Radiators on with hot water or not?

purpleparrotuk

A plumber came round today to reinstall a radiator that was removed 5 years ago. We have a Honeywell evohome system on a unvented system. The towel radiators comes on when the hot water is heated up. I have been told that’s normal and it uses the water system not the radiator system. 

But the plumber said ALL my radiators come on when the hot water is heating. He said if I open the valve the radiator will come on. He said we need another divertor/actuator. 

Surely this isn’t right? It has been working ok for 5 years as far as I know. 

ThisIsWeird

Did he say you need 'another' valve, or to replace an existing one?
We need a lot more info in general; type of boiler, photos of the plumbing surrounding your hot tank, that sort of stuff.
But, surely this is easily checked? Open the TRV on a rad, say the sitting room, and see if it comes on the next time you heat up your hot tank.

purpleparrotuk

ThisIsWeird said:

Did he say you need 'another' valve, or to replace an existing one?
We need a lot more info in general; type of boiler, photos of the plumbing surrounding your hot tank, that sort of stuff.
But, surely this is easily checked? Open the TRV on a rad, say the sitting room, and see if it comes on the next time you heat up your hot tank.

Thanks for your reply. If I open the valve on a radiator the heating will come on. That’s how the Evohome works. I have a relay for the hot water and a relay for the radiators. Both attached to the boiler. 

Maybe the plumber doesn’t know much about how Evohome works. When we have set the time for the water to heat, the water relay turns on and starts the boiler. The same for the radiator one for the heating. They can both be on the same time too but I think heating the water takes priority.

ComicGeek

So the towel radiators are on the same circuit as the heating coil to your hot water cylinder? Strange way to do it, as the heating of the cylinder wouldn't really happen at the same time as the bathrooms are actually being used. Even if the hot water heating is set to constant the towel radiators will only get warm after you've finished your shower (and probably left the bathroom) - good for drying towels afterwards, not good for warming towels beforehand.

I've also seen it set up before when the hot water coming out of the shower/bath actually passes through the towel radiator itself, so it warms up whenever the bathroom is used. Also seen the same systems completely rusted from the inside out, so really not advised.

When you open the valve on a standard radiator, do the towel radiators also get hot?

tacpot12

This is something you can easily test yourself. Set the TRVs to their highest setting and turn the heating on but leave the hot water off on the Evohome. Check to see which radiators get warm. Those radiators are on the circuit that is controlled by the heating valve and relay. 

ThisIsWeird

purpleparrotuk said:

ThisIsWeird said:

Did he say you need 'another' valve, or to replace an existing one?
We need a lot more info in general; type of boiler, photos of the plumbing surrounding your hot tank, that sort of stuff.
But, surely this is easily checked? Open the TRV on a rad, say the sitting room, and see if it comes on the next time you heat up your hot tank.

Thanks for your reply. If I open the valve on a radiator the heating will come on. That’s how the Evohome works. I have a relay for the hot water and a relay for the radiators. Both attached to the boiler. 

Maybe the plumber doesn’t know much about how Evohome works. When we have set the time for the water to heat, the water relay turns on and starts the boiler. The same for the radiator one for the heating. They can both be on the same time too but I think heating the water takes priority.

Sounds as tho' your plumber knows as much about this system as I do :-)

These are not normal radiator valves, and not even TRVs, but instead are controlled via WiFi? Can you explain - HOW do you turn on a radiator?

I'm guessing that all is actually working as it should, and that the towel rads are connected to the DHW side. This used to be a common thing to do, as it meant warm dry towels even in summer time. It sometimes also allowed to be used as a 'by-pass' for more basic boilers.

On balance, I'd rather have the towel rails on the CH system, as you could then have them running for longer in colder climes. But to replumb them might be awkward.

Are you happy with how your system works?

And could you confirm HOW you turn on a sitting room rad, for example?

