Advice: new CH system

[Doctor Drivel]

This amateur hasn't a clue. To the OP, take no notice.

[Doctor Drivel]

You are living open plan, most do not live that way. Centralised temperature control is generally not a good thing. It can be used as a high limit that is about all, but only steps in when the individual temp control fails. In the case of different temperatures during the day it "might" make a difference, but then you can have a simple tamperproof low limit stat to make sure the building never gets below a certain temperature. I know few who use more than two temps on programmer stat.

Say you switch off the heating from a simple programmer as you are going out, and you never want the house to go below say 16C, then the low limit stat will ensure it never gets below that temp and maintains it around 16C. You come in switch the heating on and a fast warm up. Cheaper and simpler and easy to operate. Few people really understand programmable stats anyway. The point is, with individual room control you can have say the vacant back rooms set to around 16-18C by the TRV. You can't do that with a centralised programmer stat.

[Dave Plowman (News)]

Continual use of foul language now, eh, dibble? Is this the real you? BTW, still waiting for the police to arrive...

[The Natural Philosopher]

In an installation the size of this onbe, it might be worth creating several programmable thermostated zones AS WELL as TRV's..the radio stats mean less wiring..just that you would have to parallel the zone valves outputs back t the boiler somehow.

TRV's are nice for living areas, with master stats in corridoors etc.

[Doctor Drivel]

Do not reply to my posts. Fuck off idiot.

[Doctor Drivel]

Nope. Wrong again. Best have zones with NO programmable thermostats and all TRVs on all rads in the zone.

[Andrew Haylett]

Wow, thanks for all the help. I'm a CH neophyte so all information is helpful. A few (quite a few) follow-up questions to help my learning experience.

Mains pressure. Yes, there are some concerns about that. When the plumber first measured the flow rate at a tap it was about 15l/min. They replaced the stopcock at the entry point (it was locked solid) and maybe they fiddled with something, but he said he can now measure

20l/min, which he professes to be adequate. What he wants to do is run 22mm from the entry point (currently 15mm) all the way up to the boiler to improve the flow rate/pressure. (The boiler is to be on the first floor, in the airing cupboard.) Is that a helpful thing to do, given that the rest of the system is 15mm which will presumably limit the flow rate at the tap?

What are the implications of the mains water pressure falling below a certain level? Sub-standard performance at the taps/shower head, or worse?

Location. He offered to put the boiler in the loft (makes the flue a bit easier if mounted on the side wall). I demurred since it seemed we weren't going to have much room for clothes in the airing cupboard anyway due to the size of the cylinder, so might as well stick the boiler there, and because we don't have a 'proper' loft ladder so I was concerned about servicing access. But it has been suggested AIUI that both the boiler and the cylinder could be put in the loft, with safety advantages. I'll ask him about that.

Shower pumps. He didn't mention about getting rid of the one we have. I guess I don't fully understand the regs. I thought as it was pumping out of the cylinder then it would be OK - or does having a pressurized system mean that the whole house effectively becomes an extension of the mains?

Unvented/heat store. I think I understand how the latter works. I guess it's a bit like a combi where the HW to the taps is heated on demand, except that the heating is done via a pre-heated body of water, right? How large is a typical thermal store compared with an unvented cylinder? How common, relatively speaking, are the two types of system? And are there any ease-of-installation issues either way?

Could the Vaillant boiler already specced drive a vented system? I guess the boiler just sees an indirect system either way, whether heating a pressurized body of water or a thermal store.

Safety/maintenance. That's obviously a concern with 6 people in the house - but how prone are unvented systems to blow up? Do they have a bad safety record (assuming appropriate maintenance)? I'll check with the plumber about servicing costs.

He hasn't said anything about building control approval for an unvented system. Whose job would this be?

TRV/room stat. I'll skirt clear of this debate. ;-) He's fitting TRVs throughout, plus an RF room controller. Hopefully that will give us enough flexibility. I haven't considered zoning - didn't even know about it - but will ask anyway. I would *think* that TRVs will give enough flexibility to save energy in lesser used areas, e.g. spare room, utility room, etc.

many thanks again, Andrew.

[Andrew Haylett]

Wow, thanks for all the help. I'm a CH neophyte so all information is helpful. A few (quite a few) follow-up questions to help my learning experience.

