Hot radiators remain when heating goes off - maybe from hot water storage cylinder ?

[miketurner201]

Hot water coming out of the hot water storage cylinder into upstairs radiators after heating/HW turns off and running out of hot water in the mornings.

I have a Glow Worm 24HX Condensing boiler on the ground floor with a pump in the same cupboard, a hot water storage cylinder in the airing cupboard upstairs (Kingspan 1500 x 450 grade 3, 162 Litre. cylinder) in the eaves area I have another pump (both pumps are Salus MP200 domestic circulating pump). Upstairs I have two Drayton 2 port Zone Valves ZA5, one on the hot water supply to the hot water cylinder and one to the central heating supply.

The hot water and central heating is timed to go on in the afternoon 4pm to 1030pm every day and has been working fine for the last 7 years, I think the whole system is around 11 years old.

One evening I found that the temperature of the water coming out of the upstairs shower was warm and I couldn't get it to go hot, no matter how much I adjusted the shower control.

It appears that when the heating and HW goes off at 10.30 pm a couple of upstairs radiators (2 in bathroom and 1 in bedroom) stay on hot for an hour or so when the others have all cooled down. I have checked the boiler and it goes off at 10.30 pm.

I'm wondering if this is a zone valve ZA5 problem either on the HW or heating where the
hot water is going through from the upstairs hot water cylinder to the radiators.

Can anyone let me know they think this is a zone valve problem, which valve is is suspect, heating or HW or anything else ?

I'm looking to change zone valve heads soon but I am trying to find out if it could be anything else causing the problem, before I make a purchase, in case it does not cure the problem.

Many thanks.

 

[Murdoch]

The hot water and central heating is timed to go on in the afternoon 4pm to 1030pm every day

I would start by setting the water to a different time ... unless you have a big family there is absolutely no need to have the water on for the same time.

Try running the hot water during the afternoon, and night, when the heating is off and see what happens

 

[miketurner201]

I would start by setting the water to a different time . unless you have a big family there is absolutely no need to have the water on for the same time.

Try running the hot water during the afternoon, and night, when the heating is off and see what happens

Hi,

There is just two of us in the house but we also run it as a bed and breakfast (1 room, occasionally 2) so I have heating and HW 6.30 am to 8.30am so guests can shower in the morning and on again from 4.30pm to 10.30pm.

I will have a look at what you suggest but still the system was working fine since we have lived here for 7 years (the system is around 11 years old), so something is not right ?

Those times are in the winter but in summer its just hot water only. My idea of just running heating/HW in the afternoon 4.30pm to 10.30pm is just when we do not have any B&B guests.

 

[JCplumb]

You're probably right with this being a zone valve issue.
Even if your system has different heating zones, it should only have one valve that controls whether the flow goes to your heating and/or hot water. If you have no setting for heating only then it's probably a 2 port, if you can set it to heating only then it'll be a 3 port.
Probably near the pump or cylinder, if you're lucky it will just be the head that needs changing so no draining down of the system to repair the issue.

 

[miketurner201]

Hi Jcplumb

I have two zone valves, one going into the hot water cylinder storage tank and one going to a pump and out to the heating. They appear to be 2 port valves (please see photo), the one on the right goes vertical and into the top of the hot water cylinder next door, the one on the left (horizontal) goes to a pump and out to the radiators around the house.

The only radiators that seem to stay warm appear to be a couple of nearby ones in the bathroom on the same floor and in a bedroom also on the same first floor.

All ground floor radiators seem to cool down normally, which makes me think that hot water it coming out of the hot water cylinder and circulating to a few radiators upstairs. I think I will probably look to buy new Drayton ZA5 zone valve heads from Screwfix and hope that cures it.
Many thanks for the advice.

 

[JCplumb]

Yeah, it'll be the one going to the heating circuit to blame, those heads come off quite easily, you can check that the valve operates easily enough by taking the head off and seeing if the spindle turns, if it doesn't budge then new full valve, if it does move fully a new head will sort it. You can sometimes free up stuck valves but they tend to stick again as there's an underlying reason they're stuck that needs addressing.
The valve not closing means that the heat will dissipate to nearby rads, the pump won't be running so no reason for the hot water to circulate - it just bleeds heat to nearby rads. Heat rises, so you'd expect your downstairs rads to stay cold in this situation.

 

[miketurner201]

Hi Jcplumb

Many thanks, that's reassured me as to what to do so I am off to Screwfix to replace the heads, will probably do HW and heating heads to be on safe side as they are around the same age. Thanks again.