Heating but no DHW

[opps]

Hi all.

My mother has heating but no domestic hot water- actually, the DHW water is lukewarm. My limited experience is, erm, limited to combi boilers.

I suspect that the diverter motor is stuck.

She will phone the plumber tomorrow. In the meantime, can the little lever be slid over to allow DHW? And if that diverts the flow to DHW, can it be slid back to provide heating after? Sorry, that is a clumsy way of asking if the lever can be used to divert the flow path? And if yes, when in auto mode, how does it know know which to prioritise either when they are both set to come on by the timer at the same time? Does it vacillate between the two? Or does it, when working properly functioning, allow both?

I am only guessing, but for some reason, I am inclined to think it might be a Honeywell Y Plan Zone Valve. I could be wrong though.

Thanks in advance
.

 

[terryplumb]

Latching a motorised valve into manual allows water to flow to both heating and domestic hot water cylinder on a Y plan set up.
Show us a picture of the valve.

 

[CountryFan]

Sounds plausible to be a y plan/3 port mid position valve but as per @terryplumb a photo would help confirm this

 

[opps]

Thanks to both of you.

I will try to take a photo later.

So given that both the heating and DHW are set for the same duration (twice a day), there is no downside if I slide the lever, and if that is the case, why not leave it on manual?

 

[terryplumb]

The disadvantage of the system being manually latched open ,is there would be no independent control between heating and DHW. They would both be either on or off.

 

[opps]

The disadvantage of the system being manually latched open ,is there would be no independent control between heating and DHW. They would both be either on or off.

Thanks mate, it means that she will have both CH and DHW.

Many thanks.

 

[opps]

Latching a motorised valve into manual allows water to flow to both heating and domestic hot water cylinder on a Y plan set up.
Show us a picture of the valve.

Sorry. It is a single motorised Honeywell dual port valve. There is a single on the central heating pipe as well.

I slided the lever, it kept popping back but I eventually got it to stay put. I then told the timer unit to run the DHW. The grunfloss pump fired up and I could feel water entering the immersion tank. After about 7 minutes the grunfloss stopped again? I wasn't expecting that.

However with both the central heating on and the DHW, the immersion tank filled up nicely. So thank you to both of you.

After the timed cycle had finished, I let the lever slide back to off in case my mother wants to run the heating during the day.

Regarding the grunfloss pump, is it just pushing the water down to/from the back boiler? The pump and immersion are on the first floor, the back boiler is on the ground floor. The header tank and cold water tank are in the attic conversion.

Apologies for the additional questions, I am trying to understand such systems work.

 

[CountryFan]

Yes basically the pump activates when there's a demand from heating or hot water, via the programmer and motorised valve(s). The pump would then overrun after demand has finished/is satisfied for a determined period. This is heated and sent round the flow pipes and returns to be heated via return pipes to and from the boiler.

 

[opps]

Yes basically the pump activates when there's a demand from heating or hot water, via the motorised valve(s). The pump would then overrun after demand has finished/is satisfied for a determined period. This is heated and sent round the flow pipes and returns to be heated via return pipes to and from the boiler.

Thanks. So why, when the DHW only was on did it (the pump) stop after 7 minutes. I wouldn't have thought that 7 minutes would be long enough to fill an immersion tank. Ordinarily, the timer is set twice a day for both CH and DHW and I am pretty sure that the Grunfloss runs continuously for both of the 2 hour sessions, even when the room stat is not calling for CH.

Thanks for explaining that it is the valve that triggers the pump, I guess that the control PCB on the valve is more faulty than I realised.

 

[terryplumb]

Was the water in the cylinder already hot when you started the call for DHW ,so the boiler and pump only needed to top up for 7 mins ?

 

[opps]

Was the water in the cylinder already hot when you started the call for DHW ,so the boiler and pump only needed to top up for 7 mins ?

I cannot say definitely, but, no, the impression was that the water was only lukewarm. Perhaps the temperature sensor strapped to the tank is faulty rather than the valve?

 

[CountryFan]

Thanks. So why, when the DHW only was on did it (the pump) stop after 7 minutes. I wouldn't have thought that 7 minutes would be long enough to fill an immersion tank.

No but maybe you activated the micro switch briefly (can happen on some valves) and then the pump overrun kicked in, which isn't uncommon to run for 5 minutes (on Vaillant ecotec pro combis anyway).

 

[oilhead]

Latching the valve will let water pass, but as far as the controls are concerned, the HW will not be on because the switch in the valve is not made. You will only get hot water whilst there is a heating demand.

 

[opps]

Latching the valve will let water pass, but as far as the controls are concerned, the HW will not be on because the switch in the valve is not made. You will only get hot water whilst there is a heating demand.

Ahh, that makes sense. Many thanks.

 

[Madrab]

Be careful, if the HW 2 port is manually latched, there will be no HW temp control. The cylinder stat controls power from the programmer to energise the valve and then shut's it down when the it reaches set point. If the valve is manually open and the boiler is being controlled by the room stat, the HW could get to an excessive temp, if the system water is hot enough.