm flow and return pipes at the cylinder but it`s not uncommon in older systems for the return to be reduced to 15mm.

 

[Muzz]

As mentioned, I'm keeping the boiler as it's only 2 years old, but replacing the cylinder. It's 25 years old and I want mains pressure HW.

I'm aware 22mm feed and return is specified on the cylinders I've been looking at. My question was would 22mm feed, 15mm return cause any problems if I couldn't replace the 15mm?

The CH/HW pipework in the house is at least 15 years old so looks like it follows the older method you mention.

I'm guessing longer to heat the cylinder would be one problem, any others?