Gravity hot water not circulating.

[R1CKY]

Got asked to look at boiler today as they had no hot water. It was an old Worcester Heatslave oil fired boiler with pumped heating and gravity hot water.

The flow was only getting hot about 6-7 inches above the boiler. The whole install is a mess, feed and vent are BOTH 15mm. The feed used to be tee'd in to the heating flow or return and the vent is still connected to the heating flow or return. The feed had been capped in the attic and is now tee'd into the primary flow. Also the primary and heating return are joined via a 15mm ballofix valve.

Here is where it gets confusing, the primary return is going to the top of the cylinder and flow to the bottom. Plus to make it more difficult, the entire upper floor is concrete, with the pipe buried in it!

My question is, will the incorrectly piped cylinder stop gravity circulation? The customer has only lived there for 3 weeks, so don't know if it has ever worked!

I mentioned converting it to fully pumped, but the vent is 15mm and there is a concrete floor between the cylinder on the first floor and the boiler on the ground floor!

 

[stevetheplumber]

if the pipes are buried how do you know its reversed

 

[R1CKY]

Forgot to mention, I cracked a compression joint on the top connection to the cylinder, the lower pipe started getting warm. Went down to the boiler and the return was still cold and the flow was hot all the way to the ceiling. Plus the flow is on the left down by the boiler and the lower connection to the cylinder is connected to the left pipe coming out of the floor, it is unlikely anyone has crossed the 28mm pipes under the concrete.

 

[stevetheplumber]

did you get water at the cylinder when you cracked the nut?

 

[Leo21]

Check for blocked cold feed.

 

[R1CKY]

Yeah, my first thought was an air lock, that's the reason I cracked it. The pipework rises from the boiler to the first floor, then has about a 4 metre horizontal run to the cylinder, I'm also thinking this is too much for gravity to work.