Hot water not getting hot enough

[lavinpj1]

Hi Folks,

I have a Worcester 40CDi boiler installed about 8 years ago (new when I bought the house) along with a Megaflow hot water tank - not sure of age, maybe 15 years old? Tank is one of the all in one pre-insulated, plastic coated types.

I know the system pretty well as the boiler was fitted by a Worcester accredited muppet who couldn’t get it fully working and then left the job and didn’t come back. As such, I replaced and rewired pretty much all of the electrics 8 years back, as hardly any of the old parts still worked.

For the past week or so, the hot water from the tank hasn’t been particularly hot. It’s warm, but not hot.

I ran the hot water cycle on the Hive timer for 5 hours this morning and still no “hot” water.

The 2 port valve opens and closes fine, when it should. The pump runs fine and also runs the CH, which works fine. The boiler turns on as it should, and reads about 72c.

The cylinder stat (set on about 62c) seems to work fine. After 5 hours of running, valve is still open and pump is running. I have to turn the stat down to about 40c before that all turns off.

I felt a slight drip from the PRV outlet from the tank last week so I drained and reprimed the tank, per the instructions on it, suspecting the air gap might have been lost. No signs of dampness around the PRV outlet today but water is still not particularly hot.

Flow pipe to the tank measures about 60c and the return about 32c. This is after 5 hours of running… I’d expect the return to be a lot hotter after that time.

Tank insulation seems fine. Tank is cold to the touch and it stays hot when water is heated with the immersion.

Any ideas on what this might be? Perhaps dirt build up in the tank’s heat coil? I don’t have a power flusher but could maybe try a mains flush as it’s only a few feet from the filling loop.

Any advice would be appreciated.

Thanks

Phil

 

[oldbuffer]

1. Hot water running to waste somewhere?
2. Mixer tap allowing back flow of cold into cylinder? Shouldn't happen on equal pressures, but possible if cold not taken off combination valve.

 

[lavinpj1]

Just tried a mains flush on the tank. Keeping it short, fill loop is on the return. Isolated CH return pipe with isolator on the magnetic filter, isolated the pump valves to keep it out of the boiler, manually opened 2 port valve to hot water tank flow. Opened the drain off, which is directly on the return pipe from the tank and some minimal water came out. Turned on fill loop and pressure is now at 2.5 bar with no water coming out drain off. Feels badly blocked to me. Any advice on unblocking it?

 

[terryplumb]

1. Hot water running to waste somewhere?
2. Mixer tap allowing back flow of cold into cylinder? Shouldn't happen on equal pressures, but possible if cold not taken off combination valve.

If this were the case ,then water heated by immersion would suffer the same fate,but apparently it doesn't and hot water is Ok.
Suspect blocked coil.

 

[lavinpj1]

Might have found the problem. There is a PRV with the pressure gauge on it installed on the return pipe from the tank. This was installed by the boiler installer as he didn’t realise the boiler didn’t have a pressure gauge built in and couldn’t get a gauge without a PRV attached quickly enough.

I removed the nut on the tank side and air was sucked in and water drained from the drain off. I took it apart and it was clogged with magnetite and the spring heavily rusted. Spring snapped when I tried to remove it.

I’ll replace it with a gauge on a tee and see if the problem is resolved.

 

[lavinpj1]

Might have found the problem. There is a PRV with the pressure gauge on it installed on the return pipe from the tank. This was installed by the boiler installer as he didn’t realise the boiler didn’t have a pressure gauge built in and couldn’t get a gauge without a PRV attached quickly enough.

I removed the nut on the tank side and air was sucked in and water drained from the drain off. I took it apart and it was clogged with magnetite and the spring heavily rusted. Spring snapped when I tried to remove it.

I’ll replace it with a gauge on a tee and see if the problem is resolved.

Pretty sure that solved it. It flushes ok now and the return feels a lot hotter. Will see in a few hours if the water is hot.

Thanks for the help all