Mains pressure. Yes, there are some concerns about that. When the plumber first measured the flow rate at a tap it was about 15l/min. They replaced the stopcock at the entry point (it was locked solid) and maybe they fiddled with something, but he said he can now measure

20l/min, which he professes to be adequate. What he wants to do is run 22mm from the entry point (currently 15mm) all the way up to the boiler to improve the flow rate/pressure. (The boiler is to be on the first floor, in the airing cupboard.) Is that a helpful thing to do, given that the rest of the system is 15mm which will presumably limit the flow rate at the tap?

What are the implications of the mains water pressure falling below a certain level? Sub-standard performance at the taps/shower head, or worse?

Location. He offered to put the boiler in the loft (makes the flue a bit easier if mounted on the side wall). I demurred since it seemed we weren't going to have much room for clothes in the airing cupboard anyway due to the size of the cylinder, so might as well stick the boiler there, and because we don't have a 'proper' loft ladder so I was concerned about servicing access. But it has been suggested AIUI that both the boiler and the cylinder could be put in the loft, with safety advantages. I'll ask him about that.

Shower pumps. He didn't mention about getting rid of the one we have. I guess I don't fully understand the regs. I thought as it was pumping out of the cylinder then it would be OK - or does having a pressurized system mean that the whole house effectively becomes an extension of the mains?

Unvented/heat store. I think I understand how the latter works. I guess it's a bit like a combi where the HW to the taps is heated on demand, except that the heating is done via a pre-heated body of water, right? How large is a typical thermal store compared with an unvented cylinder? How common, relatively speaking, are the two types of system? And are there any ease-of-installation issues either way?

Could the Vaillant boiler already specced drive a vented system? I guess the boiler just sees an indirect system either way, whether heating a pressurized body of water or a thermal store.

Safety/maintenance. That's obviously a concern with 6 people in the house - but how prone are unvented systems to blow up? Do they have a bad safety record (assuming appropriate maintenance)? I'll check with the plumber about servicing costs.

He hasn't said anything about building control approval for an unvented system. Whose job would this be?

TRV/room stat. I'll skirt clear of this debate. ;-) He's fitting TRVs throughout, plus an RF room controller. Hopefully that will give us enough flexibility. I haven't considered zoning - didn't even know about it - but will ask anyway. I would *think* that TRVs will give enough flexibility to save energy in lesser used areas, e.g. spare room, utility room, etc.

many thanks again, Andrew.

[Owain]

The 22mm needs to go to the cylinder, not the boiler. Remember that if each tap is fed by 15mm you want 22mm to allow full flow from several taps simultaneously, or to stop the flow dropping suddenly when someone turns on a tap elsewhere.

If you don't have any mains pressure you won't have any water at all.

There aren't really any safety advantages IMHO. You need a proper loft ladder, boarding below and safety rail around the boiler area.

Probably.

Not very, but they can be spectacular if they do.

Yours, ultimately; you should specify in the quote that the plumber is responsible for compliance with Building Regs and the obtaining of all permissions required, and that fees for such are included in his quote.

The drawback to TRVs is they don't adjust themselves and can be left on 'full' inadvertently. Zoning and a programmable thermostat would allow you to have, eg, your bedrooms come on warmer in the morning for waking/dressing, but be cooler in the evening for sleeping.

The extra plumbing is minor - just another zone valve located in the appropriate position.

Owain

[Dave Plowman (News)]

What a fool. Going back years in time to when you could only have one pre-set temperature. And you call yourself a professional. Professional catalogue reader definitely.

[Dave Plowman (News)]

If you balance up the system carefully with all the TRVs fully open so you're relying on the main thermostat in the living area set to the maximum you want, the TRVs will then take care of other rooms getting too hot and wasting energy - but will still cool down to the lower temperatures that you may programme in. It can work very well.

[Doctor Drivel]

Idiot, you don't know what you are on about.

[Doctor Drivel]

Idiot, you don't know what you are on about. Best you eff off.

[Andy Hall]

It is if you just want to run one shower at a time or fill one bath - not if you want to do more than this.

Also, it would be a good idea to check this at peak water usage times and the times that you are likely to want to shower or bath.

This may well improve the flow rate depending on the supply.

It depends on the length of the runs. Unless they are particularly long - i.e. one side of the house to the other - that should be OK for showers. The bath plumbing may already be 22mm - it usually is if there is a roof tank system originally.

Substandard performance and variation in flow as other things are used. A thermostatic valve on showers will maintain temperature reasonable well unless there are gross changes in available flow.

