boiler insulation

[Michaelr]

Incidentally I forgot to mention that the powerflush option that we were being given the "hard sell " before we finished the contract was £650. It must be the "grey hair" that attracts the sales approach with this product, they were certainly well trained in the pitch , pity they could not be so attentive to the technical side with us.

Anyway three years on I am £1000 ahead.

Mike

[Ed_Dinning]

Hi Gents, thanks for a very comprehensive set or replies which will take a little while to digest; it is a great relief to see some "Engineering" replies rather than "technician" or worse "sales" replies.

I had seen the adverts for modern condensing boilewrs with copper cylinders, but had thought them a form of Combi, thanks for the clarification David.
Comments on servicing noted!; also coments on modulating gas appliances.

Boiler is a Glow-worm 65/80 in a 5 bed house at 600ft ASL.

The present unit is a conventional flue type with an 8M chimney, located in the utility room with the appropriate gholes everywhere for combustion air. The room gets much warmer than needed, hence the thoughts on insulation.
The system is run with inhibitor and is flushed every 5-8 years and re-filled. The tank is an indirect type with seperate headers, fitted with top covers and min water surface.
The control valve system is home brew but to high standards. It shuts down both boiler and pump when all system demand ceases and does not leave the boiler on short cycle. The cylinder is fitted with high and low level DHW sensors.
The summer project is to add solar HW via an additional worm at the base of the DHW cylinder. At the same time the system will be fully flushed as there is presently some kettling; motorised valves will be installed in more accesssible positions and insulation will be improved, hence the request for thoughts on insulating the boiler waterjacket. The flue pipe S Stl will be left un-insulated as a heat source for the room.

The DHW cylinder is used with a timed immersion heater in summer as an energy saving measure, solar would also be of benifit at this time.

Any further thoughts/ questions?

Thanks, Ed

[pwdrive]

Hello Ed, I don't know if this would be applicable to your situation or not but two systems can be run together using a relatively small neutralizer tank (google neutralizer dunsley if you have never heard of it) primarily I think it's designed for gas/oil with solid fuel/wood supplimenting, might be suitable for solar, I guess you can check that out though.
600ft ASL can suck a lot of heat out when the wind blows I would imagine.

Lawrence.

[Yorkie]

The idea is to insulate the free standing boiler to reduce heat losses from its water jacket by means of a modern insulating blanket that is a similar material to shuttle tiles. This will fit inside the boiler sheet metal casing and be clipped against the outside of the boiler, obviously leaving gaps where there are air intakes, flues and other combustion access. This should considerably reduce losses from the boiler shell.

Your thoughts Gents?

Ed

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Just a few observations on those comments.

1) Very little heat is emitted from a modern condensing boiler. The casing is warm to the touch, but certainly not hot. I've just checked our Worcester Bosch and the casing is 26C at the front, and 24C at the side. The flue outlet is 24C, but then the outer part of the flue is the cold air intake.

2) Boilers are usually sited where any heat given off isn't waste heat but useful heat - utility rooms, garages, lofts etc, (no bad thing to have a little heat up there, with all the plumbing, however well insulated it might be). Admittedly when sited in kitchens, the heat isn't always welcome, but wherever a condensing boiler is sited, it will emit far less heat than your old Glow Worm boiler. Apart from that, I wouldn't personally modify a boiler by fitting insulation inside the casing as the boiler has been designed, tested and approved without such additions, and it's difficult to predict what effect such modifications might have on the operation of the boiler.

3) In terms of making economies on heating bills, do bear in mind that for every hundred pounds of gas you are using in your Glow Worm, about £40 of that is going out of the flue into the big wide world as your personal contribution to global warming, (not to mention other heat losses if you don't have such things as double glazing, cavity wall insulation, [unless solid wall of course] and at least 30cms of loft insulation). With a condensing boiler, that £40 loss per £100 of gas used drops to about £5 - £10. Your Glow Worm also has a permanent pilot operating 24/7/375 even when the boiler isn't calling for heat. It has to do that to keep the thermocouple energised and the main gas valve operational. A condensing boiler pilot light only comes on when the boiler is operating, and serves as a flame failure device. The sequence of events when a condensing boiler comes on is broadly as follows:

i) The fan comes on to purge the combustion chamber and introduce fresh combustion air.

ii) Gas passes to the pilot, and ignition sparks ignite the pilot. A flame will conduct and rectify AC current to DC, so a very small AC electric current passes across electrodes through the pilot flame, and provided a pilot flame is indeed present, the current is rectified to DC, so when the flame protection circuitry sees that DC current, it brings on the main burner. No DC current present? - no gas to the main burner as there would be no pilot flame to ignite it.

iii), whe the heat requirements are satisfied, both the main burner and the pilot light go out. The fan will continue to run for a short while to prvent the cool the boiler down, and there will be a pump 'over-run' for a short while to ensure that the hot water in the heat exchanger goes into the heating/hot water circuits rather than being retained in the boiler.

The condensate drain within the boiler has a reservoir into which electrodes are present at above the level of water when the drain is working properly. However, if the drain is blocked, (iced up for example), the water level in the reservoir rises, shorts out the electrode and tells the boiler control circuitry that the condensate drain is blocked.

That's a very broad generalised and simplistic explanation, and these days, is about as much as I know, or for that matter, want to know, about modern gas boilers!

I'm always dismayed - especially when I drive round the North Cicular in London - to see very long condensate drains in exposed positions on outside walls, contrary to all sensible advice by manufacturers. It's quite commonplace to see white 22mm condensate drains on outside walls for two or three storeys from boilers sited in lofts. I can only imagine the grief that this must have caused last winter, an what a nice little earner it would have been for out of hours callouts at premium rates to remove the ice from the drain, only to risk a repetition.

