Radiator trv's

[Mark Newport]

I have a conservatory which is fitted with a radiator. The conservatory never gets warm as the house heats up faster and reaches the room thermostat temperature and cuts off before the conservatory can get warm. The room thermostat is in the hall which also has a radiator. I have TRV's on all the radiators in the house bar the one in the hall. My plan is to fit a trv to the hall radiator and turn it down, along with the other room radiators. I will leave the conservator one turned up thus allowing the conservatory to warm up before the rest of the house reaches the desired temp. What I am asking is if there is any sort of problem with this. I have read that there shouldn't be a trv in the same room as the room thermostat.

Thanks for any advice offered.

Mark

[Mark]

I have a conservatory which is fitted with a radiator. The conservatory never gets warm as the house heats up faster and reaches the room thermostat temperature and cuts off before the conservatory can get warm. The room thermostat is in the hall which also has a radiator. I have TRV's on all the radiators in the house bar the one in the hall. My plan is to fit a trv to the hall radiator and turn it down, along with the other room radiators. I will leave the conservator one turned up thus allowing the conservatory to warm up before the rest of the house reaches the desired temp. What I am asking is if there is any sort of problem with this. I have read that there shouldn't be a trv in the same room as the room thermostat.

Thanks for any advice offered.

Mark.

[Roger Mills]

In order to make this work, you will have to turn the room stat up to max - so that it never turns the boiler off, and so that the conservatory continues to receive heat.

The trouble with this is that there will be no control over the conservatory temperature. When it gets *too* hot, there will be nothing to turn the boiler off.

A better scheme would be to zone the heating system - having a separate zone with room stat in the conservatory. You can then heat the house and conservatory independently without either getting too hot. If you use programmable stats, you can even heat them at different times from each other should you so wish.

[Have a look at the "S Plan Plus" details in to see what I mean.

Roger

[Christian McArdle]

This won't work. If the hall TRV is set above the room thermostat, than the TRV will never operate. If the TRV is set below the room thermostat, the heating will never turn off and is the equivalent to shorting out the room thermostat. This will keep the conservatory warm. However, the boiler will remain on constantly, even when no heat is required, costing you a fortune if the boiler cutout doesn't operate.

The only solution that will really be satisfactory in your situation is to have a separate zone for the conservatory. This means that the conservatory will have its own programmable thermostat totally independent from the rest of the house. It also allows different time scales to be used. If, for example, the conservatory is used as a dining room, the timer can be set to only heat it for the early evening, saving you loads in keeping a poorly insulated conservatory hot for the entire day and evening.

Another alternative is to have TRVs in every room and remove the room thermostat. Then an automatic bypass loop is used (any old manual one removed) with a flow switch that can turn off the boiler when the automatic bypass opens. This solution is not as good, as there isn't separate timing for the conservatory. However, it may be easier to implement if the pipework isn't conducive to sub zoning.

Christian.

[The Natural Philosopher]

Put TRV on hall rad, and turn hall thermostat to 'max' and forget it exists.

Leave one small rad somewhere - bathroom? Airing cupboard? without TRV so the pump doesn't stall.

[The Natural Philosopher]

But they do.

I ran my old house like that for 6 years no problem. TRV's on all rads except bathroom, and stat on max. the PUMP runs all the time. The boiler does not...eventually there is just one super hot bathroom, and the pipes going to it, and the boiler occasionally firing up to keep it that way.

Short of a zone for every room with its own thermostat, its actually the best way to do it. You CAN balance everything and hope that the heat losses stay teh same, and the master stat will do everything right, but its a darned sight cheaper to TRV everything, so you can turn down certain rooms when not in use.

I disagree..

That is pretty much what I suggested. Except why remove the stat? Just whack it up to full...and the auto bypass? That's a neat idea..except that without the pump running all the time, and using the boiler to monitor flow temp, how does it know when to cut in again?

All I can say is the bodge described WORKS. Short of re-engineering everything, its a good compromise between economy, cost of installation, and pump life.

Its IMHO the best compromise to upgrading an existing system to get better control over room temps without going to a proper fully zoned system complete with loads of motorised valves and thermostats, which need a lot of wiring as well as re-plumbing.

[Christian McArdle]

It is against the building regulations to install such a system. It keeps the bathroom too hot and the central heating pipes hot when they could be cold. Central heating pipes do lose a lot of heat.

You can TRV every room except the room thermostat one. Balance the system properly and then turn down the room thermostat room half a turn. This ensures that other rooms warm up quicker and the TRVs shut off before the room thermostat is satisfied. Then, when this happens, the boiler interlock cuts in, preventing the central heating pipes being kept warm for no reason, which can be very wasteful, particularly on a marginal day when heating is only really required in the morning and late evening, but is selected on all day.

Christian.