You would have to check the construction in the loft if the cylinder is to go up there. Should be OK if it goes in the position of an existing storage tank but needs to be checked - it's a lot of weight if you have a large cylinder. If the boiler goes up there, the area from the access hatch to it must be boarded and there must be a safety rail around the hatch.

In effect, yes. The pump would have to go.

A thermal store can be run at 75-80 degrees as opposed to the 60 degrees of stored HW. The implication of that is that for an equivalent amount of HW production, the thermal store cylinder can be

3/4 of the size of a storage cylinder. However, there are additional plumbing components such as valves, pump and a heat exchanger. By the time those are added, there is not really any saving of space. Also a thermal store needs some kind of header tank to supply the water in the main part of the cylinder because this is vented. Either this can be a small tank in the loft, or if the cylinder goes in the loft, there are thermal stores with the header tank integrated on the top. Again by the time you add this, there is no space saving. On the other hand, space may not be as critical in the loft. If you want an airing cupboard, you can always put a small radiator in there.

If you use an indirect store, there are, in effect, three lots of water.

- The primary, which runs through the boiler, the heating circuit and a coil in the cylinder. This can be sealed and pressurised or open vented according to boiler requirements and preference. There are a lot of advantages in going for sealed and no real disadvantages.

- The water in the store cylinder. This is open vented and is circulated, on HW demand between store and heat exchanger. Having it open vented gets around the regulatory requirements of a pressurised cylinder.

- The HW being heated from the mains. With a thermal store, there is again no large volume storage in this part either.

They are widely fitted in many countries outside the UK and do not have a bad reputation or safety record.

He needs to have a particular training and certification to install/service an unvented system. Ask him about that. Assuming he does, then he can self certify the installation and there is no need for other approvals.

You could get him to fit TRVs on all the radiators - even the one where the room thermostat is going. Normally, the radiator in that location does not have a TRV in order to prevent the two controls conflicting. However, you may find that the initial location for the room thermostat is not ideal for one reason or another - for example a hallway and someone leaves the door open or living room and you want a separate log/gas fire or something. Either can affect the behaviour of the heating in an unwanted way.

If you fully open the TRV on the radiator where the room thermostat is located, then that room becomes the "controlling" room. You cn even take the thermostat from room to room if you want.

[David Hansen]

On 12 Aug 2006 15:43:12 -0700 someone who may be "Andrew Haylett" wrote this:-

Right. Think of it as a bit like a siege engine. One slowly winds the mechanism up, it being impossible to wind the mechanism up rapidly. Then all the energy is released in one go and the rock shoots off at a far higher speed than one could throw it.

The store stores energy at the maximum rate that the boiler can provide, but can release it more quickly.

The sizes are given on the links people provided. The answer is that it depends.

Plumbers go by fashion. The fashion for some time has been unvented systems, which have the additional advantage of a nice little earner every year. Thermal stores are also somewhat newer and so news of them has not penetrated everywhere.

It depends. Generally the thermal store has slight advantages.

[Doctor Drivel]

Pressure equalisation valves should be used, or mixers with them incorporated.

Can be as low as 60C.

Some thermal stores/heat banks have the plate heat exchangers inside the cylinder. Some can be sealed to 1 bar, like a CH system.

Not if it is sealed. One 24 litres expansion vessel will act on the cylinder, CH pipes and boiler. But you have the same explosion points of an unvented cylinder, but the boiler and cylinder have independent relief valve giving two blow-off points.

Abroad they do. I read one case in the US where they think a nasty neighbour broke into a house while they were on hols. He put a compression cap on open vent relief pipe and by-passed the electric immersion stat. He then switched it on. Many hours later while he was elsewhere - kaboom, the side of the house gone.

There is no debate, it is just me explaining it the amateurs.

Just have a Grundfos Alpha pump when using a thermal store/heat bank. TRVs all around, and no wall stat just a simple programmer.

Until it gets lost down the back of the sofa with the rest of the remotes.

[Dave Plowman (News)]

You being a fool? You prove it each time you reply to my posts.

Like now. But at least you've had the decency to stop using foul language.

Just as well...

[Dave Plowman (News)]

And that's the fault of the device?

Hint. Any water heater of any type can be made to explode if tampered with in the intention of making it do so.

[Andy Wade]

I wonder what became of the system you were working on a few years ago with the individually addressable Sauter valve heads - as mentioned in this article?

you mentioning commercial potential and patentable features in later postings, but don't recall hearing anything since. Is is on the market yet... ?

[Doctor Drivel]

Best that you eff off as you are an idiot.