No hot water away from boiler

[Shevek]

Hi all, hope someone can give some advice.

We have a 2.5 year old Vaillant Ecotec Plus 837 (installed May 2014) that has had it's 2 annual services (May 2015 & June 2016).

CH is fine, no problems at all.

HW goes to kitchen sink (mixer), downstairs sink (separate), downstairs shower (thermostatic mixer), upstairs sink (mixer), upstairs bath (mixer), and upstairs shower (thermostatic mixer)

Kitchen sink is fine but it gets colder the further away you get.

In summer we don't really notice it but now the weather is colder it's really becoming a problem.

It's been like this every winter since we got it but it seems to be worse this year

Downstairs bathroom tap is warm at best and upstairs taps are almost no heat. The shower upstairs will only get hot if you run the cold tap in the sink at the same time.

I just ran the bath tap for a while and then checked the copper feed and the pipe is not hot at all.

The boiler temp is set to the maximum 65 degrees.

Any suggestions as to what might be causing it?

TIA

Shevek

 

[wannocks]

Turn the cold supply into the boiler off. If there's still flow at the hot taps there's a faulty mixer or cross connection somewhere.

 

[JohnD]

You have a lot of mixers.

Without running them, feel the "hot" pipes of each. Are any of the hot pipes surprisingly cold?

This can happen when the hot water is fed from a tank, and the cold water to the same tap is fed at mains pressure (i.e. you can't stop the cold flow by pressing your thumb over the spout) and the mixer is faulty, allowing cold water to flow up the hot pipe.

 

[Shevek]

You have a lot of mixers.

Without running them, feel the "hot" pipes of each. Are any of the hot pipes surprisingly cold?

This can happen when the hot water is fed from a tank, and the cold water to the same tap is fed at mains pressure (i.e. you can't stop the cold flow by pressing your thumb over the spout) and the mixer is faulty, allowing cold water to flow up the hot pipe.

It's a combi so no hot water tank and all cold is mains fed.

 

[Shevek]

Turn the cold supply into the boiler off. If there's still flow at the hot taps there's a faulty mixer or cross connection somewhere.

I'm not sure how to do that - all the pipes to the boiler are boxed off

 

[AGAS]

should have access to the boiler isolating valves , other words take the boxing off

 

[Shevek]

should have access to the boiler isolating valves , other words take the boxing off

That's what I though, but they are all sealed up by the guy who did it... Even though I asked him not to and he said he wouldn't! Oh well, I'll have to crack it open and reseal it.

 

[Shevek]

I have just tried something with the upstairs sink - mixer over to hot, full on, water comes out quite hot but not too hot to hold my hand under. Switch the flow down to around half and it immediately goes completely cold. Does that suggest the mixer being fubar and the mains cold is pushing back into the hot?

 

[wannocks]

If there are isolators on each tap or mixer you can try them all one at a time to find it. Turning the boiler isolator off is easiest. Just wondering, how were your services carried out properly if the service valves are inaccessible?

 

[Shevek]

If there are isolators on each tap or mixer you can try them all one at a time to find it. Turning the boiler isolator off is easiest. Just wondering, how were your services carried out properly if the service valves are inaccessible?

Heh, the box was put in after the last service - the same bloke who does the servicing (and installed the boiler)... I asked him to box it off when he serviced it last time.

 

[Doggit]

Do you have a thermometer that you can put in a hot water pipe as close to the boiler as possible, and see what the temperature is. It's possible that the temp reading on the boilers wrong (try setting it to 70), and being a combi, the water heater exchange plate might need descaling.

 

[Shevek]

Do you have a thermometer that you can put in a hot water pipe as close to the boiler as possible, and see what the temperature is. It's possible that the temp reading on the boilers wrong (try setting it to 70), and being a combi, the water heater exchange plate might need descaling.

65 is as high as it goes for DHW... only CH goes to 70. I can check the hot water in the kitchen tap as that is ~2m from the boiler

 

[Doggit]

Sorry Shev, didn't spot the "maximum" in your OP. If you're checking the kitchen tap which is a mixer, can you turn off the cold water to it to make sure only the hot comes out.

In theory, if the kitchen sink is okay, but it gets colder as you go further away from the boiler, then the question becomes are the pipes steel or copper, and are they accessible, or bedded in the wall, as this will suck the heat out of the water. If the pipes are copper, and can be got at, can you put pipe insulation on them.

 

[Shevek]

Sorry Shev, didn't spot the "maximum" in your OP. If you're checking the kitchen tap which is a mixer, can you turn off the cold water to it to make sure only the hot comes out.

In theory, if the kitchen sink is okay, but it gets colder as you go further away from the boiler, then the question becomes are the pipes steel or copper, and are they accessible, or bedded in the wall, as this will suck the heat out of the water. If the pipes are copper, and can be got at, can you put pipe insulation on them.

Yep, there are isolators on that one. That is the newest of all the sink mixers though, I changed it myself a couple of years ago.

 

[Shevek]

So, I finally got round to sorting this...

I noticed that the hot feed to the upstairs shower was hot when running the shower - too hot to touch.

So on a hunch I bought a new bar shower (non-thermostatic this time) and fitted it this afternoon.

Lo and behold, everything is now wonderful!

Shower, bath, and sink hot taps now working as they should be.

Thanks to all for your advice