Changing the tank but should I change the boiler?

[PC Plod]

My thermal store has scaled up so I am not getting much hot water although the heating is fine. I am getting quotes for a megaflo and to change the boiler which has cut out three times over recent months when the thermal cut out has tripped. As my heating system is 18 years old do I actually need to get the boiler changed when I would imagine that a power flush will fix the boiler? With little to go wrong in an old boiler should I keep it or pay over £2000 to change it?

[Doctor Drivel]

DO NOT get a megaflow. They require an annual service which costs, are expensive and can do this:

do you mean "scaled up"? The internal DHW take off coil is scaled up? The inside is sludged up because you never added inhibitor? What?

The coil can be descaled.

A thermal store/heat bank using a plate heat exchanger is the best route. The Range Flowmax is good and runs the CH off it too. Also have a Magnaclean filter on them, which grabs ferrous particles.

The boiler is now old and probably past spending money on it.

Look at a Worcester Bosch HighFlow 440 - floor mounted boiler with integral heat bank. Also an Ethos 54kW combi. That pours out the flow rate. A Vaillant 937 combi. A Worcester Bosch 42kW combi

Stick with a thermal store/heat bank or combi one-box solution. Thermal stores and combis have changed a lot in 18 years.

[PC Plod]

"Doctor Drivel" wrote

I actually have a Range flowmax.

I have read that thermal stores are liable to scaling which has happened to me as I don't get much hot water now before it runs cold. The biggest issue with the flowmax is that plumbers don't seem to understand them and don't want to touch them. I understand that I could go for a descaling but other tanks on our estate have failed and I don't want a lounge full of water.

The boiler needs to be wall mounted and I don't fancy a Worcester as it has an aluminium heat exchanger and I would rather go for a Vaillant which is stainless steel. As for a combi well my next door neighbour has one which I have tried out. I just don't fancy waiting for 30 seconds for a limited supply of hot water.

[stevelup]

You tried a bad combi then!

[Steve Firth]

partly fill with water, seal up all the holes and then heat it until the steam pressure exceeds the safe working limit of the tank.

You can even make golden syrup tins explode like that, I used to blow them up when I was a schoolboy with an interest in things that go "bang". It's obviously unsafe to have syrup on supermarket shelves.

[Steve Firth]

Ignore Drivel, he's the group clown.

As to the boiler, it needs inspection to determine the answer to your question. We thought the same about our 18 year old oil boiler. It seemed to work and we hadn't any complaints. However it needed to be moved because Mrs F. didn't like where it was. When it was disconencted we discovered that flue gasses had corroded the flue where it coudl not be seen, and the heat exchanger was mostly shot.

A new high efficiency boiler halved out fuel consumption and that resulted in saving the £1800 cost of the boiler over three years. If your boiler is oil-fired, £2000 sounds a reasonable cost to have one fitted. If it is gas, it sounds excessive.

[PC Plod]

No they have a Vaillant 837 which has a 37kW output. I filled half a bowl of water in their kitchen sink before I got hot water. When I have a shower I count to 5 and its red hot. Dr Drivel made a valid point about the annual service for the Megaflo so should I go for a thermal store again seeing that they are prone to scaling up as I live in one of the worst areas in the UK for scaling. Also are megaflo's reliable?

[Steve Firth]

Go for a thermal store and a water softener.

[Doctor Drivel]

Oh look! A plantpot.

[Doctor Drivel]

Oh Look! A plantpot.

[Doctor Drivel]

The new Flowmax does not have an interal DHW coil. It has a high efficient plate heat exchanager. These resist scale by have plates that flex. If they need descaling you unscrew the plate and descale. Easy. The new versions are som much more efficient.

Best replace the Flow max with the latest model, and have Magnaclean on the return of the radiator circuit.

When there is a lot in an area many up to speed on them If plumber can't understand one don't employ him, as he is thick.

Failed in what way? If the CH is off the store, you are supposed to put 2 cans of X-100 in every 4 years.

Not a proplem as it is silicon coated.

Dead leg pipe is the same for any combi or cylinder. The Ethos has a secondary circulation kit to ensure "instant" water at all taps.

The Vaillant 937 has little lag it has small water store.

[Doctor Drivel]

Is the blending valve OK?

[PC Plod]

I think so as I can put my hand between the blender valve and the tank which goes luke warm to the touch when I loose hot water.

I have had a look at the price of the flowmax thermal store. God they make a megaflo tank seem cheap

[Doctor Drivel]

It could be blocked. I would be inclined to remove the valve and clean it and de-scale the coil, before buying another unit. If it is OK, I would clena out the CH circuit and insdie teh cylidner too. Then put a Magnaclean filter on the CH return to cylinder. Then put 3 to 4 can of X-400 in the system. It should last another 10 years then.

Price up an Albion Mainsflow - they have a normal DHW take up coil inside though. Look at: Newark Cylinders & McDonald engineering too (also coils). Gledhill Boilermate (uses plates) & the integral boiler Gulfstream.

The great advantage of direct CH and boiler heat up thermal storage is the integral buffering it gives. This must not be underestimated.

Have TRVs on all rads and no room stat - use a Wilo Smart pump or Grundfos Alpha on the CH circuit. Makers generally supply these as options.

[Ed Sirett]

and a blending valve on the outlet (pretty much standard kit these days).