Greenstar 28i & rads over 35kbtu @60deg C + Isorad tails

[oldman2]

2 questions in one post.

Plumbers just fitted a Greenstar 28i boiler, 3 bed detached house, trv's on all but bathroom rad.
I just totaled the btu's at 60degC for the rads they fitted from the manufactures tables and they come to just over 35181btu.

Does this mean the boilers undersized for the job, or the rads are over spec'd though you cant tell that without room specs of course?

Secondly Isorad tails, these are tails with service valves set into them to enable you to turn off the trv & lockshield, plus the pair of service valves and then remove rads for decorating without loss of system water.
Anyone used them?

It seems the older style of these were longer than a standard tail meaning pipework changes but they now have a new model which is directly interchangable with a standard length tail, seemed like a good though not cheap @ £10 a pair idea to me.

 

[D_Hailsham]

Plumbers just fitted a Greenstar 28i boiler ...

I just totaled the btu's at 60degC for the rads they fitted ...and they come to just over 35181btu.

Does this mean the boilers undersized for the job, or the rads are over spec'd though you cant tell that without room specs of course?

You are mixing units

The 28 in the Greenstar's name is the input in kilowatts. The output is about 25kW, which is equivalent to 82,000 BTU. So you have plenty of heat for your rads. This is normal as combi boilers are always sized for the hot water demand.

As for the rads being over sized, did the installers provide any calculations or were the rads sized by "experience".

Never heard of Isorad tails, so did a google. Brilliant idea! Why don't all valve and TRV manufacturers do this as standard?

 

[oldman2]

Thanks for the reply, silly me mixing my units

The only drawback I can see with the Isorad tails is maybe the bore is reduced, not seen one so cant really be sure. Full bore service valves are I think usually slightly oversized externally to allow for the bore.
Also you maybe wouldnt use them on big rads due to the weight of water held?

As to the rad sizing, I just got a quote with rad dimensions per room for the job.

I have just run my room sizes through an on line calc and the total overall specified by the plumber comes to 32352btu for the house (my previous number of 3518 was an error) and the online calc gave 32536btu for average heating temp.
His numbers look pretty close for the bedrooms, he's slightly low (700btu down) for the lounge diner so I guess thats ok too, the hall looks to be 500btu oversized but as the heats going up the starway too thats prob ok. The bathroom has 1532btu where the calc gave 2318btu so thats the biggest variation, though there is a small towel rail (500x1000) that I dont have a btu for, but it must be at least 1000btu so that makes that room about right too.

So all's looking ok now, I think

 

[Agile]

All rad calculations are only approximate!

The full output is only required when the outside temperature is at -1° outside ( except in Norfolk where its -2°C ).

Oversizing rads is no problem and results in faster heat up and more efficient running with a condensing boiler.

The 28 in your boiler is the maximum OUTPUT in kW. Thats to the hot water but the output to the heating is sometimes lower and I think yours may be 24 kW. Thats fine as the heat loss for your house is about 10 kW.

BTUs are an old imperial unit and the sooner people stop using them the better, same with feet and inches and pounds and stone. I weigh 84 kg and run at 10 km/hour !

Tony

 

[Gasguru]

....Brilliant idea! Why don't all valve and TRV manufacturers do this as standard?

Because they are going to cause more problems than they solve. Give them a few years and the valve will either seize or you turn it and the spindle will leak. Chinese made carp. No different than ball valves fitted to pumps...you always end up cutting them out.

 

[oldman2]

I agreed to have the gas supply run low level through the lounge to reach the boiler from the meter, I assumed it would be just above the skirting board with the radiator pipework.

I was shocked to find it sitting 2mm above the carpet, my wife will slaughter that with the vac cleaner if it stays there. Is that quite ok for gas regs like that?

View media item 3556 View media item 3557 View media item 3558

 

[D_Hailsham]

The 28 in your boiler is the maximum OUTPUT in kW. That's to the hot water but the output to the heating is sometimes lower and I think yours may be 24 kW. That's fine as the heat loss for your house is about 10 kW.

You get different answers, depending on which document you read on the WB web site.

Because they are going to cause more problems than they solve. Give them a few years and the valve will either seize or you turn it and the spindle will leak. Chinese made carp. icon_rolleyes.gif No different than ball valves fitted to pumps...you always end up cutting them out.

I was only saying that the concept was brilliant, not the actual product. Not everything made in China is sub-standard.

 

[Gasguru]

Isorad concept is ok but unless you have a stainless steel ball, PTFE seatings, PTFE gland packing followed by O ring packings with a torx drive spindle etc etc.


That pipeworks none too impressive....dumb place for the gas pipe.

From BS6891:2005 section 8:

8 Installation
8.1 General
Installation pipework shall be physically protected or located where it is not liable to mechanical damage.


Personally I would have the TRV vertical (ok they perform a little better horizontal) but it will pick up heat from the pipe below and they are more prone to damage.

And is that flux residue on the joints/pipework?

And I don't like the way the pipe runs up to the rad valves...it's not
vertical so the valves are on the tilt...looks a bodge.

What make are the TRV's ?

Before you said TRV's on all the rads except the bathroom....where is the room thermostat located and is there a radiator in the vicinity fitted with a TRV or manual (wheelhead) valve fitted?