Oh, and when ONLY the CH is running, and NOT the DHW, do the towel rads come on too?

purpleparrotuk

ThisIsWeird said:

purpleparrotuk said:

ThisIsWeird said:

Did he say you need 'another' valve, or to replace an existing one?
We need a lot more info in general; type of boiler, photos of the plumbing surrounding your hot tank, that sort of stuff.
But, surely this is easily checked? Open the TRV on a rad, say the sitting room, and see if it comes on the next time you heat up your hot tank.

Thanks for your reply. If I open the valve on a radiator the heating will come on. That’s how the Evohome works. I have a relay for the hot water and a relay for the radiators. Both attached to the boiler. 

Maybe the plumber doesn’t know much about how Evohome works. When we have set the time for the water to heat, the water relay turns on and starts the boiler. The same for the radiator one for the heating. They can both be on the same time too but I think heating the water takes priority.

Sounds as tho' your plumber knows as much about this system as I do :-)

These are not normal radiator valves, and not even TRVs, but instead are controlled via WiFi? Can you explain - HOW do you turn on a radiator?

I'm guessing that all is actually working as it should, and that the towel rads are connected to the DHW side. This used to be a common thing to do, as it meant warm dry towels even in summer time. It sometimes also allowed to be used as a 'by-pass' for more basic boilers.

On balance, I'd rather have the towel rails on the CH system, as you could then have them running for longer in colder climes. But to replumb them might be awkward.

Are you happy with how your system works?

And could you confirm HOW you turn on a sitting room rad, for example?

Oh, and when ONLY the CH is running, and NOT the DHW, do the towel rads come on too?

System works fine. To turn the radiator on you either set the timer in the Honeywell app or you can override it by turning the TRV in the radiator. 

The towel rail comes on when either water or heating is turned on. Seems like they are all going through the same pipe system and the Honeywell relays determine if it’s just going to heat the tank or the radiators depending on the timers in the app. 

The plumber that originally installed the boiler and extra rads 6 years ago said there was already a 2 pipe system present but he also told me this:

There is only one circuit essentially, the hot water is controlled by a zone valve and the heating is controlled by the Rad valves. 

FFHillbilly

so basically the second plumber didn't realise all the radiators are controlled by the evohome system.

there is probably a small bit of efficiency to be gained if the radiators were all on a separate zone valve depending on exactly how its connected now, but probably not worth going to the trouble of fitting one now

FreeBear

purpleparrotuk said: The towel rail comes on when either water or heating is turned on. Seems like they are all going through the same pipe system and the Honeywell relays determine if it’s just going to heat the tank or the radiators depending on the timers in the app. 

The plumber that originally installed the boiler and extra rads 6 years ago said there was already a 2 pipe system present but he also told me this:

There is only one circuit essentially, the hot water is controlled by a zone valve and the heating is controlled by the Rad valves.

So in effect, an S plan system with the Honeywell Evohome TRVs (smart valves) acting as the zone valve on the heating system. Putting another Evohome TRV on the towel radiator would stop getting hot every time the DHW tank is heating up.

ThisIsWeird

Ah, that makes sense.
Whenever the boiler fires up - for whatever reason - the towel rad will receive a flow as it's connected across the boiler's flow and return.
Probably not a bad thing - it'll give you warm towels winter and summer. But, you should have control over it, and that can be simple 'manual' via a hand valve.
So you still need a access to that boxing-in.

molerat

ThisIsWeird said:

Ah, that makes sense.
Whenever the boiler fires up - for whatever reason - the towel rad will receive a flow as it's connected across the boiler's flow and return.
Probably not a bad thing - it'll give you warm towels winter and summer. But, you should have control over it, and that can be simple 'manual' via a hand valve.
So you still need a access to that boxing-in.

Before my son had a new combi installed the downstairs hall rad was plumbed between the pump and the DHW and CH valves.  It was supposed to be a heat sink for boiler overheat - if boiler overheated pump kept running through that rad even if zone valves were closed - didn't work though !