[Paula A]

hehehe.. indeed.. I ended up a ladder with a hammer and a bucket of boiling water thawing out my pipe, and that included the outfall from the bathroom as well. Not nice in minus 10.

[Ed_Dinning]

Hi Folks, The solar system will use a Glycol mix to prevent freezing as the working fluid, hence seperate header tanks.

The Glow worm is a cast iron boiler with 4"-6" gap between the boiler and the sheet steel casing; with the cast iron at waterjacket temperatures, so this radiates heat well.
I intend to cover the cast iron with about 1/2" of the insulating material so there is still plenty of space within the casing.

Control on the solar thermal will be with LM 75 temp sensors and speed control of the circulating pump.


Ed

[pwdrive]

Hello Ed, if you are going to insulate the boiler you could use fibreglass or rockwool sandwiched between two sheets of masterboard, the whole can be made to any thickness needed, as far as I am aware the above three products are fire resistant however masterboard can crack if totally restrained and subject to high temperature ie: it needs to be able to expand and contract fairly freely.

Lawrence.

[Paula A]

The shuttle tile stuff you are looking for is called "Saffil" and it's strange stuff. It can be white hot on one side and yet in one inch thickenss can be cool to the touch on the other side. It comes in both board and blanket form, is soft and can be carved to shape easily.

[ex 2 Base]

Ed, regarding Solar heating The wife and I made our own 28 years ago and it failed once. We made fibre glass tray, in which we mounted domestic radiators, painted mat black. We made a mould in ply wood with reliefs all round to facilitate tray extraction. We based the tray size on Horticultural glass as used in green houses, so they were each approx 30x 54 inches in size. We bought a cylinder to our own design as they were only made to order those days by IMI Leeds or Hull. We wanted a cylinder with two coils, the lower one to have a surface area twice as large as the top one, which was a standard gas boiler size. The cylinder was about 5 feet tall by 18 diameter, with two extra inlet or outlets. We used a normal domestic circulator as a pump, to circulate anti freeze and inhibitor around the system. We piped it up ourselves using 22mm copper all round.Basically we used a two pipe manifold system, nothing complicated at all. We used a small make up water tank to create a head of water.When we were assembling the panels we mounted two Thermisters on each panel using Aradite, the Thermistor were connected via screened cable back to the control box. Another Thermistor was mounted on the lowest pipe on the Solar coil,again we used screened cable. In the top outlet of the Solar coil we fitted an inline non return valve, I made that easily adjustable as were weren't 100% sure of what was needed. I made a simple controller using a 741 op amp, a BC 107, plug in relay, tiny 240/12 tranformer bridge rec, a bit of smoothing and a zenner.We filled up the system and we were pleased to say it worked straight away and continued for 26 years, with a bit of maintenance when we remembered.We had 3 panels and were more than self sufficent for domestic hot water from mid spring to mid autumn and through out the summer.We had two teenagers and they could stand under the show for long enough and still have hot water. I modified the washing machine to take full advantage of all the hot water available. As the family moved away we thought electrical energy was be coming expensive so removed the system summer 2011 and had PV panels fitted. The rear of our house faces South, so fr the PV panel have given us a good return on our investment.Not sure about helping the earth. I could send you a layout of the system, together with circuit diagram.Ted

[Ed_Dinning]

Hi Ted, thanks for the info, I will be working on similar lines, probably using |LM35's as temp sensors.
It will be a home made collector from some surplus copper pipe as well as thin sheet to aid collection. I have a tank already so I will fit a coil into the base via a sweated plate on the side at the bottom (3" * 1/4" busbar, ).

Off to Oz tomorrow to escape the winter, might get a start on this project on my return, plus some ideas for the people down under.

Ed

Ed, regarding Solar heating The wife and I made our own 28 years ago and it failed once. We made fibre glass tray, in which we mounted domestic radiators, painted mat black. We made a mould in ply wood with reliefs all round to facilitate tray extraction. We based the tray size on Horticultural glass as used in green houses, so they were each approx 30x 54 inches in size. We bought a cylinder to our own design as they were only made to order those days by IMI Leeds or Hull. We wanted a cylinder with two coils, the lower one to have a surface area twice as large as the top one, which was a standard gas boiler size. The cylinder was about 5 feet tall by 18 diameter, with two extra inlet or outlets. We used a normal domestic circulator as a pump, to circulate anti freeze and inhibitor around the system. We piped it up ourselves using 22mm copper all round.Basically we used a two pipe manifold system, nothing complicated at all. We used a small make up water tank to create a head of water.When we were assembling the panels we mounted two Thermisters on each panel using Aradite, the Thermistor were connected via screened cable back to the control box. Another Thermistor was mounted on the lowest pipe on the Solar coil,again we used screened cable. In the top outlet of the Solar coil we fitted an inline non return valve, I made that easily adjustable as were weren't 100% sure of what was needed. I made a simple controller using a 741 op amp, a BC 107, plug in relay, tiny 240/12 tranformer bridge rec, a bit of smoothing and a zenner.We filled up the system and we were pleased to say it worked straight away and continued for 26 years, with a bit of maintenance when we remembered.We had 3 panels and were more than self sufficent for domestic hot water from mid spring to mid autumn and through out the summer.We had two teenagers and they could stand under the show for long enough and still have hot water. I modified the washing machine to take full advantage of all the hot water available. As the family moved away we thought electrical energy was be coming expensive so removed the system summer 2011 and had PV panels fitted. The rear of our house faces South, so fr the PV panel have given us a good return on our investment.Not sure about helping the earth. I could send you a layout of the system, together with circuit diagram.Ted