I had a new Glow Worm boiler fitted in June. There were problems the installer could not fix and GW sent out a fitter to deal with it. Part of his solution was to remove the thermostat on the hall radiator. The system now seems ok but the reason for removing the thermostat was not explained.
According to the installer, "He would have done this to provide a permanently open radiator flow. It's normal practice."
Before I get back to the installer for further explanation, is this in fact normal? It seems wasteful as the radiator is belting out heat during full scheduled hours and, being about 20 feet from the wall thermostat, is unlikely to be controlled by it. And there are those gas price rises on the way...
|
If it's a combi boiler the installer is correct. You must not fit TRV'S to all of the rads.
On my system the non TRV is in the bathroom.
|
Thanks. It is a combi system.
>>You must not fit TRV'S to all of the rads.
I always have up till now. What is wrong with doing it?
|
|
I don't know why but in my Worcester Bosch handbook i'm fairly sure it tells you to always have 1 non TRV radiator. The problem you had probably proves the point. If your installer knew this i'm surprised he didn't check.
|
|
It's to maintain the required minimum flow-rate to protect the boiler and pump on overrun before it switches itself out. (i.e. with full TRVs it is entirely possible for all the radiators to be in a shut state. The boiler doesn't receive sufficient flow to dissipate heat properly, and the pump can be working against full resistance. One "always on" radiator avoids that situation. A similar (though slightly different) method is to fit a bypass-valve, which allows a permanent (or automatically pressure controlled) cross-bleed between the feed and return circuits.
|
My system ( quite a few years old) has a simple by pass valve.
An aditional basic stop cock that was left partially open on its bypass circuit and the crutch handle discarded. It lives in the airing cupboard.
The delay circuit is on the PCB and is fixed at about 10 mins.
|
|
Couldn't have explained it better. Start Monday and don't be late :-)
|
|
And yes, the bathroom is the best place, well for me anyway.
|
|
...you couldn't afford my rates....
|
|
I didn't say in what capacity dear boy :-)
|
|
...my rate has just gone more unaffordable.... ;-)
|
>> I always have up till now. What is wrong with doing it?
Heat Soak. When the boiler cuts off flame, it keeps the pump going to keep water flow through the heat exchanger to prevent heat soak from warping it. The pump shuts off after about 5 minutes.
If there is no flow, this wont work. If all TRVs are shut there is no flow.
Last edited by: VxFan on Tue 5 Oct 21 at 02:49
|
>> If there is no flow, this wont work. If all TRVs are shut there is
>> no flow.
Would that apply to an ordinary boiler as well as a Combi?
|
>> Would that apply to an ordinary boiler as well as a Combi?
If it has a three way valve, no. The three way valve is incapable of shutting off all flow.
Last edited by: VxFan on Tue 5 Oct 21 at 02:49
|
>> If it has a three way valve, no.
>> The three way valve is incapable of shutting off all flow.
>>
p.s. chose to have two simple valves so no priority on my system
|
|
If you have two two way valves you need a bypass, as you have.
Last edited by: VxFan on Tue 5 Oct 21 at 02:49
|
>> If it has a three way valve, no. The three way valve is incapable of
>> shutting off all flow.
>>
I don't think this is so. With a three-way port, if the water heating is satisfied, then the cylinder (which would act as a dissipator, albeit if well-insulated a limited one) would be isolated. All flow would be diverted to the CH circuit, and with full provision of TRVs then the same issue arises.
It is conventional to fit a bypass circuit after the pump in three-port systems in this circumstance (and mine has (a manual) one). (It also has two "free" radiators, one of which is in the hall where there is a room thermostat).
|
|
I repeat, the three way valve is not capable of blocking all flow, and no bypass is required or normally fitted in that configuation
|
|
..as per my original, the three port valve will always "park" with at least one port open - generally in the position where it was when all demand is removed (so you are correct in saying that it iself will not block all flow), but when it is open to satisfy CH demand only, and if TRVs are fitted to all radiators, then the situation described in the OP is in existence. The circuit then needs a means of minimum flow/heat dissipation on overrun (either by providing a bypass valve (or by ensuring you don't have all radiators fitted with TRVs)).
