In praise of ASHPs

[ReedRichards]

On 26/07/2024 at 21:29, JohnMo said:

3. Radiators sized to allow as low as practical flow temp. Size bedroom rads to get to 18 degs or add trv's to these rads only.

 

Aren't installers obliged to fit TRVs to all radiators to conform to current regulations?  

[JohnMo]

26 minutes ago, ReedRichards said:

Aren't installers obliged to fit TRVs to all radiators to conform to current regulations

Interesting question.

 

I read the Scottish building regs compliance notes 2022. And also came Kent Council compliance notes.

 

Both say

 

For all boiler types except heat pumps, it makes very detailed mention of individual room temp control and thermostats or trv's and time controls, multiple zones etc.

 

For heat pumps it states (Scottish)

• weather compensation or internal temperature control
• timer or programmer for space heating

No mention of zones at all.

(Kent)

External controls should include:

• room thermostat to regulate the space temperature and interlocked with the heat pump unit operation;

• timer to optimise operation of the heat pump.

 

Scottish compliance notes also mentions MIS 3005, which makes no mention of trv's.

 

So don't believe current regs drive the use of trv's, certainly not in Scotland. In England the use of the singular (thermostat) as opposed to the plural could be just the heat pump controller.

[Dave Jones]

On 08/01/2024 at 15:08, Russell griffiths said:

I don’t see why the government should pay for you to upgrade your draughty 1930’s house because you haven’t done anything to it in the last 20 years. 

People need to be a bit more responsible for themselves. 

All a grant will do is manufacture loads of new crappy insulation companies 

 

 you  are forgetting about the mass of benefit scroungers who get everything for free who labour/socialists love.

[SteamyTea]

2 hours ago, Dave Jones said:

 

 you  are forgetting about the mass of benefit scroungers who get everything for free who labour/socialists love.

Do you love the right wing rioters who are taking control of the streets. Are they all hard working people like you who have never benefitted from state services.

[ReedRichards]

@JohnMo from https://assets.publishing.service.gov.uk/media/662a2e3e55e1582b6ca7e592/Approved_Document_L__Conservation_of_fuel_and_power__Volume_1_Dwellings__2021_edition_incorporating_2023_amendments.pdf

 

Quote

Thermostatic room controls 5.20

For heating systems in new dwellings, or when a heat generator such as a boiler is replaced in an existing dwelling, each room should be provided with thermostatic room controls. These should be capable of being used to separately adapt the heating output in each room served by the heating appliance. Where justified in accordance with paragraph 5.21, heating may be controlled for each heating zone rather than individual rooms.

NOTE: There is no need to install thermostatic room controls in rooms/zones without heating in new or existing dwellings.

NOTE: Installing thermostatic room controls may not be technically feasible in some cases. These may include the following

a. Dwellings with very low heat demand (e.g. less than 10W/m2 ).

b. Dwelling with buffer zones for heat absorption or dissipation with high thermal mass.

5.21 It may be justified to control a heating zone rather than individual rooms in either of the following cases.

a. In single-storey open-plan dwellings in which the living area is greater than 70% of the total floor area. In such cases, the dwelling should be considered as a single heating zone.

b. Where two adjacent rooms have a similar function and heating requirements (e.g. kitchen and utility room). In such cases, the adjacent rooms should be considered as a single heating zone. NOTE: Exhaust air heat pump systems, which extract heat from the exhaust air of a dwelling, may not need to provide independent thermostatic control to individual rooms. Providing room/ zone control on this type of system is unlikely to be economically and/or technically viable. However, other space heating systems also in use in the same dwelling should be controlled using thermostatic room controls as described above. NOTE: Commissioning heating systems is covered in Section 8.

5.22 The standards in paragraphs 5.20 and 5.21 may be satisfied by providing any of the following.

a. Both of the following. 

i. A thermostat in a room that the heating circuit serves.

ii. An individual thermostatic room control for each heat emitter, such as a thermostatic radiator valve, on all heat emitters outside the room that contains the thermostat. Thermostatic radiator valves should not be used in the same room as the thermostat.

b. An individual room/heating zone thermostat or fan coil thermostat for each room or heating zone.

c. An individual networked heat emitter control for each emitter

 

[JohnMo]

11 minutes ago, ReedRichards said:

@JohnMo from https://assets.publishing.service.gov.uk/media/662a2e3e55e1582b6ca7e592/Approved_Document_L__Conservation_of_fuel_and_power__Volume_1_Dwellings__2021_edition_incorporating_2023_amendments.pdf

 

 

The document also says in the heat pump section:

 

6.38 The heat pump unit should include controls for all of the following, in addition to meeting the

general requirements for heating and hot water systems in Section 5.

