Hot water upstairs 18degrees lower than downstairs

oldbrit · 1 Jan 2011

Hiya, this problem has only just occured and the system has been working fine up until now and no work or alterations has been done to the system.

Noticed last week that the shower (Mira Excel running from a Bosch condensing combi boiler) doesn't get hot enough for a comfortable shower and is tepid at best even with the Excel control knob set to override the max temperature stop. The only way to get a really warm shower is to set temp to max and turn the flow control down to almost minimum. The water from the bath and sink hot taps also starts off hot but soon becomes tepid.

Called British Gas to check the boiler and they say it is working correctly and they checked the temperature difference of running hot water downstairs and upstairs and there is an 18 degree difference! The kitchen tap is the first in line from the boiler.

The engineer said he had not seen that before and suggested that maybe there was cold water entering the hot water system thru the shower controls.

Is this possible. I need to be sure before forking out nearly £100 on a new cartridge for the shower ! Any suggestions please?
Many thanks

twgas · 1 Jan 2011

It is possible, especially if there is a pressure reducing device anywhere.

sherbert · 1 Jan 2011

IF possible fit some non return valves on the pipework to the shower .. sounds like the cold is going around around the shower valve

oldbrit · 4 Jan 2011

Well, I can safely say that it is not down to the shower as the cartridge has now been replaced which has fixed an annoying little dripping problem but the temperature differential still remains.

Will give Worcester Bosch a ring when they open today and hopefully they can throw some light onto the problem. I can get really hot water upstairs but only by turning the bath hot tap on by only a small amount and the water flow is pathetic, would take hours to fill the bath, but the water is hot ! Turn tap on as normal and the water is tepid at best.

Agile · 4 Jan 2011

I would agree with the BG engineer, cold water crossover is a likely cause.

Do you have joystick taps?

Turn off cold inlet to boiler and see if anything comes out of any hot taps anywhere.

Tony

oldbrit · 12 Jan 2011

British Gas called in Worcester Bosch engineers who checked the boiler over and said all was okay, he also suggested that there was cold water crossover in the taps upstairs. Turned off cold at the boiler and opened hot taps upstairs but nothing came out.
Covered by full contract with British Gas, so plumbers come and disconnect the cold water supply to the upstairs taps and guess what.... the hot water is STILL LUKEWARM !! The hot pipe under the kitchen sink is very hot, 2 metres away in the bathroom above the kitchen where the same pipe emerges from the floor, the pipe is lukewarm at best.

The plumbers suggest the boiler is still at fault, as it appears unable to push the water up a floor level. They suggest that maybe the divertor is crusted !!!

One thing that is very noticeable after all this work being done is that the pressure at the kitchen tap is extremely strong, never had it that forceful before, but the pressure out of the bathroom tap is just a slow stream, very little pressure.

Going round in circles now but still cannot have a hot shower or bath!

Agile · 12 Jan 2011

If only I had ALL the details of your installation then I could identify the fault!

If there was a SEVERE restriction in the HW supply to the upstairs and it only gave say 5 li/min then its conceivable that it could lose 18 degrees IF the pipe is old steel or lead buried in the wall for a considerable distance.

If it were proper copper pipe with insulation there is nowhere for the heat to be going.

Tony

oldbrit · 13 Jan 2011

Oh wouldn't it be nice to have a hot bath or shower!! 2 weeks now without hot water upstairs.

The pipes are copper, insulated and leave the kitchen in the void of the boxed in soil pipe which continues in the bathroom then into the loft and out onto the roof, the copper pipes obviously leaving this void under the bath.

B Gas came out again today and this time isolated EVERYTHING except the upstairs hot taps. Put an isolating valve in the cold supply to the upstairs so no mains cold is going upstairs at all.

Washing machine and dishwasher supplies turned off even tho they are only cold supply. Kitchen tap cold isolated. So the hot water from the boiler only has to supply the bath tap. Still TEPID at best!! CH checked and no hot water going into those pipes.

So, Worcester Bosch coming out again tomorrow. Hope this time they can find the cure!

But WHERE is the hot water going? It definitely seems that the hot upstairs is being mixed with cold, but WHERE is the cold coming from?

The saga continues............

I should have said earlier, the Heat exchanger plate and two sensors were replaced before the Bosch engineer was called in, and he also changed the divertor(?)

joe-90 · 13 Jan 2011

If cold water was being added to the hot I'd have thought you'd have MORE water not less. My guess is a partially blocked plate heat exchanger that is see-sawing hot/cold which equals luke warm and reduced flow.

Morris40 · 13 Jan 2011

let us know how it turns out

oldbrit · 14 Jan 2011

Sigh...............................

Worcester engineer came today, said the flow rate was set too high in the boiler so adjusted it, showed me that it was working. Great says I, at long last.

Ten minutes after he left I now have NO hot water anywhere and the Central heating is not working. The water temperature on the electronic display says '99' so to be safe I have switched boiler off and guess what ?........Yet another visit from a British Gas engineer sometime tomorrow (Saturday).

Surely there must be some redress by now. Unable to bathe for 2 weeks and now no heating just to add spice! So to date that is 8 engineer visits in 14 days and still the boiler does not work correctly. And just to rub the salt in, I cannot directly contact anyone in authority to vent my displeasure.

What would you do in my situation?

Agile · 15 Jan 2011

oldbrit said:
Sigh...............................

Worcester engineer came today, said the flow rate was set too high in the boiler so adjusted it, showed me that it was working. Great says I, at long last.

What would you do in my situation?

YOU told us it was leaving the boiler at say 50 C and arriving at the hot taps at 32 C.

But that does not fit with what the makers engineer found!

If only I had all the technical information then I could say what the fault is!

You say "no hot water"! But thats not a correct statement!

What is the flow rate from hot tap and what is the temperature?

I have no idea whats going on but you seem to have had seven visits too many! I suppose that just demonstrates the severe lack of skill in many employees.

Tony

joe-90 · 15 Jan 2011

Agile said:
I have no idea whats going on

Tony

We've noticed.

picasso · 15 Jan 2011

I had the same problem with a ferroli domicompact, the cold water pressure was slowing the hot flow through the boiler so much it was over heating, fitted a pressure reducing valve on the cold supply to the shower and the problem stopped.

sherbert · 15 Jan 2011

I would still say that its going around a shower

What shower do you have so that I can tell if it has built in NRVs

That is the most likely fault

Sherbert

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Hot water upstairs 18degrees lower than downstairs

Morris40

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