[Clive Summerfield]

Sounds right to me. So as a compromise, how about putting a wireless stat in the conservatory and replacing the stat in the hall with a TRV on the hall radiator? The timer would ensure that you're not trying to heat the conservatory all the time. And you might need to set the conservatory stat down a bit lower than you'd have set it were it still in the hall. Seems to me it would be easier than rejigging the CH to add an additional zone, and avoid having the system running all the time.

Just my 2p

Cheers Clive

[Christian McArdle]

Whilst this would work, it has the very serious problem that the radiator in the thermostat room shouldn't not be controllable (i.e. should have lockshields both ends). By putting an unzoned thermostat in the conservatory, you are basically removing the ability to turn off conservatory heating.

OK, will some of the other solutions you don't have independent timing, but at least you could manually control it.

Christian.

[The Natural Philosopher]

Firstly I don't think its against regs, secondly it doesn't keep the pipes hot. As the TRVs close the loops to which they are attached shit down, flow stops, and the pipes cool..only the bathrom loop stahs hot, and in my case, this was a positive advantage, cos it kept the bathroom floor warm as well.

Well for a start I had assumed we were time clocked anyway, secondly what the heck? As long as teh pump has somewhere to pump, you cabn even have a trickle bypass on it so that all teh rads are TRV'ed.

There is absolutley NO problem with the pump running all the time, because the TRV';s will stop the flow in unwanted pipe sections. That is, after all, what they do.Ther will be far less loss through a few lagged pipes than vast areas of radiator heating unused rooms needlessly anyway.

No mate. I don't buy it.

[Mark Newport]

Ok quite a few ideas for me to consider there !! And all much more knowledgeable than I !

Thanks for all your ideas, that'll give me something to pick through and start to investigate. Oh, and sorry for the double post.

Cheers all,

Mark.

[Andrew Gabriel]

As others have said, this won't work.

It sounds like, barring gross faults with system balancing (i.e. conservatory radiator is noticably cooler than the others), then then problem is inadequate heat input to the conservatory for the heat loss. You can fix this either by adding another radiator (or swap for a higher output one), or by reducing the heat loss from the conservatory.

[Christian McArdle]

But what turns the boiler off? The approved document requires a boiler interlock that turns the boiler off when no heat is required. You may think it OK to reduce your overall efficiency by around 10% by running the boiler when all the radiators are off, but the government disagrees.

Christian.

[The Natural Philosopher]

I don't know what turns *your* boiler off. In my case it turns itself off when the temperature of the water in the return path matches its internal thermostat settings.

Actually, in this house, one heating zone comprises a suite of TRV equpped towel rails, and a series of fan blown heat exchangers all with their own thermostats. There is no master thermostat at all on that zone.

The boiler, needless to say, does not run continuously, but the pump does.

Since all boilers I have found do the same. I don't really understand what the problem is.

[Christian McArdle]

The boiler has to turn off properly and allow the circulating water to cool down. This is for energy efficiency. In very cold weather this won't have much effect, as the water won't have much chance to cool down anyway. However, in marginal weather, where the heating might not be required for hours in the middle of the day, considerable savings can be made.

In order to promote this, hot water cylinders have to be reasonably rapid in recovery, so that the pipes don't remain hot for long periods.

Christian.

[Roger Mills]

Yes, but the point is that it then turns itself *on* again when the boiler itself has cooled to below its stat setting - regardless of whether any heating is needed in the house. This is clearly wasteful.

Roger

[The Natural Philosopher]

Yes. You switch of everything, including the pump, on a time clock...

Thats why they are lagged.

[The Natural Philosopher]

Er, no, it doen't. The fact that heat has been taken out of the water indicates that the house has cooled enough for some TRV's to open... Ok there is marginal loss through hot water pipes under floors etc that set a base level of heating that the system never drops below, but I would suggest that anyone who runs their heating at all when they don't actually need their radiators on is a bit of a plonker.

In more normal situations, the slight heat loss through the pipework is far more than compensated by not having UN TRV'ed radiators overheating rooms that are not in use, or need to be set at lower temperatures.

TRV'ing everything and ruinning the whole sytem on a time clock is far more energy efficient than having a master thermostat and no TRV's

[Christian McArdle]

Only if you want to break the law (on a recently installed system)

Part L1

1.41 Gas and oil fired hot water central heating system controls should switch the boiler off when no heat is required whether control is by room thermostats or by thermostatic radiator valves:

a) The boiler in systems controlled by thermostats should operate only when a space heating or vessel thermostat is calling for heat.

b) Where it is proposed to effect control by thermostatic radiator valves, a room thermostat (or other device such as a flow switch) should also be provided to switch off the boiler when there is no demand for heating or hot water.

Christian.

[Christian McArdle]

Both of these systems would not be not permitted. You may have a master room thermostat and TRVs, or all TRVs and a flow switch to detect the TRVs are all closed. You may not use all TRVs and then pump hot water through the bypass all afternoon.

Christian.