Recommendations

[Jb]

What does the group recommend for a new combi boiler.

Four bed det house with proposed kitchen extension (small). Presently eight rads but probably need at least two more. MUST have a good output to shower, I hate puny showers.

Many thanks

Jb

[Doctor Drivel]

High flow models available:

Wall mounted: Alpha CD 50 Glow Worm Extramax

Floor mounted: Viessmann 333 Worcester Bosch 440 Highflow Vokera ACV HeatMaster Atmos Multi Gledhill Gulfstream Ideal Istore Potterton Powermax ..and so on...

Your mains must have enough pressure and flow. Test it.

[Jb]

Thanks, I should have added that I want it fitted in the loft space and will be using a wireless programmer.

I have no idea how to test water pressure but i live half way down a good hill so it seems quite good to me.

i have googled till i'm totally confused so i was hoping for specific brand recommendations base on experience.

Thnaks Jb

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[Jb]

Thanks. I should have added that I want it fitting in the loft space and will be using a wireless programmer.

I don't know that water pressure but living half way down a good hill it seems pretty good to me.

I have Googled till I'm totally confused, i was hoping for brand recommendations based on experince.

Thanks Jb

>

[John Rumm]

On a gable wall? That will probably rule out any of the storage models since they are fairly heavy.

If your primary requirement is a shower, then a 35kW combi without storage will deliver 15 lpm even in the winter, which is usually adequate for most showers unless you want body jets or drencher heads etc.

Test the flow rate using a stop watch and a bucket. Unless you cold main can deliver 20 lpm or better you may find any combi a bit disappointing.

Its hard to give anything other than anecdotal accounts which don't really have any statistical significance. I fitted a Idea Isar HE35 a few years ago, and it has worked very well since - small and neat, good on showers, and borderline acceptable for baths. Most people seem to have reasonable experiences with Worcester Bosch and Valiant as well. The general rule is you get what you pay for. If you have not read it then have a look at Ed's boiler choice FAQ. Link in the article here:

[Doctor Drivel]

If you can get them in the loft and the floor can hold the weight then the floor models are good, especially: Viessmann, Atmos, ACV may be way too big. The Powermax breaks down for lifting into the loft.

The wall mounted: the Alpha. Measure your flowrate by timing a bucket fill in litres per minute.

If you are DIYing then: Viessmann 333, Vokera, Worcester-Bosch, Gledhill. The Viesssman and Gledhill are he better.

The ACV, Viessmann, Gledhill and Atmos are very good but expensive, so you get what you pay for.

[Doctor Drivel]

You mean wall mounted. The wall can have steel straps bolted to the wall from top to bottom. Put the combi between the straps, or better directly on them. Cheap enough.

[Jb]

Thanks chaps. I have asked BG (six local plumbers never even bothered to quote or turn up for appointments) for a quote but £2600 for what looks like the smallest and cheapest on the market seems a tad to high. I don't mind paying but I'd like to think I'm getting a reasonable deal. I asked this question because I'm toying with the idea of buying it, DIY and asking a corgi mate of mine to do the gas bits.

[Doctor Drivel]

Depends on the flowrate you want. How many baths, showers, etc? A Glow Worm

38kW or Worcester-Bosch 40kW, may be fine. If you want a DIYable high flow boiler then the list I gave as they have thermal stores inside not unvented cylinders which need G3 certified installer. If going in the loft you may have to enlarge the hatch. Make sure there is boarding to the hatch and around the boiler, a bright light, shoot down ladder and if near the hatch, then a rail around it of some sort.

[Jb]

Thanks, I like the look of the Bosch and may go for that. the loft work is no prob, most of it is done. I'd really like an unvented system but they are way out of my budget.

Thanks again

Jb

[Doctor Drivel]

The W-B 40 kW or the Highflow 440 will do. Highflow is floor mounted and a higher flowrate like an unvented system.

[John Rumm]

How about a thermal store or heat bank system? The advantages of unvented, without the complexities and price of unvented systems:

can DIY one easy enough:

[Doctor Drivel]

Read

for an explanation of how heat banks work

1. Fit a Surrey type of flange in the top tapping of cylinder. 1" if you can.
2. The plate heat exchanger connects to the Surrey flange port that is immersed in the cylinder water. Drill a few holes in the protruding tube that goes into the water to ensure heat is extracted from cylinders dome, not being pumped to the bottom of the cylinder. The protruding tube has a plate over the end to stop the water heat right to the bottom of the cylinder.
3. The boiler flow is taken from the other connection of the Surrey flange on the top of the cylinder. The return into the old cold feed tapping.
4. From the Surrey to the plate and then to the pump the to a spring loaded check valve and back into the bottom cylinder port. Make a diffuser by inserting 22mm pipe into the bottom cylinder port and drilling holes in and stopping up the end with an internal pipe stop (available from BES). File down the inside of a brass compression fitting that screws to the cylinder port, removing the pipe stop so the pipe can go straight through. This will spread the returning water mainly down, so it will not upset stratification in the cylinder.
5. Two cylinder stats can be used to give a long efficient boiler recovery burn. One stat about half way up and the other about 25% of the way up the cylinder. Set bottom say to 70-80C, set top say to 60-65C. The stats must be latched in with a relay.
6. The cold mains direct from the cold mains stoptap with no tee offs. Take into the flow switch then into the bottom connection of the plate heat exchanger and then to the DHW blending valve.
7. Have thermostatic shower mixers and take the hot supply for these directly off the plate heat exchanger "before the TMV (blending valve). No need to run DHW through two thermostatic mixers.
8. Install a phosphor de-scalar on the incoming mains pipe.
9. Install isolation valves on heavy usage appliances such as the washing machine, and throttle back so it will not rob showers and baths of hot water.
10. Have the F&E tank top up at the bottom of the cylinder and vent at the top. You may want to vent from the boiler flow pipe.
11. Fill with inhibitor - about 1% of total system volume. An average system is approx 100 litres, so a system has one 1 litre can. If say 150 litre cylinder then two cans for the cylinder alone, which is three.
12. Fit a Magnaclean filter on the rads return pipe to the boiler.

The performance is brilliant and you will be delighted with the mains fed showers and no vibrating power shower pump noise. High pressure mixers can be on all appliances.

Gledhill will supply a Plate Heat X. The model for the 145 litre Systemate will do. If you can get another cheaper source then try them. A 100kW plate heat exchanger is needed

or Screwfix will supply most of the fittings. They don't do the plate heat exchangers.

Farnell will supply the flow switch Farnell number: 1006771 with 22mm compression joints.

Flow Switch, makers site: The FS06

flow switch is about the best - very good.

If the boiler requires to be in a sealed system then have a cylinder with a quick recovery coil, the boiler heats this ASAP. Most boilers can be fitted to an open vented system.

[Doctor Drivel]

Now Maxie!!!! You are famed for passing bowl wind as loud as a 500 Norton. Have you progressed to a BSA Thunderbolt on backfire?