Plate heat exchanger considerations
Considering an ASHP and an issue has cropped up. Heat loss calcs show 5-8kW (depending on who you believe).
We currently have a vented central heating system, I'm worried about moving to a pressurised system because of the danger of pipe leaks.
I suspect the copper pipe in the concrete floors downstairs is as old as the house (~60 years), and I see no evidence of there being separation between the concrete and copper. We did have a minor pinhole leak in the loft when an old pipe had corroded probably due to flux corrosion.
The consequences of a leak in the floor would be quite large, we have fairly new flooring throughout.
So I'm thinking to request there be a plate heat exchanger to keep the ASHP and DHW tank pressurised, and leave the CH vented. Clearly both sides need pumping, which is a disadvantage, and clearly some efficiency will be lost, does anyone have direct experience?
Let's say the CH system should have a flow of 45C, how hot would the ASHP have to run, 46, 47?
What about the difference in flow rates?
Are there other problems?
@scalextrix I cant help with the CH side but you might look at the plate heat exchanger used with a mixergy cylinder to get a handle on the DHW. By all accounts it works very efficiently. see here https://energy-stats.uk/mixergy-heat-pump-performance/
House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60
suspect the copper pipe in the concrete floors downstairs is as old as the house (~60 years), and I see no evidence of there being separation between the concrete and copper. We did have a minor pinhole leak in the loft when an old pipe had corroded probably due to flux corrosion.
You are sitting on a ticking bomb, which isn't going to do you any favours at some point. Good chance the pipe is too small as well (?).
I would bite the bullet and do a proper job, especially as the tax payer is likely to pick-up most the cost.
Posted by: @scalextrixhow hot would the ASHP have to run, 46, 47?
Depends how big the PHE is. At low temperature they need to be huge to get minimal differences in flow temperature.
Maxa i32V5 6kW ASHP (heat and cooling)
6.5kW PV
13.5kW GivEnergy AIO Battery.
Posted by: @johnmoGood chance the pipe is too small as well (?).
No, the pipe sizing is very adequate, 15mm to rads and 22mm primary for each floor in the building. None of it needs changing from a sizing perspective.
Posted by: @johnmoDepends how big the PHE is.
Ok so how big does it need to be?
@bontwoody thanks, I see they are supposed to be 90% efficient or more.
So maybe if I use that as a rule of thumb, a 45C flow from the ASHP would give 40.5C into the radiators.
Posted by: @scalextrix@bontwoody thanks, I see they are supposed to be 90% efficient or more.
So maybe if I use that as a rule of thumb, a 45C flow from the ASHP would give 40.5C into the radiators.
There are sizing calculators online. The basics are the the higher the temperature the smaller the PHE can be. The PHE in a combi boiler is pretty small. But your max temperature will in the 40s, assuming you run weather compensation that is your max temperature on a typical 7 Deg day your nearer 35, so that will affect PHE size. Get it wrong you could have a heat pump cycling at lowish flow temperature.
Do the job correctly - replace the dodgy pipes, route them elsewhere to get from A to B.
Maxa i32V5 6kW ASHP (heat and cooling)
6.5kW PV
13.5kW GivEnergy AIO Battery.
@scalextrix As @JohnMo says though at lower temperatures they need to be bigger so that will probably be the worse performing one in the CH. Also they arent cheap, the Mixergy one is about £300.
House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60
@bontwoody £300 on a £7k ASHP project isn't really a major issue. The designer will have to size it anyway, my real question is how much efficiency impact it might have, plus any other unexpected issues.
@johnmo not clear the pipes are dodgy, but they could be, nobody can know until after they are pressurized. Right?
The only routing is the current routing through the concrete slab, not digging that up for an ASHP, if that's he only way then we have to remain on gas.
Posted by: @scalextrixthey could be, nobody can know until after they are pressurized. Right?
Do an air test on them then you will know. Passes test they are fine. If it fails it would have done pretty soon anyway. A pressurised system will only be running at less than 1.5 bar.
Our plate exchanger (working in a hybrid system) doing 36 degs is 460mm tall and 80mm wide and has 40 plates. Bigger would be better.
Maxa i32V5 6kW ASHP (heat and cooling)
6.5kW PV
13.5kW GivEnergy AIO Battery.
Posted by: @johnmoOur plate exchanger (working in a hybrid system) doing 36 degs is 460mm tall and 80mm wide and has 40 plates. Bigger would be better.
Useful information thanks, we have a cupboard where all that can go, seems pretty small.
Currently viewing this topic 2 guests.
Recently viewed by users: Scalextrix 33 minutes ago, Johnmo 1 hour ago.
- 22 Forums
- 2,054 Topics
- 44.8 K Posts
- 62 Online
- 3,285 Members
Join Us!
Trusted Installers
Struggling to find a reliable heat pump installer? A poor installation can lead to inefficiencies and high running costs. We now connect homeowners with top-rated installers who deliver quality work and excellent service.
✅ Verified, trusted & experienced installers
✅ Nationwide coverage expanding
✅ Special offers available
Latest Posts
-
RE: Volumisers in Heat Pump Systems: Does Placement Matter?
You’re absolutely right that during defrost the refrige...
By Mars , 40 minutes ago
-
RE: Advice for ground source heat pump in new build with PV and batteries
When looking at room sealed stoves, you need to ensure ...
By Johnmo , 54 minutes ago
-
RE: Yes, the "zoning with ASHP" topic again...
@johnmo That’s a clever use of defrost behaviour to gui...
By HarryRea , 1 hour ago
-
RE: Plate heat exchanger considerations
Useful information thanks, we have a cupboard where all...
By Scalextrix , 2 hours ago
-
@editor thanks Mars that’s the same table I found in th...
By Gary , 6 hours ago
-
RE: Tariff and charging strategy advice please
They haven't asked me to prove that I have an EV (I do)...
By JamesPa , 9 hours ago
-
RE: Solar Power Output – Let’s Compare Generation Figures
Took a while to find on the OFGEN site: ”The FIT sche...
By AgentGeorge , 14 hours ago
-
RE: why solar diverters for HW instead of the heat pump?
For me there are few factors why you may want to heat w...
By Johnmo , 15 hours ago
-
RE: Hydronic plinth heaters and ASHPs
@editor yes I think so. It will be a while until I get ...
By benson , 15 hours ago
-
RE: Aira Heat Pump: Stylish Scandinavian Heating
I’m an Aira customer with a 6kW Outdoor Unit in a small...
By KevinPotts , 1 day ago
-
RE: Is your heat pump insured?
@richard24738 good to hear. I’ll also review them this ...
By Mars , 1 day ago
-
RE: Warm weather and heat pumps.
Just looked at my WC setting, it is programmed for 25 D...
By Johnmo , 1 day ago
-
RE: How to disable radiator heating in LG HM161MR
Just to add to above,when adjusting WC heat pump should...
By JamesPa , 1 day ago
-
@johnmo yes I can believe that. It seems to be human na...
By SUNandAIR , 2 days ago
-
RE: Help optimising my system!
I would be doing things a little more simply. Your heat...
By Johnmo , 2 days ago
-
RE: Renewables & Heat Pumps in the News
If you want to read a huge amount of speculation, fabri...
By Judith , 2 days ago
-
IVT Greenline high pressure switch and electrical cassette errors
I have an IVT Greenline HT Plus C heat pump that is con...
By tdudgeon , 2 days ago
-
RE: Additional Battery v Wind Turbine v Ripple
There was a call today for Ripple investors and amongst...
By Judith , 3 days ago
-