Hot Water Cylinder for ASHP

[sinaloa]

Hi,
I wonder if someone will help me resolve conflicting advice from various plumbers regarding the replacement of my old hot water cylinder (20+ years old) which has begun to leak. I had a 14 Kw Ecodan fitted last year (thats a whole other story!!!) but retained my old cylinder in a vented system.
The installers of the system originally recommended that we convert to an unvented system when the hot water cylinder needed replacement but are now recommending that they replace the old hot water cylinder with an unvented 300l Megaflo but used in our vented system and with the two coils "plumbed together" to improve recovery time. If I were to go this route it seems that the Elson Zircon 300 or a Plumbase "badged" version would be a much cheaper alternative with the same benefits?

Would there be any benefits from converting to an unvented system - we have shower pumps installed so don't have pressure problems in the house? And the loft tanks are not a problem.

Other plumbers who I have contacted have suggested that the bespoke cylinder from Gledhill with a single coil with a 34 Kw output would be more suitable but I can work out the comparison in heatup times and economy from plumbing together two coils in a cheaper dual coil cylinder. The price differentials seem considerable. They have recommended keeping the vented system.
Ideally I would like to have two horizontal immersion heaters but that is not a deal breaker.

Thanks in advance for any guidance/recommendations

 

[Gas]

The reason you have had no replies, is because it is a job that needs a site visit. You have already said that you have found cheaper alternative(s) with the same benefits, over the Megaflow, assuming you have no knowledge of either, but then ask much more basic questions

We call this nightmare ville.

 

[sinaloa]

Sorry if I have unwittingly breached some forum etiquette. I have virtually no knowledge whatsoever of the hot water system - that's why I asked much more basic questions. I have had site visits, all of which give me conflicting recommendations, which is why I posted.
Gas - I did indeed say that I had found cheaper alternatives that SEEM to give the same benefits - but that was a question to the unbiased experts in the forum.

If my question is out of order I'll willingly stop bothering people.

 

[Gray0689]

As said it would be better to get opinions from a site survey
If you post up your location there may be a member near you to give you advice

Depending on what you got to spend if it's just reheat times your after acv tank in tank is best
Or joule has just brought out a new tank in tank cylinder too bit as never use done yet unsure what they are like

 

[sinaloa]

I am in the Bicester/Aylesbury area.

 

[Nostrum]

No point using a megaflow as a vented cylinder, your better off with one that has an external expansion vessel as it will be cheaper and most space efficient. Megaflows have an internal bubble which make the unit larger in comparison to the same volume cylinder with an external vessel.

Your presumably looking for the coil with the greatest surface area so use the manufacturers spec's to figure this out. Heat up times will not be accurate as the input will vary depending on outside temperature and the flow temp will be lower than the manufacturers have tested them at. They do make heat pump cylinders which have a large surface area to ensure efficient heat transfer and will quote heat up times which are more akin to lower flow temps I would imagine.

 

[Gray0689]

As said it would be better to get opinions from a site survey
If you post up your location there may be a member near you to give you advice

Depending on what you got to spend if it's just reheat times your after acv tank in tank is best
Or joule has just brought out a new tank in tank cylinder too bit as never use done yet unsure what they are like

Sorry re read your post
For a heat pump you are better going for something with a big coil think ones for heat pumps are normally 1 1/4 inch coils
Don't work with heat pumps so not very clued up but there a few members that could help you out

 

[Reg Man]

Looking at similar things in my own property. I have ASHP with rubbish cylinder.. Inherited from house purchase. Unvented is not an option as we have low water pressure and flow. I am actively looking for the best large bore coil heat recovery vessel at a realistic price. Why anyone recommended de-unventing a megaflow is beyond reason.

 

[Killy Bing]

Looking at similar things in my own property. I have ASHP with rubbish cylinder.. Inherited from house purchase. Unvented is not an option as we have low water pressure and flow. I am actively looking for the best large bore coil heat recovery vessel at a realistic price. Why anyone recommended de-unventing a megaflow is beyond reason.

i have seen a solar one used, both coils linked

 

[sinaloa]

Thanks Reg Man. I'd love to hear what you decide. At the moment the only thing I can find is an Albion Aerocyl AAU 300 for Heat Pumps at about £1400 plus fitting or a Gledhill HP with a 34 Kw coil at about £1130 plus fitting. You will be much better placed than me to know if they are suitable - I have virtually no knowledge at all. I've spoken to Mitsubishi but their units are about £4k !! I've spoken to Ariston and they don't produce a unit suitable for ASHP's.
I'll post again if I make any progress.

 

[Killy Bing]

another option that I have read HOWEVER you would want to get in touch with them is ACV. apparently their tank in tank design goes rather well with heat pumps.

 

[sinaloa]

Thanks 1 King 55. My original ASHP installer recommended fitting the Plumbase version of the megaflow (I believe it is called a Centrestore) with the solar and main coils linked. It is an unvented cylinder but they say it can be used in our vented system (which I believe is correct).
My starting post was prompted because I could not see how to calculate if this arrangement would give the same heat-up time as the min 3 sq metre surface area coil that Mitsubishi recommend.

 

[Nostrum]

The centerstore solar 300 has an auxiliary coil surface area of 0.79m2 and the solar coil in 1.1m2.

 

[Nostrum]

Gledhill do a slimline heat pump cylinder in 210L size, I've seen it online for a touch over £800 incl vat if that helps, won't go into detail of where as we have forum sponsors who may not take to kindly 3m2 coil.

 

[Ermintrude]

Gledhill do lots of things I wouldn't want any of them. ACV SLME 400 or 800 if it's a biggie!