6.39 The heat pump should have external controls that include both of the following.
a. Weather compensation or internal temperature control.
b. Timer or programmer for space heating

 

So for a heat pump you can either have room controls or WC. The timer or programmer normally comes with the heat pump or a timer thermostat can be used as overheat protection.

 

[ReedRichards]

7 minutes ago, JohnMo said:

So for a heat pump you can either have room controls or WC.

 

That's not my reading of the regulations.  This section is "in addition to meeting the general requirements for heating and hot water systems in Section 5."  Weather Compensation and TRVs or other room thermostats are entirely compatible.  Most gas boilers do WC, not just heat pumps.    

 

Yes, I know there is a "hard core" school of thought that if you get your radiators perfectly balanced then you can keep every room at the right temperature by relying entirely on WC without any internal temperature controls. But Building Regulations tend to be conservative and I don't think they so much as dreamt of that.  

 

[JohnMo]

7 minutes ago, ReedRichards said:

Yes, I know there is a "hard core" school of thought that if you get your radiators perfectly balanced then you can keep every room at the right temperature by relying entirely on WC without any internal temperature controls

Not really true, have you actually read many of my posts. I have run every mode possible, over the last couple of heating seasons, to get the best output per pound spent. Had a thermostat in every room (still have, but no longer connected). The best cost wise with thick screed given a large enough heat source, is batch charging the floor with gas or ASHP on TOU tariff. But my heat pump isn't big enough for that below zero. So straight WC is the next best thing.

 

My house doesn't need, thermostats or TRVs, but like a good radiator system, the UFH loops are sized to give a equal output to heat loss expected for each room, the difference is made up by tweeking flow rate. Heat losses are low, floor temp extremely close to room temperature so the heating system responds to changes in room temp without intervention. The further the room and heater diverge from each other the more reliant you are on control. So flow temperature of 35 for radiators, is way better than a lot systems being installed at 45 to 55. A 35 deg radiator can much better vary it's output on its own in response to solar gains, than a 45 Deg one.

 

Currently cooling the heat pump compressor ran 9 times over the last 24 hrs. Gaps between run varied from one hour to four hours, in response to room temp changes. Compressor restarts when average return temp goes above 19.8 degs.

 

22 minutes ago, ReedRichards said:

But Building Regulations tend to be conservative and I don't think they so much as dreamt of that

 

22 minutes ago, ReedRichards said:

general requirements

The word general makes the whole sentence meaningless. As it permits deviation and allows you not exactly follow to the letter. So wide open to interpretation. If you are to follow exactly, it would say must or shall or even should.

[jack]

On 08/01/2024 at 16:45, ProDave said:

... when the market wakes up to reality.

 

If the recent spike in energy prices didn't wake people up, I just don't see it happening at all.

[ReedRichards]

@JohnMo The acid test would be to omit all TRVs and thermostatic controls, rely on WC then call in a Registered Building Inspector to see if it passes muster.  I believe HeatGeek installers favour pure WC control (although how they find the time and opportunity to balance every radiator I don't understand).  So do they not fit TRVs? Are there heat pump installers with the courage of your convictions?  

[JohnMo]

1 minute ago, ReedRichards said:

So do they not fit TRVs?

Easy install them and then set to 24 or above, so they stay fully open, as if they are not there.  Risk taken away. Various way to achieve the same thing. Why would you call in a Building Inspector?

[ReedRichards]

@JohnMoSo can we agree that whilst installers may or may not be obliged to fit TRVs (to all radiators in rooms without another form of heating control) they would be incautious not to fit those TRVs?  Even if they intend not not use them.  

Edited August 5 by ReedRichards

[JohnMo]

Yep

[sharpener]

7 hours ago, ReedRichards said:

But Building Regulations tend to be conservative and I don't think they so much as dreamt of that.  

 

As it happens I had a Building Inspector here today to look at my recent HP installation. There are also (wireless Honeywell) TRVs on all radiators in habitable rooms. I asked if they were still required on a heat pump system, but he didn't know and said he would find out in order to satisfy his curiosity and mine.

[JohnMo]

1 hour ago, sharpener said:

Building Inspector here today to look at my recent HP installation. There are also (wireless Honeywell) TRVs on all radiators in habitable rooms. I asked if they were still required on a heat pump system, but he didn't know

Pretty useless inspection, if he doesn't know the details of what he is there to inspect.

[ReedRichards]

16 hours ago, sharpener said:

There are also (wireless Honeywell) TRVs on all radiators in habitable rooms.

So your system will gradually shut off radiator after radiator as each room reaches its set temperature until the last room reaches temperature, all the TRVs are off, so the heat pump is shut down?

[sharpener]

7 hours ago, ReedRichards said:

So your system will gradually shut off radiator after radiator

 

Your timing is perfect as this morning I tested the behaviour of the HP starting with all the rad valves fully open. Have started a new thread here.

 

 

 

 

Edited August 6 by sharpener