 

[oldman2]

All the other Heatline trv's are vertical just that one for some reason got made horizontal.

Thats a solder blob not flux.

As to the stat and trv's I wanted to be able to control the heating from either the 12mtr long lounge diner or the hall as I have an RF controller/roomstat and i'm unsure which would be the best position to use so the plumber suggested no trv on the bathroom rad, leaving me free to figure which was the best stat location.
I also have a heat and cool aircon unit in the lounge so thought sometimes I may want to run that to warm the lounge (elec costs may be less) with the stat in the hall controlling the gas ch to take the chill off the rest of the house.

 

[Gasguru]

Heatline hmm..

No, the green snot on the pipework...they also look very black...I don't think they've been wiped down properly after soldering.

You should not have a room thermostat in conjunction with a TRV....the TRV may shut off the rad before the room stat hits its setpoint so the boiler continues to cycle on/off.

Electricity is more expensive than gas.

 

[oldman2]

Pipes not cleaned properly then yes.

I made an assumption that the trv's if wound fully open wouldnt shut until well after my set point of say 22-23 deg c

Electricity may well be more expensive than gas at the moment, but that may change and I would like to have the option to use it if so.

Also remember that when using AC as a room heater your putting say 1kw of energy in and getting 2.5kw out so savings to be had there if its a point in the year where you just need to take the chill off.

Always willing to learn here, so thanks for any replies.

 

[Gasguru]

Ok well learn this

Most of our electicity is generated at an efficiency of only 30-35% by burning GAS, oil and coal. Electrical energy for the forseeable future will ALWAYS cost significantly more than gas since its production is extremely wasteful of the source fuel and should only be used for heating if no other viable sources are to hand. Large scale nuclear power is a long way off but that will also be expensive. Wind farms on a significant scale is unlikley. Deuterium fusion is a distant dream.

The Coefficient of Performance figures are often reported by users to be significantly lower than manufactuers claims and it is directly linked to the temperature difference. It is often more cost effective to burn gas in the first place.

Heat pumps have been pushed by the industry (since they make far more profit on them than boilers) but are really only suited to countries where hydro or nuclear power is the significant form of electrical energy generation. No surprise that these are the countries where they were developed.


Yes if you open up the TRV where the room stat is located that will have the desired effect. Just make sure the radiator is correctly balanced on the lockshield. If it's open too much the room may heat up too quick and the stat shut down the boiler before the rest of the property is up to temperature. And fit the stat in a suitable location on the wall...I see too many RF stats sitting on window sills in the glaring sun.

 

[oldman2]

Thanks for the info on the TRV's and the lockshield.

I have mounted the stat on a non sunny wall in the hall, but your comment is noted

I double checked tonight and the 22mm copper gas feed is passing through 2 cavity walls with no sleeve in place at either wall which I think is contary to the (Gas Safety (Installation & Use) Regulations.

Having googled some I find this:
All pipes that pass through a wall or floor of a building must be sleeved.
This applies to all walls not just load bearing walls. (Gas Safety
(Installation & Use) Regulations. Part D Regulation 19 (2b))

The sleeve should be sealed
1) Between the sleeve and the brickwork
2) On the inside between the sleeve and the pipe, with fire resistant
mastic. The sleeve should normally be sealed at one end only, preferably to
open air, where applicable. In the case of meter boxes the sleeve should be
sealed at the point of entry to the building.

Pipes that go through walls must be sleeved to prevent damage in the event of settlement, to prevent any leaks entering the cavity, and to avoid corrosion. There must not be any joints within the wall (i.e. within the sleeving). The pipes must go directly through the wall.
Pipes must not be run inside wall cavities as any leakage there is very dangerous.
The pipe must be sealed to the sleeves except on the end of the sleeve that is outdoors. This is to allow any leak inside the sleeve to be vented outside.
The gap (generally quite small) between the sleeve and the wall it is passing through should be sealed.

I will be talking to the plumbers (corgi reg) tomorrow about repositioning the gas supply pipe and using the correct method through the cavities.

Thanks again.

 

[cider]

I double checked tonight and the 22mm copper gas feed is passing through 2 cavity walls with no sleeve in place at either wall which I think is contary to the (Gas Safety (Installation & Use) Regulations.

very naughty
think you should ask to see his corgi id card

 

[Agile]

Also remember that when using AC as a room heater your putting say 1kw of energy in and getting 2.5kw out so savings to be had there if its a point in the year where you just need to take the chill off.

Always willing to learn here, so thanks for any replies.

Most of the cheaper a/c units are just plain electric fan heaters in the heating mode and are not reversible refrigeration units. So their efficiency is a plain 100% on the electric power supplied.

The heat pump manufacturers usually quote a " ( maximum ) COP of about 4.0 " Purchasors read that as a " ( ) COP of 4.0 " as it helps to justify their purchase and makes them think they are getting something for nothing !

Whilst Gasguru gave a very true overview of the false "green" aspects of heat pumps. But he did not explain the money aspects!

A 1 kW heat pump might realistically produce 3 kW of heat output. 1 kWH of electricity costs about 12p whereas 3 kW of gas costs about 12 p. So there is no financial benefit. In fact a gas heating boiler installation will be about £2k and a heat pump about £6k.

There is only a potential benefit if mains gas is not available.

Tony