|
|
I know that the heating systems, whether combi or system boiler, in every house I’ve owned have always had at least one radiator without a TRV, usually in a hall or cloakroom. And I don’t think any of the towel rails have had them either. I moved this year to a newish conversion in a red brick Victorian hospital building, which claims to be carbon neutral, and has a district heating system that provides hot water and central heating. I just have a heat exchange unit in the utility room that draws heat as needed, but even so there’s a radiator in the hall without a TRV.
|
I will try never to have another heating system with TRVs. The ones I've had have been useless.
I've found them very hard to regulate even when they worked, and if there's a room stat (always in the hall where nobody lives IME) then you clearly can't use a TRV there unless you wish to render the others even more useless.
Our present rental has TRVs everywhere except I think the bathroom, and no room stat at all. At least I can make sense of the theory there, but in practice the TRVs are hard to get adjusted and half of them have jammed actuators anyway. And who wants the boiler going all the time which is the only way all the TRVs can have control as opposed to power of veto? We just open them all up, then turn on the heating when we are cold and off when we reach tropical conditions. I shall be glad to see the back of it.
I'm hoping the new house arrangement will just work. It has maybe 12-13 zones, many thermostats, and runs at mains pressure including all the hot and cold taps. I have only a vague idea of how it works. There are no TRVs, because there are no R's, just many metres of what I hope is very robust pipe under the first floor decking and the ground floor fibre screed. The screed is about 90-95mm thick so I expect we'll need to give the system 24 hours notice of when we're going to be cold.
|
|
With UFH you just need to leave it on all the time, and allow it to regulate the temperature as it sees fit. In a new house built to current specs, which are almost ' Passiv Haus' there's a good chance you will not need much heating anyway!
|
>> With UFH you just need to leave it on all the time, and allow it
>> to regulate the temperature as it sees fit. In a new house built to current
>> specs, which are almost ' Passiv Haus' there's a good chance you will not need
>> much heating anyway!
I'm hoping that is the case. I think the current standards imply a U-value of about 0.2 (watts per m^2 per degree Kelvin IIRC). Ours is designed to be around 0.13 for the inner leaf (timber frame with insulation infill, total of about 120mm of Kooltherm). We are some way off passive but a fair but better than the minimum. We also have a mechanical ventilation system with heat recovery, no window vents and no airbricks. The multifuel stove uses external air so I don't have to knock open holes in the walls. We have no gas appliances.
Several people who don't have a heat pump themselves have told me we won't be warm enough without some supplementary heating. I hope and believe they're wrong - I suspect they have heard stories from people who have put heat pumps into older houses. Anything pre-1980 that is unimproved could easily have heat loss of more than 10 times current minimum standard. Nationally there is a huge amount to be gained from better insulation.
|
I've got TRVs in four of my rooms and find they work very well. OK, I've had to replace a couple of them over the years.
I've an old gas fired back boiler with a thermo-syphon hot water system and pumped heating.
The times I've seen TRVs not to work are when one partner walks into room, thinks it feels cold and turns the TRV up full, only for the other to later think the room's too hot and close it right down. One such family asked me how much it would cost to install TRVs, only to look surprised when I asked if the fitted ones weren't working.
|
|
Been trying to integrate TRV's into the hive system. Its a PITA, TRVs are only useful in abnormally hot rooms. Its better to balance the flow properly through the rads measuring the heat drop.
Last edited by: Zero on Tue 5 Oct 21 at 17:02
|
>> >> Would that apply to an ordinary boiler as well as a Combi?
>>
>> If it has a three way valve, no. The three way valve is incapable of
>> shutting off all flow.
>>
Providing the darn thing is working. I went for many years changing them annually.
|
>>Would that apply to an ordinary boiler as well as a Combi?
My boiler is not a combi - see above.
Unless you are interested or have a failure mine would be unnoticed.
A repaired PCB was fitted to my set up after advice here.
|
"Permanently open radiator flow" - maltrap
