Rads won’t get warm unless hot water is on

123Kiwi

Hoping someone can help. Heating and hot water controlled by a Drayton MiTime T720R.
I had heating programmed to come on and off a few times a day, and hot water only for an hour in the morning and an hour in the evening. The water stays plenty hot enough. (There is a storage tank). However, now that it’s heating season, I’ve found that the radiators won’t warm up unless the hot water program is on as well. This doesn’t seem right. Why would both be programmable if they both need to be on for it to work? So I’ve changed the hot water program to the same as the heating program. Could it be a fault, or is this just the way it’s supposed to work? Concerned about wasting energy and spending too much.

JJ_Egan

Could be the motorised valve thats sticking .
HW only works ??
CH only fails .

Talldave

When you say the radiators don't get warm, is it that when CH only is on, the boiler doesn't fire up at all? If so, it sounds like a classic three port valve failure and the signal from the valve that calls for heat from the boiler isn't being sent. Time to replace the three port valve.


I would replace the whole valve and not just the motor head because the valve is obviously being opened to a certain extent by the motor, otherwise the radiators wouldn't get warm at all. Either the switch that sends the CH call for heat is broken or there's crud inside the valve stopping its full travel so the switch never closes.

123Kiwi

“When you say the radiators don't get warm, is it that when CH only is on, the boiler doesn't fire up at all?“

Yes that’s it. I found a thing next to the water tank. It’s a Honeywell Sundial Y Plan 3 position diverter valve.
I believe that is what you’re referring to. Thanks!

matelodave

Classic symptoms of a jammed 3 port valve.

You might get a temporary reprieve by taking the motor unit off and working the valve with a pair or pliers to dislodge the crud that's causing it to jam but in general once it's got to that stage the only real answer is to replace the lot because it will do it again and again.

Fitting a new motor to the old valve body will probably end up damaging the new motor as there's a fair chance that the drive gears get stripped when the valve jams.

It;s always a good idea to run the heating for a short while once a month in the summer to exercise the valve and breakup up the limescale that causes it to jam before it become rock hard

123Kiwi

I’m not going to touch it. I’m a tenant. I’ll ask the property manager to investigate. I’ve only been here a few months. Will keep in mind for next summer to run the heating once a month. Thanks!

Smodlet

It does sound exactly like what happened in our last house; do I wish I had known to turn the heating on every month then. It is a really good tip, I think.

123Kiwi

Further to my previous post, the problem has not been fixed. What are the consequences of not repairing it-is it just that I’m overheating and paying too much to heat my water when it’s not required? Or could there be a more serious issue if it’s left too long?

Gerry1

It's relatively inconsequential because if you need CH you will presumably need HW. The main problem is that you will have a tank full of HW when the CH finishes at the end of the day, so this will be wasting some heat overnight.

However, if you have a fully insulated tank this shouldn't be too problematic. Some primitive motorised timers operated this way, the switch settings were HW or HW + CH.

Talldave

123Kiwi wrote: »

Further to my previous post, the problem has not been fixed. What are the consequences of not repairing it-is it just that I’m overheating and paying too much to heat my water when it’s not required? Or could there be a more serious issue if it’s left too long?

That probably depends on whether there's a thermostat on the hot water tank. If there was, you might find he boiler goes off when the hot water reaches the temperature set on the thermostat - regardless of whether the radiators have heated the rooms sufficiently or not.


However, why has it not been fixed? Have you reported it? My experience of rubbish landlords is that there's only one way to get them to react - stop paying the rent. I've found that letting agents suddenly gain magical powers to get heating engineers on site within 48 hours!


Don't be fobbed off with excuses. There is a fault, it doesn't work properly and you want it repaired.

123Kiwi

There is a thermostat on the tank, it’s set at 60. however I thought it was only active when the immersion heater is switched on (I’ve had no need to use it so far). The heat has never gone off as long as I have the HW and CH programs set to ‘on’.

Why isn’t it fixed? I’m going to ask today. Just wanted my question here answered so I’m prepared for the conversation with the property manager. No more excuses now that the holidays are over.
Thanks!